Which single clinical finding best distinguishes serotonin syndrome from neuroleptic malignant syndrome at the bedside?

• A Autonomic instability
• B Hyperreflexia and inducible clonus ✓
• C Altered mental status
• D Elevated creatine kinase

Explanation

Serotonin syndrome produces neuromuscular hyperactivity with hyperreflexia, inducible and spontaneous clonus, and myoclonus, whereas NMS produces lead-pipe rigidity with bradyreflexia. Fever, altered sensorium, autonomic instability, and raised CK occur in both conditions and therefore cannot discriminate between them. Drug history supports the diagnosis but the reflex pattern is the decisive bedside sign.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.