Neuroleptic Malignant Syndrome (NMS)

Definition:
Neuroleptic Malignant Syndrome (NMS) is a rare, potentially life-threatening condition associated with the use of antipsychotic medications. It shares clinical features with Malignant Hyperthermia (MH) but has distinct causes and pathophysiology.

Key Features:

• Triggers:
  • Antipsychotic medications, including phenothiazines, clozapine, risperidone, and other dopamine antagonists.
  • It can also occur with abrupt withdrawal of dopamine agonists.
• Symptoms:
  • Neurological: Muscle rigidity, altered consciousness ranging from agitation to stupor.
  • Systemic: High fever, tachypnea, tachycardia, hypertension, and diaphoresis.
  • Laboratory Findings: Elevated serum creatine kinase (CK), indicating rhabdomyolysis, which may lead to renal failure.
• Time Course:
  • Symptoms develop over hours to days, slower than Malignant Hyperthermia.

Differential Diagnosis:

• Serotonin Syndrome:
  • Similar features caused by excessive serotonin activity, typically due to selective serotonin reuptake inhibitors (SSRIs).
  • Differentiation is essential as treatments vary.
• Malignant Hyperthermia:
  • Triggered by specific anesthetics and muscle relaxants.
  • Onset is usually rapid during surgery or the postoperative period.

Complications:

• Rhabdomyolysis: Can result in acute renal failure.
• Cardiac Arrhythmias: Secondary to autonomic dysregulation.
• Disseminated Intravascular Coagulation (DIC): Rare but severe.

Management:

• Immediate Interventions:
  • Discontinue the triggering medication immediately.
  • Initiate active supportive care, including hydration, temperature control, and correction of electrolyte imbalances.
• Pharmacological Treatments:
  • Dopamine Agonists: Bromocriptine or amantadine to counteract dopamine blockade.
  • Muscle Relaxants: Dantrolene to alleviate rigidity and hypermetabolic state.
  • Adjunctive Medications: Levodopa and benzodiazepines may help in selected cases.
• Supportive Care:
  • Monitor for and manage complications like renal failure and arrhythmias.
  • Intensive care unit (ICU) support is often required for severe cases.

Prognosis:

• Early recognition and treatment significantly improve outcomes. Delayed diagnosis can lead to severe complications and increased mortality.