Extrapyramidal symptoms
Extrapyramidal symptoms are a time-ordered family of movement disorders caused by dopamine D2 receptor blockade from antipsychotics or antiemetics: acute dystonia within hours to days, akathisia within days to weeks, drug-induced parkinsonism within days to months, and tardive dyskinesia after months to years. Diagnosis is clinical; treatment is syndrome-specific, from intramuscular benztropine for dystonia to a vesicular monoamine transporter 2 (VMAT2) inhibitor such as valbenazine for tardive dyskinesia.
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What this article covers
- Overview
Definition: extrapyramidal symptoms (EPS) are drug-induced movement disorders caused by dopamine D2 receptor blockade in the nigrostriatal pathway, most often from antipsychotics and, less commonly…
- Epidemiology
Antipsychotic class drives risk: high-potency first-generation antipsychotics (haloperidol, fluphenazine, trifluoperazine, pimozide) carry a substantially higher risk of extrapyramidal symptoms than…
- Risk factors
High-potency first-generation antipsychotics: haloperidol, fluphenazine, trifluoperazine, and pimozide carry the greatest extrapyramidal symptom burden of any class.
- Pathophysiology
Nigrostriatal D2 blockade is the shared mechanism: the nigrostriatal dopamine pathway supports smooth motor control; blocking D2 receptors there reduces dopaminergic tone and produces the acute and…
- Clinical features
Acute dystonia (hours to days): sudden, prolonged, painful tonic muscle spasm, most often torticollis (neck), oculogyric crisis (sustained upward eye deviation), trismus, or laryngeal or pharyngeal spasm causing difficulty swallowing.
- Differential diagnosis
Neuroleptic malignant syndrome: fever, rigidity, autonomic instability, and elevated creatine kinase, absent in the isolated movement findings here; can occur at any time, not on a fixed timeline.
- Diagnosis
The diagnosis is clinical: it rests on recognizing the characteristic movement pattern in temporal relationship to starting, increasing, or switching a dopamine-blocking agent; no laboratory test or…
- Management
First, identify which syndrome is present and treat it specifically, since the four syndromes do not share a treatment: give benztropine 1-2 mg IM or IV as a single dose for acute dystonia, or…
- Complications
Airway compromise: laryngeal or pharyngeal dystonia can impair swallowing and, rarely, breathing, making acute dystonia a true urgency.
- Prognosis
Acute dystonia resolves rapidly with anticholinergic treatment, typically within minutes of an IM or IV dose.
- Prevention
Prefer second-generation antipsychotics over high-potency first-generation agents when clinically appropriate, since they carry a substantially lower risk across the whole extrapyramidal symptom spectrum, including tardive dyskinesia.
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