The
two most common complications following
surgery of the cerebellopontine angle
are CSF leakage and cranial nerve
palsies. Less commonly encountered
complications include bacterial and
aseptic meningitis, wound infection,
hydrocephalus and haemorrhage.
CSF
leakage most often results from a
mastoid air cell opened during the
craniectomy or during the drilling of
the posterior wall of the internal
auditory canal. Fluid then drains from
these cells into the middle ear and
through the eustachian tube down into
the pharynx or the nose. A CSF leak may
not present immediately, but may start
several days following surgery when the
patient is mobilized. A small drainage
of clear fluid occurring in the
immediate postoperative period may
represent fluid that has accumulated in
the mastoid air cells at the time of
surgery. A drainage that persists longer
than 24 h, or one that worsens with a
Valsalva manoeuvre, is more likely to be
a true CSF leak and should be managed
aggressively. This includes placement of
a lumbar drain, administration of
prophylactic antibiotics, and daily
measurement of CSF cell counts. After 5
to 7 days, the drain is removed and, in
usual conditions, the leakage does not
recur. If that is unsuccessful, patients
usually undergo a mastoidectomy for
obliteration of the air cells and the
eustachian tube without re-exploring of
the surgical site.
A CSF
leak can also occur from the wound. This
is usually a result of poor
wound-healing, hydrocephalus, or wound
infection. The treatment of the leak
actually begins at the time of the
initial incision. A clean, sharp
incision and careful handling of the
wound edges is important. Also, the
surgeon must obtain a meticulous closure
of the fascial layers, especially along
the inferior aspect of the wound
overlying the mastoid tip, where clear
fascial planes are not always present.
In spite of good technique, a CSF leak
may still occur if intracranial pressure
is elevated or if a wound infection
develops. In patients with
hydrocephalus, simple stitching of the
wound seldom solves the problem unless
the hydrocephalus is treated
simultaneously. If there is no
underlying infection, a
ventriculoperitoneal shunt is placed. If
the patient has a concurrent infection,
a ventriculostomy is placed until the
infection has cleared and a shunt can be
inserted.
Dysfunction of cranial nerves V, VII,
VIII, IX, X and (rarely) VI can be
encountered following surgery of the
cerebellopontine angle. Although cranial
nerves IX and X are not by definition in
the cerebellopontine angle, their
function can become impaired with the
resection of large tumors.
Postoperative facial nerve paresis of
various degrees can be evident
immediately following surgery.
Interestingly, if there is complete
anatomic disruption of the nerve at the
time of surgery, the patient may be able
to close the eye for a period of 24 to
48 h following surgery with a subsequent
progression to complete facial
paralysis. More commonly, however, the
patient has a variable degree of
preserved eye closure and facial
movement immediately postoperatively.
This function also can decline between
the third and the fifth postoperative
days, which may be due to oedema or
ischemia of the nerve. If the facial
nerve paralysis is so severe that the
cornea is inadequately covered, the eye
should be covered with a protective
shield, and artificial tears and a
lubricant given every 2 to 4 h. Further
therapy depends on whether the nerve is
anatomically intact and whether there is
adequate coverage of the cornea. If the
nerve is intact but dysfunctional and
the patient has adequate eye closure,
the patient should be followed by
recovery of the nerve. If after 12
months the facial nerve function has not
returned, then a facial reanimation
procedure can be planned. Various
techniques and results for facial
reanimation are discussed in more detail
below. Poor lid coverage of the cornea
in more severe cases of facial nerve
paresis can be addressed with a
tarsorrhaphy or with the placement of
either a spring or weight in the lid. If
the facial nerve is disrupted, facial
reanimation is performed early.
Fifth
cranial nerve injury can follow removal
of a tumor of any size. The fifth nerve
function should be evaluated immediately
postoperatively. If corneal sensation is
diminished, the eye should be covered
with a protective shield and artificial
tears applied every 2 to 4 h. If corneal
sensation is completely absent, the
patient is at an increased risk of
developing a corneal abrasion, and a
tarsorrhaphy should be considered
strongly.
Dysphagia with aspiration or hoarseness
due to impairment of the
glossopharyngeal or vagus nerves can
also occur following resection of large
tumors in the cerebellopontine angle. If
glossopharyngeal or vagus nerve
impairment is suspected, then vocal cord
and pharyngeal sensation and function
should be assessed as soon after
extubation as possible. A modified
barium swallow with video fluoroscopy is
often helpful in determining oral
pharyngeal function and the patient's
risk of aspiration. If there is evidence
of aspiration, NGT or a feeding
gastrostomy tube should be placed until
there is adequate recovery of these
nerves.
Diplopia can occur after resection of
large tumors. It is usually from
abducens nerve paresis and the majority
of patients improve spontaneously.
Patching the affected eye can give some
relief to the patient until the nerve
function returns.
A
postoperative fever and/or headache,
with or without nuchal rigidity suggests
the possibility of either bacterial or
aseptic meningitis. Patients with
aseptic meningitis present with symptoms
several weeks after surgery, usually as
their steroid dose is being tapered.
Evaluation of these patients should
include a CT scan and immediate lumbar
puncture with the CSF analyzed for cell
counts, Gram stain and cultures. The
glucose levels of the CSF and the serum
should be measured as well.
Broad-spectrum intravenous antibiotics
with good gram-positive and
gram-negative coverage should be started
and the steroid dose increased. If the
cultures are negative after 48 h. the
antibiotics can be stopped and the
steroids can be slowly tapered off over
several weeks.
Although postoperative epidural,
subdural and intracerebellar hematomas
are rare, they represent the most
serious complications and if not
properly diagnosed and treated, may lead
to catastrophe. The diagnosis is usually
not difficult in the patient who has
awakened from anaesthesia and then
become stuporous or comatose. During the
early postoperative period, monitoring
of the intracranial pressure via a
subdural posterior fossa monitor may
help in the early detection of a
developing hematoma. If the
deterioration is slow, there may be time
for a CT scan: however, if the
deterioration is rapid, the patient is
best taken to the operating room for
re-exploration.
Hydrocephalus can occur in the early
postoperative period, especially in
patients with a large tumor and
preoperative distortion of the fourth
ventricle. The patient may become
symptomatic from increased intracranial
pressure or may develop a full flap at
the surgical site. A CT scan can confirm
the diagnosis and the patient can be
treated initially with a
ventriculostomy. Most patients recover
spontaneously and rarely is a
ventriculoperitoneal shunt required.
