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facial nerve under the dura. The tumor is followed
laterally, and the vestibular nerve is identified pos-
terior to Bill’s bar and transected by using a sharp
hook. The facial nerve is identified first distal in
the canal just anterior to Bill’s bar and is con-
firmed using a facial nerve stimulator. Because
the translabyrinthine approach is a non- hearing
preservation procedure, the tumor can be partially
dissected off the facial nerve in this position in a
medial-to-lateral direction. Next, a linear incision
is made anterior to the sigmoid sinus and inferior
to the sinodural angle. Care must be taken not to
injure the underlying cerebellar tissue, veins, or
arteries. This dural opening is widened superiorly
and inferiorly in a funnel shape toward the upper
and lower extent of the IAC. The dural flap
between the IAC and presigmoid region is tran-
sected and removed to expose the tumor. The
arachnoid of the CPA is divided sharply, and the
tumor should be apparent. Every effort is made to
preserve the arachnoid plan and preserve all neu-
rovascular structures of the CPA. In most cases,
the facial nerve is located in the anterior surface of
the tumor, running anterior-superior or anterior-
inferior; however, the facial nerve stimulator is
used to stimulate the posterior surface of the
tumor to ensure absence of stimulation where the
tumor is opened. Bipolar cautery at a low setting
can be used to coagulate the posterior surface of
the tumor, and a small window is made in the back
side of the tumor using a microscissors. A piece of
tumor is removed and sent for pathological analy-
sis. An ultrasonic aspirator is used next to debulk
the tumor from the center. During this step, it is
important to stay inside the tumor capsule and
avoid aggressive debulking so that the tumor cap-
sule can be manipulated during tumor dissection
off the brainstem and facial nerve. A small hook is
used to visualize the thickness of the remaining
capsule after debulking to ensure enough debulk-
ing and maneuverability of the tumor. The goal of
this maneuver is to make the tumor smaller and
easier to manipulate without too much traction on
the facial nerve or brainstem.
Once enough debulking is achieved, the facial
nerve should be identified at the root exit zone at
the brainstem level. The origin of the facial nerve
is located ventral and caudal to the vestibuloco-
chlear nerve origin. A hook is used to gently lift
the tumor capsule away from the brainstem, and
the space between the tumor capsule and brain-
stem is inspected. The facial nerve stimulator is
used to confirm the position of the facial nerve,
and the vestibulocochlear nerve is divided
sharply. Tumor capsule is peeled away gently
from the facial nerve in a medial-to-lateral direc-Fig. 11.7 (a) Axial T2-weighted and (b) coronal
T1-weighted MRI of the brain with gadolinium demon-
strate a large right CPA VS extending into the right IAC
fundus. Note the significant brainstem and fourth ventri-
cle compression causing hydrocephalusG. Alzhrani et al.