extrapyramidalism

Extrapyramidalism refers to disorders of movement arising from dysfunction of extrapyramidal motor pathways, which involve the basal ganglia and related structures outside the pyramidal tracts. It is typically used to describe drug-induced or disease-related motor symptoms that are distinct from weakness or spasticity due to pyramidal tract disease.

Most commonly, extrapyramidal symptoms arise from dopamine blockade in the nigrostriatal pathway, especially with antipsychotic medications (typical and, to a lesser extent, atypical) and antiemetics such as metoclopramide and prochlorperazine. Other causes include neurodegenerative disorders (such as Parkinson's disease or multiple system atrophy), metabolic disturbances, and toxins. The underlying mechanism is an imbalance between dopamine and acetylcholine within the basal ganglia.

The major syndromes are acute dystonia (sustained muscle contractions), akathisia (subjective restlessness), drug-induced parkinsonism (bradykinesia, rigidity, tremor), and tardive dyskinesia (involuntary, often repetitive movements such as facial grimacing or tongue movements). Tardive dyskinesia commonly emerges after months of treatment and can be persistent, sometimes continuing after the offending drug is withdrawn.

Diagnosis is clinical, often aided by standardized scales such as the Abnormal Involuntary Movement Scale (AIMS). Management focuses on minimizing exposure to offending drugs, switching to agents with lower extrapyramidal risk, and symptom-targeted therapies: anticholinergics for dystonia and parkinsonism, beta-blockers or benzodiazepines for akathisia, and vesicular monoamine transporter 2 (VMAT2) inhibitors such as valbenazine or deutetrabenazine for tardive dyskinesia. Regular monitoring and patient education are recommended.