Extrapyramidal System

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extrapyramidal system

[¦ek·strə‚pir·ə′mid·əl ′sis·təm]
Descending tracts of nerve fibers arising in the cortex and subcortical motor areas of the brain.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Extrapyramidal System


a group of brain structures in the hemispheres and brainstem involved in the central control of movements without the participation of the corticospinal, or pyramidal, system.

From the standpoint of evolution the extrapyramidal system is the most ancient system of motor control. It consists of the basal ganglia, red and interstitial nuclei, tectum, substantia nigra, reticular formation of pons varolii and medulla oblongata, nuclei of the vestibular system, and cerebellum. Some structures of the extrapyramidal system do not proceed directly to the spinal motor centers. Others are connected by conducting pathways to the segmental levels of the spinal cord, where they serve as an essential switching station for impulses traveling from the brain to moto-neurons. The impulses that travel along the fibers of the extrapyramidal system can reach the motoneurons through direct mono-synaptic connections or by switching in the various interneurons of the spinal cord.

The extrapyramidal system plays an important role in the coordination of movements, locomotion, and maintenance of posture and muscle tone. It is closely associated with the control of truncal muscles and proximal portions of the limbs. It is also involved in emotional manifestations, for example, laughing and crying. Injury to the pyramidal system decreases muscle tone and impairs motor functions (causing, for example, hyperkinesia and parkinsonism).


Kostiuk, P. G. Struktura i funktsiia niskhodiashchikh sistem spinnogo mozga. Leningrad, 1973.
Shapovalov, A. I. Neirony i sinapsy supraspinal’nykh motornykh sistem. Leningrad, 1975.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Commonly Observed Adverse Reactions: The most common adverse reactions (incidence [greater than or equal to] 5%, in either dose group, and at least twice the rate of placebo) in patients treated with LATUDA were akathisia, extrapyramidal symptoms, somnolence, nausea, vomiting, diarrhea, and anxiety.
Side Effects Noted in Studies of Risperidone in Children Side Effect Percentage or Range Weight gain 1.1 to 15.3 kg Increased appetite 15 to 31.8% Decreased appetite < 12.5% Nausea/vomiting 8 to 33% Gastrointestinal 18 to 29% Fatigue/Drowsiness !i 42 to 72.5% Insomnia 15 to 22% Fever/febrile seizure 15 to 34.2% Headache 18 to 50% Dizziness < 16% Drooling < 27% Dystonic/Dyskinesias 12 to 15.4% Extrapyramidal Symptoms < 27.5% Enuresis 12.5 to 31% Upper Respiratory Symptoms 15 to 51% Anxiety < 24% Tachycardia < 12.5% Increased prolactin levels 13.2 to 65% Sources: Malone et al.
Other adverse effects associated with specific antipsychotics include extrapyramidal symptoms, sedation, increased prolactin secretion, weight gain, and other metabolic abnormalities.
Like to the literature dystonia was the dominant extrapyramidal symptom in our patient (9).
Rather, it is important to differentiate them from extrapyramidal symptoms such as tardive dyskinesia and vocal tics, especially in adolescent patients.
Adverse reactions occurring in at least 5% of the study population and at a rate of twice that in the placebo groups were extrapyramidal symptoms, akathisia, dyspepsia, vomiting, somnolence, and restlessness in the bipolar group.
Decreased biliary copper excretion and reduced incorporation of copper into apoceruloplasmin caused by defunctionalization of ATP7B protein lead to accumulation of copper in many tissues and organs, including liver, brain, and cornea, finally resulting in liver disease and extrapyramidal symptoms. It is the most common genetic neurological disorder in the onset of adolescents, second to muscular dystrophy in China.
Patients with Parkinson's Disease or Dementia with Lewy Bodies are reported to have an increased sensitivity to antipsychotic medication, Manifestations of this increased sensitivity include confusion, obtundation, postural instability with frequent falls, extrapyramidal symptoms, and clinical features consistent with the neuroleptic malignant syndrome.
The first case of FD with a pure and presenile dementia without either extrapyramidal symptoms or metabolic abnormalities has been reported by Modrego and coworkers.
During the first week of treatment her dosage was increased to 10 mg/d but at this dose she experienced akathisia and other extrapyramidal symptoms. Adjunctive treatment with trihexyphenidyl 6 mg/d only partially ameliorated this adverse effect.
29, 2008, identified 69 cases of neonatal extrapyramidal symptoms (EPS) or withdrawal associated with different antipsychotics, with symptoms that varied in severity.

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