What is the main function of the trochlear nerve?

The trochlear nerve is a purely motor nerve that innervates only the superior oblique muscle of the eyeball, enabling downward and lateral gaze.

What are the unique anatomical features of the trochlear nerve?

It has several distinctive traits: it is the only cranial nerve to emerge dorsally from the brainstem, it is the smallest and slenderest cranial nerve, and its fibers decussate before exiting the brainstem.

What happens if the trochlear nerve is damaged or paralyzed?

Damage leads to paralysis of the superior oblique muscle, causing symptoms like diplopia (double vision) that worsens during downward gaze, extorsion of the eyeball, and a compensatory head tilt to the opposite side.

Where is the trochlear nucleus located?

The trochlear nucleus is situated in the midbrain and gives rise to the nerve's general somatic efferent fibers.

What is the anatomical course of the trochlear nerve?

It emerges dorsally below the inferior colliculus, winds around the cerebral peduncle, passes between arteries, enters the cavernous sinus, and reaches the orbit via the superior orbital fissure to supply the superior oblique muscle.

Why is the trochlear nerve important for eye movements?

By innervating the superior oblique muscle, it controls specific eye movements essential for downward and lateral gaze, which are critical for activities like reading or navigating stairs.

Trochlear Nerve (CN IV) – Superior Oblique Function