Neuroleptic Malignant Syndrome (NMS)

Neuroleptic Malignant Syndrome (NMS) Information

Neuroleptic Malignant Syndrome (NMS) is an uncommon but potentially fatal complication of antipsychotic and neuroleptic drug treatment. Its defining features include elevated body temperature, muscle rigidity, changes in mental state and abnormal vital signs. Although NMS is uncommon, the widespread use of antipsychotic drugs suggests that the absolute number of cases is not insignificant. Because it occurs infrequently, individual practitioners may have limited experience in diagnosing and treating NMS.

What drugs are associated with Neuroleptic Malignant Syndrome (NMS)?

Neuroleptic Malignant Syndrome (NMS) has been associated mostly with neuroleptic or antipsychotic drugs. These drugs have been essential in improving the lives of people with severe mental illness and are safely tolerated by the majority of patients. Newer drugs in this class may have even fewer side effects. However, NMS is not seen only in psychiatric patients. Other similar drugs used in medicine in the treatment of gastrointestinal complaints, sedation, or neurologic disorders have also been associated with NMS on rare occasions.

What are the Symptoms of Neuroleptic Malignant Syndrome (NMS)?

The defining features of Neuroleptic Malignant Syndrome (NMS) may develop dramatically within hours or insidiously over several days. NMS is diagnosed by the development of muscle rigidity and elevated temperature following the administration of antipsychotic medication. Additional features include changes in mental state (obtundation, catatonia), vital signs (tachycardia, unstable blood pressure), and extrapyramidal function (tremors, dysarthria, dysphagia, drooling). Associated laboratory findings include increased white blood cell counts, elevated blood enzymes, like creatine phosphokinase, and arterial blood-gas abnormalities.

What are the Incidence and Risk Factors of Neuroleptic Malignant Syndrome (NMS)?

The exact incidence of Neuroleptic Malignant Syndrome (NMS) is unknown, but several large studies suggest that the incidence rate is about 0.2%. This suggests that one in 500 to 1,000 patients treated with antipsychotics may develop NMS. There are no proven risk factors for NMS that outweigh the benefits of prescribing antipsychotic medication or identify patients at risk. However, dehydration, agitation, mood disorders, catatonia, organic brain syndromes, drug or alcohol withdrawal states, and the use of rapid dose escalation and drugs given by injection have been suggested as contributing to the risk of NMS.

What is the Treatment for Neuroleptic Malignant Syndrome (NMS)?

It is essential to recognize signs of Neuroleptic Malignant Syndrome (NMS) early and discontinue antipsychotic medications. Intensive medical and nursing care are critical. These measures are probably effective in many cases. There are essentially no comparative, prospective, randomized clinical trails of specific remedies. Nevertheless, several agents may be administered empirically, based on the severity, character and duration of symptoms in an individual patient. Opinions vary, but dopamine agonists (bromocriptine, amantadine), benzodiazepines (lorazepam) and dantrolene have been advocated, particularly in severe cases. Electroconvulsive therapy (ECT) has also been used successfully. About one-third of patients may be at risk for a subsequent episode, but the majority of patients may be treated safely with antipsychotics after complete recovery from NMS, provided they are carefully monitored.

Neuroleptic Malignant Syndrome (NMS) Differential Diagnosis

A broad range of conditions may resemble Neuroleptic Malignant Syndrome (NMS), some of which are themselves life-threatening. These include acute encephalitis and structural brain lesions resulting from tumors, stroke, abscesses, or head trauma. Patients with schizophrenia or mania who are not receiving antipsychotics may develop an NMS-like condition called malignant catatonia. Systemically, causes of fever such as infections and dehydration must be ruled out or treated. Thyrotoxicosis, pheochromocytoma, vasculitides, and heatstroke must be considered. Finally, other drugs used in medicine and psychiatry may produce a similar syndrome including inhaled anesthetics, succinylcholine, withdrawal from dopamine agonists, alcohol or sedative withdrawal, atropinic drugs, stimulants and psychedelic drugs, salicylates, and serotonergic agents. Careful diagnostic evaluation is important in distinguishing these conditions.

Additional Neuroleptic Malignant Syndrome (NMS) Information

Despite the wealth of clinical data on Neuroleptic Malignant Syndrome (NMS), controversies abound. Although research criteria have been proposed, a number of fundamental questions remain to be resolved: which patients are at risk; is dose or potency related; are newer antipsychotic drugs less likely to cause NMS; are patients best treated with dopamine agonists, benzodiazepines, dantrolene, or supportive therapy alone; is ECT the best treatment for all NMS patients; what is the risk of rechallenge; and how does NMS relate to other drug-induced disorders?