 Preoperative and Operative
Approach
In patients with supratentorial
tumors a craniotomy is performed. and a total gross resection may
be done, depending upon
the location and the extent of the tumor.
The principle here is that of reducing the tumor
burden (the number of tumor cells) as much as possible.
Most patients
with infratentorial tumors present with hydrocephalus. This
should be treated before any other
operative procedure is done. In a few patients
the hydrocephalus may revolve with the use of steroids
preoperatively, however. Almost all patients, need
VPS before the posterior fossa is opened so that
the brain does not herniate downward. Usually the patient improves clinically
to
the point of reaching a plateau, then the
tumor may be operated on. As these tumors can
seed via the CSF, incorporation of a
filter device into the shunt is desirable.
Preoperative insertion of external drain is
another option.
Infratentorial ependymomas
excision is preferred to be done in setting
position with the use of Doppler. Midline
incision with suboccipital approach with the
performance of flap, reflected down or
sometimes, laminectomy of C1 and even C2 is
needed, when the extension of the tumor go down.
The dura is opened in Y-shaped fashion.
Most of these tumors are midline, therefore the
vermis is splitted and the tumor is exposed.
Many of these tumors derive their blood supply
from the brain stem, therefore, total gross
resection of the tumor is often not possible.
At
the time of exposure of the surface of the dura, in
patients with supra-
or infratentorial ependymomas, real-time
ultrasound may be used to dynamically image the
tumor. The precise location of the tumor can be
obtained from this as well as the tissue
characterization (solid tumor versus necrotic
tumor vs. cyst), If a large cystic component is identified, a probe
may be advanced with
continuous ultrasound guidance and the cyst
can be drained. The immediate reduction in the mass of the
lesion and the resulting decrease in
intracranial pressure lessen the risk of injury to
the brain when the dura is opened. Depending upon
the circumstances, an operating microscope and microinstruments may be of use with certain
ependymomas. as may a laser for vaporization and an
ultrasonic aspirator.
In general, the patients undergo
treatment with steroids (dexamethasone 4 to 12 mg q
6 h) preoperatively for a minimum of several days
but always to the point where they have improved
clinically and then have plateaued. The principle is
that of improving brain function as much as possible
before any operation. At the time of operation, if
the dura is tight despite pretreatment with steroids
and perhaps a CSF diversion procedure, mannitol ( 1.5 gm/kg) is given until there is a
good urinary response. Usually at that time the dura becomes slack and pulsatile.
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