92
or MR venography [ 13 ]. This is especially rele-
vant for transpetrosal approaches in dominant
hemispheres [ 13 ]. Apart from the venous anat-
omy, the arterial supply and its relation to the
tumor can be assessed using MR angiography. If
the cavernous segment of carotid artery is encased
by the cavernous sinus extension of the PC menin-
gioma, a digital subtraction angiogram may be
warranted to assess the cross- flow from the con-
tralateral circulation and ipsilateral posterior cir-
culation. This can be performed using balloon
occlusion test or carotid compression test [ 11 ].
Similarly, the dominance and cross-flow of blood
across the posterior circulation need to be assessed
in tumors encasing the basilar, posterior cerebral,
and superior cerebral arteries if radical resection
is planned. Tumor embolization may also be tried
preoperatively if a particularly large arterial
feeder is identified on angiogram, although in
most cases, there are multiple small-caliber feed-
ers (tumor blush), which cannot be embolized.
The senior author rarely utilizes preoperative
embolization for meningiomas in this location, as
the primary supply often arises from internal
carotid artery branches and the risk-benefit ratio is
not in favor of embolization.
Preoperative Hearing Status
Hearing status is one of the primary factors to
consider when choosing the appropriate skull
base approach for PC meningiomas. Assessment
via pure tone audiogram and speech discrimina-
tion score helps classify the hearing as service-
able or nonserviceable. Serviceable hearing
(<50 dB hearing loss or >50% speech discrimina-
tion score) corresponds to American Academy of
Otolaryngology – Head and Neck Surgery class
A/B and Gardner-Robertson class I/II and war-
rants choosing a skull base approach that pre-
serves hearing [ 1 , 3 , 4 ]. It is especially relevant
for transpetrosal approaches, which put the ves-
tibulocochlear apparatus and cochlear nerve at
risk of iatrogenic injury. The anterior transpetro-
sal approach carries a lower risk of hearing dete-
rioration than the posterior transpetrosal
approaches. Among the various posterior trans-
petrosal approaches, the retrolabyrinthine and
transcrusal approaches may enable hearing pres-
ervation in contrast to the more extensive trans-
labyrinthine, transotic, and transcochlear
approaches [ 1 , 3 , 4 ].Preparation for Cerebral
RevascularizationIt is vital to anticipate and prepare for a cerebral
revascularization procedure in PC meningioma
surgery where the intent of surgery is radical
resection, especially in younger patients with
recurrent and more aggressive tumors (WHO
grade II/III) with a poor cerebrovascular reserve
[ 14 , 15 ]. In general, the approach to these
tumors is subtotal with adjuvant radiation ther-
apy if the cavernous cranial nerves are function-
ally intact. However, at recurrence following
radiation therapy in the central skull base,
aggressive surgical resection is considered. The
common indications for a high-flow or high-
capacitance extracranial- to- intracranial bypass
include (1) acute vascular injury during the sur-
gical procedure along with preoperative evi-
dence of intolerance to sacrifice; (2) the desire
to preserve cerebrovascular reserve in a young
patient with long life expectancy; (3) the inva-
sion of tumor into major intracranial arteries
requiring sacrifice of the pivotal vessel to
achieve radical resection, especially for malig-
nant or aggressive tumors; (4) poor preoperative
vascular reserve with symptoms of preoperative
ischemia; and (5) high risk of intraoperative
vessel injury due to tumor encasement or inva-
sion, especially in cases with prior radiation or
surgical treatments [ 14 , 15 ]. Although the pri-
mary assessment tool for cerebrovascular
reserve is the balloon occlusion test, the false-
negative rate means up to 8% of patients can
still be missed [ 14 , 15 ]. Given this risk, the
senior author prefers to augment cerebrovascu-
lar reserve via a revascularization procedure in
younger patients with longer life expectancy
after radical surgical resection. The risk of sur-
gical complications in this subset of patients is
relatively low (<5%).A. Raheja and W.T. Couldwell