What is the role of the pyramidal and extrapyramidal systems in the pathophysiology of tardive dyskinesia (TD)?

Updated: Oct 17, 2018
  • Author: James Robert Brasic, MD, MPH; Chief Editor: Selim R Benbadis, MD  more...
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The pyramidal system, controlling voluntary movements, includes precise anatomic pathways from the cortex to muscle. Voluntary movements through the pyramidal systems are visible. An example of a classic disorder of the pyramidal system is a stroke, resulting in paralysis of an extremity.

Corticospinal lesions above the pyramidal decussation typically result in paralysis of volitional movements of the contralateral half of the body and a fixed posture with flexion of the upper extremity and extension of the lower extremity. Bilateral corticospinal lesions of the upper pons and midbrain typically cause extension of all 4 extremities and decerebrate rigidity with dorsiflexion of the cervical and thoracolumbar spine. Unilateral lesions of the upper pons and midbrain often result in extension of the ipsilateral arm and leg.

By contrast, extrapyramidal motor activities result in automatic movement and static, postural movement activities that are not noticeable (see Table 1 below). The extrapyramidal system includes theorized connections within the basal ganglia, the striatopallidonigral system, and other structures of the central nervous system that contribute to the regulation of movement, including related brainstem nuclei and the cerebellum.

Table 1. Classic Characterization of Pyramidal and Extrapyramidal Systems (Open Table in a new window)





Precisely demarcated pathways from cortex to muscle

Hypothesized pathways among basal ganglia and other structures of the central nervous system

Physiologic movements



Pathologic movements

Paralysis, paresis, hyperreflexia, and spasticity

Akathisia, athetosis, ballismus, chorea, dystonia, myoclonus, stereotypy, tic, and tremor

Classic disorders of the extrapyramidal system include a variety of involuntary movement disorders. Some of these movement disorders include dyskinesias such as akathisia, chorea, dystonia, myoclonus, stereotypy, tic, and tremor.

The pathophysiology of extrapyramidal disorders has been disputed on the grounds that some of these disorders may not involve lesions of the basal ganglia and, in addition, may not be involuntary. Because of the problems inherent in the concept of the extrapyramidal system, caution must be exercised in the classification of movement disorders as EPSs, and new approaches to the classification of movement disorders may be helpful.

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