234 Arteriovenous Malformations of the Brain

Temporal Sylvian Arteriovenous Malformations

Special Temporal sylvian arteriovenous malforma-
Considerations tions (AVMs) are frequently midsized and
located in the sylvian fissure adjacent to the
uncus of the temporal lobe. The arterial
supply is from M-,, M,, and occasionally M₄
branches of the middle cerebral artery
(MCA) with venous drainage anterior into
the sylvian veins and basal sinuses and pos-
terior into the vein of Labbe. Patients usu-
ally present with intracerebral hemorrhage

or seizures. Radiosurgery is considered for
temporal sylvian AVMs buried in the poste-
rior fissure beneath the angular gyrus, par-
ticularly on the dominant side. Cerebral
dominance may be determined by Amytal
injection. When surgery is performed in
cases of epilepsy, intraoperative recording
is advisable to detect secondary epileptic
foci commonly found in the medial tempo-
ral nuclei.

235

Supratentorial Convexity Arteriovenous Malformations: Temporal Sylvain

Approach A modified pterional craniotomy (see
Chapter I) is performed with the patient in
the supine position. The thorax is elevated
15 degrees to improve venous drainage.
The head is rotated 45 degrees and main-
tained in a radiolucent head-fixation device
for intraoperative angiography. A wide cra-
niotomy provides access to the proximal
and distal sylvian fissure and adjacent re-
gions of the frontal and temporal lobes.

Vein of
Labte

MCA

4.9

4.9 Frontal view of the mal-
formation shown in this procedure depicts
the arterial supply originating from the
M₂-M₃ branches of the MCA. Venous
drainage terminates anteriorly into the syl-
vian veins and basal sinuses and posteriorly
into the vein of Labbe.

236 Arteriovenous Malformations of the Brain

4.10

4.10 The dural flap is re-
flected interiorly and attached to the tem-
poralis muscle. A mass of dilated, red,
draining veins exits the sylvian fissure. The
nidus of the malformation buried deeper in
the mid-sylvian region is not visible. Two
self-retaining retractors are placed on oppo-
site sides of the proximal sylvian fissure.
The pia-arachnoid membrane of the sylvian
fissure is incised and cerebrospinal fluid is
aspirated from the proximal cistern. A
plane of dissection is developed in the syl-
vian fissure along the superior border of the
malformation by coagulating pia-arachnoid
and bridging vessels.

4.11

4.11 Dissection proceeds in
the fissure, keeping a relatively even depth
of exploration along the entire border of the
malformation. Bridging veins and arteries
that cross the fissure are coagulated and
divided to deepen the exposure. This expo-
sure is pursued until all the major feeding
arterial branches (M₂-M₄) of the MCA are
identified.

237

Supratentorial Convexity Arteriovenous Malformations: Temporal Sylvian

Temporal
branch of
MCA

Vein of
Labbe

4.12

1

Hematoma
cavity

MCA

4.12 The dissection is shifted
inferiorly. Beginning at the vein of Labbe,
an avascular plane is developed between
the inferior surface of the malformation and
the temporal lobe. Deep penetrating
branches of the M^ MCA are identified as
they enter the malformation.

4.13 The dissection opens into
a deep hematoma cavity in the temporal
lobe that extends into the sylvian fis-
sure. The AVM is retracted posteriorly and
branches of MCA are identified and coagu-
lated as they enter the malformation.

4.13

I

238

i

4.14

Arteriovenous Malformations of the Brain

4.14 Multiple branches from
M₂ and M₃ are identified and coagulated as
the malformation is retracted toward its pri-
mary venous drainage, the vein of Labbe.

4.15

4.15 The malformation col-
lapses as its arterial supply is progressively
eliminated. The final draining vein is
coagulated.

4.16 The vein is sectioned.
The malformation bed is inspected for re-
sidual malformation and sites of potential
hemorrhage.

Supratentorial Convexity Arteriovenous Malformations: Temporal Sylvian 239

4.16

Superior
temporal
gyrus

4.17

I
I

4.17 The remaining cortex of
the superior temporal gyrus and the wall of
the hematoma cavity are resected by sub-
pia dissection to remove a potential seizure
focus. The right femoral artery is cannu-
lated and intraoperative angiography is per-
formed to document complete excision of
the malformation prior to dural closure.

Closure Closure is performed using standard pterio-
nal craniotomy techniques (see Chapter I).

240

Arteriovenous Malformations of the Brain

Occipital Arteriovenous Malformations

4.18

Special Occipital arteriovenous malformations
Considerations (AVMs) increase in complexity as they ap-
proach or involve the calcarine cortex. The
arterial supply to medial, paramedian, and
polar occipital AVMs is derived from distal
branches of the posterior cerebral artery
(PCA). The posterior choroidal arteries
(from the PCA) may contribute blood sup-
ply to the deep and intraventricular por-
tions of the AVM. Venous drainage
empties into the transverse sinus, sagittal
sinus, tentorial veins, and internal occipital
veins preceding the vein of Galen.

Options for treatment include radio-
surgery for lesions that abut or involve the
visual cortex in patients with a normal visu-
al examination. Endovascular embolization
can be considered except in medial occipi-
tal AVMs for which embolization carries a
significant risk of visual field deficit. Occip-
ital lobectomy is an option limited to exten-
sive lesions in patients with a complete
hemianopsia. Most occipital AVMs are
treated by conventional surgery.

241

Supratentorial Convexity Arteriovenous Malformations: Occipital

Approach An occipital craniotomy is performed with
the patient in the lateral oblique position.
The thorax is elevated 15 degrees to im-
prove venous drainage. The head is main-
tained in a radiolucent head-fixation device
for intraoperative angiography. A femoral
artery sheath is placed prior to position-
ing and maintained with heparinized solu-
tion under pressure. For medial occipital
AVMs, the hemisphere containing the le-
sion is placed in a dependent position (side

down). A 6 x 6 cm skin flap is based on the
superior nuchal line; its medial border is
2 cm across the sagittal suture. Two burr
holes are drilled adjacent to the sagittal si-
nus; the inferior one is 2 cm above the
superior nuchal line, which approximates
the location of the transverse sinus. The
dura is separated from the bone at each
burr hole to clearly identify the edge of the
sinus. A 5 x 5 cm bone flap is elevated.

Convexity

draining

vein

4.19

4.ao

4.19 A dural flap is incised
and reflected medially toward the sagittal
sinus. A large convexity draining vein that
enters the sagittal sinus is identified in the
pia-arachnoid space.

4.20 The vein is followed
through the sulcus toward the subcortical
malformation. Multiple retractors are
placed as the dissection continues into the
deep white matter.

242

Arteriovenous Malformations of the Brain

4.21

4.21 The malformation and
its draining vein are retracted medially as
perforating vessels from the middle cere-
bral artery are coagulated and sectioned.

4.22 The malformation is re-
tracted superiorly as a pedicle of vessels
from the PCA (P₄,P₅) is coagulated and

243 Supratentorial Convexity Arteriovenous Malformations: Occipital

23. The malformation is retracted medially, exposing large feeding branches of the PCA.

4.24 The occipital horn of the lateral ventricle is opened. The branches from the posterior choroidal artery are coagulated.

244

Arteriovenous Malformations of the Brain

4.25

4.25 With the dissection now
directed medially, the major arterial branch
from the distal PCA is identified. An aneu-
rysm clip is applied, and the vessel is co-
agulated and sectioned. The collapsed
malformation remains attached only to its
major draining vein.

Supratentorial Convexity Arteriovenous Malformations: Occipital 245

4.26 The malformation is re-
flected from its bed. and the vein is coagu-
lated and sectioned. The bed is inspected
for residual malformation and potential
bleeding sites. The ventricle is inspected to
exclude hematoma. Intraoperative an-
giography is performed to document com-
plete AVM resection prior to dural closure.

Perforating
arteries

Posterior

choroid
artery

436

Closure Closure is performed using standard pterio-
nal craniotomy techniques (see Chapter I).

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