A patient on antipsychotic medication develops an abnormal involuntary movement. Before revealing the answer, decide what distinguishes tardive dyskinesia from acute dystonia.

Ask about the timing of onset and the quality of the movement. Tardive dyskinesia has a later, more gradual onset, typically after months or years of antipsychotic exposure, and consists of repetitive, purposeless oral and facial movements. Acute dystonia, by contrast, arises early in treatment, often within days or after a dose increase, and presents as a sudden, sustained muscle spasm rather than a repetitive movement pattern. The two also differ in urgency: acute dystonia is a dramatic, often frightening presentation requiring prompt treatment, while tardive dyskinesia develops slowly and is typically more persistent once established. Timing relative to treatment, together with spasmodic versus repetitive quality, is the key distinguishing pair of features.