(761) Neuroleptic Malignant Syndrome and Serotonin Syndrome: A Tale of Two Diagnoses

Introduction: Clinicians must consider overlapping pathologies in critical illness, especially when a single diagnosis fails to account for all symptoms. This is especially crucial when assessing drug-induced syndromes and interactions, which harm millions annually. Notable examples are serotonin syndrome and neuroleptic malignant syndrome, which typically present with a constellation of symptoms and are often diagnoses of exclusion.

Description: A 56-year-old Caucasian male was admitted after being found unresponsive with seizures. He was intubated and sedated with propofol, given a loading dose of phenytoin and multiple doses of midazolam, and initiated on fosphenytoin maintenance therapy. Initial assessments revealed abnormal posturing and fluctuating blood pressures, ranging from 90 – 260 mmHg systolic. Despite normal imaging, he exhibited hyper-reflexive lower extremities and autonomic dysfunction. Lab results demonstrated leukocytosis and fevers, though a lumbar puncture was normal. A review of the patient’s home medications revealed chronic use of trazodone, vortioxetine, lurasidone, lamotrigine, carbidopa/levodopa, and baclofen. After excluding other potential causes of the patient’s presentation, including Bickerstaff encephalitis and Miller Fisher syndrome, a cyproheptadine challenge was initiated which resulted in the resolution of fevers, but none of the other symptoms. After 24 hours of cyproheptadine, bromocriptine was added to the patient’s regimen, which resulted in the cessation of the patient’s hyperreflexia and the normalization of his blood pressure. The patient was ultimately transferred out of the neurocritical care unit and eventually discharged to home in stable condition.

Discussion: This patient's complex symptoms and ultimate diagnosis of serotonin syndrome and neuroleptic malignant syndrome were assessed using the Hunter and Levenson Criteria, respectively. The diagnosis of serotonin syndrome was supported by the presence of fevers and hyperreflexia, while the diagnosis of neuroleptic malignant syndrome was also supported by fevers, in addition to rigidity and autonomic lability. Drug-drug interaction screenings should be conducted routinely in all critically ill patients to minimize the risk of such clinical presentations.