Extrapyramidal System

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Related to extrapyramidal: akathisia, Extrapyramidal syndrome, Extrapyramidal effects

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.

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.


References in periodicals archive ?
The potential risk factors associated with the development of TD were reported as the presence of a past medical history of extrapyramidal symptoms, diabetes mellitus, affective disorders, female gender older age, and long-term therapy with neuroleptics at higher dosages (9).
In this study, treatment was associated with a higher incidence of akathisia and extrapyramidal symptoms, but it was not associated with a mean increase in weight or metabolic parameters or with prolactin increase or QTc prolongation, she noted.
The analysis further demonstrated that iloperidone had a favorable safety profile, most notably with regard to extrapyramidal symptoms (EPS) and akathisia rates, weight and metabolic parameters, and prolactin levels.
Adult patients with schizophrenia: akathisia (8 percent vs 4 percent) -- Pediatric patients (13 to 17 years) with schizophrenia: extrapyramidal disorder (17 percent vs 5 percent), somnolence (16 percent vs 6 percent), and tremor (7 percent vs 2 percent) -- Adult patients with bipolar mania: constipation (13 percent vs 6 percent), akathisia (15 percent vs 3 percent), sedation (8 percent vs 3 percent), tremor (7 percent vs 3 percent), restlessness (6 percent vs 3 percent), and extrapyramidal disorder (5 percent vs 2 percent) -- Adult patients with agitation associated with schizophrenia or bipolar mania: nausea (9 percent vs 3 percent)
Special Considerations: Common adverse events in bipolar mania trials included somnolence and extrapyramidal symptoms, dizziness, and akathisia.
Amantadine HCI is indicated for use as an anti-viral, anti-Parkinson and treatment of drug induced extrapyramidal symptoms.
Extrapyramidal symptoms and sedation were the two adverse events that most frequently motivated switching from a first-generation agent.
The most common side effects that occurred with INVEGA were restlessness and extrapyramidal disorder (for example: involuntary movements, tremors and muscle stiffness).
Special Considerations: The most common side effects in trials included extrapyramidal symptoms, sleepiness, dyspepsia, nausea, abnormal vision, dizziness, and parkinsonism.
Amantadine is also utilized in the treatment of Parkinson's Disease and drug-induced extrapyramidal reactions.
The jury is out even about extrapyramidal motor side effects, which were once thought to be less of a risk with second-generation antipsychotics.