93The Role of Intraoperative
Electrophysiological
Neuromonitoring and Safe
Anesthetic Techniques
The intricate relation of PC meningiomas with
multiple cranial nerves and brainstem puts these
vital neural structures at risk during surgical
resection. Recently, strong evidence has emerged
supporting the use of intraoperative electrophysi-
ological monitoring for safe surgical resection
and optimal functional outcome [ 16 ]. The senior
author has made it a practice to utilize at least
motor evoked potentials, somatosensory evoked
potentials, brainstem auditory evoked response,
and facial nerve monitoring in all cases of PC
meningioma resection. Lower cranial nerve mon-
itoring to assess the vagus, spinal accessory, and
hypoglossal nerves is also employed when indi-
cated. Finally, electroencephalography is used to
assess the depth of anesthesia in cases where
burst suppression is indicated while performing
cerebral revascularization procedures. Carefully
titrated and judicious use of safe anesthetic
agents and muscle relaxants is essential to opti-
mize the interpretation of electrophysiological
monitoring and keep the intracranial pressure
within a desirable range. Baseline potentials
should always be obtained before and after
patient positioning to assess the baseline neuro-
logical deficits and any iatrogenic deficits arising
from patient positioning, which can be rectified
appropriately [ 11 ].
Decision-Making and Treatment
Strategies
The primary factors influencing the decision-
making process in choosing an appropriate treat-
ment strategy for patients with PC meningioma
include age of the patient, functional status of the
patient, whether the patient is symptomatic or
asymptomatic, baseline hearing status, and radio-
logical parameters such as tumor size, pattern of
tumor extension and its epicenter, cavernous sinus
involvement, and tumor-brainstem interface.
Treatment strategies include the options of conser-
vative management with close radiological sur-
veillance, SRS, and surgical resection [ 1 , 3 , 4 ].
Because studies assessing the natural history of
PC meningiomas [ 3 ] have demonstrated progres-
sive increment in tumor dimensions leading to
neurological decline and death if left untreated,
watchful waiting is usually not employed as the
first line of treatment in most cases if the lesion is
symptomatic. Middle-aged or elderly asymptom-
atic patients with multiple comorbidities who have
been incidentally diagnosed with small PC lesions
suggestive of a benign meningioma may be an
appropriate exception. In such cases, first follow-
up imaging is done at 3–4 months to rule out an
aggressive variant of tumor, which may warrant
surgical exploration. If there is no significant inter-
val change in tumor dimensions at the first follow-
up, serial scans can be safely deferred to once a
year. Objective decision-making can also be aided
by calculation of the tumor growth index. These
patients are generally advised to avoid hormonal
replacement therapy, which may potentially accel-
erate the growth rate of these tumors and cause
early onset of neurological symptoms.
SRS has emerged as an invaluable alternative/
adjunct to surgical resection for these tumors [ 17 ,
18 ]. Although long-term data supporting its effi-
cacy and safety are limited, its short-term results
are reassuring. Many neurosurgeons across the
globe have switched from aggressive radical
tumor resection to more tailored safe tumor
decompression and use of SRS as adjuvant ther-
apy for better functional outcome. SRS can be
used as primary therapy for small, minimally
symptomatic, PC lesions suggestive of meningi-
oma with primary involvement of cavernous sinus,
especially in elderly patients with multiple comor-
bidities and limited life expectancy [ 17 , 18 ]. SRS
is more often employed as adjunct/adjuvant ther-
apy in the modern microneurosurgical era, particu-
larly for residual tumors along the cavernous sinus
for patients with any age group, tumors with
higher histological grade, and remnant tumors
showing progressive growth on serial imaging
[ 17 , 18 ]. Another school of thought believes that
small, benign WHO grade I residual tumors can be
safely monitored using serial imaging because
many have already been devascularized during7 Petroclival Meningiomas