CHAPTER 20

Disc Disease

Clark Watts and Howard Smith

Principles of Neurosurgery,

edited by Robert G. Grossman. Rosenberg © 1991.

Published by Raven Press, Ltd., New York.

Historical Aspects, 415
Anatomy, 415
Pathology, 416
Lumbar Disc Disease, 416

General Considerations, 416

Symptoms, 417
Signs, 418
Localization, 418

Initial Management, 419
Diagnostic Studies, 419
Surgery, 421
Chemonucleolysis, 424
Percutaneous Nuclectomy, 424
Reoperation, 424
Unusual Herniations, 425

Cervical Disc Disease, 425

General Considerations, 425
Symptoms, 425
Differential Diagnosis, 426
Localization, 426
Diagnostic Studies, 427
Management, 427
Surgery, 427

Thoracic Disc Disease, 431

General Considerations, 431
Presentation, 431
Diagnosis, 431
Surgery, 431

Discitis, 432

Vertebral Osteomyelitis, 432
Postoperative Discitis, 433
Discitis in Children, 434

References, 434

Any discussion of disc disease must begin with a defini-
tion of the scope of such disease. To some, disc disease is
defined narrowly as a disorder resulting from rupture of
the intervertebral disc. Others include primary disc de-

generation and the spondylosis that results from it. Still

others include disorders of the discs associated with se-
vere spinal trauma including fracture, as well as aseptic,
septic, and granulomatous discitis. Most of this chapter

will be devoted to the understanding and management
of ruptured intervertebral disc disease. Some of the dis-
cussion will be devoted to bacterial infections of the disc,
primarily as a complication of surgery. Disc disease asso-
ciated with primary spinal trauma is discussed in
Chapter 22, and spondylosis in Chapter 21.

HISTORICAL ASPECTS

While the brilliant work of Schmorl, published in the

German literature in the 1920s, is the cornerstone of our

C. Watts and H. Smith: Division of Neurosurgery, Univer-

sity of Missouri School of Medicine, Columbia, Missouri
65212.

current understanding of disorders of the intervertebral
discs, it took the detailed embryologic, anatomic, and
pathologic correlations of Keyes and Compere to pro-
vide the basis for our clinical application of this work (1).
This was accomplished in 1934 with Mixter and Barr's
published observations on radicular compression by her-
niated disc material as a common cause of sciatic pain
(2). In reaching their conclusions, Mixter and Barr made
use of the observations of many other investigators, in-
cluding Elsberg who reported 15 cases of chondroma of
the spinal canal in 1913, pointing out the similarity be-

tween the chondromata and the substance of the inter-
vertebral disc (3). Also of historical importance is Stoo-
key's paper in which he clearly described a cervical disc
rupture, although he misunderstood the precise patholog-
ical nature of the lesion (4).

ANATOMY

An intervertebral disc resides between the bodies of

each of the vertebrae below C2 and above SI. The discs
serve to absorb the shock of stress applied to the spine, as

416 / CHAPTER 20

well as to permit some degree of spinal motion, particu-
larly flexion and rotation (5). Each disc is composed of

three components: the nucleus pulposus, the annulus fi-
brosus, and the cartilagenous endplates (1).

The center of the disc is occupied by the nucleus pul-

posus, which consists of a protein gel containing muco-
polysaccharides (6). The annulus is composed of con-
centric laminated bands of fibrous tissue and forms the
outer border of the disc. Medially, the annular fibers are
attached to the cartilaginous endplates of the disc,
whereas laterally these fibers are attached directly to the

vertebral body by Sharpey's fibers. Anteriorly, the fibers

of the annulus merge with the anterior longitudinal liga-
ment, which imparts additional strength to the disc. Pos-
teriorly, a similar attachment with the posterior longitu-
dinal ligament is noted. The posterior longitudinal
ligament is narrower than the anterior longitudinal liga-
ment, although there is a rhomboid-shaped widening of
the posterior longitudinal ligament at the disc space. The

posterolateral aspect of the disc is unsupported by liga-

ment. This relative lack of support undoubtedly ac-
counts for the preponderance of disc ruptures, especially
in the lumbar area, occurring through the posterolateral

annulus.

The endplates of the discs, composed of hyaline carti-

lage, are cemented to the intervertebral surfaces of the

superior and inferior vertebral bodies by a thin layer of
calcified cartilage, which in some places permits the
bone marrow to reach the surfaces of the endplates. Each

cartilaginous endplate extends to the posterior margin of

the superior and inferior vertebral bodies. In the anterior

and lateral regions, however, the endplate ends abruptly,

abutting against the outer raised rim of the vertebral

body, the epiphyseal ring.

The intervertebral disc is relatively vascular in chil-

dren and young adults (7), and small arteries and veins
are even found in the region of the cartilaginous end-
plates. By the third decade, however, the arteries and
most of the veins disappear, and thenceforth nutrients
are supplied to the intervertebral disc by diffusion from
the marrow cavity through the endplates.

The nerves of the intervertebral disc are primarily un-

myelinated and present a type of terminal arborization
characteristic of pain fibers (8). They exit the spinal
nerve distal to the dorsal root ganglion by way of the
posterior primary division of the root and return through
the intervertebral foramen, entering the vertebral canal

as the recurrent sinuvertebral nerve (9). This nerve sup-
plies branches to the posterior longitudinal ligament,
periosteum, epidural blood vessels, dura mater, facet

joint, and superficial layers of the annulus fibrosus (8).

Each branch to the intervertebral disc probably supplies

the level of its entrance into the vertebral canal and one
segment below this level (9). It is this nervous network

that may be the source of back and leg pain not asso-
ciated with true disc herniation. In patients undergoing

laminectomy under local anesthesia for disc rupture,

Murphey has shown that stimulation of the posterior
longitudinal ligament and medial annulus will produce

back pain, whereas stimulation of the more lateral annu-
lus and the facet joint results in both back pain and leg
pain referred to the general region of the dermatome of
the appropriate spinal root (10).

PATHOLOGY

The primary pathology of the intervertebral disc is

produced by aging (11,12). With aging, there is fragmen-
tation of the posterior annulus, along with a loosening of
its attachment to the longitudinal ligaments. This is ac-
companied by thinning and fissuring of the cartilaginous
endplates, with invasion of granulation tissue from the
adjacent bone. By the eighth decade, the laminar struc-

ture of the annulus is lost. Nuclear degeneration in all

cellular elements of the disc is obvious. Additionally, the
water content of the nucleus pulposus decreases from 88
percent at birth to 70 percent in the eighth decade (12),
and, primarily by 20 years of age, the water content of
the annulus decreases from 78 to 70 percent. In the nu-
cleus pulposus, there develops an increased ratio of kera-

tosulfate to chondroitin sulfate; as mucopolysaccharide
is broken down, it is replaced by collagen. These changes
result in a decreased disc volume. There is also a progres-
sive decrease in elasticity, leading to increased stiffness
and residual deformation, with a decreased capacity for
recovery from compression of the disc, and poor energy
dissipation (a decreased internal-dampening capacity)
by the disc. This leads to an increased vulnerability to

disc rupture until the sixth decade. Disc rupture after the

sixth decade is unusual, but increasing vertebral spondy-

losis or osteophyte formation is noted. These bony

changes are especially prominent in the posterior and

posterolateral regions of the vertebral bodies and discs,
leading to the radicular and myelopathic syndromes of
spondylosis.

LUMBAR DISC DISEASE

General Considerations

While there is disagreement in the literature about the

exact incidence and prevalence of intervertebral disc dis-
ease, there is general agreement on certain demographic
features of this condition. Disorders of the spine are prob-
ably the most common cause of disability in the working

population, with most complaints referred to the lumbar

area. In some series, lumbar disc disorders outnumber

cervical disc disorders by ten to one, with thoracic disc

disorders being rare (although clinically very important
in terms of the disability they can produce). With regard
to intervertebral disc rupture, males outnumber females

Disc DISEASE / 417

by three to one. The greatest incidence of disc rupture

occurs in the fifth decade, with the more acute syn-

dromes appearing earlier and the more chronic ones ap-
pearing later. The average neurosurgeon will spend ap-
proximately 18 percent of his or her time in the
outpatient treatment of intervertebral disc disease (ap-
proximately 20 percent of case load). The inpatient
treatment data are similar, with the time spent on disc
disease being 16 percent and the frequency of cases being
approximately 17 percent (13).

Approximately 90 percent of adult lumbar disc rup-

tures occur at the two most caudal discs (L4-L5 and L5-
Sl), with each contributing half of this total (14,15).
Most of the remaining ruptures occur at L3-L4, with

ruptures of the upper lumbar discs (T12-L1, L1-L2, and

L2-L3) being quite rare (16).

Although unusual, intervertebral disc rupture does oc-

cur in adolescents (17). In most instances, it is associated
with a documented traumatic episode. The presentation

is similar to that in the adult. Small numbers of cases

involving preadolescent children and due to specific trau-
matic episodes are recorded in the literature, with a 9-
year-old child representing the youngest case (18). Unfor-

tunately, the lack of awareness among physicians of the

possibility of intervertebral disc rupture in children re-
sults in a more protracted period of observation and eval-
uation in such cases. Most are given the diagnosis of
either a psychological disorder or, ultimately, a spinal
tumor. However, a careful examination of the findings

in these cases indicates that they present with histories
similar to those of older children and adults.

Symptoms

The patient with lumbar intervertebral disc disease

will present with either of two basic symptom com-

plexes. The most easily recognized occurs in the person

with a job that requires significant bending and lifting

throughout the day. The affected individual usually has a

history of occasional nagging backache, which is relieved
by a temporary reduction in physical activity. The acute
symptom complex begins with the sudden onset of dis-
comfort in the lower back. This may range from a pull-
ing or tearing sensation to excruciating localized pain.
There may be paresthesias into the leg, which may or

may not be localized to a dermatome of a lumbar spinal
root. With decreased physical activity, the pain contin-

ues but is reduced in intensity. Within a few hours the
paresthesias, which may have persisted or disappeared

shortly after the onset of pain, are replaced by pain ra-

diating into the leg in an appropriate dermatomal distri-

bution. As in the case of disc-related back pain, this ra-
dicular pain is usually eased by reduced physical activity.

For several days following the onset of symptoms, the
patient will note that increased activity exacerbates both

back and leg pain. The pain also increases with straining,
such as in coughing, bowel evacuation, and lifting.

The foregoing are the typical symptoms of a herniated

lumbar intervertebral disc. More careful evaluation of
these symptoms will reveal details that may be of addi-
tional value in localizing the site of the rupture. Back
pain associated with vague, aching, deep leg pain, and
approximating in distribution a known dermatome, sug-
gests an annular rupture with the herniation of fibrotic
nuclear material into the annulus and the stimulation of
pain fibers within the annulus. With bed rest, the leg pain
usually disappears and the back pain decreases because
of decreased pressure within the disc and partial internal
decompression of the nuclear fragment brought about

by the recumbent position. The presence of back and leg

pain in a specific dermatomal pattern that is reduced in
intensity by the recumbent position suggests a disc her-
niation with compression and distortion of the spinal
root, but without foraminal entrapment of the root.
There may or may not be weakness in the motor distri-

bution of the spinal root. The persistence of severe leg

pain beginning hours after the onset of back pain and
despite bed rest suggests the impaction of a herniated
disc fragment into the foramen. This is usually asso-
ciated with numbness and weakness in the distribution
of the spinal root.

Minor bladder dysfunction in cases of disc injury,

such as hesitancy in voiding, is usually due simply to

back pain produced by straining. The same can be true

of sexual dysfunction, especially in male patients. If, how-
ever, there are significant urinary system symptoms,
such as retention, or the inability to develop penile erec-

tion in a male patient, and especially if these are asso-
ciated with profound back pain, a large midline hernia-
tion with cauda equina compression should be

suspected. In such instances, sensory and motor com-

plaints usually reflect the involvement of multiple roots,

often bilaterally. This point should be kept in mind when
one is presented with a patient who experiences sudden

bilateral sciatic and femoral pain, paraparesis, and uri-

nary retention.

The more common symptom complex of lumbar in-

1

tervertebral disc disease is a chronic pain syndrome. The

patient notes intermittent back pain for months or years,
requiring periods of decreased physical activity for sev-
eral days and often resulting in loss of work time. With

the passage of time, the initial back pain gradually be-
comes associated with leg pain preceded by a period of
intermittent paresthesias. The leg pain and paresthesias

may have a dermatomal distribution but, more often,

are less well localized. Generally, pain, extremity weak-

ness, and urinary and sexual dysfunction are described

by the patient in less dramatic and discrete terms than in

the case of an acute herniation and are not unlike the
symptoms of spinal stenosis and spondylosis. The acute
symptoms of the chronic pain syndrome may be precipi-

418 / CHAPTER 20

tated by minor episodes of trauma, such as coughing,
taking an awkward step, or turning over in bed.

Signs

In seeking physical abnormalities in the patient with

lumbar intervertebral disc disease, the physician should
examine the undressed patient and begin by observing
the patient's posture and gait. In such cases, the normal
lumbar lordotic curve is flattened, and the patient tends
to list toward the side contralateral to the diseased disc,

with an elevation of the ipsilateral hip. It is as if the pa-
tient were attempting to open the foramen on the af-

fected side and accomplish a decompression of the root.
Paravertebral muscle spasms, more pronounced on the
affected side, may be palpated. However, this is an unre-
liable sign of disc disease, since any painful condition of
the spine or muscles may produce muscle spasms. Addi-

tionally, the disturbance of posture may make one group
of paravertebral muscles appear more prominent. Pain
will limit the motion of the lumbar spine in all directions
and is increased upon lateral bending to the affected side.
This is in contrast to unilateral myositis, in which .lateral
bending to the opposite side is restricted by the intense

muscle spasms on the affected side. Percussion over the

diseased intervertebral disc space will usually elicit a
complaint of localized back pain and may produce leg
symptoms. However, this also is a nonspecific sign, since
other painful disorders of the back, such as a simple
strain, may yield the complaint of pain upon percussion.

If performed properly, the sciatic nerve stretch test can

be most helpful in diagnosing disc disease. As described
by Lasegue in 1864, the test first involves flexion of the
hip at right angles to the trunk, followed by extension of
the knee with the patient in the recumbent position (19).

A positive result of the test consists of leg pain in the

distribution of the patient's spontaneous symptoms and
suggests rupture of the intervertebral disc with compres-
sion of a nerve root contributing to the sciatic nerve,
usually at L4 to S1. Elevation of the straightened leg by

itself may give a false-positive response, owing to the

stretching of irritated muscle groups in the proximal part

of the leg. Modifications of the Lasegue test may also be

useful in diagnosing disc disease and include simulta-

neous dorsiflexion of the foot as the knee is extended.

Another suitable variation of the test is to have the pa-
tient sit with the distal leg dangling over the edge of the

examining table. The leg is extended at the knee. If this is
done while the examiner is testing deep tendon reflexes
or sensory function in the distal leg, it may elicit a more
objective response from the patient, at least with regard
to the angle of the extension required to produce the first
complaint of pain. If the Lasegue test on the contralat-
eral leg results in ipsilateral complaints (the crossed-
straight-leg raising sign), the results are felt by some to be

even more confirmatory of disc disease. Internal and ex-

ternal rotation of the hip is performed to exclude hip

disease, which will yield Patrick's sign or the fabere sign.

Muscle strength in the affected leg may be tested in a

variety of ways. As noted above, the physician should
observe the patient's gait for patterns of weakness. The
patient's thigh strength may be observed by asking the
patient to step up onto a low stool repeatedly with the
affected leg. Dorsiflexion of the feet may be observed by
asking the patient to walk on his heels toward the exam-
iner. Plantar flexion may be observed while the patient
walks on the toes and balls of the feet. An evaluation of
specific muscles should then be done. Quadriceps weak-
ness can be detected by having the patient resist flexion
of the extended knee. The physician can apply force
against the dorsiflexed foot to test the tibialis anterior
muscle, against the great toe to test the extensor hallicus

longus, and against the plantar flexed foot to test the

gastrocnemius and soleus muscles, comparing the
muscle strength in the affected leg with that in the unaf-
fected leg.

Sensory examination is accomplished by testing the

individual dermatomes for light touch and pin prick. Oc-
casionally, however, especially with pin prick, the pa-

tient will note hyperesthesia, often associated with hy-
perpathia, in the appropriate dermatome.

Reflex testing of the lower extremities in lumbar inter-

vertebral disc disease is less reliable than the tests dis-
cussed above. The reflexes may be exaggerated or sup-
pressed by pain and muscle spasms. Additionally, the
myotatic reflexes diminish in intensity with age. The ex-

aminer should compare the patient's reflexes bilaterally,

looking for asymmetry.

/

Localization

Before discussing the localization of disc disease, it

should be recalled that the lumbar spinal roots exit at the

foramen below the appropriate vertebra. For example,

the LI root exits at the foramen between LI and L2, and
the L5 root exits at the foramen between L5 and SI. It

should also be recalled that the anterior border of each

foramen is formed by the most lateral extent of the disc
at each level, and that the root travels caudally and lat-
erally within the spinal, canal prior to entering the fora-
men. Thus, for example, the L4 root enters the epidural
space opposite the posterolateral aspect of the L3-L4 disc
and is associated with the L4-L5 disc only in its most
lateral extent, as the root enters the foramen. The typical
disc rupture occurs through the posterolateral annulus
and, therefore, tends to cause compression of the root

that exits at the foramen below. Thus, the typical L3-L4
disc rupture will affect the L4 root, an L4-L5 rupture will
affect the L5 root, and an L5-S1 rupture will affect the S1

root.

An L4 root syndrome will be characterized by back

and radicular pain along the medial aspect of the knee

Disc DISEASE / 419

and distal leg to the ankle. Hypesthesia will be noted in
this distribution. Weakness in the quadriceps will be
found, and a diminished quadriceps deep tendon reflex
will be noted. In an L5 syndrome, the pain and hypesthe-
sia will be on the dorsomedial aspect of the foot, invari-
ably in the dorsal web space between the first and second
toes. Weakness or atrophy of the muscles supplied by the
peroneal nerve will be observed, expressed as a weakness
of dorsiflexion of the great toe, or the foot, or both. An

absent or diminished posterior tibial deep tendon reflex

is inconsistently noted. The findings in an S1 syndrome
are paresthesias, pain, and hypesthesia on the lateral

aspect of the foot and sole including the heel; weakness

or atrophy of the gastrocnemius and soleus muscles,
demonstrated by a weakness of plantar flexion; and a
diminished Achilles' deep tendon reflex.

Syndromes produced by ruptures of the first and sec-

ond lumbar intervertebral discs are not as clear as those
described above, for several reasons. One reason is that
the epidural space is less generous at these locations than
in the lower lumbar area; the cauda equina contains

more nerve roots, more closely packed together. There-
fore, even small ruptures can readily involve multiple
roots as they descend past the rupture site. Conse-

quently, a greater number of bilateral symptoms and
signs occur with L1-L2 and L2-L3 disc ruptures. Also,
the ruptures tend to be more medially located. Thus,
back pain without radicular pain, or with referred pain,
is more common than with ruptures at lower levels. The
pain may radiate in a multidermatomal pattern into the
leg. Additionally, there is a greater propensity for more

severe motor and bladder symptoms, and both the quad-

riceps and the Achilles' deep tendon reflexes may be af-
fected. Finally, although true disc ruptures in this area
usually present with acute syndromes, the chronic pro-
gression of symptoms may make it difficult to distin-

guish between disc disease and neoplasm.

Initial Management

The overwhelming majority of patients with interver-

tebral disc disease, no matter how acute the presentation,

can be managed satisfactorily with an appropriate non-

surgical regimen. The patient should be put on bed rest
for several days and, since it is virtually impossible to
keep the patient totally on bed rest, advised to arise

briefly only for the maintenance of personal cleanliness

or the relief of boredom. Generally the patient will re-
quire little beyond aspirin or 0.5 grain of codeine every 3

to 4 hours for the relief of pain. There are no satisfactory
"muscle relaxants" for use in disc disease, but a minor
tranquilizer such as diazepam, 2 to 10 mg given two to
four times daily for two to three days may be helpful.
Local heat application for the relief of muscle spasms is
advised but should be limited to mild heat for periods of
no longer than 20 to 30 minutes. Longer periods tend to
increase muscle irritability as the heat accumulates, and

increased muscle blood flow occurs. Generally, after
four to five days of this management, the patient will
experience greater intervals of asymptomatic ambula-
tion and can resume relatively normal activity within 10
days to 2 weeks. The patient should be advised to avoid
heavy lifting and straining for an additional two weeks.
At that time, attention should be given to factors contrib-
uting to the underlying musculoskeletal deficits responsi-
ble for the patient's disc disease. These usually stem from
obesity, poor muscle tone, and poor work habits. Proper
diet and an appropriate, enjoyable exercise, such as
swimming, dancing, tennis, or some other activity, can

be prescribed.

Certain symptoms and signs are indications for hospi-

talization. If the initial history and exam discloses a sig-
nificant neurologic deficit, particularly motor and blad-
der dysfunction, the patient should be admitted. By the
same token, hospitalization should be considered if de-
spite conscientious home treatment the patient's symp-

toms do not improve, if the patient is unable to return to
normal activity because of a recurrence of symptoms
with each period of ambulation, or if the home environ-
ment is such that adequate home management is not
possible. Whatever the reason for hospitalization in such
cases, the initial hospital care should be the same as
would be prescribed at home. The medical and nursing
staff should pay special attention to the patient's descrip-
tion of his or her pain, to evidence of changing neuro-

logic deficits, and to the pattern of requests for medica-

tion, in order to evaluate the causes and severity of the
patient's disability.

In most instances, an acute presentation of severe pain

with a significant neurologic deficit warrants immediate
hospitalization. However, rarely is immediate surgery
required for herniations at the L4-L5 or L5-S1 level. Re-
covery will almost always occur in such cases, even with

a major herniation. A period of observation will usually

indicate that bladder dysfunction is primarily the result
of pain and not of primary nervous system injury. Even a
major foot drop will begin to diminish in a few days with

the nonsurgical regimen outlined. The dogmatism of

this advice must be modified when dealing with lesions

of an upper lumbar intervertebral disc. When major
symptoms and signs are associated with ruptures in this
area, protracted delay will afford the patient less chance

of recovery, especially if the conus of the spinal cord is

compressed. The decision to intervene surgically must

be made individually, on the basis of the acuteness of the

presentation, the severity of the deficit, and the patient's
general medical condition.

Diagnostic Studies.

General Laboratory Studies

The basic laboratory studies in cases of disc disease

include a hemoglobin measurement, hematocrit, and

I

420 / CHAPTER 20

erythrocyte sedimentation rate (ESR). The differential

diagnosis of back pain with or without leg pain, espe-
cially if the pain is chronic, must include neoplasia and
those chronic diseases revealed by anemia. The ESR will
be elevated in neoplasia, in a wide variety of inflamma-
tory disorders such as infection (discitis), and in rheuma-

toid spondylosis. The ESR will be normal in degenera-
tive intervertebral lumbar disc disease with or without
rupture. If the patient is being considered for surgery,

appropriate screening tests should include a platelet

count, a prothrombin time test, and a partial thrombo-

plastin time test.

Special Diagnostic Studies

In this age of rapidly advancing medical technology,

the neurosurgeon has available several diagnostic study
modalities for evaluating the status of the lumbar inter-
vertebral disc. These include roentgenography of the
lumbar spine, electromyography, bone radionuclide
scanning, venography, discography, myelography, body
computed tomography (CT), and magnetic resonance
imaging (MRI). A considerable amount of useful infor-
mation will be obtained by reviewing plain films of the
lumbar spine. Spondylosis, especially beyond that ex-

pected for the age of the patient, and disc-space narrow-
ing will suggest degenerative disc disease. Bony changes
of a chronic nature, such as erosion, sclerosis, or local-
ized areas of radiolucency will suggest disorders other

than intervertebral disc disease. Malalignment—scolio-
sis, excessive kyphosis, and subluxation—will suggest

congenital disorders or/6ld trauma. Careful inspection

for such specific evidence of congenital disease as spon-

dylolisthesis, spina bifida, and spondylosis (although this
may be secondary to trauma) may yield information
helpful in understanding the patient's symptomatology.
The usual findings in patients with ruptured interverte-
bral disc disease of the lumbar spine are minimal at best
and consist primarily of spondylosis and disc-space
narrowing. Polytomography should be limited to delin-
eating the true nature of localized lesions found on plain
films.

Despite its widespread use, electromyography is of lit-

tle value in the diagnosis of the typical case of a ruptured

intervertebral disc because of its lack of specificity. And

although in skilled hands it is quite accurate in delineat-
ing a single-root radiculopathy, it does so with no greater
accuracy than a careful history and physical examina-
tion. Electromyography may be of value in those cases of
disc disease in which the history and physical examina-

tion do not suggest the diagnosis of a ruptured disc, or

those in which the differential diagnosis includes other
forms of neuropathy. It can be misleading in the patient
who has had a prior laminectomy with or without disc

excision. In such instances, abnormal findings will per-
sist indefinitely in both the paraspinous muscles and the
extremity muscles innervated by the previously involved
root (20).

Radionuclide scanning of the spine may also be help-

ful in diagnosing disc disease but, like electromyography,
may be misleading. The bone scan may be locally posi-

tive in a wide variety of active processes, including neo-
plasia, acute trauma, surgical healing, and infection. Al-

though a radionuclide scan is not usually positive in

degenerative disc disease or in the case of a ruptured disc,
it may be positive in spondylosis (21).

Lumbar epidural venography, or phlebography, may

be useful in identifying the site of rupture of a lumbar
disc (22). This technique involves the opacification of
the epidural venous system by the selective catheteriza-
tion of ascending lumbar veins. A unilateral displace-
ment of the antero-internal and sometimes the antero-
external venous channels may be produced by lateral
disc herniations. Venography is felt to be of value when
myelography is rendered inadequate by an enlarged
dural sac, an extremely lateral herniation, or arachnoid-
itis. It is not of value in patients who have undergone
surgery in the epidural space. Furthermore, while venog-
raphy is accurate in the patient with the typical ruptured
disc syndrome who has had no previous surgery, the in-
constant nature of the epidural venous anatomy makes
it of dubious value in the atypical case.

Enthusiasm for lumbar discography has waxed and

waned since its introduction by Eindeblom in 1948. It
involves the injection of 1 to 5 cc of a radio-opaque
water-soluble contrast medium into the region of the nu-

cleus pulposus through a 20-gauge spinal needle inserted

percutaneously. Its proponents argue that it can give
valuable information concerning the anatomical status
of the disc and can differentiate between a normal disc, a
degenerative disc, and a ruptured disc (23).

In a lumbar discogram, the extrusion of contrast me-

dium through the annulus into the epidural space sug-
gests the presence of a ruptured disc. If the procedure is
performed under local anesthesia and the injection is
associated with reproduction of the patient's pain, this is
felt to confirm disc rupture. The opponents of discog-
raphy as a diagnostic procedure argue that the introduc-
tion of a needle into a normal nucleus pulposus may
result in hastened degeneration or later rupture of the

punctured disc, or both. Moreover, no criteria exist for
distinguishing the asymptomatic degenerative disc from
the symptomatic degenerative disc on the basis of discog-
raphy; patients asymptomatic for lumbar disc disease

may exhibit the extrusion of contrast medium into the
epidural space (24). Beyond this, studies correlating the

accuracy of the pain reproduced in lumbar discography

as a diagnostic entity have not been generally accepted as
valid. If the efficacy of the treatment of disc disease by
percutaneous discectomy or the intradiscal injection of

Disc DISEASE / 421

chimopapain, collagenase, or steroids is established, dis-

cography will require further evaluation.

Myelography has been the mainstay of radiographic

evaluation of a suspected lumbar disc herniation. lo-

hexol has replaced metrizamide and iophendylate as a

contrast medium because it produces fewer untoward
effects (25). CT has earned a prominent role in the evalu-
ation of lumbar disc herniations and has been shown to
be effective in the demonstration not only of nerve roots
but also of the structures likely to compress them (26).
CT is more sensitive to lateral disc herniation than my-
elography (27). In the patient with a straightforward disc
herniation syndrome, a CT that demonstrates nerve-
root compression at the appropriate site is sufficient to

plan therapy. If, however, the CT does not unequivoca-

bly reveal the pathology, myelography followed by CT
with the intrathecal contrast present should be under-
taken. This will allow visualization of the lower thoracic
and upper lumbar regions and can reveal unusual lesions

(e.g., tumors) as well as standard lumbar disc hernia-
tions.

Some authorities feel that it is not necessary to per-

form a myelogram or a CT prior to surgery in the typical
case of disc rupture. However, it must be pointed out
that while an L5 root syndrome (for example) is com-
monly caused by a posterolateral disc ruptured at L4-L5,
it may also be due to a more lateral disc ruptured at
L5-S1. It is for this reason that patients with ruptured

discs usually undergo myelography or CT prior to disc
surgery. Additionally, myelography or CT may be used
to exclude the presence of a significant disc rupture in
patients with chronic pain simulating disc disease, but in
whom there are no neurologic findings. This indication
for such studies has widespread use for patients whose

lives are complicated by personal liability litigation or

job-related compensation claims.

MRI holds promise of largely replacing myelography

and CT (28,^9). MRI offers excellent resolution, free-
dom from (ztone artifact, and the ability to image the
spine in any plane. High cost and long acquisition time

are problems to be surmounted, but MRI is rapidly be-

coming the imaging method of choice for diagnosing

disc disease.

Surgery

The primary indication for the surgical treatment of

disc disease is the failure of conservative management
and it occurs in three clinical settings. In the first of these,
involving the patient who presents with an acute disc
rupture associated with a severe neurological deficit, the

neurosurgeon may be required to proceed urgently. This

will rarely occur, but when it does, immediate surgery is
indicated. This situation is more likely to exist with rup-
tures of the upper lumbar discs. The patient will present

with back and leg pain, often bilateral, as well as parapa-
resis and urinary retention.

The patient for whom surgery is most commonly indi-

cated will be the one who presents with a typical history
of acute or chronic back and leg symptoms. The exami-
nation will reveal mild evidence of radiculopathy, in-
cluding hypesthesia, reflex depression, and mild weak-
ness. The patient will have had recurrent bouts of mild
disability culminating in a more significant episode re-

quiring hospitalization. After appropriate conservative

management, extending to 10 days or so, it will be clear
that little progress is occurring.

The indication for surgery in the third type of patient

is more controversial. This is the patient who has re-
peated bouts of disability characterized primarily by
back pain, with occasional paresthesias or pain in the leg.
The course of the disease in such cases is protracted,
sometimes extending to many months or years. Yet
while the patient is repeatedly able to describe a quasi-
dermatomal distribution of the pain or paresthesias, ob-

jective findings of weakness and reflex changes are in-

consistently noted. For many reasons, primarily
socioeconomic, the patient is finally admitted to the hos-

pital, where studies reveal a questionable epidural defect

at the appropriate level. In this case, the decision whether
or not to operate is a highly individualistic one in which
the physician must consider not only the medical facts
but the effect of the recurring disability on the patient,
and on his or her work and private life. Moreover, the
physician, while remaining as objective as possible, must
also keep in mind that neurosurgery, no less than all
disciplines of medicine, is as much an art as a science.

Since most surgery for ruptured lumbar intervertebral

discs is done electively on relatively healthy individuals,

it involves the usual presurgical evaluations. Assurance
is obtained of a normal physiological cardiorespiratory
and hematologic status of the patient. Appropriate con-
sultation is made with the anesthesiologist, depending
upon the type of anesthesia to be used. While some sur-

geons prefer the use of local, spinal, or epidural anesthe-
sia (30,31), general anesthesia is preferred by most sur-
geons for lumbar disc surgery. This involves the use of
intravenous pentothal supplemented by various mix-
tures of nitrous oxide, oxygen, and isoflurane delivered

through an endotracheal tube. Blood replacement is
rarely necessary during the surgery. Nevertheless, either
2 units of packed red blood cells should be available in
the operating room or the blood bank should perform
preoperative typing and antibody screening of the pa-
tient in the event that blood replacement becomes neces-
sary (32).

Procedure

Various techniques and positions for the surgical

treatment of lumbar disc disease have their advocates.

422 / CHAPTER 20

We prefer a hemilaminotomy and foraminotomy, with

the excision of a modest amount of disc material. Imme-

diately before the operation, the patient is asked to con-
firm the side on which he has leg pain, and the myelo-
gram films (if obtained) are arranged on the view box in
the operating room as if the spine were viewed from pos-
terior, corresponding to the operative field with the pa-

tient prone. The patient is then intubated under general

anesthesia and put in the prone position on either blan-
ket rolls 4 to 6 inches in diameter extending from the
shoulders to the iliac crests or on a frame of similar di-
mensions. The table is flexed slightly so that the normal
lumbar lordosis of the spine is flattened or reversed. A
midline incision is made from the spinous process above

the involved level to the level below. Skin-edge hemosta-
sis is obtained with hemostatic clamps and bipolar coagu-
lation. Another midline incision is then made through

the lumbodorsal fascia overlying the exposed spinous
processes, and the paravertebral muscles are stripped
subperiosteally with appropriate elevators from the spi-
nous processes and laminae on the involved side. Retrac-
tion is subsequently maintained with a self-retaining re-
tractor. During the periosteal dissection and retraction

of the paravertebral muscles, it is sometimes helpful to

briefly produce muscle relaxation with intravenous succi-
nylcholine or a deepened level of anesthesia.

After completion of the steps described above, a small

hemilaminotomy is accomplished, including in the re-
section the medial portion of the facet joint. The inter-

laminar ligament is incised longitudinally, then resected
sharply with a number 15 blade or an angled Kerrison

rongeur. A foraminotomy is done next, to allow more
gentle retraction of the nerve root. Exploration of the
epidural space is performed, and proper identification of
the nerve root is made. The offending disc abnormality
is identified, and the nerve root is gently retracted me-
dially with an appropriate nerve-root retractor. If a free
disc fragment is identified, it is removed with the disc
rongeur. The disc space is then entered and, with me-

dium-sized straight and angled curettes and upward-an-

gled rongeurs, the disc material from the postcrolateral
quadrant of the disc is removed. No attempt is made at
significant additional removal of intradiscal material.

Following adequate removal of disc material, the epi-

dural space is further explored, the wound is thoroughly

irrigated with saline. Some authorities have advocated
placing a small free graft of subcutaneous fat over the
root to replace the normal epidural fat and to try to pre-

vent the epidural scarring which has been demonstrated
in animal experiments (33). Hemostasis is obtained in

the epidural space by bipolar coagulation. The wound is
then closed in layers (muscle fascia, subcutaneous fat,

and skin), and a suitable dressing is applied. The patient
is taken to the recovery room, extubated at the discretion
of the anesthesiologist, and observed for approximately

2 hours. After this, the patient is taken to his room.

There is usually no reason to put the patient in an inten-

sive care unit postoperatively.

With excessively obese patients, the surgery for a rup-

tured disc may more easily be accomplished with the
patient in the lateral position, with the involved side fac-

ing up and the table flexed in the middle as with the

prone position. This position prevents the compromise
of diaphragm movement due to abdominal compres-
sion. It is, however, somewhat more difficult for the as-
sistant. Technically the operation is performed in a man-
ner similar to that described above.

Another frequently used position for surgery is the

knee-chest position. The purpose of this position is to

avoid any abdominal pressure whatsoever and thus de-
crease epidural bleeding.

Concerns of possible transmission of human immuno-

deficiency virus with the transfusion of blood products
have prompted use of methods available to minimize
intraoperative blood loss. However, blood loss is usually
limited to less than 100 cc using standard positioning.
Some surgeons feel that the knee-chest position may pro-
duce a tourniquet effect on the muscles of the lower ex-
tremities, resulting in damage to muscles with the release
of myoglobin, which may be renotoxic (34).

Variations in the surgical technique will depend upon

the training and experience of the surgeon. Some prefer a
much smaller incision than that described above, with
microscopic epidural dissection and removal of the disc

(35). It is suggested that the smaller wound makes for
quicker healing and less scar formation. The use of intra-

operative magnification with loupes or a microscope will

result in less chance of trauma to veins and the dura, but

the value of micro-incisions is not proven.

Postoperative Care

Postoperatively, the patient is permitted food and am-

bulation as tolerated. The sutures are removed in five to
six days, and the patient is discharged from the hospital
by the third to sixth day. For two to three weeks thereaf-
ter, the patient is permitted to ambulate to whatever de-

gree is comfortable, but with the intensity of his physical

activity limited to that which was practiced in the hospi-

tal. Some surgeons prescribe physical therapy and exer-
cise almost immediately after surgery; however, we do

not think that this is wise. The patient is at risk for addi-

tional disc herniation during the first month postopera-
tively since complete removal of all disc material from
the interspace is not possible, and the process of old col-
lagen lysis and new collagen synthesis results in a signifi-

cant gain in tensile strength between the fifth and seven-

teenth days postoperatively, with a slower addition of

strength for another 10 days (36). At the end of one

month, depending upon how the patient is progressing,
an additional two to four weeks of increasing physical

activity is prescribed. The patient who has employment

Disc DISEASE / 423

in an office environment can usually return to work by

three to eight weeks postoperatively. It may take two to

four months for a person in a strenuous occupation to
resume work. During this period of convalescence, the
patient normally requires little if any pain-relieving med-
ication. With this regimen, patients with a ruptured lum-
bar intervertebral disc who have undergone surgery have
a 90 percent chance of a successful return to work and a
long-term asymptomatic postoperative course (37).

Causes of Failure

The major causes of failure of the surgical treatment of

a ruptured disc are improper diagnosis and improper
selection of patients for surgical treatment. The longer
the duration of the patient's symptoms (in terms of
months or years), the more "soft" the symptoms and
signs, the less definite the radiographic defect, and the
less impressive the disc herniation at surgery, the less
likely it is that the surgeon can expect a cure.

Complications

Other than a low incidence of wound infection (less

than 1 percent), serious complications of disc surgery
should virtually never occur. Nevertheless, there are cer-
tain operative complications that can occur. One serious
complication of surgery is nerve-root injury. This can
range from nerve contusion resulting in temporary post-
operative worsening of the patient's neurologic deficit, to
laceration of the nerve root and permanent damage. In-

jury to the nerve is most likely to occur while the inter-

laminar ligament is being sharply excised either with a
knife blade or a curette, or when the foraminotomy is

being performed with rongeurs. It is therefore imperative

that the surgeon identify the nerve root as soon as possi-
ble, and either keep it in direct vision at all times or cover
it with a cotton pledget so that he knows where it is.
Perineural adhesions resulting from chronic compres-
sion of the nerve root by disc material may make it diffi-
cult to dissect the nerve root away from the disc. This can

best be accomplished by identifying normal dura and
nerve root distal to the site of the adhesions and then,
under magnification and with excellent lighting, dissect-
ing away the adhesions. If a large disc fragment lies me-

dial to the nerve root, attempts to retract the nerve root
medially over the fragment may cause a stretch injury of
the root. The surgeon should first decompress the nerve
root by removing all disc material from the axilla of the
nerve (i.e., from between the medial aspect of the nerve

root and the dura as the nerve root proceeds distally
from the point at which it exits from the dural canal).

Tearing of the dura and arachnoid, which often occurs

as only a pinhole-sized opening or injury, may lead to a

cerebrospinal fluid leak or a pseudomeningocele. Extra-

dural bleeding during exposure of the nerve root or dur-

ing disc removal should not be controlled by excessive
packing of sponges into the epidural space. This may
result in injury not only to the root but also to other
intradural structures. The surgeon should notify the anes-
thesiologist of the difficulty so that the latter can prepare
for blood replacement if necessary. With good lighting,
bipolar cautery forceps, and magnification with loupes
or, in certain cases, the operating microscope, epidural
veins can almost always be coagulated before bleeding
occurs. If bleeding occurs, the source will usually be a
single large epidural vein lying in the anterior lateral epi-

dural space. The vein may lie in the lateral recess (under-

lying the partially resected facet joint), where it may be

injured by the rongeur during the bony resection. In this
case, the bleeding can easily be controlled by temporarily
packing into the lateral recess a small piece of absorbable
hemostatic material held by a small ( 5 x 5 mm) cotton

pledget. The total blood loss in most disc operations
should be no more than 100 to 150 cc, and is often much
less.

Another serious complication of disc surgery is injury

to intra-abdominal structures, especially the great vessels

that lie in the prevertebral space (38). This is most likely
to occur with excision of the L4-L5 disc and to result
from perforation of the anterior longitudinal ligament
by a curette or rongeur. Laceration of an iliac artery or
vein is the characteristic injury. Vascular laceration may

be heralded by excessive blood presenting itself through

the intervertebral disc space. More common, however, is

a precipitous decrease in blood pressure and the develop-

ment of shock. Although this may occur during the oper-
ation, it is more likely to be seen at the termination of the
procedure as the patient is transferred from the operating
table to the recovery room cart, or at the time of the
patient's arrival in the recovery room. The treatment is

immediate abdominal exploration. Vascular injury may
also present months after disc surgery as an arteriove-

nous fistula between an iliac artery and vein (39). It
should be suspected with the development of unilateral

leg swelling, and varicosities may exist as well. Cardio-
megaly and heart failure may occur. A to-and-fro mur-
mur located in the lower portion of the abdomen is
pathognomonic of an abdominal arteriovenous fistula.
Treatment consists of the restoration of arterial conti-
nuity.

Rarely documented in the literature are cases of injury

to an abdominal organ, such as the ureter, bladder, or
ileum (40). Nothing occurs at the time of surgery to sug-
gest that such an injury has occurred. In the case of in-

jury to the ureter or bladder, the patient may have post-

operative hematuria. With injury to the ileum,

prolonged ileus is generally seen, followed by the develop-

ment of signs of peritonitis within a few days. Appro-

priate management depends upon the organ injured.

424 / CHAPTER 20

Proper consultation should be obtained as soon as the

possibility of this complication enters the surgeon's

mind.

The role of spinal fusion in intervertebral disc disease

is currently less controversial than in the past. It is not
indicated during the first operation for a single ruptured
intervertebral disc. Patients who do not undergo fusion
have a better long-term outcome than those who do (41).
This is the case even if spondylolisthesis, whether congen-
ital or degenerative, exists. Fusion is indicated in young
patients with spondylolisthesis who have clear symp-

toms and signs of mechanical instability, and in whom
degenerative changes are limited to a single level. Fusion
is also indicated in some cases in which decompression
itself has resulted in facet instability (42). The patient
who has had multiple back operations at multiple levels,
with bilateral laminectomies and foraminotomies, and
who develops instability should be considered for fusion
(43). Fusion is currently also being recommended for
some patients with single-level degenerative disc disease

who do not have true disc rupture or herniation. These
patients are usually young and have had occupations
that have rendered their backs more susceptible to
trauma, or have had a specific traumatic episode from
which their back pain dates. They have no neurologic
deficits and their myelogram is normal. The discogram

shows a single degenerated disc that appears to be dis-

eased out of proportion to the disease of adjacent discs or
to the age of the patient. Initial follow-up studies on such
patients suggest that they experience a reduction of
symptoms and return to a more active social existence
following fusion. However, there has not yet been ade-

quate long-term follow-up of a large series of such cases.

Chemonucleolysis

A proteolytic enzyme, chymopapain, has been advo-

cated for the enzymatic digestion of lumbar interverte-
bral disc material, a procedure termed chemonucleoly-
sis. It has been reported to be effective in approximately
65 percent of patients with physical symptoms and signs
and radiographic (including myelographic) evidence of
lumbar disc disease (37). The procedure is not used for

cervical disc disease. The mechanism of action of the
enzyme is unknown, but it is ineffective in vitro against
extruded disc material. The apparent effectiveness of the
enzyme may relate to its known neurolytic activity on
poorly myelinated nerve fibers (44) of the type found in
the posterior longitudinal ligament and annulus (which
may be pain fibers) (8) rather than on digestion of the

disc itself. The chymopapain procedure has been asso-

ciated with a number of serious complications. Anaphy-
laxis occurs in about 0.5 percent of injections with a
mortality rate of 0.06 percent. Additionally, a number of
patients have developed a delayed paraplegia from trans-

verse myelitis two or three weeks after the procedure.

Due to these complications, most surgeons have aban-
doned chymopapain (45).

Percutaneous Nuclectomy

Recently, a new surgical technique called percutane-

ous nudectomy has been introduced (46). To perform

this procedure, a 2-mm blunt-tipped suction-cutting de-
vice is passed percutaneously via a posterolateral ap-
proach into the disc space. Disc material is removed only
from inside the disc space. Although this technique is

inadequate for the treatment of a substantially herniated

or extruded disc, it may hold promise for the treatment
of a herniation into the layers of the annulus (47). In
such cases, the back and leg pain is referred from annular
pain fibers. It could be reasoned that decompressing the
disc space would relieve pressure on the annular hernia-
tion and relieve the pain. Experience has not yet permit-
ted an analysis of the long-term results or complications

of the procedure.

Reoperation

The consideration of reoperation for disc disease sug-

gests in most instances that the initial diagnosis was in-
correct (48). However, there are times when the original
surgery was properly undertaken but was incomplete.
Patients who postoperatively exhibit no change in their

signs and symptoms may, for example, have retained
extruded disc fragments. This is likely if the surgeon
found a ruptured disc with some extruded fragments at

the time of surgery. The retained fragments will usually
be found quite laterally, often in the foramen. Patients
who have an acute recurrence of their preoperative signs
and symptoms in the first two to three weeks postopera-

tively should be suspected of having extruded an addi-

tional fragment from a surgically treated intervertebral
disc. Additionally, a recurrence of intervertebral disc
rupture may occur months or years after an earlier disc
operation. In such instances, the patient should be man-
aged in the same way as for a primary attack. Reopera-
tion on the spine is complicated by the presence of epidu-
ral scarring from previous operations. But since the
surgeon can proceed safely into the distorted, scarred
area only after proper orientation, made possible by ex-
posing the normal anatomy of the spine, surgery should

begin by exposing this normal anatomy, including the

epidural space, at the extremes of the scarred anatomy.

Testing both the surgeon's patience and understand-

ing of back disorders will be the patient who either never
returns to work postoperatively or, following recovery,
returns to work only to note vague symptoms of back

and leg pain with activity, similar to but not quite the

same as the preoperative symptoms. Such patients often

either have no neurologic deficit or may have a de-

Disc DISEASE / 425

pressed deep tendon reflex and minor dermatomal sen-
sory loss—findings present since the initial evaluation.
These patients will want "something done" and will
have settled any litigation involved in their injury. The
electromyogram (EMG) in such cases will probably be
abnormal, and the myelogram will be interpreted, at the
very least, as consistent with "postoperative change."
These patients should not be explored; "exploration"
means the surgeon does not know what to expect to find

and, in all likelihood, will therefore not "find" the pa-

tient's problem. Instead, such patients must be managed
with compassion but firmness. Their life-styles should be
examined for any factors contributing to their symp-
toms. They may have to change their occupation. Pro-
grams of dieting, exercise, and adjuvant therapy utilizing
all modalities employed by the physical therapist must
be undertaken in such cases. Steroidal and nonsteroidal
anti-inflammatory agents, administered orally, and anti-

depressant drugs may provide some pain relief. Above
all, the physician should support the patient psychologi-
cally. These patients will ultimately carry the diagnosis
of arachnoiditis, facet syndrome, spinal stenosis with epi-
dural fibrosis, or others. They may ultimately enter com-
prehensive pain-control programs, a discussion of which
is beyond the scope of this chapter.

Unusual Herniations

Two unusual types of lumbar disc herniation may be

encountered by the surgeon: the intradural rupture of a

disc and the simultaneous rupture of multiple discs. The
ruptured lumbar intervertebral disc may rarely be found

within the subdural or subarachnoid space (49). The pa-

tient will usually have a long history of persistent back
pain, with intermittent leg pain that may be unilateral or

bilateral. The presenting episode is acute in nature and is

associated with signs of significant cauda equina com-

pression, including paresis (unilateral or bilateral), multi-

level sensory deficits, and bladder dysfunction (retention

or incontinence). The patient will not improve with a

few days of bed rest. The myelogram or CT reveals an
intradural mass at the level of the disc space. The rup-

tured intradural disc should be approached with a bilat-
eral laminectomy and transdural excision. It is not clear
why this injury occurs, but one can postulate that a mid-
line-bulging or partially extruded disc causes adhesions
to the dura, with dural thinning. Subsequent complete
extrusion of the disc then ruptures through the weakened

dura. Most such ruptures occur at the L4-L5 interspace.

While the true incidence of multiple disc ruptures is

impossible to obtain from the literature, it certainly

comprises less than 5 percent of all cases of disc rupture

(15). The vast majority of multiple ruptures are unilat-
eral and occur at the L4-L5 and L5-S1 levels. In such
cases, one of the disc ruptures may be more midline than

the other. Rarely are extruded fragments found at both
levels. Usually there is a recognized precipitating event,
such as heavy lifting. The clinical signs indicate that

more than one level is involved, and myelography or CT

reveals the appropriate extradural defects. Rather than
myelography or CT, some surgeons recommend the rou-
tine surgical exploration of the lower two disc spaces (L4-
L5 and L5-S1), even if only one level is clinically sus-
pected of being injured. If the surgeon determines that

both levels are involved, each level should be handled

technically as in the patient with a single disc rupture,
and the postoperative management should also be the
same. We have operated on one patient, a 36-year-old
man presenting with an acute cauda equina syndrome
following heavy lifting, who had an extruded fragment at
L4-L5 on the right and an intradural midline rupture at
L5-S1. Postoperatively, the patient returned to his
previous occupation in four months with no neurologic
deficit.

CERVICAL DISC DISEASE

General Considerations

The term cervical disc disease covers several clinico-

pathologic entities. The "soft" or herniated (protruding
or extruding) disc presents with acute and chronic syn-

dromes similar to those resulting from a ruptured lum-
bar intervertebral disc. The "hard" or osteophytic disc

syndrome is known as spondylitic disc disease and will

be covered in the chapter on spinal stenosis.

There is considerable disagreement in the literature

about the relative frequencies with which the neurosurg-
eon will see the "soft" or herniated disc and the "hard"
or spondylitic disc. The older literature suggests that the
herniated disc is much more common, while more re-
cent literature suggests a predominance of cervical disc

disease as the result of spondylosis. The latter has been

our experience.

Except for a few specific considerations, the anatomy,

pathology, and biomechanics of the cervical disc are
clinically similar to those of the lumbar disc. Although
the cervical disc is not subjected to the same loading
stresses that occur in the lumbar spine, the greater mobil-
ity of the cervical spine results in a rate of degeneration
of the cervical disc which matches, for the age of the
patient, that of the lumbar disc. The rate of degeneration
of the C5-C6 and C6-C7 discs is much greater than that
of the other cervical discs, and more than 90 percent of

the clinical syndromes of cervical disc disease are asso-

ciated with disease at these two interspaces.

Symptoms

As with the ruptured lumbar intervertebral disc, the

ruptured cervical disc may present with two basic symp-

426 / CHAPTER 20

torn complexes: acute and chronic. With the acute rup-
ture of a cervical disc, the patient will invariably note a
specific time of onset. Little trauma may be experienced;
a large number of patients appear to develop the symp-
toms of such a rupture during sleep, perhaps due to tor-
sion of the neck when turning in sleep. The symptoms of
the chronic complex are more insidious in onset. How-
ever, a careful analysis reveals the complaints to be quite
similar, except for their rate of onset, to those of the
patient with an acute rupture. The laterally herniated
cervical disc will produce unilateral neck pain radiating
to the medial aspect of the scapula and into the upper
extremity. The pain will be associated with isolated mo-
tor and reflex deficits, determined by the level of the
rupture. There is a variable degree of upper anterior
chest pain. Compression of the head from above will

exacerbate the pain, especially if the latter is associated

with a lateral rotation and extension component of neck

movement. The pain is relieved by traction.

The most impressive complaint of the patient with a

ruptured cervical disc relates to the pain and not to the
accompanying motor weakness. The pain is constant
and tends to prevent sleep. As opposed to most lumbar
disc ruptures, the patient with a cervical disc rupture
often can find no comfortable position, although occa-
sionally flexing the neck to the opposite side and holding

the ipsilateral hand and arm resting on the head will give
relief akin to that produced by flexing the leg in lumbar
disc disease.

Spontaneous midline cervical disc herniations are ex-

tremely rare in the absence of trauma sufficient to pro-
duce a fracture dislocation (50). The patient with such a
herniation may complain of sudden posterior and mid-
line neck pain. There may be some radiation of the pain
into the shoulders and interscapular area. Anterior chest

pain is usually not a feature of midline herniations. Also,

although a large rupture may be associated with an acute
myelopathy, there is usually little spinal cord dysfunc-
tion in these cases. They may present with Lhermitte's
sign, a "shock"-like radiation of pain down the midline
and into the lower extremities with neck flexion.

Differential Diagnosis

The symptoms and signs of an acutely ruptured cervi-

cal disc are so characteristic that the physician will have
little trouble in making the diagnosis. However, the pa-
tient who presents with a chronic history may present a
problem in diagnosis (10). Nerve-root-related spinal tu-
mors such as neurofibromas or meningiomas will cause
a long history of symptoms of gradually increasing sever-
ity. The motor deficit in such cases may be more promi-
nent than with the ruptured disc, and the pain less promi-
nent. Symptoms of myelopathy may be more prominent

than with a lateral cervical disc rupture. The changes

seen on plain x-ray films and the myelographic defects

are both often characteristic of these tumors. Intramedul-

lary neoplasms and cervical syringomyelia will usually
present with a chronic syndrome of weakness and atro-
phy in the upper extremities, and spastic paraparesis.
When pain is present, the clinical differentiation of these
conditions from myelopathy secondary to cervical disc
disease may be difficult.

Spillane's neuritis, or neuritic amyotrophy, is usually

unilateral and most often involves the C5 root. Although
the pain is disconcerting, it is generally not as severe as
that produced by acute nerve-root compression. The

pain develops gradually over a few days, then subsides
over an additional few days. It is associated with marked
paresis, usually greater than that seen with nerve-root
compression by a ruptured disc. The symptoms of le-
sions of the brachial plexus, such as those produced by a

neurofibroma, Pancoast's tumor, or thoracic outlet syn-
drome are only superficially similar to those of disc dis-

ease. The pain and paresthesias are not in a root distribu-
tion, are unrelated to motion of the neck, and are usually
reproducible by local compression of the brachial

plexus. Additionally, Homer's syndrome may be seen in
cases of Pancoast's tumor.

Tardy ulnar nerve palsy and carpal tunnel syndrome

usually will not be confused with cervical disc disease.
They are not related to neck movements, and the pain is
usually in the distribution of the nerve, with percussion
at the point of the local compression exacerbating the

symptoms. Occasionally there may be a distribution of
pain proximal to the point of compression of the ulnar

nerve or the median nerve, radiating up the arm. How-

ever, this rarely reaches the shoulder and does not pro-
duce symptoms in the scapula or anterior chest. Thus,
one should have no difficulty in distinguishing nerve
compression from cervical disc disease or from internal
derangements of the shoulder, which occur with adhe-
sive capsulitis, tendonitis, and injury to the rotator cuff.
The relationship between the pain and movement of the
neck and shoulder will aid in this differentiation.

Localization

Ninety percent of disc ruptures occur at C5-C6 and

C6-C7. A small number of ruptures occur, in equal fre-
quency, at C4-C5 and C7-T1. Scoville reported that 1
percent of ruptures occur at C3-C4 (51). We know of no
reports of spontaneous ruptures at C2-C3.

Unlike herniations in the lumbar area, cervical hernia-

tions at a specific cervical interspace compress the root

exiting at the foramen made by the articulations of that

interspace. Therefore, a herniation at C4-C5 compresses
the C5 root, which exits at the C4-C5 foramen. With a

C4-C5 rupture compressing the C5 root, the symptoms
are primarily in the deltoid region of the lateral aspect of

Disc DISEASE / 427

the upper arm. One will note weakness of the supraspin-

atus, infraspinatus, and deltoid muscles. The biceps

muscle may be weak. Deep tendon reflexes may be di-
minished in the biceps and brachioradialis. Ruptures at

IC5-C6 with C6 nerve root compression result in pain

and paresthesias extending into the lateral aspect of the

proximal arm and into the dorsum of the forearm. Char-
acteristically, the pain and paresthesias extend to the
thumb and index finger. There may be mild to moderate
weakness of the biceps and brachioradialis muscles. Oc-

casionally the only weakness noted will be that of the

extensor carpi radialis. The reflexes of the biceps and
brachioradialis may be diminished or absent.

With C6-C7 ruptures (which affect the C7 root), the

sensory symptoms are found in the index and middle
fingers. Weakness of the triceps is noted, as is a dimin-
ished reflex in that muscle. The C8 root is compromised
with a C7-T1 rupture. The sensory symptoms of a rup-
ture at this level are found in the ulnar aspect of the

upper arm and forearm, with radiation into the ring and

little fingers. Weakness is noted in all extensor muscles
of the wrist except for the extensor carpi radialis, in all
flexors except the carpi radialis and palmaris longus, and

in all intrinsic muscles of the hand. The triceps reflex
may be diminished, as may the finger flexor reflexes.

Diagnostic Studies

With regard to the diagnostic study of cervical disc

disease, little can be added to the information presented

in the discussion of lumbar disc disease. The electromyo-

gram may be more helpful here, especially when per-

formed in conjunction with nerve-conduction timing in
patients with disorders of the brachial plexus, tardy ulnar
palsy, and carpal tunnel syndrome. However, peripheral
nerve conduction may be delayed with the chronic com-

pression of nerve roots. Discography and venography are
of no help.

A few surgeons believe that the clinical syndromes of

cervical disc disease are so diagnostic that myelography
or other suitable studies, namely CT and MRI, are not
indicated. However, most prefer the aid of localizing
studies. This is because the brachial plexus may be pre-
or postfixed. In the prefixed plexus, the neural compo-

nents of the plexus are shifted upwards, with the effect

that there is a greater contribution to the plexus by C4. In
the postfixed plexus, there is a greater contribution by
T2. This can have bearing on the patient's subsequent
neurologic deficit. For example, in a prefixed plexus the
biceps receives more innervation from C5, while in a
postfixed plexus it receives more innervation from C6.

Myelography or CT with intrathecal contrast is stan-

dard for evaluation of cervical radiculopathy. MRI has
been shown to offer accuracy rivaling that of contrast CT
with the advantage of being noninvasive (52).

Management

As in the case of lumbar disc disease, the majority of

patients with a cervical disc rupture, whether acute or
chronic, will respond satisfactorily to nonsurgical ther-
apy. This consists of reduced physical activity and sup-
portive measures during the symptomatic episode, fol-
lowed by proper musculoskeletal care. Patients are
advised to seek bed rest during the painful state. Cervical
traction through a halter device is most helpful. Gener-
ally, the attitude of the neck in traction is maintained
slightly flexed. This permits the facet joints to open, en-
larging the foramen and decompressing the nerve. The
use of muscle relaxants and analgesics for the first two to

three days after rupture will be of help in relieving pain,

muscle spasm, and the boredom of bed rest. If for per-

sonal reasons the patient must be up and about periodi-
cally during this time, a firm cervical collar may be help-
ful. This reduces neck motion and the downward
compressive force of the head on the cervical disc. Soft

collars serve no purpose other than to advertise that the
patient has a neck disorder. As the patient becomes com-
fortable with the upright position he or she may be per-

mitted increasing activity. However, as with lumbar disc
disease, it may take four to six weeks before the patient is

comfortable enough to resume full normal activities.

If the patient's symptoms persist despite traction or

are made worse by traction, one should consider an al-
ternative diagnosis. The most common diagnosis is sim-
ply cervical myositis from ligament or muscle strain or
both, often associated with emotional tension. These pa-
tients are most difficult to manage, often being very de-|
pendent or having passive-aggressive personalities. The

physician must be patient and encouraging and not

make great use of medication. Requiring significant per-
sonal involvement by the patient is important. Unfortu-

nately this state is quite common in patients suffering

from "whiplash" injuries, especially if litigation is in-
volved.

Hospitalization may be required for the same reasons

noted in the management of patients with lumbar disc
disease, either because the home environment does not
permit adequate therapy or because the patient has a
significant neurologic deficit that warrants continued
close observation by the physician.

Surgery

The indications for the surgical treatment of cervical

disc disease are similar to those for surgery in ruptured
lumbar disc disease. The primary indication is a signifi-

cant neurologic deficit that has not improved within a

reasonable amount of time. It is difficult to quantitate
the adjectives "significant" and "reasonable"; this must
be individualized on the basis of the patient's state of

428 / CHAPTER 20

health and work requirements, and the physician's expe-
rience. Generally, a weakness of an acute or subacute
onset that prevents the patient from undertaking normal
daily activities and that does not improve in seven to ten
days fits this description. The persistence of pain requir-
ing large doses of medication is an indication for surgery

if the pain is clearly of root origin.

The operative approach will depend on many factors,

including the surgeon's training and operative experi-
ence. There are those who believe that the only approach
to the cervical disc is the posterior approach (50). Others
feel that the approach should only be made anteriorly
(53). We believe that the posterior approach should be
used in all patients who have a single-level lateral her-
niated (soft) cervical disc. The anterior approach is ap-
propriate for the single-level central herniated disc,
spondylotic ridge, and lateral osteophyte. Multiple levels

(more than two) of involvement, with bilateral radicular
syndromes or myelopathy, should be dealt with posteri-
orly. This is especially true if three or more levels are
associated with posterior ligamentum flavum hyper-
trophy as seen on radiographic studies. These consider-
ations apply whether one is dealing with herniated cervi-
cal discs or spondylotic lesions.

The preoperative evaluation for cervical disc disease is

Ihe same as for lumbar disc disease, and general anesthe-

sia is similarly used.

Procedure

For the posterior approach in the uncomplicated case

we prefer the sitting position. In elderly patients or those
with cardiovascular disease a prone position may be pre-
ferred. After induction of anesthesia, the patient is gradu-

ally raised to the sitting position with the head stabilized

in a suitable pinion head holder. The neck is kept in the
neutral position with the head slightly flexed. A central
venous catheter is introduced into the right atrium for

aspiration in the case of air embolism, although meticu-
lous attention to operative technique has resulted in no
clinically significant air embolism in our practice. The
technique involves the coagulation of large vessels before
they are electively cut, the immediate coagulation of all
smaller sectioned vessels, and the absence of any nega-
tive phase in mechanical ventilation (54).

A midline incision is made over the spinous process

bisecting the level of interest. For unilateral disease, the
paravertebral muscles are stripped subperiostially from
the spinous processes and laminae only on the appro-
priate side. An intraoperative x-ray may be used to iden-
tify the interspace if a limited incision that does not allow

the identification of C2 is used. Self-retaining retractors

are placed, and a hemilaminotomy is performed, using a
curette and a ronguer, in the adjacent laminae overlying

the appropriate nerve root. The nerve root is then identi-

fied and traced into the foramen, and a foraminotomy is
performed. If the nerve root is significantly compressed
within the foramen, the foraminotomy is performed

with a small electrically driven or air turbine drill. Com-
pression is significant if a small nerve hook cannot be
easily passed into the foramen alongside the root. The
foraminotomy is carried for 5 to 8 mm out along the
nerve root, depending upon the underlying pathology.
The use of magnification or the operating microscope is
often helpful during drilling and the subsequent disc re-
moval. The nerve root is retracted either cephalad or
caudad, according to the location of the disc herniation.
Rarely, there is a free disc fragment. However, with inci-
sion of the posterior longitudinal ligament such a frag-
ment will appear. In contrast to fragments generally
found in the lumbar area, those found in the cervical
region are rarely more than 2 to 3 mm in size, although
fragments as large as 5 mm may be encountered. No

effort is made to enter the intervertebral disc space. He-
mostasis is obtained within the epidural space by bipolar
electrocautery. The wound is closed in layers, including
the skin, with nonabsorbable sutures. Copious irrigation
is utilized throughout the procedure.

If there is a central disc herniation and the choice is

made to treat it through a posterior approach, a bilateral
laminectomy is done involving the appropriate level and

the immediately adjacent upper and lower levels. While
in such cases the centrally ruptured disc fragment may
be removed through an extradural approach from one

side or the other, particularly if it is paracentral in loca-

tion and is associated with a lateralizing radiculopathy,
the surgeon must be prepared for a transdural excision.
The dura is opened in a paramedian manner. The appro-
priate dentate ligament is sectioned and utilized to
slightly rotate the cord, permitting visualization of the
site of protrusion of the ruptured disc through the ante-
rior dura. The dura is opened in a longitudinal manner
overlying the protrusion, and the disc material is re-
moved with the use of a small angled curette and a small
disc (pituitary-type) rongeur. If the arachnoid has not
been opened, it is not necessary to close the anterior
dural defect. The posterior dural incision is closed with
nonabsorbable sutures, and the wound is closed in
layers, as in the unilateral approach.

Upon completion of the surgery, the patient is ob-

served in the recovery room, and once returned to the
ward is permitted ambulation as tolerated. Although a
collar is not necessary, some patients report less pain
during their first few days of ambulation when a firm
collar is used. Transient symptoms related to the pres-
ence of the intraoperative endotrachcal tube, such as
coughing and discomfort on swallowing, are managed
symptomatically.

The anterior approach is also performed under general

Disc DISEASE / 429

endotracheal anesthesia. The patient is put in the supine

position, with a small towel roll posterior to the lower

neck and upper thorax. A central venous line is not neces-
sary in this approach (55). If an anterior cervical fusion is

to accompany the discectomy, the bone for the graft is
taken from the iliac crest. The crest is elevated slightly by
the use of a small towel roll placed beneath the ipsilateral
buttock. Some surgeons prefer to make the skin incision
on the side of the disc extrusion. Being right-handed, we
always operate from the right side of the patient, making
the skin incision on that side, since the discs tend to be
oriented slightly cephalad from anterior to posterior.
Also to be considered is the fact that the thoracic duct is
at greater risk of injury if lower cervical discs are ap-

proached from the left side.

The skin incision is made through a natural skin

crease beginning at the midline and extending posterior
and cephalad. The initial incision is carried through the
subcutaneous tissue and the platysma. Hemostasis is ob-

tained with the use of skin clips and cautery. The basic

plane of dissection lies between the sternocleidomastoid
and omohyoid muscles laterally, and the sternohyoid
muscle medially. This plane is easily developed by blunt-

finger dissection until the anterior surfaces of the verte-

bral bodies are encountered. Further exposure is facili-
tated by the use of hand-held retractors. The pre vertebral
fascia is opened sharply, using bipolar cautery for the
occasional venous bleeding. A needle is placed in the disc
space suspected of being involved, and the location is

confirmed with a lateral x-ray.

If a bony fusion is to be done, a suitable bone plug is

removed from the iliac crest while the x-ray film is made
and developed. A 6-cm incision is made overlying the

iliac crest, beginning anterior to the anterior gluteus me-
dius muscle (53). A circular bone plug is removed from
the anterior iliac fossa just beneath the iliac crest. Bone

wax is not used for hemostasis; instead, the bone defect
and the soft-tissue wound are packed with a surgical

sponge, the tail of which is left outside the wound for

easy accountability. The graft wound is closed at the end

of the overall surgical procedure, while the neck wound
is being closed. This insures satisfactory deep-wound he-
mostasis, reducing the incidence of postoperative hema-
toma and seroma formation, which can be a source of
annoyance to the patient.

If a rectangular segment of bone is to be used for the

cervical fusion [the Smith-Robinson technique (56)], the
iliac crest posterior to the anterior iliac spine is exposed
subperiosteally. An osteotome is used to remove an ap-
propriate length of the iliac crest. Hemostasis is obtained
by packing until wound closure, which commences with

closure of the periosteum.

After the appropriate cervical disc interspace has been

identified by intraoperative x-ray, the longus colli mus-

cles are cauterized along their attachments to the ante-

rior half of the superior vertebral body, the disc space,
and the anterior superior half of the inferior vertebral

body, and are elevated. A self-retaining retractor is
placed, the blades located deep to the muscles. The anes-
thesiologist palpates the ipsilateral superficial temporal
pulse to be certain that the carotid artery is not occluded
by the retractor. Although this cannot be universally re-

lied upon, obliteration of the pulse is significant. An inci-
sion is made through the anterior longitudinal ligament
into the disc, and the discectomy is begun with curettes
and disc rongeurs. If the Cloward technique is used, the
anterior half of the middle of the disc is removed in this
fashion. The Cloward guard and an appropriate drill are
then used to make a drill hole into the remaining disc
space. If a lateral disc herniation is present, the drill is
offset slightly to the opposite side. This permits drilling
through to the anterior epidural space without the

danger of pushing additional disc material through at the
site of the rupture and further compromising the nerve

root. If a central disc herniation is present, the drill is

placed midline but is centered more into the inferior ver-
tebral body rather than being placed squarely over the
disc space. This permits drilling through the superior

aspect of the inferior body into the epidural space before

breaking through the disc at the site of rupture, a tech-
nique especially helpful if the epidural space at the disc
space is compromised by central osteophytes. This pro-»
cedure avoids the tendency to drive additional disc mate-
rial through the site of rupture into the epidural space

with the drill, which would create the risk of additional

cord compression.

During the drilling process with the Cloward drill, it is

imperative that the depth of the drill hole be inspected
frequently. With the aid of good lighting and one's tactile
sense, the surgeon should be able to detect when the drill
engages the cortical bone just prior to its entry into the

epidural space. The remainder of the bone is then re-

moved with a small curette. At this point, an intact poste-
rior longitudinal ligament may or may not be encoun-
tered since portions of the ligament are often removed
with the bone during the curetting process. The ligament
and additional bone are then removed with the use of
small angled Kerrison rongeurs, beginning in the inferior

aspect of the drilled defect. The surgeon works progres-
sively superior and lateral to either side, removing the
osteophytic material, the posterior longitudinal liga-
ment, and the disc material with angled curettes and
small angled Kerrison rongeurs. At this point, it is im-
portant to pay special attention to the degree of compres-
sion of the dura by the material to be removed. The
surgeon should not add to that compression by inserting
large instruments into the epidural space. We believe

that it is this action that results in most of the injuries to.
the spinal cord that occur during this procedure (57).
The injuries result either from direct compression of the

430 / CHAPTER 20

cord or from damage to the anterior spinal artery with
subsequent spinal cord infarction.

If the Cloward technique is not to be used, the disc

material is removed in its entirety with curettes and ron-

geurs, employing various modifications of the Smith-

Robertson technique (56). A disc-space spreader is help-
ful for visualization during the procedure, and posterior
or lateral osteophytes may be more easily removed with
a high-speed electric or air drill. We prefer the Cloward

technique simply because it permits better visualization
through the defect created by the Cloward drill. In the

other techniques, this advantage can be gained by the use
of magnification with appropriate lighting.

To fuse or not to fuse is a question currently debated

with some vigor in discussions of cervical disc surgery
(58). It is clear that spontaneous bone fusion can occur

even if bone is not implanted at the time of surgery,

although this will require a longer period than if a bone
graft is inserted. However, there is also evidence that fu-

sion of the disc space will result in an exacerbation of

degeneration in the adjacent disc spaces. This may be
due to an inability of the fused space to absorb its share
of the stress applied to the cervical spine, which must
then be absorbed by the adjacent disc spaces, increasing

their exposure to trauma. We prefer not to employ fu-
sion if the patient is under 50 years of age and does not

have significant evidence of degeneration at the adjacent

disc spaces as evidenced by disc-space narrowing and
asymptomatic osteophyte formation. There is no differ-
ence in the rate or extent of fusion with a round bone
graft (the Cloward technique) versus that with a rectangu-
lar graft (the Smith-Robertson technique).

Following completion of the surgical procedure, the

wound is closed in layers, including the skin. A small soft
rubber drain is left in the prevertebral space for 24 hours.

The patient is permitted food and ambulation as toler-
ated. A collar is not needed for stability, although some

patients feel more comfortable wearing a firm collar for

partial support of the head for a few days. Physical activ-

ity is resumed according to the patient's wishes. Most
patients are returned to full normal activity within four
to six weeks after surgery. Patients with manual occupa-

tions that require the use of the upper extremities, as in
heavy lifting, may require three months of convales-
cence before returning to work.

Complications

Several significant complications of the anterior ap-

proach have been reported. The most significant one is

injury to the spinal cord, to which reference was made in

the discussion of technique. It should also be remem-

bered that a patient who has a small anteroposterior di-
ameter of the spinal canal, either congenitally or as the
result of spondylosis, is at risk during intubation if the

neck is subjected to extremes of flexion or extension.

Additionally, injury to the cord can occur during the

insertion of the bone plug. This can be avoided by insur-
ing that the plug is cut to an appropriate size and is in-
serted with traction on the cervical spine so that it ulti-
mately rests snugly in its proper place when the traction
is released. The traction is produced by the anesthesiolo-

gist, who reaches under the drapes and pulls against the

angles of the mandible. Tapping of the bone should be
performed gently with the impactor partially overlying

the vertebral body above or below the disc space. A small

shelf of bone left posterior to the plug may protect
against posterior protrusion of the plug.

Injury to the esophagus may occur with sharp dissec-

tion in the prevertebral space or with the inappropriate

placement of a retractor blade with prongs. If such an
injury is suspected, it can be confirmed by applying an
anesthetic mask to the nose and mouth and exerting posi-
tive pressure while the wound is filled with saline solu-

tion. Bubbles will disclose the point of injury, which may

be repaired primarily with absorbable sutures. The

wound should be drained. An injury to the carotid artery

can occur if sharp dissection is used beneath the sterno-

cleidomastoid muscle into the prevertebral space. A ca-
rotid laceration may be repaired with appropriate 5-0 or
6-0 arterial sutures once proximal and distal control of
the bleeding has been obtained by the use of vascular
clamps. With the use of self-retaining retractors, the ca-
rotid artery may also be significantly compressed. There-
fore, the surgeon should use these retractors to the least
possible extent. This is one reason to place the retractors

beneath the elevated longus colli muscles.

Results

In patients who have undergone surgery for cervical

disc herniations, the long-term results with the anterior
approach do not differ from those with the posterior ap-
proach.

Good results, occurring in about 90 percent of pa-

tients, are probably achieved in a higher percentage of
cervical disc operations than lumbar disc operations. Re-

current herniations are rare. Also, although there is no
evidence that patients with cervical disc herniations at a
young age have an increased propensity to symptomatic

degenerative disc disease at a later age than do members
of the general population, an understanding of the patho-
physiology of disc degeneration would suggest that this is

possible. Therefore, both younger and older patients

should be instructed, as in lumbar disc disease, about
physical activity and work habits. This instruction will
depend upon the patient's habitus, current state of cervi-
cal disc degeneration, and occupation, and upon the ex-

perience of the physician.

Disc DISEASE / 431

THORACIC DISC DISEASE

General Considerations

Thoracic disc herniations are quite rare, representing

less than 1 percent of all disc herniations (59). However,
an examination of the literature published early in this
century, which led to the seminal conclusions of Mixter
and Barr, reveals that thoracic disc herniations, as well as
those of the cervical and lumbar area, were recognized.
The relative rigidity of the thoracic spine imparted by the

articulating ribs is thought to be the main factor in the

paucity of thoracic disc herniations; herniation is more
common in the lower thoracic spine, which has greater

mobility (60).

Presentation

As in cervical and lumbar disc disease, thoracic disc

herniations present in the form of acute or chronic
symptom complexes. They can occur spontaneously or
in association with minor trauma, such as heavy lifting
or a fall. The symptoms are primarily those of spinal axis

and thoracic radicular pain, with evidence of myelopa-

thy being less frequent.

Acute lateral thoracic disc herniations result in radicu-

lar pain, whereas paramedian or central herniations,
which occur less frequently, will usually produce varying
degrees of myelopathy ranging from an incomplete

Brown-Sequard syndrome to complete paraplegia. Ra-
dicular pain may not be present with paramedian or cen-
tral herniation. The chronic symptom complex usually
begins with a small central or lateral herniation, produc-
ing spinal axis pain. This subsides with time, during
which the true nature of the disorder remains unde-

tected. Progressive fibrosis occurs around the herniated
fragment, often with calcification, resulting in a more

insidious disability. The history of chronic back or ra-

dicular pain, or both, in association with a progressive

myelopathy, will suggest a neoplasm rather than disc

rupture.

The physical findings associated with herniated tho-

racic discs are quite variable. Percussion over the spin-
ous process at the appropriate level will elicit localized

discomfort and perhaps accentuate the radicular compo-
nent of the pain. In the absence of myelopathy, one will
rarely find disturbances of sensation in the distribution
of the involved thoracic root, because of the considerable
overlap of dermatomes. The signs of myelopathy may be
variable. In severe cases, there will be a distinct sensory
level of the injury, combined with paraparesis. With less
severe involvement, the examination will reveal variable
alterations in function of the corticospinal and spinotha-

lamic tracts. There may be a sensory level appropriate to

the involved intervertebral disc, either unilaterally or bi-

laterally. In chronic cases associated with mild myelopa-

thy, however, the sensory level may be several segments

below the appropriate intervertebral level. As previously
noted, the finding of a Brown-Sequard syndrome, espe-

cially in the patient with a chronic history of symptoms

associated with disc injury, is not uncommon. Except
with an acute transverse myelopathy, posterior-column
function is usually intact. Corticospinal dysfunction will
be heralded by lower-extremity paresis and spasticity,
with clonus and Babinski signs present. These may be
unilateral or bilateral depending upon the extent of the
myelopathy.

Diagnosis

While in most cases the physician should suspect the

diagnosis of thoracic disc disease in the acute case, the

history and physical examination in the more chronic
disorder may suggest a neoplasm. Consequently, the
diagnosis in such cases must be confirmed either myelo-
graphically, with CT, or with MRI (61). lohexol is the
contrast medium of choice; few today support the use of
air myelography in thoracic intervertebral disc ruptures.
Venography and discography are of no value, and elec-

tromyography is of little value in the diagnosis.

Because of the normal kyphosis of the thoracic spine

and because of its length, it is necessary to use larger
volumes of iohexol in performing the myelogram than
are necessary for the lumbar or cervical area—from 12 to

18 cc may be necessary. It is helpful to place the patient

in the appropriate lateral decubitus position. The typical
finding is an extradural defect posterior to the appro-

priate intervertebral disc space. In the case of a complete

cerebrospinal-fluid block, it may be necessary to intro-
duce the contrast medium directly into the subarachnoid
space through a lateral puncture of the dura at C1-C2 in
order to determine the upper level of the disorder.

Surgery

In contrast to the situation with a ruptured cervical or

lumbar disc, a thoracic disc rupture in a symptomatic
patient is an indication for surgery without further con-
servative treatment: the small diameter of the thoracic
spinal canal puts the spinal cord in constant jeopardy.
Additional trauma, resulting from minimal anatomical
change, may produce a devastating neurologic deficit.
Although it is safe to manage symptomatically the pa-
tient in whom a thoracic disc rupture is suspected but
who has no signs of myelopathy while the diagnosis is

being electively confirmed, one should proceed expe-

ditiously to surgery when signs of spinal cord compres-
sion are noted. The urgency with which surgery is under-

taken will depend upon the degree of myelopathy and
the acuteness of the presentation.

432 / CHAPTER 20

In denning the surgical approach to a ruptured tho-

racic disc, one must keep in mind that the thoracic cord

can tolerate only minimal manipulation, especially
when it is already compromised in the small thoracic
canal, and that the contribution of the spinal radicular
arteries to blood flow in the spinal cord is important. The
standard laminectomy is not suitable for the removal of
a ruptured thoracic disc. With this approach, there is
little opportunity to explore the disc space without unac-
ceptable retraction on the dura and thus on the spinal
cord. The same holds true for a transdural approach.

Most surgeons today prefer a variation of one of the fol-
lowing approaches: (1) transthoracic, transpleural ap-

proach, in which the disc space is approached from the
right anterior lateral direction (62); (2) costotransversec-
tomy, or posterior rachotomy, in which the incision is a
posterior paramedian muscle-splitting incision (63); or
(3) an approach that involves resection of the facet and
pedicle (64). After personal experiences with all three of
these approaches, we prefer the last.

The procedure is performed under general endotra-

cheal anesthesia, with the same preoperative evaluation

as discussed under the management of lumbar and cervi-
cal disc ruptures. The patient is placed in a prone posi-

tion. A midline incision is made, and ipsilateral subperi-

osteal dissection of the paravertebral muscles is
undertaken. The dissection is carried laterally beyond

the facets. A hemilaminectomy is done on the vertebra

caudal to the involved disc space. The superior articulat-
ing facet of the inferior vertebra and the inferior articulat-
ing facet of the superior vertebra are removed. Using
appropriate rongeurs and occasionally the air drill, the
pedicle of the inferior vertebra is removed down to the

body of the vertebra. This permits adequate visualiza-

tion of the lateral aspect of the disc space. The nerve root
is identified during the bone resection and protected. Re-

traction of the nerve root cephalad or caudad will reveal
the lateral disc protrusion. An incision is made into this
protrusion, the intervertebral disc space is entered, and

disc material is removed with small angled curettes and

appropriately sized disc rongeurs. More medially located
protruding disc material can be pressed into the disc
space with a number 4 Penfield dissector or an angled
dental instrument and can be removed within the disc

space. Central disc herniations may also be treated in
this fashion.

In the case of a large central herniation, it may be

helpful to perform a bilateral laminectomy. In the un-
usual case in which intervertebral disc material has

eroded through the dura, the dura may be entered lat-

erally with a longitudinal incision and the material re-
moved. Occasionally, for appropriate visualization, sec-
tion of the root lateral to the dorsal-root ganglion may be
performed. However, the importance of the radicular ar-
tery must be kept in mind. Some have advocated preop-

erative angiography to identify the location of the artery
of Adamkiewicz prior to surgery in the lower thoracic
spine.

Intraoperative monitoring with somatosensory

evoked cortical potentials may be of value. In one of our
patients, prior to sectioning the left T11 spinal root, the
root was temporarily clamped with a vascular clamp.

Within minutes, the patient's evoked potentials flat-
tened. The clamp was removed, and the evoked poten-
tials returned to normal over approximately 60 minutes.
The root was not sectioned, and postoperatively, the pa-
tient had no deficit. The usefulness of this monitoring
technique, however, must be further verified before it
can be fully accepted.

Following completion of the disc removal, the wound

is thoroughly irrigated with saline and the dura is re-

paired, if previously opened. The wound, including the

skin, is closed in layers. The patient is permitted ambula-
tion as tolerated. Postoperatively, neurologic recovery
will depend upon the degree and duration of the deficits
present prior to surgery. Because of the relatively small
number of cases of thoracic disc disease, the long-term
frequency of recurrence of the disease in such cases is

unknown.

DISCITIS

Inflammation of the disc, or discitis, is seen in three

clinical situations: in association with vertebral osteo-
myelitis (65); following intervertebral disc surgery (66),
both septic and aseptic; and spontaneously, usually in

children (67).

Vertebral Osteomyelitis

Pyogenic vertebral osteitis can be caused by any patho-

genic organism; in the majority of cases, staphylococcal
infections are the etiology (68). Although rare instances

of direct infectious extension do occur as the cause of

such osteitis, it seems that most of these lesions are meta-

static. The vascular pathway may be arterial in some
cases but, because of the predominance of infections as-
sociated with intra-abdominal and intrapelvic pathol-

ogy, Batson's venous plexus (69) has been incriminated

by most authorities as the major route of infection. In

the case of an epidural-space infection or an infection in
the vertebral body, the intervertebral disc space becomes

infected by direct extension. The relatively avascular na-

ture of the disc space in adults makes direct extension,

rather than metastasis, the most plausible explanation

for infection in this population.

The patient will complain of back pain, insidious in

onset and progressing to become quite severe. Examina-

Disc DISEASE / 433

tion reveals an exquisite local tenderness to percussion,

much greater than that seen with a disc herniation or

spinal neoplasm. The patient may have a low-grade
fever. The erythrocyte sedimentation rate (ESR) is mark-
edly elevated, often over 100 mm/hour. The peripheral

blood leukocyte count may be quite high, but is usually

only moderately elevated. Radiographs will show evi-
dence of destruction of one or two vertebral bodies, with
areas of rarefaction and body collapse. The interverte-
bral disc space will be narrowed, with indistinct cortical
surfaces of the vertebral body adjacent to the disc space.
New bone formation appears early in acute pyogenic os-

teitis, in contrast to the prolonged rarefaction seen in
tuberculosis. With appropriate antibiotic therapy, sclero-

sis will be seen in two months, and evidence of fusion

across the intervertebral disc space will be seen by three

months.

Procedures for confirmation of the suspected diagno-

sis will depend upon the clinical state of the patient. If

the patient has no neurologic deficit, a needle biopsy

with aspiration of the involved vertebral body or inter-
vertebral disc space is appropriate. If, however, the pa-
tient has a neurologic deficit, and especially if the tho-
racic vertebrae are involved, myelography should be
used to reveal evidence of epidural involvement and pos-
sible spinal cord compression. If this is noted, a standard

decompressive laminectomy is undertaken, with mate-
rial being taken for pathologic examination (70).

The treatment of vertebral osteomyelitis will be dic-

tated by the causative organism, the extent of neurologic

involvement, and the degree of spinal instability. Prior to
obtaining positive cultures, a cephalosporin or a semi-

synthetic penicillin with antistaphylococcal activity and

an aminoglycoside for gram-negative coverage, can be
given, although this may suppress growth from the
biopsy. If the discitis has been associated with an epidu-
ral infection requiring laminectomy, the wound may be
left opened and irrigated daily with an appropriate antibi-
otic solution, such as one containing 100,000 units of
polymixicin-B, 50,000 units of bacitracin, and 1 g/liter
of neomycin in saline. After two to three weeks, when

the depths of the wound are covered with good granula-
tion tissue and cultures are negative, the irrigating cath-
eters and sponge packs may be discontinued, and a sec-
ondary closure with wire can be done. If vertebral
instability is suspected, it is best to maintain the patient
on bed rest until radiographic evidence of fusion is seen.
The patient may then ambulate with the aid of an appro-
priate brace.

Tuberculous vertebral osteomyelitis is a virtually non-

existent clinical entity in the United States, except in
refugee populations. It should be suspected in any pa-

tient with evidence of vertebral osteomyelitis and in
whose natural habitat tuberculosis is still a clinical prob-
lem (71).

Postoperative Discitis

Bacterial (Septic) Discitis

It is not uncommon, following routine surgery for disc

disease, for a patient to run for one to two days a low-
grade fever that is self-limiting and requires only aspirin
for symptomatic relief. However, the patient who has
developed a disc-space infection will, between one and
two weeks postoperatively, begin to complain of increas-
ingly severe back pain. This may be associated with

marked temperature elevation, with temperatures of

104°F not uncommon. These findings are associated

with a markedly elevated ESR and peripheral leukocyto-
sis. The pain is unrelieved by bed rest and exacerbated by
ambulation. Organisms may be recovered from the in-
tervertebral disc space by blood culture or percutaneous
aspiration. Initial radiographs in such cases are unre-

markable. With time, however, the changes typically as-

sociated with discitis will be seen, with further narrowing

of the disc space and the development of an irregular
indistinctness to the cortical margins of the adjacent ver-
tebral bodies. With healing, sclerosis and fusion will
occur.

External evidence of infection with wound drainage

will occur in approximately 20 percent of patients with
septic discitis (72). In these instances, appropriate surgi-
cal drainage is indicated. Proper antibiotic therapy
should be instituted, and the patient should be kept on
bed rest until asymptomatic. In the absence of osteomye-
litis, the spine is not unstable and the patient will not

need external orthotic support during ambulation.

Aseptic Discitis

In some patients with symptoms similar to but milder

than those of septic discitis, there will be evidence of
infection but without organisms being obtained from ei-
ther the blood or disc space. The onset of this condition
may be weeks or months after surgery, usually after the
patient has resumed essentially normal activity. The pa-
tient will complain of increasingly severe back pain
made worse by activity. Progressive narrowing of the
disc space will occur, along with the development of in-
distinct cortical margins. This entity has loosely been

termed aseptic discitis, suggesting the lack of an in-

fectious organism as its cause and the relatively benign

nature of this disorder. It is probably due to aseptic ne-

crosis of portions of the vertebral bodies adjacent to the
disc space, perhaps as the result of excessive curettage

within the disc space at the time of surgery. The disorder
may progress over a period of several months to fibrous
ankylosis or bony fusion. The patient should be man-
aged symptomatically, with physical activity being lim-

434 / CHAPTER 20

ited to that which the patient can tolerate. Some patients
will benefit from the relative immobility imparted by an

external brace or corset. Differentiation between aseptic
and infectious discitis may be difficult, and some
patients with the clinical symptoms of discitis without
positive cultures may nevertheless be treated with a pro-
longed course of intravenous broad-spectrum antibi-
otics.

Discitis in Children

Primary infection of the intervertebral disc space in

children is uncommon, although it does occur with
greater frequency than in nonsurgically-treated adults.
Presumably this is due to the increased vascularity in the
disc space in childhood. The clinical presentation is very
similar to that in the postoperative adult, without exter-
nal evidence of infection. Fever, low back pain, the re-
fusal to stand or walk, and general malaise and irritabil-
ity constitute the common clinical findings. There is

usually spasm of the back muscles, but no abnormal neu-

rologic findings. Cultures of the blood or disc-space aspi-
rate generally yield Staphylococcus, and usually S. au-
reus. An elevated erythrocyte sedimentation rate is
noted. Radiographs reveal narrowing of the appropriate
intervertebral disc space, with demineralization of the
adjacent vertebral body margins.

There is no indication for radical surgical treatment of

this condition. The appropriate antibiotics should be
given. The child is kept on bed rest until ambulation is

comfortable. This may take three to five weeks. With

ambulation, external bracing is usually not necessary.
Recovery of normal activity without residual neurologic

or skeletal sequelae is the rule.

REFERENCES

1. Keyes DC, Compere EL. The normal and pathological physiology

of the nucleus pulposus of the intervertebral disc. JBone Joint Surg

1932; 14:897-938.

2. Mixter WJ, Barr JS. Rupture of the intervertebral disc with involve-

ment of the spinal canal. N Eng/J Med 1934;211:210-215.

3. Elsberg CA. Experiences in spinal surgery: Observations upon 60

laminectomies for spinal disease. Surg Gynecol Obstet

1913;16:117-132.

4. Stookey B. Compression of the spinal cord due to ventral extra-

dural cervical chondromas. Arch Neural Psychiatr 1928;20:275-
291.

5. Panjabi MM, White AA III. Basic biomechanics of the spine. Neu-

rosurgery 1980;7:76-93.

6. Eyring EJ. The biochemistry and physiology of the intervertebral

disc. Clin Orthop 1969;67:16-28.

7. Smith NR. The intervertebral discs. Br J Surg 1931;18:358-375.
8. Roofe PG. Innervation of annulus fibrosus and posterior longitu-

dinal ligament. Arch Neurol Psychiatr 1940;44:100-103.

9. Bogduk N, Long DM. The anatomy of the so-called "articular

nerves" and their relationship to facet denervation in the treat-
ment of low back pain. J Neurosurg 1979;51:172-177.

10. Murphey F. Sources and patterns of pain in disc disease. Clin Neu-

rosurg 1968;15:343-351.

11. Coventry MB, Ghormley RK, Kernohan JW. The intervertebral

disc: Its microscopic anatomy and pathology. I. Anatomy, develop-
ment, and physiology. J Bone Joint Surg 1945;27:105-112.

12. Coventry MB, Ghormley RK, Kernohan JW. The intervertebral

disc: Its microscopic anatomy and pathology. II. Changes in the
intervertebral disc concomitant with age. J Bone Joint Surg

1945;27:233-247.

13. Mendenhall RC, Watts C, Radecki SE, Girard RA. Neurosurgery

in the United States: a log-diary study. Neurosurgery 1981;8:267-
276.

14. Raaf J. Removal of protruded lumbar intervertebral discs. J Neuro-

surg 191032:604-611.

15. Spurling RG. Lesions of the Lumbar Intervertebral Disc. Spring-

field, IL: Charles C Thomas, 1953.

16. Gutterman P, Shenkin HA. Syndromes associated with protrusion

of upper lumbar intervertebral discs: Results of surgery. J Neuro-
surg 1973:38:499-503.

17. Epstein JA, Lavine LS. Herniated lumbar intervertebral disc in

teenage children. J Neurosurg 1964;21:1070-1075.

18. Kobrine A, Bucy PC. Spondylolisthesis following lumbar disc sur-

gery in a child: Case report. J Neurosurg 1971;34:563-568.

19. Laseque C. Considerations sur la sciatique. Arch Gen Med

1864:2:558.

20. Lambert EH. Elcctromyography. In: Youmans JR, ed. Neurologi-

cal Surgery, A Comprehensive Reference Guide to the Diagnosis
and Management of Neurosurgical Problems, vol 1. Philadelphia:
WBSaunders, 1973.

21. Patton DD, Woolfenden JM. Radionuclide bone scanning in dis-

eases of the spine. Radial Clin North Am 1977:15:177-201.

22. Roland J, Treil J, Larde D, Picard L, Manelfe C. Lumbar phlebog-

raphy in the diagnosis of disc herniations. J Neurosurg

1978:49:544-550.

23. Patrick BS. Lumbar discography: A five year study. Surg Neurol

1973:1:267-273.

24. Hirsch C. Efficiency of surgery in low-back disorders: pathoana-

tomical, experimental, and clinical studies. J Bone Joint Surg

1965;47A:991-1004.

25. Maly P, Bach-Gansmo T, Elmquist D. Risks of seizures after my-

elography: Comparison of iohexol and metrizamide. AJNR

1988:9:879-883.

26. Firooznia H, Benjamin V, Kricheffll, Rani M, Golimbu C. CT of

lumbar spine disc herniation: Correlation with surgical findings.

AJNR 1984;5:91-96.

27. Williams AL, Haughton VM, Daniels DL, Thorton RS. CT recog-

nition of lateral lumbar disc herniation. AJNR 1982; 139:345-347.

28. Szypryt EP, Twining P, Wilde GP, Mulholland RC, Worthington

BS. Diagnosis of lumbar disc protrusion: A comparison between
magnetic resonance imaging and radiculography. J Bone Joint
Surg[Br] 1988;70:717-722.

29. Forristall RM, Marsh HO, Pay NT. Magnetic resonance imaging

and contrast CT of the lumbar spine: Comparison of diagnostic
methods and correlation with surgical findings. Spine

1988:13:1049-1054.

30. Spurling RG. Lumbar disc. In: Metrowsky AM, ed. Neurological

Surgery of Trauma. Washington, DC: Office of the Surgeon Gen-
eral, 1965:437-474.

31. Tice WP. Use of epidural anesthesia for excision of the lumbar

disc. J Neurosurg 1957;14:l-4.

32. Sarma DP. Use of blood in elective surgery. JAMA

1980;243:1536-1538.

33. Keller JT, Dunsker SB, McWhorter JM, Ongkiko CM. The fate of

autogenous grafts to the spinal dura: An experimental study. /
Neurosurg 1978;49:412-418.

34. Keim HA, Weinstein JD. Acute renal failure—A complication of

spine fusion in the tuck position: A case report. J Bone Joint Surg

1970:52:1248-1250.

35. Wilson DH, Kenning J. Microsurgical lumbar discectomy: Prelimi-

nary report of 83 consecutive cases. Neurosurgery 1979;4:137-

140.

36. Peacock EE Jr. Wound healing and wound care. In: Schwartz SI,

ed. Principles of Surgery, 3rd ed, vol 1. New York; McGraw-IIill,

1979:303-324.

37. Watts C, Hutchison G, Stern J, Clark K. Comparison of interverte-