Neuroleptic Malignant Syndrome

Today we had a great case of NMS that lead to discussion about the differential and the causes:

What is NMS?

  • Life threatening neurologic emergency associated with the use of neuroleptic agents and characterized by mental status changes, rigidity, fever and dysautonomia
  • Mostly commonly seen with the “typical” high potency agents (haldol and fluphenazine) but also seen in atypical anti-psychotic class and with anti-emetics (metoclopramide – reglan, promethazine – phenergan and prochlorperazine- compazine)
  • Symptoms:
    • Mental status changes (82%) – often presenting as agitated delirium but may lead to profound encephalopathy and eventual coma
    • Muscular rigidity – generalized increased tone and “lead pipe rigidity”
    • Hyperthermia – defining symptom wtih temperatures > 38 in 87% of cases and >40 in 40% of cases
    • Autonomic instability – tachycardia, labile or elevated BP and tachypnea. Often with dysrhythmias and profuse diaphoresis.
  • Differential diagnosis:
    •  Serotonin Syndrome – similar presentation to NMS
      • More likely to be seen in SS – shivering, hyper-reflexia, myoclonus and ataxia with prodrome of N/V and diarrhea
      • More likely to be seen in NMS – rigidity  and severe hypertheramia
    • Malignant hyperthermia – rare genetic disorder occurring with the use of potent halogenated inhalational anesthetics agents and succinylcholine
      • Clinically similar in that it presents with hyperthermia, muscle rigidity and dysautonomia
    • Also consider anti-cholinergic toxicity, cocaine, ecstasy, PCP or amphetamine intoxication, CNS infection, heat stroke, thyrotoxicosis
  • Treatment: stop offending agent, treat supportively (ICU care, cool patient, tx dehydration and correct electrolyte imbalances) and medically with dantrolene, bromocriptine or amantadine.