Neuroleptic Malignant Syndrome (NMS)

Summary

Neuroleptic malignant syndrome, or NMS, is a rare but serious reaction that can be caused by antipsychotic medications. NMS is more likely to be seen with typical antipsychotics than atypical antipsychotics. It is a medical emergency that carries a risk of death if not promptly identified and treated.

Clinical features of NMS include "lead pipe" muscle rigidity, which can cause muscle breakdown leading to increased creatine kinase and increased myoglobin levels. Patients often have altered mental status with confusion as a common symptom. In addition, autonomic dysfunction is common, manifesting as a fever, sweating, rapid heart rate, and high blood pressure.

Treatment of NMS involves immediately stopping the causative antipsychotic medication. Medications like bromocriptine and amantadine, benzodiazepines, and the muscle relaxant dantrolene can be used to manage symptoms.

Key Points

• Neuroleptic Malignant Syndrome (NMS)
  • Definition
    • Life-threatening medical emergency
    • Caused by antipsychotics (neuroleptics)
      • Typical antipsychotics (1st Generation) more likely than atypical antipsychotics (2nd and 3rd Generation) to cause NMS
  • Clinical Features
    • Autonomic Dysfunction
      • Fever
      • Sweating (diaphoresis)
      • Tachycardia
      • Hypertension
    • Altered mental status (encephalopathy)
      • Confusion, stupor, coma (severe cases)
    • Muscle rigidity (“lead pipe” rigidity)
      • This is one of the hallmark signs that differentiates it vs. serotonin syndrome
      • ↑ myoglobin
      • ↑ creatine kinase (CK)
  • Treatment
    • Dantrolene
      • Muscle relaxant
    • Bromocriptine
      • Dopamine agonist
    • Amantadine
      • Dopamine agonist typically used to treat Parkinson’s disease that is also used off-label to treat NMS
    • Benzodiazepines
    • Stop antipsychotic medication