Extrapyramidal Mechanisms

Abstract

“Extrapyramidal lesions” and “lesions of the extrapyramidal system” are terms that have been used extensively in neurology for decades. They were proposed for those neurological motor disorders in which there are no clinical signs of pyramidal lesions or sensory disturbances. Such terms as “hyperkinesias” or “dyskinesias” are also frequently used in literature in reference to this group of syndromes. To a considerable extent, the term “dyskinesia” accurately reflects the clinical essence of this group of disorders, which are traditionally related to lesions of the extrapyramidal system. Ojemann and Ward (1973) emphasize that the term “dyskinesia” includes not only pathological involuntary movements but also related deviations of muscular tonicity such as rigidity, spasticity, changes in the activity (intensity) of voluntary movements, e.g., hypokinesia, and impaired associative movements.

The brain mechanism which performs involuntary. reflex movements has two additional parts. One of them inhibits the movementand the other increases it. . . .I. M. Sechenov, Reflexes of the Brain, 1863

We must identify individualreflex mechanisms wherever possible and yet strive to understand how these mechanisms are integrated into a functional whole. Wilder Penfield