Table 3. Differential diagnosis and distinguishing features of neuroleptic malignant syndrome.

Differential diagnosis		Distinguishing features
Systemic causes
Environmental	Heatstroke	History of exposure to heat
Endocrine	Pheochromocytoma Thyroid emergencies – thyrotoxicosis	Significantly elevated catecholamines and metanephrines Absence of neuroleptic medication
Infections	Sepsis Central nervous system infections, e.g. brain abscess, meningitis, encephalitis	Prodromal of viral illness Presence of seizures
Toxins / Pharmacologic agents
Anaesthetics agents causing malignant hyperthermia Withdrawal from antiparkinsonian drugs, baclofen, alcohol Substance abuse – amphetamines, hallucinogens Serotonin syndrome		History of anaesthesia/surgery Positive toxicology/drug screen Presence of nausea, vomiting, diarrhea
Psychiatric/Neurological causes
Extrapyramidal side effects Nonconvulsive status epilepticus Midbrain structural lesions.		Absence of fever or leucocytosis Presence of hyperkinesia Absence of neuroleptic treatment