Hydrocephalus can be defined as a disturbance of
formation, flow, or absorption of cerebrospinal
fluid (CSF) that leads to an increase in
intracranial volume occupied by this fluid.
Shunts are performed in most patients. Only
about 25% of patients with hydrocephalus are
treated successfully without shunt placement.
The principle of shunting is to establish a
communication between the CSF and a drainage
cavity (peritoneum).
The
sixth nerve rises at the
base of the skull, it is vulnerable to injury
from increased
intracranial pressure. Therefore, unilateral or
bilateral sixth nerve palsies may occur in
hydrocephalus.
Conversely, a
sixth nerve palsy can also arise in cases of low
intracranial pressure.
Patients underwent shunting for hydrocephalus
may develop sixth nerve palsy in the first two
weeks after surgery. This uncommon complication
is usually transitory following the same pattern
of abducens palsy after lumbar puncture or
spinal anesthesia. Traction on the nerve with
local ischemia has been involved as the
responsible mechanism in both instances.
Nuclear sixth nerve palsy affects the
ipsilateral sixth nerve as well as the
contralateral medial rectus. This lesion causes
an abduction deficit of the ipisilateral eye as
well as an adduction deficit of the
contralateral eye; together, this is a conjugate
gaze palsy. In contrast, a lesion affecting the
sixth nerve fascicle will produce an ipsilateral
abduction deficit but spare adduction of the
contralateral eye.
Ultimately, once the amount of esodeviation
has been stable for 6 to 12 months, surgical
correction can be considered. Treatment of
partial sixth nerve palsy include a combined
medial rectus recession and lateral rectus
resection on the affected side. In addition,
surgery on the contralateral horizontal rectus
muscles may further expand the field of
binocular single vision. In cases of complete
sixth nerve palsy, the affected lateral rectus
is typically left intact to preserve anterior
segment circulation. Restoration of abduction on
the affected side may be attempted by
transposition procedures that aim to move the
vertically acting rectus muscles into the
horizontal plane. Of these, a full tendon
transposition with posterior fixation suture
seems to be the most effective
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