The trochlear nerve (the fourth cranial nerve, also called the fourth nerve, IV) is a motor nerve (a “somatic efferent” nerve) that innervates a single muscle: the superior oblique muscle of the eye.
The trochlear nerve is unique among the cranial nerves in several respects. It is the smallest nerve in terms of the number of axons it contains. It has the greatest intracranial length. Other than the optic nerve (cranial nerve II), it is the only cranial nerve that decussates (crosses to the other side) before innervating its target. Finally, it is the only cranial nerve that exits from the dorsal aspect of the brainstem.
Homologous trochlear nerves are found in all jawed vertebrates. The unique features of the trochlear nerve, including its dorsal exit from the brainstem and its contralateral innervation, are seen in the primitive brains of sharks.
The human trochlear nerve is derived from the basal plate of the embryonic midbrain.
Other articles related to "trochlear nerve, trochlear, nerves, nerve":
... Central damage is a damage to the trochlear nucleus ... The nuclei of other cranial nerves affect ipsilateral structures (except of course the optic nerves - cranial nerves II - which innervate both eyes) ... The trochlear nucleus and its axons within the brainstem can be damaged by infarctions, hemorrhage, arteriovenous malformations, tumors and demyelination ...
... Bringewald postulated that superior oblique myokymia resulted from vascular compression of the trochlear nerve (fourth cranial nerve), which controls the action ... had been only one reported case of compression of the trochlear nerve by vessels ... compression at the root exit zone of the trochlear nerve can result in superior oblique myokymia ...
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