Extrapyramidal symptoms

Extrapyramidal symptoms (EPS) are symptoms that are archetypically associated with the extrapyramidal system of the brain's cerebral cortex. When such symptoms are caused by medications or other drugs, they are also known as extrapyramidal side effects (EPSE). The symptoms can be acute (short-term) or chronic (long-term). They include movement dysfunction such as dystonia (continuous spasms and muscle contractions), akathisia (may manifest as motor restlessness),^[1] parkinsonism characteristic symptoms such as rigidity, bradykinesia (slowness of movement), tremor, and tardive dyskinesia (irregular, jerky movements).^[2] Extrapyramidal symptoms are a reason why subjects drop out of clinical trials of antipsychotics; of the 213 (14.6%) subjects that dropped out of one of the largest clinical trials of antipsychotics (the CATIE trial [Clinical Antipsychotic Trials for Intervention Effectiveness], which included 1460 randomized subjects), 58 (27.2%) of those discontinuations were due to EPS.^[3]