When the oculomotor nerve is
completely paralyzed, the position of the
affected eye is determined by the function of
the only two remainin intact muscles, the
lateral rectus and the superior oblique muscles.
Thus the paralyzed eye will be in a position of
abduction, slight depression, and intorsion.
Concurrent paralysis of the levator palpebrae
will cause ptosis of the upper lid, and general
relaxation of tonus of four of the six
extraocular muscles may produce a small degree
of proptosis. The motility of the affected eye
will be limited to abduction, to small degrees
of depression in abduction and to an adduction
movement of the eye that does not go beyond the
primary position. With a complete cranial nerve
III paralysis, the intrinsic muscles of the eye
also are involved, causing the pupil to be
dilated and nonreactive and a paralysis of
accommodation.
Congenital oculomotor
nerve palsies are rare and are often associated
with neurological abnormalities.
Aberrant
regeneration is common,which, if present, argues
against a nuclear lesion. Many of these can be
associated with perinatal trauma. A neurologic
evaluation is therefore advisable and an
evaluation by neuroimaging to search for
associated structural anomalies of the brain has
been recommended
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