EXPERIMENTAL AND HISTOLOGICAL STUDY OF MIDBRAIN DYSKINESIAS

Abstract

Neurological changes consecutive to lesions of the tegmental area of the upper pons and midbrain are correlated with the histological study of the same lesions in 20 monkeys (Macaca mulatta). Hypotonia is related to the interruption of the ventral component of the brachium conjunctivum and hypokinesia to the involvement of the same structure in association with the interruption of nigral efferent fibers. Sustained postural tremor of the limbs is related to the combined interruption of nigral efferent fibers and the corresponding rubro-tegmento-spinal system without excluding the ventral component of the brachium conjunctivum. Sustained postural tremor at the level of the head might depend on the concomitant interruption of nigral efferent fibers and the medial longitudinal fasciculus. Interruption of the efferent fibers from the substantia nigra resulted in a severe loss of the magnocel-lular elements of this structure. Ataxia and acting tremor are related to the involvement of the intermediate and dorsal components of the brachium conjunctivum.