Differentiating the hyperthermic and movement toxidromes — neuroleptic malignant syndrome, serotonin syndrome, malignant hyperthermia, anticholinergic toxicity, sympathomimetic toxicity and acute dystonic reaction

FOR REGISTERED CLINICIANS Decision support only. The ranking is a prompt for structured thought, never a diagnosis — verify every dose against trust policy, the BNF and TOXBASE.
Hot · Agitated · Rigid

Six conditions,
told apart by four findings.

NMS, serotonin syndrome, malignant hyperthermia, anticholinergic toxicity, sympathomimetic toxicity and acute dystonia are routinely confused with one another. They separate cleanly on onset speed, muscle tone, reflexes, and whether the skin is wet or dry. Enter what you find; the ranking updates live.

Exclude first, in every case

Meningitis, encephalitis (including anti-NMDA receptor), sepsis, intracranial haemorrhage, non-convulsive status, thyroid storm, and hypoglycaemia. Malignant catatonia may be indistinguishable from NMS and can coexist with it. A toxidrome label is only safe once these are addressed — work the ABD algorithm alongside this page.

The discriminator field

Muscle tone against reflex response
Hyporeflexia Reflex response → Sustained clonus Normal tone Muscle tone ↑ Lead-pipe rigidity

Acute dystonia is plotted at mid-tone because its rigidity is focal and sustained — a fixed abnormal posture — rather than the generalised tone of NMS or MH. Click any condition to open it below.

Differentiator

Answer what you know — partial input still ranks

Ranked fit

Nothing entered yet. Start with drug exposure and onset — they carry the most weight.

Comparison matrix

Full reference — scroll horizontally

Rows marked in bold are the highest-yield discriminators at the bedside.