what is the function of CN IV (trochlear)?
eye movement for superior orbital oblique (somatic motor)
The trochlear nerve (CN IV) is a motor nerve that is responsible for the innervation of the superior oblique muscle of the eye, which controls eye movement. The superior oblique muscle is responsible for depressing and abducting the eye, and the trochlear nerve supplies the nerve fibers that allow the muscle to perform these actions.
The trochlear nerve is unique among the cranial nerves in that it arises from the dorsal surface of the brain stem and crosses the subarachnoid space to the opposite side of the brain stem before turning anteriorly. This anatomical feature makes it the longest of the cranial nerves and the only one that exits the brain stem dorsally.
Damage to the trochlear nerve can result in weakness or paralysis of the superior oblique muscle, which can lead to double vision, particularly when looking down or inward. It may also affect the ability to coordinate movements of the eyes, which can impact activities such as reading, driving, and playing sports.
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