The oculomotor nuclear complex in humans: Microanatomy and clinical significance

Abstract

The oculomotor nuclear complex was examined in 12 serially sectioned midbrains. The complex comprised the somatic portion (formed by the multipolar motor neurons), and the parasympathetic portion (formed by the oval or fusiform preganglionic cells) on each side of the midbrain's raphe. The somatic portion consisted of the lateral somatic cell column and the caudal central nucleus. The somatic column measured from 0.2 x 0.1 mm to 3.4 x 1.4 mm (mean = 2.4 x 1.2 mm) in transverse sections. It was divided into the principal, intrafascicular and extrafascicular parts. The principal part was subdivided into the dorsal, intermediate and ventral portions. Neurons within the column were multipolar, with pale nucleus, prominent Nissl bodies, and 1-7 processes. The number of motor neurons in the entire column ranged from 1 to 209 per section. The diameter of neurons was 40 x 26 microns on the average. The authors also revealed the isolated multipolar neurons in the periaqueductal gray, the interstitial nucleus of Cajal, the Edinger-Westphal nucleus, and the fibre bundles of the oculomotor nerve. These cells most likely represent the displaced motor neurons of the oculomotor nerve. The caudal central nucleus was 0.8 x 0.6 mm in size, and it contained 12-58 neurons. These multipolar neurons measured 35 x 22 microns in size. The parasympathetic Edinger-Westphal nucleus usually consisted of the rostral, ventral and dorsal parts, which contained from 8 to 283 neurons per section. The longest rostrocaudal diameter of this nucleus measured 7.1 mm. The oval or fusiform neurons contained bands of the congregated Nissl bodies. The neurons measured 34 x 17 microns in size. The authors discussed the clinical significance of the obtained anatomical data, i.e. the neurologic signs following complete or partial lesions of the oculomotor nuclear complex.