trochlear nerve (CN IV)
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Introduction
Somatic motor function (superior oblique).
Efferents
- somatic motor
- located in midbrain near aqueduct of Sylvius just inferior to the occulomotor nucleus at the level of the decussation of the superior cerebellar peduncles & the substantia nigra
- Trochlear nerve fibers cross over & exit the brainstem posteriorly, an exception to the rule that cranial nerves do not cross over & exit anteriorly
- fibers originating in the trochlear nucleus innervate the superior oblique
Course
- arises from dorsal aspect of midbrain just inferior to the inferior colliculus on either side
- passes around the midbrain under the free edge of the tentorium cerebelli