Normal Nuclear and Infranuclear Pathway

Oculomotor Nerve Pathway The oculomotor nerve arises from the complex oculomotor nuclei situated ventrolaterally in the periaqueductal gray matter of the midbrain at the level of the superior colliculus. The nuclei consist of groups of large and small multipolar cells which are arranged longitudinally on each side of the midline supplying one of the four extraocular muscles. A single median nucleus controls the levator palpebrae superioris muscle on either side. The interconnecting, paired, wing-shaped EdingerWestphal subnuclei lie cranial and dorsal to the main nuclei and subserve pupillary function supplied by the parasympathetic fibers for the ciliary ganglion. Axons from the bilateral oculomotor nuclei run ventrally and slightly caudally through the midbrain tegmentum traversing the medial longitudinal fasciculus (MLF), the red nucleus, the substantia nigra, and the medial aspect of the cerebral peduncle, and finally exit the brain stem medial to the cerebral peduncles as oculomotor nerve rootlets which immediately converge to form the oculomotor nerves in the interpeducular cistern (Fig. 1A). At this point, the oculomotor nerve, with its accompanying J Korean Radiol Soc 1999;40:4 35-4 4 1