Acute Dystonia — MRCPsych Paper B MCQ

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EasySchizophrenia & PsychosisAcute DystoniaMRCPsych Paper B

A 38-year-old man with schizophrenia develops sustained involuntary contraction of his neck muscles, pulling his head to one side, 2 hours after his first dose of haloperidol. He is afebrile with normal observations and no generalised rigidity. Which adverse effect is this?

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Correct answer: D — Acute dystonia

Explanation lettering: E = shown as C · C = shown as E

The correct answer is D, acute dystonia. Sustained involuntary contraction of the neck muscles producing torticollis within hours of a first dose of a high-potency first-generation antipsychotic is the classic presentation; other forms include oculogyric crisis, trismus, tongue protrusion and opisthotonus, and young men are at higher risk. It responds rapidly to an anticholinergic such as procyclidine. Akathisia (B) is a subjectively distressing restlessness with an inability to keep still, not a fixed contraction. Antipsychotic-induced parkinsonism (C) causes tremor, rigidity and bradykinesia, usually emerging over days to weeks. Tardive dyskinesia (A) follows prolonged exposure and typically produces repetitive oro-bucco-lingual choreiform movements, incompatible with onset 2 hours after a first dose. Neuroleptic malignant syndrome (E) features generalised rigidity, hyperthermia, autonomic instability and altered consciousness, all explicitly absent here.

Reference: Electronic Medicines Compendium, HALDOL 2 mg/ml oral solution, Summary of Product Characteristics, section 4.4 (Extrapyramidal symptoms/acute dystonia). https://www.medicines.org.uk/emc/product/15252/smpc