Third nerve palsy has been mentioned in ptosis (refer
to ptosis section for questions). Here we will look at the features
of ocular motility in third nerve palsy.
In complete third nerve palsy, the patient will have complete
ptosis. The eye appears as down and out when the lid
is elevated. In isolated third nerve palsy, the functions
of the fourth and sixth nerves can be demonstrated by normal
intortion and abduction respectively. Note: intortion
can be seen by getting the patient to look down. If this is not
obvious you may want to examine the patient on the slit-lamp
and observe movement of a landmark such as a superior
conjunctival blood vessel for intact intortion.
Aberrant regeneration of the third nerve is seen only
in compressive lesion and never in medical cause of third nerve
palsy. The physical signs are the results of misdirection
of the third nerve fibres. The commonest ones being :
a. Lid-gaze dyskinesis: the most common
one being upper lid elevation on down-gaze (see picture above).
Less commonly there is lid elevation
on adduction
b. Pupil-gaze dyskinesis: the pupil constricts
on down-gaze or adduction.
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