PARALYSIS WITH HYPOTONICITY AND HYPERREFLEXIA SUBSEQUENT TO SECTION OF BASIS PEDUNCULI IN MONKEYS

Abstract

Tower has demonstrated that the inhibitory motor pathway presumably arising from cortical area 4s in the monkey does not course through the medullary pyramid. Further information may be gained by observing the effect of destruction of the efferent cortical paths at higher levels. In the present investigation the basis pedunculi was selected. The results of routine neurological examination showed that interruption of the basis pedunculi in this series of six monkeys gives rise to a paralysis which is intermediate between spastic paralysis and hypotonic paresis. This paralysis is characterized by hypotonicity of all muscle groups, excepting the extensors of the digits, by hyperactive deep reflexes and by the absence of clonus. This leads to the assumption that inhibitory pathways descending from the cerebral cortex do not course entirely within the basis pedunculi. Fibers whose interruption is responsible for the phenomena of hypertonicity and clonus, have, for the most part, deviated from the cortico-spinal projection prior to reaching the cerebral peduncle. Those whose interruption leads to hyperreflexia accompany the cortico-spinal projection while passing through the cerebral peduncle but deviate before reaching the pyramids.