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Trochlear Nerve
Nervous System

Trochlear Nerve

Nervus trochlearis

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Origin

The trochlear nerve originates from the nucleus of the trochlear nerve in the midbrain. Its fibers decussate across the median plane of the brainstem. Thus, it is the only cranial nerve to run contralaterally relative to its nucleus.

Course

The trochlear nerve emerges from the dorsal midbrain just inferior to the inferior colliculus. It runs anteriorly, piercing the dura covering the apex of the petrous portion of the temporal bone, roughly between the trigeminal and oculomotor nerves. It runs through the superior orbital fissure to enter the orbit. Running medial to the frontal nerve, the trochlear nerve turns medially and innervates the belly of the superior oblique muscle.

Branches

There are no named branches.

Supplied Structures

The trochlear nerve is a motor nerve. It innervates only one target, the superior oblique muscle of the eye.

List of Clinical Correlates

—Diplopia

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