150
Surgical Risks and Complications
The reported mortality rate for retrosigmoid
approach for VS is 0.3% [ 1 ]. Morbidities includ-
ing CSF leak in 10.3%, postoperative headache in
17.5%, postoperative symptomatic hemorrhage in
2.2%, major neurological complications in 1.8%,
postoperative hydrocephalus in 2.3%, and menin-
gitis in 3% have been reported [ 1 , 27 ]. Inspection
for air cells while opening and drilling the IAC,
careful tumor dissection, and meticulous dural
closure may help reduce the risk of these morbidi-
ties. A systematic review for this approach found
residual tumor on imaging postoperatively in
5.6% of the patients planned for gross-total resec-
tion and tumor recurred in 6.2% [ 1 ].
Surgical Outcome
The hearing preservation rates after retrosigmoid
approach are 55.7%, 35.7%, and 28.4% for intra-
canalicular, <1.5 cm, and 1.5–3-cm tumors, respec-
tively [ 1 ]. The facial nerve function preservation
rate is >90% for intercanalicular tumors ≤ 3 cm in
diameter and 69.8% for tumors >3 cm [ 1 ].
Middle Fossa Approach
The MFA was used by otolaryngologists to treat
pathologies involving the inner and middle ear
long before it was adapted by neurosurgeons for
resection of intracanalicular VSs. This approach
and its modifications provide an excellent
corridor for middle and posterior fossa patholo-
gies. The MFA was first performed in Glasgow
by R. H. Parry, a Scotch otolaryngologist, in
1904 to treat a 30-year-old patient with left ear
pain, tinnitus, and vertigo. The surgery was car-
ried out to divide the vestibular nerve, but unfor-
tunately, the facial nerve was injured when
additional bone was removed over the most prox-
imal portion of the fallopian canal during the
approach [ 23 ]. For this reason, the MFA did not
gain popularity until William House and
Theodore Kurze described their microsurgical
technique in 1961; they used the MFA in 14
patients for treatment of Ménière’s disease and
otosclerosis of the middle ear and later treated
106 patients with intracanalicular VS via the
MFA without permanent facial nerve paralysis
[ 12 – 14 ]. This approach has undergone few modi-
fications over the years, most of which are related
to the methods for localization of the IAC.IndicationsMénière’s disease, dehiscence of the posterior
semicircular canal, and VS are the most common
indications for MFA. Other indications include
facial nerve decompression and repair in trauma
and Bell’s palsy, facial nerve neuroma, cholestea-
toma drainage, middle fossa encephalocele, CSF
leak through the middle ear, petrous carotid
exposure for high-flow intracranial bypass for
complex aneurysms, skull base tumors, and fun-
gal infections. For patients with VS, we use the
MFA for hearing preservation in relatively young
patients with purely intracanalicular tumor, for
VS located in the IAC with cisternal extension of
less than 1–1.5 cm (Fig. 11.3), and for tumor
extending to the fundus of the IAC (lateral VS).Relevant Surgical AnatomyThe middle fossa is bordered by the sphenoid
ridge anteriorly, squamosal bone laterally, mas-
toid bone posterolaterally, petrous ridge postero-
medially, and cavernous sinus and sella medially.
The floor of the middle fossa hosts a number of
important structures. Rhoton et al. [ 33 ] divided
the floor of the middle fossa using a vertical plane
through the anterior border of the cochlea into
anterior and posterior parts. The anterior part
contains, from lateral to medial, respectively, the
eustachian tube, tensor tympani, and petrous
carotid artery, parallel and deep to the greater
superficial petrosal nerve (GSPN) in the space
between the V3 divisions of the trigeminal nerve
anteriorly and the cochlea posteriorly. The eusta-
chian tube and tensor tympani are almost always
covered by the bone, but in 63% of cadaveric
specimens, the horizontal segment of the petrousG. Alzhrani et al.