Principles ofNeurosurgery,

edited by Robert G. Grossman. Rosenberg © 1991.

Published by Raven Press, Ltd., New York.

CHAPTER 13

Pain

John D. Loeser

Concepts, 293
Ablative Procedures, 295

Peripheral Neurectomy, 295
Sympathectomy, 296
Spinal Dorsal Rhizotomy, 296
Anterolateral Spinal Tractotomy, 297
Commissural Myelotomy, 298

Facet Rhizolysis, 298
Cranial Neurectomy, 298

Gangliolysis, 299
Cranial Rhizotomy, 299
Microvascular Decompression of the

Trigeminal Nerve, 299

Medullary Trigeminal Tractotomy, 300
Thalamotomy, 300

Cingulumotomy. 301
Hypophysectomy, 301
Electrical Stimulation, 301

References, 302

CONCEPTS

The clinician's approach to the management of the pa-
tient with pain is a function of the model used to explain
the patient's signs and symptoms. Most patients and
their physicians adhere to the Cartesian model for pain,
which argues that a noxious stimulus is responsible for
the patient's complaint. The error of this viewpoint
should be obvious to every neurologist and neurosur-

geon; yet, inappropriate prescriptions for medications
and rest and excessive numbers of operations are ample
testimony to the failure to understand the mechanisms

underlying the patient's complaints of pain. Since pa-

tient selection is the most important factor in the surgical

management of pain, a valid scheme for analyzing the
relevant factors contributing to the patient's complaints
is the first step toward successful therapy (1).

Physicians must recognize that the only measures of

the success or failure of a treatment for pain are the pa-
tient's pain behaviors—those things the patient says or
does that can be used to infer events within the patient's
body. Pain behaviors are quantifiable and they are all
real. One should never challenge the validity of the pa-
tient's pain behaviors; instead, one should ask: "What
are the factors that lead this patient to manifest pain
behaviors?"

J. D. Loeser: Department of Neurological Surgery, Univer-

sity of Washington, Seattle, Washington 98195.

It is helpful to recognize four phenomena that can lead

to the complaint of pain and other behaviors suggesting
tissue damage (Fig. 1). Nociception is the activation of

specialized nerve endings and their axons in the tissues
designed to convey to the spinal cord and brain that tis-
sue damage is about to or has occurred. Nociceptive in-
formation is carried exclusively by A delta and C fibers,
but not all of these finely myelinated or unmyelinated
axons are utilized for nociception. Nociceptive axons ap-

pear to be targeted on specific neurons in the dorsal
horn, but it is clear that there is no nociceptive specificity
to spinal cord or higher systems. Nociception can exist
without pain, as seen with spinal anesthesia, after spinal
cord injury or during hypnosis. Most experimental stud-
ies of pain relate only to nociception. Nociception is the
preponderant factor in acute pain, but it often plays little
or no role in chronic pain due to benign diseases.

The response of the nervous system to a nociceptive

event can be labeled pain. In an intact animal, nocicep-
tion is the usual cause of pain. Injuries to the peripheral

or central nervous system can, in some patients, lead to

the complaint of pain in the absence of tissue damage
(and the ensuing nociception) where it hurts. These are

known as central pain states or deafferentation pains (Ta-
ble 1). With the exception of tic douloureux, all of these
pains are notoriously difficult to alleviate. It is critically
important to recognize those pains that exist without no-
ciception; treatment strategies, both pharmacologic and
surgical, must be different. Both the peripheral events

293

294 / CHAPTER 13

FIG. 1. Components of pain.

and the central pathways of pain resulting from injury to

the nervous system are different from those pains that
are due to tissue damage.

Pain, which is a sensation, is one of the many causes of

suffering, defined here as a negative affective response to

pain, or to depression, isolation, fear, or anxiety. Cassell

has insightfully denned suffering as a perceived threat to
the physical or psychological integrity of the individual
(2). Suffering is a ubiquitous condition in the industrial-

ized world; pain is only one of its many causes. Yet, we

(patients and doctors) use the vocabulary of pain when
we mean suffering. An annoying person is called "a pain
in the neck." A book entitled Worlds of Pain is about life

in the Chicago stockyards at the turn of the century. Suf-

fering is frequently associated with depression; narcotics,
muscle relaxants, and sedative-hypnotics are all causes

of depression and often increase suffering.

Pain behavior is the result of suffering; it is best de-

nned as the things a person says or does that are usually
interpreted as indicating the presence of nociception.
Pain behaviors include moaning, grimacing, lying down,
taking medications, refusing to work, and talking about
pain. Like all other forms of behavior, pain behaviors are

strongly influenced by environmental responses: they

can be learned. Learning is not under conscious control;
it just happens, especially when the behavior is present

over a period of time. Pain behavior will be subject to

environmental consequences, regardless of the factors

that initially led to the pain behavior. Observations

______TABLE 1. Deafferentation pain states

Postparaplegic pain
Postthoracotomy pain
Postherpetic neuralgia

Tic douloureux

Atypical facial pain (some)

Brachial plexus avulsion pain

Arachnoiditis
Phantom limb pain
Stump pain
Thalamic pain
Peripheral neuropathy pain
Tabes dorsalis
Lumbosacral plexus avulsion pain

made repeatedly in comprehensive pain management
clinics indicate that environmental factors are often the
cause of chronic pain; nociception may have been the
inciting event, but the body has long since healed the

original injury.

The neurologist or neurosurgeon infrequently deals

with acute pain (which almost always results from noci-
ception). Most referrals involve chronic pain, either
from injury to the nervous system (pain without noci-

ception) or from affective or environmental factors (suf-

fering or pain behavior). The potential roles of tissue
damage, pain without tissue damage, affective distur-
bance, and environmental reinforcers must be consid-
ered in the assessment of the patient manifesting pain
behaviors. It is important to recognize that chronic pain
resulting from cancer is almost always due to continuous
nociception and/or to injury to nerves. Like acute pain,

this type of chronic pain must be treated aggressively to

relieve the patient's suffering and thereby reduce pain
behaviors. In contrast, chronic pain due to a benign dis-
ease rarely, if ever, results from nociception; pharmaco-
logic, physical, and surgical management strategies must

be aimed at a different target. The patient with chronic
pain from a benign disease is usually not a candidate for
an ablative surgical procedure, in part because affective
and environmental factors are so likely to be playing a
major role. Those patients with chronic pain from an
injury to the peripheral or central nervous system may
be candidates for neurosurgical procedures, but further
deafferentation is rarely successful. Electrical stimula-
tion of the nervous system may be an effective alterna-
tive. It is always possible that additional knowledge
about the anatomy and physiology of the nervous system
may lead to new surgical procedures with higher success
rates.

There is little doubt that the results of an operation are

directly related to the surgeon's knowledge and skill. Ap-
propriate training and experience are the prerequisites
for neurosurgical procedures aimed at eliminating pain.
Most neurosurgeons have the necessary technical skills,
but few have had adequate experience dealing with pa-
tients with chronic pain. The majority of errors that lead
to unsuccessful outcomes do not occur in the operating

room but are made during the evaluation of the patient
by the surgeon. Short-term successes are too frequently

considered adequate reasons for major surgery; there are

few reported series with valid long-term analyses of out-
come. This is particularly true of the older, well-estab-

lished procedures.

In general, patients with chronic pain from a malig-

nant disease are better candidates for ablative surgical

procedures than those with chronic pain from a benign

disease process, in part because of the short life expec-

tancy common in patients who have a malignant disease
and because ablative procedures interrupt nociception.
which is the major component of pain due to cancer.

Affective and environmental factors are much more

PAIN / 295

likely to be significant components in chronic pain from

a benign disease.

Recent increases in knowledge about the endogenous

opioid systems have reduced the need for ablative surgi-
cal procedures in patients with cancer pain. The delivery
of narcotics directly to the spinal cord and brain by intra-
thecal and epidural routes has dramatically improved
pharmacologic pain management and has resulted in
fewer referrals for neurosurgical operations. Patients

with life expectancies of less than a few months are rarely
surgical candidates; epidural or intrathecal narcotics are
capable of providing pain relief for months and some-
times years.

A major problem for the neurosurgeon is the predic-

tion of long-term results for the individual patient. Al-
though there are some series with adequate numbers to
make statistical predictions, how does this relate to the
individual patient? There do not, at present, appear to be
any reliable predictors of outcome. Psychiatric evalua-

tion of the patient with chronic pain may identify the

rare psychotic patient, who should not be offered sur-

gery, but it has not been very helpful in the usual patient
population. Psychological testing can identify the so-

matically preoccupied or hysterical personality types,

but standardized testing, such as the Minnesota Multi-
phasic Personality Inventory (MMPI) or McGill Pain
Questionnaire, does not appear to be useful in predicting
individual patient outcome from a pain-relieving proce-
dure. They do predict who is likely to return to work

after a discectomy, but this is not the same as whose pain
will be abated by a cordotomy.

It is clearly unwise to perform any operation on a se-

verely depressed patient, as pain behavior is likely to per-
sist independent of any nociception. The patient's past

history should not be ignored: excessive health care con-

sumption, prior unsuccessful surgeries, and the existence
of potent environmental reinforcers may be predictors of
surgical failure.

The role of nerve blocks in the selection of patients for

surgical procedures must be thoroughly understood. A
single nerve block is of little value; there are too many
extraneous factors that can influence the patient's re-
sponse. A carefully planned series of blocks can provide
valuable information about the anatomy and physiology
of the pain problem, but there has never been a study

that correlates the long-term surgical result with the re-
sponse to local anesthetics used to block the somatic ner-
vous system. Nerve blocks will identify the nerves or
roots that must be cut to isolate a peripheral region from
the brainstem or spinal cord; they can be used to evalu-

ate patient reliability by correlating duration of response
to the known effects of the agent utilized to perform the

block. Placebo responders are not known to have a more

or less favorable response to a surgical procedure. Nerve
blocks can also be used to allow the patient to experience
the expected numbness on a short-term basis. Some pa-
tients will prefer their pain to the numbness. Sympa-

thetic blocks do have more predictive value than somatic
blocks.

There are advantages and disadvantages to every oper-

ation and to all other forms of therapy for pain. What is
appropriate for one patient at a particular time may not
be optimal at another phase of the patient's manage-
ment. Surgical procedures often must be performed in
conjunction with other modes of therapy if the patient is
to be fully rehabilitated. In general, destructive proce-
dures should not be considered until other therapies
have been evaluated. When indicated, surgical interven-

tion should not be delayed. That decision is the art of

neurosurgery.

ABLATIVE PROCEDURES

Peripheral Neurectomy

Although it is intuitively obvious that pain originating

from extremity or trunk pathology can be alleviated by
sectioning the peripheral nerves that go to the involved
part, this is, in fact, rarely a successful surgical strategy.
Theoretical advantages are greatly outweighed by practi-

cal failures. There are few indications for peripheral neu-

rectomy. It is occasionally helpful for the amputee who

has a neuroma in a weight-bearing area. Resecting the

nerve so that its new neuroma will lie in a more pro-
tected area can provide relief from a distressing pain syn-
drome. A traumatized nerve can develop a neuroma in
continuity; resection and neurorraphy or cable grafting
may provide both pain relief and restoration of function.

Meralgia paresthetica (painful dysesthesias in the distri-

bution of the lateral femoral cutaneous nerve) is usually

best managed without surgery. Pain following trauma to

the sensory branch of the radial nerve is notoriously re-
fractory to neurectomy. Neurectomy for a pain syn-
drome of vague etiology is not often successful.

If a peripheral neurectomy is to be undertaken, it is

imperative that the proximal stump be managed so as to
minimize the risks of postoperative neuroma pain. The
level of the neurectomy should be carefully planned so as
to avoid placing the site of transection in a weight-bear-
ing area. The literature is replete with nostrums to pre-
vent the formation of a neuroma; I am unaware of any
conclusive evidence that such measures are beneficial.

Intercostal neurectomies have fewer drawbacks than

sectioning an extremity nerve, yet they too are often only
of short-term value. Since nearly all peripheral nerves
are mixed, the motor loss is usually not an acceptable

trade for the relief of pain. Sensory nerve overlap, loss of

anesthesia because of peripheral nerve sprouting or cen-

tral reorganization, and anesthesia dolorosa can all con-

tribute to the high failure rate. Intercostal neurectomy

may occasionally be useful in the management of chest

wall pain resulting from a malignancy; it rarely, if ever,
helps postherpetic neuralgia or postthoracotomy pain. If
this procedure is to be utilized, preoperative assessment

296 / CHAPTER 13

with intercostal nerve blocks to determine the appro-
priate segmental patterns is valuable. Neurectomies
must be performed one or two levels above and below
the involved segments to eliminate peripheral sensory
overlap. Even more generous borders must be estab-
lished if chest wall pain results from a growing malig-
nancy.

Sympathectomy

Two distinct types of pain may be alleviated by sympa-

thectomy: those originating from tissue damage in the
thoracic and abdominal viscera, and those associated
with trauma to nerves or other injuries in the extremi-
ties. The latter are now commonly classified as "sym-
pathetically maintained pains."

Sympathectomy for visceral pain is analogous to so-

matic deaiferentation but has a much more favorable
outcome in properly selected patients (3). When sympa-

thectomy is contemplated to relieve the pain of a visceral

malignancy, it is important to rule put invasion of the

body wall structures and involvement of the somatic
nervous system. Even when the pain is totally relieved by

sympathetic blockade, subsequent tumor growth may

lead to body wall involvement and pain recurrence. The
pain associated with chronic, nonmalignant visceral pa-
thology such as angina pectoris, pancreatitis, renal pelvis

or ureteral distention, or dysmenorrhea can be alleviated

by appropriate Sympathectomy. However, the develop-
ment of new therapies for diseases of most of these or-
gans has largely rendered Sympathectomy obsolete; the

jgxception is pain associated with pancreatitis (4-5).

Causalgia, Raynaud's disease, and reflex sympathetic

dystrophy are the common pain states treated by sympa-
thectomy. The mechanisms for these sympathetically
maintained pains are debated, but the clinical observa-
tions have been repeated for over 50 years (6). Certainly,
ischemic pain is relieved by Sympathectomy, but that is a

result of increased blood flow. The dysesthetic pains as-

sociated with nerve injury or just trauma to a limb do not

seem to be related to blood flow and are often relieved by

Sympathectomy. Prompt Sympathectomy is more likely
to relieve the pain than that performed years after the
pain has started.

When a sympathetically maintained pain syndrome is

suspected, the first step is a reversible sympathetic block-

ade by local anesthetic block of the sympathetic chain or

by regional infusion of a peripheral agent such as gua-
nethidine (7). If a series of blocks provides temporary
relief, then a permanent Sympathectomy should be con-
sidered. In addition to surgical Sympathectomy, newer
strategies such as chemical or radiofrequency lesions of
the sympathetic chain should be considered (8).

Pains that include a dysesthetic component should be

evaluated by sympathetic block, whatever their sus-
pected etiology, as Sympathectomy may be an effective

treatment. Similarly, if there is a vasomotor or sudomo-
tor abnormality associated with chronic pain, a sympa-
thetic block should be part of the diagnostic assessment.
Unlike somatic neurectomy, Sympathectomy seems to
provide a good long-term result. It has been my experi-
ence that the more an extremity pain syndrome resem-
bles true causalgia, the more likely it is that sympathec-
tomy will be efficacious.

Spinal Dorsal Rhizotomy

One of the oldest neurosurgical procedures, spinal

dorsal rhizotomy has remained a commonly performed
operation in spite of its poor long-term efficacy. Its pri-

mary advantage over peripheral neurectomy is the spar-

ing of motor fibers and the absence, therefore, of signifi-
cant paresis. However, the sectioning of all of the dorsal

roots to an extremity in a human does render that limb
both anesthetic and unusable for any purposeful action.
Total dorsal rhizotomy to a limb is rarely a satisfactory
procedure unless the limb has already been rendered
functionless by a disease process. However, .extensive
dorsal rhizotomies of the upper cervical, thoracic, or
lumbar regions can be undertaken without significant
loss of function. Midline or bilateral pain requires bilat-
eral rhizotomies; in the sacral region this leads to loss of
sphincter control. Patients who have had urinary and
fecal diversionary procedures may be candidates for bilat-
eral sacral rhizotomy for relief of pelvic or perineal pain

(9). Dorsal rhizotomies seem to be of greatest value for
unilateral trunk pain, although some authors have

claimed good results in patients with persistent radicular
pain after lumbar discectomy (10-11). Most of the larger
series which have been reported indicate long-term suc-
cess rates of 25 to 50 percent (12).

Whether or not the addition of dorsal root ganglionec-

tomy to dorsal rhizotomy will increase the long-term suc-
cess rate is unclear, as too few cases with long enough
follow-ups have been reported. The recognition of affer-
ent fibers in the ventral root and subsequent debate as to
whether or not these fibers actually entered the cord
through the ventral roots or made a U-turn to travel into
the cord through the dorsal roots has stimulated some
surgeons to routinely do ganglionectomies. The develop-
ment of a percutaneous technique for dorsal rhizotomy
by radiofrequency or cryoprobe techniques has extended
the potential utility of this operation to patients who
could not withstand a major operation. The percutane-
ous techniques are hazardous when performed in the
upper thoracic or thoraco-lumbar region because of po-

tential damage to essential arteries supplying the spinal
cord (12-14).

The evaluation of a patient for dorsal rhizotomy by

any method requires selective nerve blocks to identify

the involved segments. It is prudent to section at least

one level above and below the localized nerve roots be-

PAIN / 297

cause of sensory overlap. If the patient has an expanding

malignancy, additional roots above and below the in-

volved area should be resected. Dorsal rhizotomy is par-

ticularly likely to fail in postthoracotomy pain or post-
herpetic neuralgia; whether or not destruction of the
ganglion will increase success rates is unknown. Patients
who fail to get relief of pain after dorsal rhizotomy that
has made them anesthetic in the painful area rarely get a
good long-term result when additional roots above and
below are sectioned. We do not yet have an adequately
performed analysis of dorsal rhizotomy to determine its
proper place in the neurosurgeon's repertoire of proce-
dures for pain relief.

Anterolateral Spinal Tractotomy

Commonly known as cordotomy, anterolateral spinal

tractotomy used to be one of the most frequently per-

formed operations for chronic pain. The original de-

scription was by Spiller and Martin in 1912. The innova-

tive studies of Mullan, Lin, and Rosomoff in the 1960s
have led to widespread acceptance of the percutaneous
methods utilizing radiofrequency current rather than

open surgical cordotomy (12,15-18). The advent of in-

traspinal narcotics for the treatment of pain from cancer
has dramatically reduced the need for cordotomy.

Although the entire length of the spinal cord has been

a target for cordotomy, currently utilized percutaneous
techniques are done at C1-C2 laterally or in the midcer-
vical region anteriorly; open techniques are usually at
C1-C2 or in the upper thoracic area. The major advan-
tage of cordotomy is the selective loss of pain and temper-
ature sensation that occurs contralateral to the lesion
site. There is no nerve block that mimics this type of
sensory loss, and patients, as well as many physicians, do

not understand the effects of cordotomy. Although care-

ful psychophysiological studies can demonstrate a vari-
ety of sensory changes, the patient will experience three
distinct phenomena if the operation is technically suc-
cessful: stimuli capable of damaging tissue no longer
elicit an unpleasant or alarming quality; thermal gra-

dients cannot be detected; and articulate patients will
describe a vague alteration in other sensory modalities.

Indeed, a few patients will complain of dysesthesiae and
paresthesiae, and a small percentage will have major

problems with "postcordotomy allesthesia," a pain syn-
drome that is refractory to treatment. Anterolateral cor-
dotomy does not lead to clinically significant alterations
in vibration, joint position, or light touch sensation, and
skeletal muscle function is unaltered.

A useful feature of cordotomy, when used in the pa-

tient with pain from a malignancy, is the extensive re-

gion of analgesia produced by an operation at a single

spinal level. This contrasts with dorsal rhizotomy, where
an additional laminectomy is required for each segment
to be denervated, and each rhizotomy only denervates a

narrow segment. In general, cordotomy can be expected

to produce analgesia beginning three to five segments

below the level of the spinal lesion, although a large Cl-
C2 cordotomy may sometimes achieve analgesia up to
the level of the mandible. The extensive region of analge-
sia provides insurance against the local expansion of a
painful neoplastic process.

The results of cordotomy are highly correlated with ,

the surgeon's experience; they are also influenced by the I
duration of follow-up and the accuracy of reporting
(12,19). An overview of the reported cases and my own
personal experience suggest that about 85 percent of pa-
tients initially have good pain relief, but that there is a
significant drop-off at one year and beyond. Return of

pain often, but not always, parallels the loss of the sen-
sory changes induced by cordotomy. Pain recurrence

seems to be more common after lesions that are not

complete, i.e., the entire contralateral body below the

lesion is not rendered analgesic. Cordotomy may also

fail to relieve pain if the sensory level is not high enough.

Additionally, about one-third of patients will deny pain
ipsilateral to the proposed cordotomy but will complain
of ipsilateral pain after the lesion is performed, probably

because of an unmasking of a minor pain when the more

severe pain is relieved by the operation. Such a patient
will require bilateral lesions.

The complications of cordotomy are quite well docu-

mented. Unilateral cordotomy will cause bladder dys-
function in about 5 percent of patients; bilateral cordot-

omy in about 20 percent. This may be permanent.

Sexual dysfunction in the male is common after bilateral

cordotomy but is very rare after a unilateral lesion. High
cervical cordotomy, especially bilateral, carries a low in-
cidence but high risk of respiratory failure (Ondine's
curse) (20). Postoperative testing with 5 percent inspired
CO

2

will show if the normal stimulation of ventilation is

lacking. If so, the patient is at high risk to develop sleep
apnea; careful monitoring is required. Orthostatic hypo-
tension may develop after cordotomy and can be treated
with elastic stockings or mild vasoconstrictive drugs.

All of the above complications occur because of the

admixture of axons subserving different functions in the
anterolateral quadrant. In contrast, the occurrence of ip-
silateral paresis or even greater motor deficits is a sign of
technical error; the corticospinal tract has been dam-
aged. The incidence of temporary paresis is 10 to 15 per-

cent; long-term paresis occurs in about 5 percent of pa-
tients. Paraplegia is a rare complication of too large a

lesion or injury to a key blood vessel.

The indications for cordotomy are a function of the

patient's diagnosis and expected survival. Cordotomy is
best suited for patients with pain from a malignancy that

cannot be controlled directly by surgery, radiation, or
chemotherapy. Pain originating rostral to T6 requires a

cervical cordotomy; pain below this level can be con-
trolled by an upper thoracic cordotomy. Many neuro-

298

CHAPTER 13

surgeons always perform a cervical cordotomy regardless
of the pain level (20). Some argue that only the percuta-
neous method should be utilized; others prefer open pro-

cedures. The percutaneous technique requires frequent

utilization to be perfected; the casual operator cannot

expect the results published by the experts. Epidural or
mtrathecal narcotics are also highly successful in this
type of patient. They have largely become the initial
treatment of choice, with cordotomy being reserved for
failures of this strategy.

Cordotomy is not often effective for the treatment of

pain resulting from injury to the central or peripheral

nervous system (deafferentation or denervation pain).
Patients with injury to the nervous system are also much
more likely to develop postoperative complications such
as painful incisional site or postcordotomy allesthesia.
This operation rarely helps patients with demyelinating
diseases, arachnoiditis, phantom limb pain, postparaple-

gic pain, or nerve root avulsion.

Bilateral or midline pain requires bilateral cordoto-

mies; this does raise the risk of complication. Such a

patient should be considered for intrathecal or epidural

narcotics or for commissural myelotomy. Those who
frequently perform percutaneous cordotomy can offer

their patients this option and compete successfully with

alternative procedures, both for effective pain relief and

low risk of complications. Those who only occasionally
use this technique do not have as high a chance of such
salutary results.

Commissural Myelotomy

This operation has been more extensively utilized in

Europe than in the United States. It is effective in reliev-

ing midline and bilateral pain, as it transects the decus-

sating fibers of the spinothalamic tract to produce a gir-
dle zone of analgesia. However, by mechanisms as yet
unclear, it also produces pain relief in segments caudal to
the region of analgesia that manifest no clinically detect-
able sensory loss. Long-term pain relief has not often
been reported, and myelotomy, like cordotomy, is best
utilized in patients with pain from a malignancy (21-
24). The long-term success rate in patients with cancer is
approximately 70 percent. Most often utilized in pa-

tients with abdominal or pelvic midline or bilateral pain,
myelotomy requires a laminectomy of T9 through LI
when cord segments LI through S5 are the sites of pain.
The operating microscope facilitates midline bisection of
the conus. Advantages over cordotomy are one opera-

tion for bilateral pain and a lower incidence of bladder
and leg weakness. Most patients will, however, have pos-

terior column deficits that are usually transient.

Percutaneous Cl myelotomy was initially described

by Hitchcock; pain relief without analgesia over most of

the body was observed (25). Only a small number of

patients have been reported, and this procedure certainly
has not been widely accepted. It deserves careful atten-
tion, especially in patients with widely disseminated
painful malignant diseases (26-27).

Facet Rhizolysis

Deriving from the work of Rees, who claimed excel-

lent results for back pain when he "sectioned the articu-

lar nerves to the facet joints," a radiofrequency percuta-
neous technique has been used in large numbers of

patients (28). Shealy first presented the radiofrequency

technique (29). However, not only did Rees' knife not
reach these nerves but the radiofrequency lesion has had
different target sites and little evidence exists that any

nerve was destroyed. The reported results have varied
from excellent to poor (12). Patients with previously un-
operated backs seem to have the best results, failed disc
operations have intermediate results, and those who

have already had a fusion almost never have good results

from facet rhizolysis. The procedure is performed under
local anesthesia and fluoroscopic control; complications

have been minimal. It does not appear to further damage

the lumbar spine and does not lead to additional scarring
about the nerve roots. The surgeon's faith in its efficacy

may be one of the major determinants of outcome.

Cranial Neurectomy

The accessibility of the peripheral nerves of the face

and scalp has made them the targets of surgical therapy

for at least 200 years. Trigeminal neurectomy was used
to alleviate tic douloureux in 1730; by 1900 avulsion of a
branch of the trigeminal nerve was standard therapy.
The early reports never claimed more than a 50 percent
one-year success rate, but this was the only treatment
available. The development of local anesthetics, alcohol
injection, anticonvulsants, and modern neurosurgical
techniques has greatly reduced the indications for periph-
eral neurectomy (30). A number of surgical procedures
for the treatment of tic douloureaux are discussed below.
The reader is also referred to Chapter 11, "Trigeminal
and Glossopharyngeal Neuralgia and Hemifacial
Spasm."

The advantages of trigeminal neurectomy include a

predictable area of complete sensory loss and low surgi-
cal morbidity. The disadvantages are the dense sensory
loss and about a 75 percent recurrence rate by one year

after surgery. Peripheral neurectomies are rarely success-

ful for cancer pain. They are never useful for atypical

facial pain or any other type of pain associated with

nerve injury or deafferentation. In a few patients with tic
douloureux, however, neurectomy may still be useful.
For example, if the tic pain is exclusively in the first

PAIN / 299

division, a supraorbital neurectomy may avoid any risk
of neuroparalytic keratitis and might, in some patients,
be preferable to gangliolysis.

Gangliolysis

As noted above, gangliolysis is usually preferable to

neurectomy as the primary strategy to relieve the pain of

tic douloureux (30). A very dense gasserian lesion may

also be helpful in the management of cancer pain (31).
Pains of unclear etiology or those due to deafferentation,
however, are rarely alleviated by gangliolysis. Three
methods of damaging the gasserian ganglion and thereby

alleviating the pain of tic douloureux now are in com-
mon use: radiofrequency thermal lesion, glycerol injec-
tion, and balloon compression. The existence of three
popular strategies suggests that each has some advan-
tages and drawbacks. The surgeon's preference seems to
be the major determinant of which procedure is used.

Percutaneous radiofrequency trigeminal gangliolysis

has been extensively utilized and many large series re-
ported (32). There are minor variations in technique
among neurosurgeons. In general, an insulated needle
with 2 to 8 mm of exposed tip carrying a thermister is

passed through the cheek into foramen ovale and the
position checked fluroscopically. Electrical stimulation
is used to localize the needle tip in the appropriate divi-

sion and radiofrequency current is utilized to heat and
partially destroy the ganglion and rootlets. Proper tech-
nique results in partial sensory loss, which is restricted to
the involved division(s). Analgesia is not a desired result.
This technique results in 80 to 90 percent one-year pain
relief in patients with tic douloureux; 60 percent five-

year relief is typical. The complication rate is less than
0.5 percent (33). The procedure can be repeated if neces-
sary with similar chance of success.

Glycerol gangliolysis involves the injection of small

amounts of a neurotoxic substance, glycerol, into the
trigeminal cistern (34). Although some have claimed su-
perb results without sensory loss, this has not been the
customary observation in recent years. It is my impres-
sion that glycerol gangliolysis is not as reliable as a radio-
frequency lesion and is not as likely to provide long-term
pain relief (35).

Balloon compression of the gasserian ganglion is ac-

complished by placing a balloon catheter through a nee-
dle at the orifice of foramen ovale (36). It does not result
in a selective lesion and long-term follow-up data is not
yet adequate to permit meaningful contrast with other

techniques.

Cranial Rhizotomy

The afferent cranial nerves (trigeminal, glossopharyn-

geal, and nervus intermedius of the facial) may all be

sectioned in the subarachnoid space to render their sen-
sory fields anesthetic. Unilateral section of one or more
of these nerves can be valuable for the patient with face
and pharyngeal pain from a malignancy. Bilateral rhi-

zotomies are not prudent, as the patient is likely to have
a severe impairment of chewing, swallowing, and facial
sensation. The trigeminal and glossopharyngeal roots
and ganglia can be approached percutaneously and a le-
sion effected by radiofrequency current, thus sparing the
patient a major procedure (31,37). When cancer pain is
bilateral, the older literature suggests rhizotomies on one
side and a trigeminal tractotomy on the other to mini-
mize loss of function. Other procedures, such as intraven-

tricular opioids, might be suggested today for such a pa-
tient.

Cranial rhizotomy for atypical facial pain or any other

form of facial pain not resulting from cancer, other than

tic douloureux, is most likely to fail (12).

Rhizotomy for tic douloureux used to be a commonly

performed operation, and large series have been pub-
lished. Partial trigeminal rhizotomy offers a 75 percent
long-term pain relief with a 5 percent risk of painful par-
esthesiae or anesthesia dolorosa. Total trigeminal rhi-
zotomy has a 90 percent long-term success rate but a 10
percent risk of painful paresthesiae or anesthesia dolo-

rosa. The surgical technique (via the middle fossa or pos-

terior fossa) does not appear to influence the results.
Whenever the first trigeminal division is rendered anes-
thetic, there is a risk of neuroparalytic keratitis. Trigemi-
nal rhizotomy is no longer a primary procedure for tic
douloureux, as it has been replaced by gangliolysis and
microvascular decompression.

Microvascular Decompression of the Trigeminal Nerve

Microvascular decompression of the trigeminal nerve

(MVD) is an exceedingly effective method of treating the
tic douloureux patient who has failed medical manage-
ment (38). By means of a retromastoid craniectomy, the
trigeminal nerve is visualized and mechanical compres-
sion in the juxtapontine area is relieved. Most patients
have a loop of the superior cerebellar artery impinging
upon the nerve; occasionally it is the anterior inferior

cerebellar artery; rarely it is another artery or a vein. A
few patients have a neoplasm or arteriovenous malfor-
mation compressing the nerve. MVD has the great ad-
vantage of producing no sensory loss; its major disad-
vantage is the magnitude of the surgical procedure
requiring general anesthesia and several days of hospital-

ization.

Although it was originally hailed as a curative opera-

tion for tic douloureux, more recent data has indicated
that patients do often relapse 5 to 15 years after surgery
(Fig. 2) (39). The conceptual basis of this operation has
also been attacked. Nonetheless, the large numbers of

300 / CHAPTER 13

FIG. 2. Kaplan-Meier plot of the proba-
bility of remaining pain-free over time
following microvascular decompres-
sion (MVD). Thirty-six patients under-
went 36 MVD procedures. Minor and
major refer to the magnitude of recur-
rence of pain. Patients were censored
at the following rate: year 7: 2 pa-
tients; year 8: 1 0 patients; year 9: 25
patients; and year 10: 33 patients.

(From reference 39, with permission.)

cases reported by many authors permit some meaningful
generalizations about this operation. Pain relief does not
require clinically detectable sensory loss. The mortality
rate is 1 to 2 percent; the complication rate is about 5
percent. About 10 percent of patients fail to get initial
relief, and an additional 10 percent will experience recur-
rence of pain in the first postoperative year. After the

fifth postoperative year about 3 percent of the patients

per year will have a recurrence.

MVD is certainly preferable to trigeminal rhizotomy

in the treatment of tic douloureux. It does not appear to

be useful for any other painful condition of the trigemi-

nal distribution. Similar cross-compressing lesions have
been described for the glossopharyngeal nerve and the
nervus intermedius, and implicated in tic douloureux
resulting from their sensory distributions. If MVD is
planned and no lesion is found, a rhizotomy should be
undertaken.

Medullary Trigeminal Tractotomy

The feasibility of dividing the descending trigeminal

tract in the medulla was demonstrated by Sjoquist in

1938 (40). In the past 50 years, new techniques have

made tractotomy less hazardous and more likely to pro-
vide pain relief. The pain and temperature fibers from

the entire orofacial region travel in the descending tri-

geminal tract, so it is possible to alleviate pain from fa-

cial, oral, and pharyngeal structures by lesions in this
tract.

Open descending trigeminal tractotomy is performed

through a C1-C2 laminectomy; the optimal lesion site is

10 to 12 mm caudal to the obex. Accurate anatomic

localization requires the operating microscope; physio-

logic confirmation is obtained by recording from the cer-
vicomedullary junction the responses evoked by stimula-

tion of the median nerve (fasiculus cuneatus) and
trigeminal cutaneous branches (descending tract) (41).

Lesions can be made to produce analgesia selectively in

the glossopharyngeal or nervus intermedius territories
(42). This operation leads to the selective loss of pain and
temperature sensation but does not affect touch or posi-
tion sense.

A percutaneous method for stereotactic trigeminal

tractotomy has been described by Hitchcock (43) and by
Schvarcz (44). Their lesion also destroys the trigeminal
nucleus, and they claim that it is successful for both deaf-
ferentation and cancer pains. Published results by others
are nonexistent, but these authors claim that about half
of the patients have gotten long-term relief.

Trigeminal tractotomy is a valuable secondary proce-

dure for the patient with tic douloureux who has failed to
respond to rhizotomy or microvascular decompression.
Pain from orofacial malignancies can be successfully

controlled; it may also have value in the treatment of the
deafferentation pains that afflict the face.

Thalamotorny

In spite of its theoretical attractiveness and apparently

good short-term results, stereotactic thalamotomy rarely
provides even one year of pain relief (45,46). Its use,
therefore, is best restricted to patients with short life ex-
pectancies, as seen in cancer pain. Assessment of long-
term results is hampered by differing nomenclature, lack
of anatomic proof of target site, wide range of etiologies
for the patient's pain, and, all too frequently, inadequate
follow-up. Although the development of CT and MR
scanning has dramatically improved stereotaxis for
biopsy of lesions, it has not significantly improved target
location for ablative or stimulation operations. Morbid-
ity and mortality are reported to be low, but thalamot-
omy should probably be restricted to tertiary centers pos-
sessing significant experience with stereotaxis for pain
and other purposes such as movement disorders and
biopsy of lesions.

The most common target sites have been the medial

posterior nuclear masses: the centremedian, parafasicu-

PAIN / 301

laris, intralaminar nucleus, and pulvinar. All of these
regions receive fibers from the nonspecific ascending sys-
tems and project to a wide range of subcortical and corti-
cal association areas. Another target group has been the
dorsomedial and anterior thalamic nuclei, which project

to limbic and frontal structures. Lesions in these areas
seem to alter the affective response to noxious stimula-
tion, in contrast to the posteromedian lesions, which
alter the perception of pain itself (47). Lesions in these
areas usually need to be bilateral to have any lasting ef-
fect.

Tasker reviewed the literature and his own experience

with thalamotomies for pain (46). Approximately 60
percent of the patients with pain secondary to tissue dam-

age or cancer got some pain relief; only 25 percent of the

patients with dysesthetic pains secondary to nervous sys-
tem injury were relieved. Follow-up periods were vari-
able for this heterogeneous group of patients.

Thalamotomy is clearly not a primary procedure for

relief of either cancer pain or that associated with injury

to the nervous system. When other, more focal surgical
procedures as well as alternative strategies for pain man-
agement have failed, it can be a useful procedure, particu-
larly for cancer pain.

Cingulumotomy

The unsatisfactory experience with frontal leucotomy

for pain led to the development of cingulumotomy by

Foltz and White (48). This procedure has been most ex-
tensively studied by Ballantine and his associates (49).
Cingulumotomy appears to be effective in attenuating

the exaggerated suffering that some chronic pain pa-
tients manifest. It does not alter nociceptive thresholds
and does not lead to cognitive defects. This operation is
also valuable for patients with severe phobic neuroses

who have failed to respond to other therapies. Cingulu-
motomy is an affect-altering operation that has replaced
frontal leucotomy. Bilateral lesions are performed ster-
eotactically in the anterior cingulum bundles under local

anesthesia. Cingulumotomy also has been performed in

conjunction with anterior thalamic and frontal lesions.
The public protest against any type of psychosurgical
procedure has all but eliminated this operation in the
United States; it is still frequently used in Sweden and
other European countries. It can be of great value to the
properly selected patient whose suffering is out of pro-
portion to the apparent noxious stimulus and in whom
no other method of pain relief has succeeded.

Hypophysectomy

Ablation of the pituitary gland has been effective ther-

apy for the relief of pain resulting from osseous metas-
tases from carcinoma of the breast or prostate. Its value
in other neoplasms is unproven. Hypophysectomy

seems to be of greatest value in postmenopausal women
with breast carcinoma who have previously demon-
strated a favorable response to oophorectomy or hor-
monal therapy, who do not have vital organ involve-
ment, and who have survived many years between the
original diagnosis and dissemination. About 50 percent
of the women with breast carcinoma or men with pros-

tatic carcinoma will experience pain relief: it is not al-
ways correlated with signs of tumor regression (50). Hy-
pophysectomy can be accomplished transcranially. but
the transsphenoidal approach appears to have a lower
morbidity and mortality and a shorter period of hospital-
ization.

Electrical Stimulation

Electrical stimulation of the skin, peripheral nerves,

spinal cord, and brain has become an increasingly com-

mon method of treating chronic pain during the past 20

years. Skin stimulation [transcutaneous nerve stimula-
tion (TNS) or transcutaneous electrical nerve stimula-
tion (TENS)] has been extensively used to treat chronic
pain owing to benign diseases. It will, in some patients,
ameliorate both acute and chronic pain but has not been
very effective in cancer pain. A spin-off of the space-age
need for microelectronics, spurred on by the Melzack-
Wall gate hypothesis, TNS has been a very useful nonin-
vasive treatment modality.

Controlled studies of its utility have been few, and

there are no diagnoses associated with a high or low

chance of success (51). Long-term relief will be obtained

in about 25 percent of unselected patients with chronic

pain associated with benign diseases. Stimulation is most
effective when delivered in the painful area; if the pa-
tient's sensory loss is profound this strategy will not

work. There are virtually no complications of TNS, but
the patient does require training for its optimal use.

Peripheral nerve, spinal, and brain stimulators all re-

quire a surgical procedure, and they have not been as
extensively utilized. The neurophysiologic basis for pain
relief with electrical stimulation is unknown, but periph-
eral nerve stimulation, spinal cord stimulation, and lat-
eral thalamic-internal capsule stimulation probably have
a common underlying mode of action, as they all require

that paresthesiae be felt in the painful area if stimulation

is to be effective. They probably do not involve the en-
dogenous opioid system.

Spinal cord stimulation, originally called dorsal col-

umn stimulation (DCS), was the first to have widespread
clinical trials and is still the most common form of im-
planted stimulation. There are two ways of implanting

the spinal electrode: percutaneously, via an epidural nee-
dle, and open, requiring a small laminotomy. Although

the percutaneously inserted electrode obviates the need
for a surgical procedure, problems with electrode migra-
tion and impedance changes have plagued this system.

302 / CHAPTER 13

Larger electrodes inserted through a laminotomy have
proved more durable. The lead wires are tunneled under

the skin to either a radio-frequency coupled receiver or a
battery driven stimulator very similar to a cardiac pace-
maker. The former requires that the patient carry a stim-
ulator box and antenna affixed to the skin over the re-
ceiver; the latter is fully programmable via telemetry. It
has been my experience and that of most other surgeons
who have reported their series that about one-half of the
patients report initial adequate pain relief but that only
one-half of these will have adequate pain relief at follow-
up one year later (52). Hence, one-fourth of those
deemed suitable for spinal cord stimulation will be long-
term successes. The complication rate is low and no ad-
ditional neurological deficits are required to obtain pain
relief, so spinal cord stimulation has advantages over ab-

lative surgery.

The optimal parameters for stimulation vary among

patients; some report pain relief only during stimulation;

others have pain relief for hours from brief intervals of

stimulation. Good results have been reported with pain
due to nociception or to nerve and spinal cord injury
(53-55). Other authors have reported the best results

with postherpetic neuralgia and vasculopathic pain and

the poorest results with cancer pain and spinal cord in-

jury pain (56). It is difficult to identify diagnostic groups

that are likely to respond more or less favorably.

Peripheral nerve stimulation (PNS) has not been as

commonly utilized as spinal cord stimulation, but the
results appear to be at least as good (57). An electrode is
placed around the nerve to be stimulated and connected
to a stimulator device as described above for spinal cord

stimulation. Stimulation must be perceived in the pain-

ful area if the device is to be effective. PNS is useful in

patients with pain owing to peripheral nerve injuries.

Stimulation of the brain for pain relief has been valu-

able in a small number of patients (58). A multicontact
electrode is inserted stereotactically into the target area
under local anesthesia. After a trial period with external-
ized lead wires, the electrodes are connected to an im-
planted stimulator of either the radio-frequency coupled
type or the fully implanted pacemaker type.

Two target areas are commonly utilized: rostral mesen-

cephalic periventricular gray (PVG) or lateral thalamus-
internal capsule (1C). Stimulation of the former appears
to activate a downstream inhibitory system that reduces

the responsiveness of the lamina V neurons to nocicep-

tive input. This is the descending inhibitory system in-
volved in opiate analgesia, and PVG stimulation mani-
fests habituation and is blocked by naloxone. Other
mechanisms may also be involved. This target area ap-
pears to be optimal when the chronic pain results from

tissue damage and not from deafferentation.

Stimulation of the lateral thalamus-internal capsule is

not blocked by naloxone and does not show habituation.
It does not appear to involve endorphins or downstream

opioid modulation; its mechanism of action is unknown
but probably similar to spinal cord stimulation. It is not
as effective against pain from tissue damage but is useful
for deafferentation pain seen after injury to the periph-
eral or central nervous system. Effective stimulation of
the internal capsule requires that the patient perceive
paresthesiae in the painful area. Complications of brain
stimulation are few; electrode migration and loss of ef-
fective stimulation can occur. Stereotactic procedures
require specialized resources and skills that are not

widely disseminated in the neurosurgical community.

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