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Trochlear nucleus

Brain: Trochlear nucleus

Outline of the nucleus raphe dorsalis: DRif interfascicular subnucleus, DRv ventral subnucleus DRvl ventrolateral subnucleus DRd dorsal subnucleus mlf medial longitudinal fasciculus Aq cerebral aqueduct IVn trochlear nucleus.

The cranial nerve nuclei schematically represented; dorsal view. Motor nuclei in red; sensory in blue. (Trochlear is "IV")
Latin	nucleus nervi trochlearis
Gray's	subject #188 807
NeuroNames	hier-504
MeSH	n_11

The nucleus of the trochlear nerve is located in the midbrain, at the level of the inferior colliculus. It is a motor nucleus, so located near the midline.

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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.

Additional images

v • d • e Brain: mesencephalon (midbrain)
Tectum	Corpora quadrigemina (Inferior colliculi, Superior colliculi) • Subcommissural organ • Pretectum
Peduncle tegmentum	Periaqueductal gray (Cerebral aqueduct, Dorsal raphe nucleus) • Ventral tegmentum • Pedunculopontine nucleus • Red nucleus • MLF (riMLF) • lemnisci (Medial, Lateral) • cranial nuclei (III: Oculomotor nucleus, III: Edinger-Westphal nucleus, IV: Trochlear nucleus, V: Mesencephalic)
Peduncle base	Substantia nigra • Cerebral crus (Corticospinal tract, Corticobulbar tract, Corticopontine tract/Frontopontine fibers/Temporopontine fibers)