Vigilance of Rare Diseases: A Case of Neuroleptic Malignant Syndrome

Abstract Introduction: Neuroleptic malignant syndrome (NMS) is an unpredictable and potentially life-threatening neurologic emergency with incidence rates between 0.01% to 0.02% among individuals on antipsychotic medications. Case: 70-year-old male with history of cerebral vascular accident complicated by post-stroke seizures, dementia, and atrial fibrillation on anticoagulation underwent a diagnostic colonoscopy found to have post-procedural tachypnea and tachycardia sent to the Emergency Department (ED) for further evaluation. In the ED, he had atrial fibrillation with rapid ventricular rate managed with antiarrhythmic medications and agitation for which he received Haldol 0.5mg intramuscular (IM) at 1524, 1.0mg Haldol IM at 1608, and 5mg Zyprexa IM at 1649. At 1749, nurses requested re-evaluation given ongoing agitation. On assessment, he was tachycardic with labile blood pressures, awake, tremulous, and had muscle rigidity with his head and gaze fixed to the right, not responding to verbal or physical stimuli, concerning for stroke, seizure, or dystonic reaction. Head computed tomography was negative for acute pathology. Low suspicion for seizure given last seizure was six months prior and are tonic clonic. Dystonic reaction likely given receipt of antipsychotic medications. However, he quickly thereafter developed diaphoresis and fevers up to 104.4 Fahrenheit for which the clinical team was now most suspicious for malignant hyperthermia, neuroleptic malignant syndrome (NMS), or sepsis possibly from perforated bowel during the colonoscopy. Radiographs were without evidence of free air, making bowel perforation less likely. Malignant hyperthermia was thought to be less likely given general anesthesia was not administered for the colonoscopy. Given development of altered mental status, hyperthermia, muscle rigidity, and autonomic instability after receiving antipsychotics that improved with diphenhydramine and lorazepam, NMS was highest on the clinical team's differential. He was admitted to the Intensive Care Unit and continued to have autonomic instability and muscle rigidity that improved with benadryl and lorazepam. Additionally, he continued to have severe agitation that required a dexmedetomidine drip given risk of developing NMS with restarting antipsychotic agents. He was transitioned to scheduled lorazepam and trazodone with marked improvement in his symptoms and discharged home. Importance: Mortality from NMS has decreased from 30% to 10% likely from increased awareness, and the introduction of lower potency neuroleptic medications. As this case exemplifies, NMS can develop in patients even with relatively low-doses of antipsychotic medications. Prompt detection and management of rare diseases, including NMS, will contribute to a decrease in mortality and morbidity and improve patient outcomes.