Corticonuclear tract (Latin)

The corticonuclear tract originates from the upper motor neurons (UMN) in the regions of the primary motor cortex where the head and face is represented by the motor homunculus. The fibrae corticonucleares follow a similar trajectory as the fibrae corticospinales, passing through the crus posterior and the genu capsuale internae to reach the truncus encephali. While passing through the truncus encephali their trajectory changes, and the fibers go on to synapse with the nuclei motorii nervorum craniales of the mesencephalon, pons and medulla oblongata. They include the motor nuclei of n. facialis (CN VII), n. trigeminus (CN V), n. glossopharyngeus (CN IX) and n. accessorius (CN XI). These cranial nerve nuclei represent the lower motor neurons (LMN) that go on to innervate the muscles of the face, head and neck. The fibrae corticonucleares also indirectly controls the motor nuclei of n. oculomotorius (CN III), n. trochlearis (CN IV) and n. abducens (CN VI). It does so via intermediary structures such as the fasciculus longitudinalis medialis and formatio reticularis.