Bottom Line:
NMS (neuroleptic malignant syndrome) is a potentially life threatening condition thought to be caused by blockade of the dopamine D2 receptor pathway. SS (serotonin syndrome) is also a potentially life threatening condition associated with increased serotonergic activity. Both conditions result in mental status changes, fever, dysautonomia (autonomic dysfunction), leukocytosis, and neuromuscular symptoms. Both conditions have a wide array of possible presentations, and both conditions are clinical diagnoses (lab tests do not confirm the diagnosis).
Generally speaking, SS has a more rapid onset (symptoms present within 24 hours of starting a drug or changing a dose) whereas NMS takes several days or weeks to appear. SS involves neuromuscular hyperactivity (e.g. clonus, hyperreflexia) whereas NMS involves bradykinesia (typically “lead-pipe” rigidity). In SS the clonus can involve the eyes and pupils can be dilated, neither of which occur in NMS. Both NMS and SS cause hyperthermia, but shivering is apparently unique to SS.
Treatment is similar for both conditions. Remove the offending agent and provide supportive care to normalize vital signs and prevent renal damage. Sedation with benzodiazepines may be considered. Resolution of the syndrome with treatment occurs over hours with SS, but can take days to weeks with NMS.
Memory Aids:
NMS – FALTER
F – Fever
A – Autonomic instability
L – Leukocytosis
T – Tremor
E – Elevated enzymes (CPK, LDH, AST, ALT)
R – Rigidity
SS – SHIVERS
(this is taken from an article by Christensen in Current Psychiatry)
S – Shivering (is apparently one symptom that distinguishes SS from other hyperthermic conditions)
H – Hyperreflexia (especially in lower extremities)
I – Increased temperature
V – Vital sign instability
E – Encephalopathy
R – Restlessness
S – Sweating (anticholinergic toxicity, in contrast, has a similar presentation, but with hot, dry skin) Continue reading “NMS VS SS”
