98
degree of removal of the vestibulocochlear struc-
tures to gain better access along ventral brain-
stem, the modifications of this approach can be
retrolabyrinthine, transcrusal, translabyrinthine,
and transcochlear, although at the cost of pro-
gressively greater hearing loss and facial weak-
ness in the successive approaches [ 21 ]. The
retrolabyrinthine approach preserves the hearing
by leaving the otic capsule intact. The transcrusal
approach has been modified from the classical
translabyrinthine approach in that it only sacri-
fices the superior and posterior SCCs from their
ampullae to the common crus. The translabyrin-
thine approach involves the removal of all three
(superior, posterior, and lateral) SCCs including
the common crus. With the openings of the SCCs
and common crus occluded using bone dust and
wax, the endolymph is contained within the otic
capsule in the transcrusal approach, which helps
preserve hearing in many instances; on the other
hand, the translabyrinthine approach is almost
inevitably associated with complete hearing loss
[ 21 ]. The transcrusal approach also provides
~89% of the clival exposure afforded by the much
more aggressive transcochlear approaches, which
include removal of the complete vestibuloco-
chlear apparatus and its otic capsule by drilling
along the most anterior aspect of the petrous
bone, ventral to the IAC [ 22 , 23 ]. The transco-
chlear approaches also require facial nerve trans-
position from its bony canal, which leads to at
least a transient grade III facial palsy. The poste-
rior fossa dura is then opened to tackle the intra-
dural pathology.
Complications and Their Avoidance
The morbidities most commonly associated with
these approaches include hearing loss, vertigo,
tinnitus, dizziness, facial palsy, CSF leak, and sig-
moid sinus thrombosis. Hearing loss can be pre-
vented by opting for hearing-preserving posterior
transpetrosal approaches and using intraoperative
brainstem auditory evoked response monitoring
in select patients with preoperative serviceable
hearing status. Careful application of bone dust
and wax in occluding opened SCCs and common
crus in the transcrusal approach helps prevent
inadvertent hearing loss from the loss of endo-
lymph. Taking care to prevent fat graft filling the
mastoidectomy defect from prolapsing in the
middle ear cavity will reduce the incidence of
conductive hearing loss after hearing preservation
surgery [ 21 ]. Vertigo, tinnitus, and dizziness are
often transient in nature, and the contralateral ves-
tibular apparatus usually spontaneously compen-
sates for the loss of ipsilateral vestibular function
in a few days. Facial palsy is common with the
transcochlear approaches but can also arise in
translabyrinthine approaches while drilling in the
vicinity of bony facial canal. Therefore, it is
imperative that the facial nerve is not skeletonized
if its transposition is not intended, and a thin layer
of bone must remain to protect the nerve. Use of
intraoperative facial nerve monitoring and neuro-
navigation may help reduce the risk of iatrogenic
facial paresis. CSF leak is another common, pre-
ventable complication of transpetrosal approaches.
Appropriate packing of the dural defect with
autologous fat graft harvested from the abdomen
helps to reduce the risk of postoperative CSF
leak/paradoxical rhinorrhea. Use of a postopera-
tive lumbar drain may further reduce the inci-
dence of postoperative CSF leaks. Intraoperative
injury to the sigmoid sinus predisposes for the
risk of sinus thrombosis that can lead to cata-
strophic raised intracranial pressure symptoms
and cerebellar venous infarct. Therefore, ensuring
adequate hydration in such cases along with the
use of antiplatelets/anticoagulants is mandatory,
especially in cases of dominant sinus injury.Combined Transpetrosal ApproachIndications and Limitations
The combined transpetrosal is the most versatile
transpetrosal approach available for approaching
PC meningiomas; it combines the advantages
offered by both anterior and posterior transpetro-
sal approaches, although it is a much more
aggressive skull base approach that carries a
higher risk of iatrogenic complications and a
greater propensity for longer operative duration,
increased blood loss, and prolonged anesthesia
[ 11 ]. Radical resection is afforded for almost the
complete spectrum of PC meningiomas usingA. Raheja and W.T. Couldwell