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.

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 ?
Therefore, benefits with antipsychotics, such as risperidone and aripiprazole, must be weighed against potential long-term risks of treatment, including sedation, weight gain, metabolic syndrome, and extrapyramidal side effects.
Extrapyramidal side effects (EPSEs) are more commonly associated with the typical antipsychotics.
Aripiprazole###15-30###Lesser propensity to cause sedation, extrapyramidal side effects
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Background: Atypical antipsychotics are the drugs of first line treatment in schizophrenia because compared to typical antipsychotics, they have minimum extrapyramidal side effects and hence better tolerance by the patients resulting in better compliance.
Atypical antipsychotics (olanzapine, risperidone, quetiapine) are increasingly being used to treat delirium because they have fewer extrapyramidal side effects.
In my opinion, most of the SGAs, which included in order of appearance: Risperdal, Zyprexa, Seroquel, Geodon, Abilify, and Invega, reduced the risk of extrapyramidal side effects like tremors and stiffness.
In addition to covering classes of psychiatric medications, the book also covers agents for treating extrapyramidal side effects, drugs of abuse, treatments for substance use disorders, new unapproved treatments for psychiatric disorders, and herbal and natural products.
Akinesia, and other extrapyramidal side effects of antipsychotics without tremors with accompanying low mood or dysphoria can also mimic depression, and termed as 'akinetic depression' (20).
Data from preclinical and Phase 1 studies demonstrated that the compound may retain the efficacy of currently available typical and atypical antipsychotic drugs while achieving a much higher safety profile as evidenced by a lack of metabolic or extrapyramidal side effects.
However, Didriksen and Christensen (1993) argued that the suppression of schedule-induced polydipsia by dopamine blockers is not due to the induction of extrapyramidal side effects, because that suppression was not antagonized by scopolamine (an anticholinergic drug used to counteract neuroleptic-induced dystonia) or by diazepam (a benzodiazepine used to counteract akathisia).

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