90
Natural History and Clinical
Presentation
PC meningiomas account for approximately 2%
of all intracranial meningiomas and 0.15–0.4% of
all intracranial tumors [ 2 ]. They occur predomi-
nantly in middle-aged and older women, with
three times the incidence as compared with men
[ 2 ]. The natural history of PC meningiomas dem-
onstrates insidious and progressive growth leading
to neurological decline from cerebellar dysfunc-
tion, cranial neuropathy, and brainstem compres-
sion, leading to death if left untreated [ 3 ]. In a
cohort of patients who were managed conserva-
tively (i.e., no neurosurgical or radiosurgical treat-
ment) and monitored for a minimum of 4 years, up
to 50% of asymptomatic patients developed cra-
nial nerve (CN) palsy, and 20% of patients with
preexisting CN palsies developed new CN deficits
[ 10 ]. Even within the same histological tumor
grade, there was a wide variation in growth rates.
Overall, the average growth rate was 0.81 mm/
year in diameter or 0.81 cm^3 /year in volume [ 10 ].
Havenbergh et al. [ 10 ] also found a statistically
significant correlation between infratentorial
growth and moderate/severe functional deteriora-
tion and between tumor growth index and the
severity of functional deterioration. They also
observed that brainstem compression/displace-
ment influenced functional outcome, and an
increase in tumor growth index correlated with
functional or clinical deterioration. In other words,
an increase in the tumor growth rate often pre-
cedes neurological decline, thereby highlighting
the importance of close radiological surveillance
in patients with smaller asymptomatic lesions.
Petroclival meningiomas often reach sizeable
dimensions (usually >2–3 cm) before they
become clinically symptomatic from cranial
nerve or brainstem compression. These benign
tumors commonly present with a varied constel-
lation of symptoms, including headache, facial
numbness, chewing difficulties, dizziness, gait
disturbances, facial weakness, hearing impair-
ment, and diplopia. If there is further extension of
the lesion, patients may have visual disturbances,
ptosis, hormonal imbalance, swallowing difficul-
ties, nasal regurgitation, hoarseness of voice, and
tongue deviation. Out of this wide range of symp-
tomatology, headache, gait disturbance, and tri-
geminal neuropathy are the most common
presenting complaints, occurring in approxi-
mately 90% of patients [ 11 ].Preoperative Assessment
and Planning
Radiological ImagingThe radiological imaging of choice for patients
with PC meningiomas is gadolinium-enhanced
magnetic resonance imaging (MRI) to assess the
site, size, and extent of the tumor [ 1 , 2 , 4 ]. Of
particular importance is to understand where the
epicenter of tumor is located. If the bulk of the
tumor is located in the supratentorial compart-
ment, then anterior and anterolateral approaches
like the transbasal, pterional, orbitozygomatic,
and transzygomatic subtemporal/pretemporal
approaches are preferred. For tumors with the
epicenter lying in the infratentorial compartment,
lateral and posterolateral approaches such as the
anterior/posterior/combined transpetrosal and
retrosigmoid/far lateral approaches are more suit-
able for safe tumor resection [ 1 – 4 ]. In addition,
T2/FLAIR MRI needs to be carefully examined
to ascertain whether there is encasement of the
basilar and internal carotid arteries (ICA) along
with their major branches and to assess the pres-
ence of brainstem edema, which may be a surro-
gate for tumor invasion into the brainstem pia
mater [ 1 – 4 ]. Both of these parameters have
implications for the safety of radical tumor resec-
tion. To assess the bony anatomy and presence of
any associated bony hyperostosis, thin-slice com-
puted tomography (CT) of head is essential.
Pneumatization of skull base should also be
examined before performing any skull base
approach to preemptively plan the reconstruction
measures necessary to prevent postoperative
cerebrospinal fluid (CSF) leak. Statistically, the
most commonly utilized approach by the senior
author for removal of petroclival tumors is the
retrosigmoid approach, used in approximately
60% of cases (Fig. 7.1) [ 11 , 12 ].A. Raheja and W.T. Couldwell