Dr. High Yield Psychiatry Practice Test

Both NMS and serotonin syndrome involve an autonomic storm with excessive motor activity, which can drive fever. The symptom cluster they share is fever with muscle rigidity. In NMS, this rigidity tends to be severe and “lead-pipe” in character after dopamine blockade or withdrawal, with fever as a common accompanying sign. In serotonin syndrome, there is often brisk neuromuscular activity with hyperreflexia and clonus, but fever can still be present, reflecting the overall hypermetabolic state. The combination of fever and rigidity captures the overlap between the two conditions. Other features like myoclonus, rash, or bradycardia are not the shared hallmark; myoclonus is more characteristic of serotonin syndrome, while rash/pruritus are not typical, and hypothermia is not a usual feature of either.