Article Sections

Introduction

Extrapyramidal symptoms (EPS) are movement disturbances caused by dopamine receptor blockers (eg, antipsychotics, metoclopramide, prochlorperazine).  EPS include acute dystonia, akathisia, drug-induced parkinsonism, tardive dyskinesia (TD), and withdrawal-emergent dyskinesia.  Acute dyskinesia (eg, acute dystonia, akathisia) typically presents within a few hours or days after initiation/dose increase of a dopamine receptor blocker, whereas TD and withdrawal-emergent dyskinesia present much later (usually >6 months later).

Pathogenesis and risk factors

The nigrostriatal pathway is a major dopaminergic pathway in the brain and plays a critical role in motor control ( Figure 1).  It is a component of the basal ganglia ( Figure 2), which is part of the extrapyramidal system (ie, does not involve the corticospinal [pyramidal] tract).  Normally, the inhibitory effects of dopaminergic neurons are balanced by the excitatory actions of muscarinic cholinergic neurons. 

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