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depth of the tumor in the CPA. The CO2 laser is
small enough to fit easily into the angle and can
be used to cut pieces of tumor out, debulk the
central portion of the tumor, and vaporize the
base of the tumor attachments.
MPFM
The main challenge in removing MPFMs is their
relationship to the cranial nerve 7–8 complex and
the risk of hearing loss or facial weakness. Similar
to tumors around the optic apparatus, we have
found it beneficial to debulk the tumor first before
attempting to dissect the nerves from the surface
of the tumor. Often there is a tongue of tumor or
hypervascular tissue that extends into the internal
auditory canal (IAC). Removal of the bone 270°
surrounding the IAC with round diamond and
cutting burrs permits the removal of these tumor
extensions allowing more complete removal. If
hearing preservation is a priority, then care should
be taken to not enter the vestibule laterally. This
limits the dissection of the lateral most few milli-
meters of the IAC. The preoperative scans should
also be evaluated for evidence of a high-riding
jugular bulb which may compromise the bony
removal over the IAC. All of the drilling of the
IAC should be completed prior to opening the
dura of the IAC. If it appears that the meningioma
extends into the IAC like a carpet, we accept near
total removal while monitoring evoked potentials
from the seventh and eighth nerve. It should be
noted that there is often enhancement that extends
into the IAC visible on preoperative MRI scans
that may correspond to hypervascular dura rather
than frank tumor involvement. Indeed, often
residual enhancement seen on early post-op scans
fades over the subsequent 12–18 months, suggest-
ing in these cases that the enhancement was sim-
ply hypervascular tissue and not residual tumor.
PPFM
Small tumors in this location may be operated
on when there is a consistent and disabling
audiovestibular syndrome presumably related to
the function of the endolymphatic sac.
Hyperostotic bone should be drilled down in
this region when encountered. When the tumors
are very large in this location, a modified far lat-
eral approach can assist with CSF release in the
upper cervical spine as reported previously by
Sanai et al. [ 14 ].Case Examples
Case 1: APFMA 73-year-old woman presented after several
years of left facial numbness and atypical facial
pain, multiple dental procedures, and root canal
surgery with no relief. She was evaluated by a
neurologist who identified trigeminal sensory
loss. MR imaging revealed a small/medium
APFM impinging on the fifth nerve root entry
zone (Fig. 8.2a). A retrosigmoid craniotomy
was done with neuromonitoring, suprameatal
drilling, and the use of the CO2 laser to com-
plete a Simpson Grade 2 removal (Fig. 8.2b).
Her postoperative course was uncomplicated
with relief of her facial pain syndrome and grad-
ual improvement in facial numbness over the
next 18 months.Case 2: MPFMA 43-year-old woman presented with reduced hear-
ing, dizziness, and fullness in her right ear. She was
unable to use the phone with her right ear due to
reduced auditory perception. She was diagnosed
with benign positional vertigo, but because of per-
sistent symptoms, she requested an MR scan. The
study showed a contrast- enhancing mass arising
above the IAC, spanning the internal acoustic
meatus with enhancement in the auditory canal
(Fig. 8.3a). A right retrosigmoid craniotomy with
superior and posterior meatal drilling with neuro-
monitoring was performed (Fig. 8.4). Gross total
resection of the CPA mass and the extension into
the first 5 mm of the IAC was achieved (Fig. 8.3b).S.T. Magill et al.