Supratentorial Deep Brain Arteriovenous Malformations: Medial Temporal 253

Medial Temporal Arteriovenous Malformations

4.36

Special Medial temporal arteriovenous malforma-
Considerations tions (AVMs) are located deep to the syl-
vian fissure, medial to the temporal horn
of the lateral ventricle and hippocampus.
They vary in size from small to medium and
receive arterial supply from numerous
branches of the anterior choroidal and mid-
dle and posterior cerebral arteries. Venous
drainage is deep and terminates in the syl-
vian veins, basal vein of Rosenthal, and
petrosal veins. Epilepsy is the most com-
mon presenting complaint of patients with a
medial temporal AVM. Hemorrhage can
occur, usually rupturing into the temporal
lobe or deep frontal lobe.

Surgical exposure of these malforma-
tions is often difficult owing to their deep
location, especially those located posteri-
orly in the dominant temporal lobe. There-
fore, radiosurgery should be considered for
patients with dominant posterior malforma-
tions who have no neurologic deficit. Oblit-
eration of the AVM by radiosurgical treat-
ment may be associated with a reduction in
seizure frequency. Surgical extirpation is
preferred for lesions presenting with hem-
orrhage or intractable seizures. Preopera-
tive embolization often eliminates most of
the medial feeders from the anterior choroi-
dal and posterior cerebral arteries.

254

Arteriovenous Malformations of the Brain

Approach Surgical exposure is gained through a com-
bined transsylvian and subtemporal ap-
proach. A modified pterional craniotomy
(see Chapter I) is performed with the pa-
tient in the supine position. Zygornatic os-
teotomy is an option to supplement basal
exposure. A gelatin roll is placed beneath
the ipsilateral shoulder and the thorax is
elevated 15 degrees. The head is main-
tained in a radiolucent head-fixation device
for intraoperative angiography and rotated
60 degrees to the contralateral side. The
groin is prepared for intraoperative an-
giography. A lumbar catheter is placed pri-
or to positioning for intraoperative cere-
brospinal fluid drainage.

4.37

4.37 This coronal section il-
lustrates dissection of the sylvian fissure
(A) and an infratemporal approach to the
malformation (B). Circumferential dissec-
tion through the sylvian fissure, temporal
horn, and choroidal fissure exposes the en-
tire lesion.

Supratentorial Deep Brain Arteriovenous Malformations: Medial Temporal 255

4.38

4.39

4.38 The dura is widely in-
cised to expose the sylvian fissure, inferior
frontal lobe, and entire temporal lobe. A
halo self-retaining retractor is attached to
the head-fixation device and two 15-mm re-
tractors are placed on opposite sides of the
sylvian fissure. Cerebrospinal fluid is aspi-
rated from the basal cisterns as the arach-
noid is opened along the proximal middle
cerebral artery (MCA). Systemic blood
pressure is lowered to 60 mmHg and intra-
venous osmotic diuretics are infused to re-
duce intracranial pressure. The sylvian
veins and M₂-M, branches of the MCA are
identified.

4.39 A pia-arachnoid plane is
identified along the dorsolateral aspect of
the malformation. Multiple arterial feeders
from M, and the anterior temporal
branches of M₂ are isolated and then oc-
cluded by bipolar coagulation.

256

Arteriovenous Malformations of the Brain

4.40

4.40 Additional retractors are
placed on the medial temporal lobe as dis-
section continues along the medial aspect
of the malformation.

4.41 The AVM is retracted
medially. Draining veins are isolated from
the sylvian vein as the lateral aspect of the
malformation is dissected.

Supratentorial Deep Brain Arteriovenous Malformations: Medial Temporal 257

4.42

4.42 Dissection enters the
medial aspect of the temporal horn where
the anterior choroidal arterial feeders are
eliminated.

"'S

I

4.43

4.43 Dissection proceeds to
the posterior aspect of the AVM, permit-
ting occlusion and incision of the posterior
choroidal feeding arteries. The choroid
plexus is separated from the AVM in the
posterior temporal horn.

258

Arteriovenous Malformations of the Brain

B

4.44

4.44 Dissection now proceeds
along a subtemporal course (B).

4.45 Retractors are removed
from the sylvian fissure. Two retractors are
placed on the basal aspect of the temporal
lobe as additional cerebrospinal fluid is
withdrawn from the spinal catheter. Dis-
section is initialed at the junction ot" the
AVM with the inferior temporal gyrus. The
malformation is reflected inferiorly as feed-
ing arteries and adhesions are separated
from it.

4.45

259

Supratentorial Deep Brain Arteriovenous Malformations: Medial Temporal

4.46 The malformation is re-
flected inferiorly as the final arterial and
venous connections are divided between
the basal temporal lobe and the malforma-
tion. Here, the dissection joins the previous
transsylvian approach in the temporal horn.

4.47 The malformation is re-
flected medially and retracted to expose the
arterial feeding vessels that arise directly
from the posterior cerebral artery (PCA).
Multiple branches of P₂ are coagulated and
divided as they enter the malformation.

PCA (P₂ segment)

4.47

260

Arteriovenous Malformations of the Brain

4.48 The large draining vein,
which courses along the medial surface of
the malformation, is coagulated and divided
proximal to ils entry into the basal vein.
When the vein is incised, the entire malfor-
mation is freed and removed. To ensure
complete removal of the AVM, the AVM
bed and temporal horn are inspected for
bleeding sites and intraoperative angiogra-
phy is performed through the carotid and
vertebral arteries.

Closure Closure is performed as for a modified
pterional craniotomy (see Chapter I).

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