Skull Base Surgery of the Posterior Fossa

46

The facial nerve is again identified using
stimulation and followed using a sharp right-
angle hook, and Bill’s bar is palpated. The supe-
rior vestibular nerve and vestibulofacial fibers
can be transected with this instrument. The infe-
rior vestibular nerve is identified and cut. Once
an adequate plane between the tumor and the
facial nerve is developed, a blunt hook is used to
continue the dissection. The motion of the dis-
section is from medial to lateral, to avoid trac-
tion on the facial nerve at its exit through the
distal internal auditory canal (Fig. 3.11). The
arachnoid enveloping the facial nerve is divided
with a sharp right-angle hook. This is sometimes
adequate to facilitate complete removal of small
tumors (Fig. 3.12) [ 43 ]. If the tumor is large, the
capsule can be incised, and the tumor can be
debulked with either microsurgical instruments
or an ultrasonic dissector. The tumor is followed
to the brainstem, developing a plane with both
blunt and sharp instrumentation. Cottonoids
should be placed along the cerebellum and brain-
stem as they are exposed to protect the underly-
ing structures. Intratumoral bleeding is controlled
with bipolar cautery or topical hemostatics (as
above), and only vessels that enter the tumor
capsule are ligated.

Once the tumor is removed and hemostasis is

complete, abdominal fat is harvested and cut into

various-sized strips. The abdominal wound is

closed with absorbable sutures and Steri-Strips,

and a Penrose drain is left in place. The fat is

soaked in bacitracin solution and packed tightly

into the CPA, IAC, and mastoid cavity. Some sur-

geons advocate placing a titanium mesh or

absorbable cranioplasty plate over the fat. The

periosteal flap is reapproximated with 3–0 Vicryl

sutures in a horizontal mattress fashion, ensuring

a watertight closure. The subcutaneous tissues

are reapproximated with buried interrupted 3-0

Vicryl sutures, and the skin is closed with either

subcuticular absorbable sutures or a running

locking 4-0 nylon suture. A standard mastoid-

type pressure dressing is applied.

Postoperative Care

The patient is typically extubated in the operating

room and observed in the intensive care unit

overnight. The Foley catheter, arterial and central

venous lines, and Penrose drains are typically

removed on the morning of postoperative day

(POD) #1. The mastoid dressing is removed on

Fig. 3.10 The internal auditory canal is exposed in 270°
of it is circumference. The facial nerve is identified adja-
cent to Bill’s bar

Fig. 3.11 The dura of the internal auditory canal is

opened. The facial nerve is identified in the anterior lateral

portion of the internal auditory canal. The superior ves-

tibular nerve is immediately posterior to the facial nerve.

The facial nerve is separated from the tumor, the dissec-

tion proceeds from medial to lateral

J.C. Sowder et al.