282 Arteriovenous Malformations of the Brain

Stereotactic Guidance for Arteriovenous
Malformations

4.83

Special Small subcortical and deep-seated arte-
Considerations riovenous malformations (AVMs) may be
difficult to localize because of the absence
of recognizable surface landmarks. The ap-
proach to malformations near critical ana-
tomic structures must be precise to avoid
morbidity. A surgical corridor can be plot-

ted on radiographic images (e.g., magnetic
resonance imaging [MRI]), but it is some-
times difficult to transfer this precise infor-
mation to the operative field. Stereotactic
guidance is an essential adjunct for these
situations.

283

Supratentorial Deep Brain Arteriovenous Malformations: Stereotactic Guidance

Stereotactic angiography is rarely nec-
essary for localization. Even small malfor-
mations or their associated hematoma can
be seen on computed tomography scan or
MRI and coordinates can be generated for
Stereotactic localization. The Stereotactic
device should be simple, preferably with an
articulating arm or arc that can move in and
out of the operative field during surgery.
The Stereotactic probe defines the site of
skin incision, craniotomy, cortical incision,
and trajectory through the brain to the sur-
face of the malformation.

The malformation in this section is a
small subcortical AVM. The Stereotactic
device depicted is the Pelorus Stereotac-
tic system with rotating arc. Other stereo-
tactic devices, including frameless arms,
may be used effectively. After the Pelorus
localizer ring is attached to the skull in the
right frontal region, imaging is used to gen-
erate localizing coordinates.

I

Approach A temporal craniotomy is performed with
the patient in the supine position. The tho-
rax is elevated 15 degrees and the ipsilateral
shoulder is elevated with a gelatin pad. The
head is held in a head-fixation device and
rotated contralateral to the lesion until the
sagittal suture is parallel to the floor.

4.84

4.84 A 5-cm incision is cen-
tered beneath the Stereotactic probe.

284 Arteriovenous Malformations of the Brain

4.85

4.86

4.85 The linear incision is
made through fascia and muscles and re-
tained with a single retractor. A single-en-
try burr hole is drilled and a 3-cm
craniotomy is made with a pneumatic crani-
otome. The dura is opened in a cruciate
fashion. The stcreotactic probe is directed
through a sulcus of the middle temporal
gyrus,

4.86 The pia is coagulated and
a Silastic cannula is stereotactically insert-
ed to a predetermined point at the external
border of the malformation. The cannula is
cut flush with the pial surface.

285

Supratentorial Deep Brain Arteriovenous Malformations: Stereotactic Guidance

4.87

4.87 Two surface retractor
arms are attached to the arc adaptor. A
cortical artery and its gyral branches are
retracted to avoid injury. The pia-arachnoid
is opened along the path of the cannula until
the deep border of the sulcus is reached. An
incision is made in the gyrus at the depth of
the sulcus.

4.88 In this coronal section,
two 2-mm retractors are used to create a
corridor to the malformation.

4.88

286 Arteriovenous Malformations of the Brain

4.89

4.90 The malformation is re-
tracted. Color-absorptive laser energy co-
agulates and cuts the delicate feeding ar-
teries and veins entering the AVM.

4.91 The malformation is re-
tracted superiorly as the final feeders are
eliminated. After the mass of the malforma-
tion is removed, its bed is inspected for
residual malformation and potential sites of
bleeding.

1

4.91

4.89 Dissection begins with
bipolar coagulation.

Supratentorial Deep Brain Arteriovenous Malformations: Stereotactic Guidance 287

4.92 The retractors are re-
moved and the pia-arachnoid is closed with
absorbable microsutures. Intraoperative
angiography is unnecessary for most small
vascular malformations, but Doppler and
color ultrasound may be used to ensure to-
tal resection.

Closure 4.93 The dura is closed, and
the bone flap is secured with stainless steel
wires. Muscle, fascia, and skin are closed
₍ in layers.

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