The differential diagnosis of tardive dyskinesia.

The evaluation, diagnosis, and treatment of involuntary hyperkinetic movements can be a difficult challenge. A thorough history, including past and present drug use, and a complete physical, neurological, and psychiatric examination, accompanied by appropriate laboratory tests, are often necessary to make the correct differential diagnosis of dyskinesias. Movement disorders in psychiatric patients are usually related to neuroleptic medicines. Extrapyramidal syndromes related to starting these drugs include dystonia, akathisia, and parkinsonism, whereas dyskinesia occurs late in the course of the treatment. Involuntary movements may, however, be idiopathic, be caused by many other drugs, or occur as part of psychoses, hereditary neurodegenerative diseases, or other medical illnesses.