Neuroleptic Malignant Syndrome: Lecture Notes
Definition and Clinical Significance
- Neuroleptic malignant syndrome (NMS) is a life-threatening syndrome associated with dopamine antagonism or abrupt withdrawal of dopaminergic therapy.
- Suspect NMS when relevant medication exposure is followed by:
- Fever
- Generalized lead-pipe rigidity
- Altered mental status
- Autonomic instability
Triggers and Risk Factors
- Relevant triggers include:
- Antipsychotics
- Metoclopramide
- Prochlorperazine
- Promethazine
- Abrupt withdrawal of dopaminergic therapy
- Factors that increase risk include:
- Rapid dose escalation
- Dehydration
- Agitation requiring intramuscular injections
- Neurologic disease
Diagnosis and Differential Diagnosis
- NMS is a clinical diagnosis. No laboratory test confirms it.
- Levenson criteria use fever and rigidity plus at least 2 additional features:
- Altered mental status
- Tachycardia
- Tachypnea
- Leukocytosis
- Elevated creatine kinase (CK)
- Obtain a medication history while evaluating competing immediately life-threatening diagnoses.
- Key differential diagnoses:
- Serotonin syndrome: commonly develops within minutes to hours after exposure and features hyperreflexia and spontaneous or inducible clonus.
- NMS: commonly evolves over days to weeks, with reduced reflexes and no clonus.
- Malignant hyperthermia: follows anesthetic exposure.
Evaluation and Monitoring
- Obtain and monitor:
- CK
- Renal function
- Urine output
- Electrolytes
- Acid-base status
- Electrocardiogram (ECG)
- Rhabdomyolysis may cause myoglobinuria, acute kidney injury, hyperkalemia, hyperphosphatemia, hypocalcemia, and arrhythmias.
- A urine dipstick positive for blood without red blood cells may indicate myoglobin, not hematuria alone.
Immediate Management
- Stop all antipsychotics and other dopamine antagonists immediately.
- Begin supportive care in parallel:
- Intravenous hydration
- Active cooling
- Cardiorespiratory monitoring
- Serial temperature, CK, renal function, electrolytes, and urine-output assessment
- Benzodiazepines are listed as first-line medication for agitation and muscle relaxation.
Escalation and Disposition
- If response is inadequate, the local source lists dantrolene or bromocriptine as escalation options.
- Amantadine or dopamine replacement are listed as adjunctive choices.
- Severe rigidity with respiratory compromise may require intubation and neuromuscular paralysis.
- Refractory cases may require electroconvulsive therapy.
- Suspected NMS warrants hospital admission, typically intensive care.
Clinical Pitfalls and Takeaway
- Avoid delayed recognition.
- Do not treat fever without removing the trigger.
- Avoid anchoring on infection before considering NMS.
- Medication choices and doses require review against current institutional toxicology, pharmacy, and critical-care protocols.
This educational summary does not establish medication dosing or replace institutional protocols.
