Trochlear nerve (IV) lesion - Disorders of cranial nerves

Trochlear nerve (IV) lesion

Anatomy

This motor nerve supplies superior oblique. It exits posteriorly from the brainstem and winds around to the front, then passes in the lateral wall of the cavernous sinus as far as the superior orbital fissue.

Function

Supplies superior oblique (moves the eye down and in).

Specific causes

Rare as isolated lesion, Generally occurs as a combined III, IV and VI nerve palsies (see below) when the eye is also intorted.

Clinical features

Diplopia on looking down or in.