extrapyramidal
[eks″trah-pĭ-ram´ĭ-d'l] outside the pyramidal tracts.
extrapyramidal disease (
extrapyramidal syndrome) any of a group of clinical disorders marked by abnormal involuntary movements, alterations in muscle tone, and postural disturbances; the group includes
parkinsonism,
chorea,
athetosis, and others.
extrapyramidal system a functional, rather than anatomical, unit comprising the nuclei and fibers (excluding those of the pyramidal tract) involved in motor activities; they control and coordinate especially the postural, static, supporting, and locomotor mechanisms. It includes the corpus striatum, subthalamic nucleus, substantia nigra, and red nucleus, along with their interconnections with the reticular formation, cerebellum, and cerebrum; some authorities include the cerebellum and vestibular nuclei. Called also
extrapyramidal tract.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.