The extrapyramidal system can be affected in a number of ways, which are revealed in a range of extrapyramidal symptoms (EPS), also known as extrapyramidal side-effects (EPSE), such as akinesia (inability to initiate movement) and akathisia (inability to remain motionless).
Extrapyramidal symptoms (EPS) are various movement disorders such as acute dystonic reactions, pseudoparkinsonism, or akathisia suffered as a result of taking dopamine antagonists, usually antipsychotic (neuroleptic) drugs, which are often used to control psychosis.
The Simpson-Angus Scale (SAS) and the Barnes Akathisia Rating Scale (BARS) are used to measure extrapyramidal symptoms.[1] Extrapyramidal symptoms are also usually present in patients with neuroleptic malignant syndrome.
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The most common antipsychotic associated with EPS is haloperidol used especially in schizophrenia. Other antidopaminergic drugs like the antiemetic metoclopramide or the tricyclic antidepressant amoxapine can also cause extrapyramidal side-effects.
Extrapyramidal symptoms can also be caused by brain damage, as in athetotic cerebral palsy, which is involuntary writhing movements caused by prenatal or perinatal brain damage.
Anticholinergic drugs are used to control neuroleptic-induced EPS, although akathisia may require beta blockers or even benzodiazepines. If the EPS are induced by an antipsychotic, EPS may be reduced by dose titration or by switching to an atypical antipsychotic, such as aripiprazole, ziprasidone, quetiapine, olanzapine, risperidone, or clozapine. These medications possess an additional mode of action that is believed to negate their effect on the nigrostriatal pathway, which means they are associated with fewer extrapyramidal side-effects than "conventional" antipsychotics (chlorpromazine, haloperidol, etc.).
Commonly used medications for EPS are benztropine (Cogentin), diphenhydramine (Benadryl), and trihexyphenidyl (Artane).