The oculomotor nuclear complex in humans. Microanatomy and clinical significance.

This study has been performed to define better the anatomical structure of the oculomotor nuclear complex and its neuronal components. The oculomotor nuclear complex was examined in fixed and serially sectioned midbrains from 12 adult subjects free from neurological diseases. The complex included the somatic portion, (formed by multipolar motor neurons), and the parasympathetic portion, (formed by oval or fusiform preganglionic cells), on each side of the median 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 (X = 2.4 x 1.2 mm) in transverse section. It was divided into the principal, intrafascicular and extrafascicular parts. The principal part was subdivided into the dorsal, intermediate and ventral portions. Isolated multipolar neurons were also found in the periaqueductal gray matter, 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. The Edinger-Westphal nucleus consisted of the rostral, ventral and dorsal parts; the longest rostrocaudal diameter of this nucleus measured 7.1 mm. The anatomical data of our study are relevant clinically and allow explanation of the neurologic signs following complete or partial lesions of the oculomotor nuclear complex.