Neuroleptic Malignant Syndrome

Neuroleptic Malignant Syndrome (NMS) is a rare, but potentially fatal adverse reaction to neuroleptic or antipsychotic medication. It is characterized by muscle rigidity, fever, autonomic dysfunction, and altered mental status. It generally occurs within days or weeks after the initiation of treatment with a neuroleptic or antipsychotic medication. However, it can occur during dose reduction or discontinuation of the medication. The exact cause of NMS is unknown, but it is believed to involve an excessive dopamine blockade. Symptoms typically begin suddenly and include high fever, confusion, agitation, and stiff muscles. Muscle rigidity is often symmetric and can involve multiple muscle groups but is usually most prominent in the neck and trunk. Hyperpyrexia and tachycardia often accompany the rigidity. The autonomic dysfunction may take the form of aggressive diaphoresis, labile blood pressure, and urinary incontinence. Rhabdomyolysis, kidney failure, catatonia, and coma are potential complications. Diagnosis of NMS is based on the clinical presentation, including the presence of appropriate signs and symptoms, and the use of a neuroleptic or antipsychotic drug. Laboratory tests may be used to determine if a metabolic derangement is present. However, absent laboratory confirmation, diagnosis is based on clinical suspicion and the gradual resolution of symptoms with drug withdrawal. Treatment of NMS is aimed at reversing the physiological effects of the drug and reversing the condition itself. The neuroleptic or antipsychotic drug causing the condition must be discontinued immediately. If present, fever can be controlled with antipyretics and benzodiazepines may be used to reduce muscular rigidity. Intravenous fluids and electrolytes, antibiotics, and cooling blankets may also be used. In severe cases, bromocriptine and/or dantrolene may be administered to decrease dopamine blockade.