Skull Base Surgery of the Posterior Fossa

157

ridor is narrow. Tumors with significant burden in
the cisternal space of the CPA are difficult to
remove. Furthermore, the infrequent use of this
approach and limited familiarity with the petrous
bone anatomy can be disadvantageous for the
inexperienced neurosurgeon, but with experience
the approach is desirable for well-selected
tumors.

Surgical Risk and Complications

All middle fossa structures are at risk during the
MFA including the temporal lobe, vein of Labbé
in the dominant side, trigeminal nerve (V3),
GSPN, GG, petrous carotid artery, cochlea, vesti-
bule, facial nerve, cochlear nerve, and labyrin-
thine artery. Air cell openings in either the inferior
or lateral aspect of the temporal bone or in the
middle ear should be recognized and sealed ade-
quately on the way in and out during this
approach. Although the reported rate of CSF leak
following MFA is 5.3–8% because of unsealed
air cells (early, within 3 days) or hydrocephalus
(late, more than 3 days) [ 1 , 6 ], in our series, there
was 0% incidence of postoperative CSF leak,
which has been attributed to meticulous closure
technique and continuous bone dust irrigation
and clearance during bony drilling [ 25 ].
Increasing body mass index and prolonged oper-
ative time have been suggested as independent
risk factors for CSF leak [ 6 ]. A systematic review
of VS resections done using MFA reported 8%
incidence of postoperative headache, 2.6% inci-
dence of residual tumor, 1.1% rate for tumor
recurrence, and 0.4% mortality rate [ 1 ]. In our
series, there was no residual tumor, no recur-
rence, and no deaths at 15 months of follow-up
[ 25 ]. Postoperative temporal lobe venous infarc-
tion, intracranial hemorrhage, epidural hema-
toma, subdural hematoma, seizure, and aphasia
are also potential risks during the MFA.

Surgical Outcome for MFA

The reported hearing preservation rate with the
MFA has ranged from 37% to 82% in the most
recently published series [ 3 , 7 , 15 , 24 , 29 , 30 , 32 ,

34 , 35 ]. In a systematic review of 35 studies for VS

resection, the hearing preservation rate was 56.4%

for tumors <1.5 cm and 59.4% for purely intra-

canalicular tumors. The facial nerve function pres-

ervation rate was found to be 96.7% for tumors

<1.5 cm and 83.3% for purely intracanalicular

tumors [ 1 ]. The authors demonstrated that the

MFA is superior to the retrosigmoid approach for

hearing preservation and superior to the translaby-

rinthine approach for facial nerve function preser-

vation for tumors <1.5 cm [ 1 ]. In our experience,

the hearing preservation rate is 75.5%, and the

facial function preservation rate is 90% at

15 months postoperatively with MFA for VS [ 25 ].

Translabyrinthine Approach

for Vestibular Schwannoma

Indications

The translabyrinthine approach is indicated for

VS resection in patients with nonserviceable

hearing or complete hearing loss preoperatively.

This approach provides the most direct access to

the CPA. Generally, all VSs that can be

approached through a retrosigmoid route can be

removed through a translabyrinthine route; how-

ever, this approach is particularly useful for

tumors that extend to the fundus of the IAC later-

ally and into the CPA angle medially (Fig. 11.7).

The entire length of the facial verve is exposed

routinely from the origin of the brainstem to the

fundus of IAC. This approach allows surgeons to

identify the facial nerve early during surgery,

minimal or no cerebellar retraction is required as

opposed to the retrosigmoid approach, and the

approach allows for early CSF drainage and

relaxation to the cerebellum [ 2 , 4 , 22 ]. The surgi-

cal positioning and bony exposure have been

described elsewhere in this book.

Tumor Removal Techniques

After the presigmoid dura and IAC dura are

exposed, under microscopic vision, the dura is

opened first superoposteriorly along the axis of

the IAC away from the presumed position of the

11 Vestibular Schwannomas