Trochlear nucleus
Encyclopedia
The nucleus of the trochlear nerve is located in the midbrain, at the level of the inferior colliculus
. It is a motor nucleus, so is located near the midline.
Oddly, fibers from the trochlear nucleus cross over in the midbrain at the superior medullary velum
and exit posteriorly, (this is the only cranial nerve to do so). The nerve then goes around the midbrain, and is visible coming out the sides.
Inferior colliculus
The inferior colliculus is the principal midbrain nucleus of the auditory pathway and receives input from several more peripheral brainstem nuclei in the auditory pathway, as well as inputs from the auditory cortex...
. It is a motor nucleus, so is located near the midline.
Oddly, fibers from the trochlear nucleus cross over in the midbrain at the superior medullary velum
Superior medullary velum
The superior medullary velum is a thin, transparent lamina of white substance, which stretches between the superior cerebellar peduncles; on the dorsal surface of its lower half the folia and lingula are prolonged.It forms, together with the superior cerebellar peduncle, the roof of the upper part...
and exit posteriorly, (this is the only cranial nerve to do so). The nerve then goes around the midbrain, and is visible coming out the sides.