Serotonin syndrome versus neuroleptic malignant syndrome: a challenging clinical quandary

Abstract

Serotonin syndrome and neuroleptic malignant syndrome are two drug toxidromes that have often overlapping and confusing clinical pictures. We report a case of a young man who presented with alteration of mental status, autonomic instability and neuromuscular hyperexcitability following ingestion of multiple psychiatric and antiepileptic medications. The patient satisfied criteria for serotonin syndrome and neuroleptic malignant syndrome, and based on the characteristic clinical features, laboratory findings and clinical course it was concluded that the patient had both toxidromes. The patient was managed with cyproheptadine and supportive measures, and recovered over the course of 3 weeks. A brief review of literature highlighting the diagnostic clues as well as the importance of recognising and distinguishing the often missed and confounding diagnoses follows.

Figure 1

Carpopedal spasm was noted, corresponding to the hypocalcaemia.

Figure 2

Graph showing clinical course of the serotonin syndrome (tremulousness, mydriasis, hyper-reflexia and hyperactive bowel sounds) and neuroleptic malignant syndrome (NMS; rigidity and bradykinesia) with respect to administration of culprit medication and treatment is plotted.