History A 69-year-old right-handed man with a history of substance use disorder, hypertension, and diabetes presented to the emergency department in an unresponsive state. Upon examination, apart from tachycardia (heart rate, 108 beats per minute), vital signs were within normal ranges (blood pressure, 134/102 mm Hg; temperature, 97.9 ºF (36.6 ºC); respiratory rate, 16 per minute; oxygen saturation, 96%). The patient had a Glasgow coma scale score of 8. Otherwise, the physical examination revealed no abnormalities. Prior psychiatric and surgical histories were unremarkable. There was no history of recent travel, camping, hiking, or vaccination. No family history could be obtained. Laboratory work-up revealed an elevated creatine kinase level (49 006 U/L [818.4 μkat/L]; normal reference range, 10–205 U/L [0.17–3.42 μkat/L]). An electrocardiogram showed sinus tachycardia without evidence of cardiac ischemia. An echocardiogram was unremarkable. Alanine aminotransferase (126 U/L [2.10 μkat/L]; normal reference range, 0–40 U/L [0–0.67 μkat/L]) and aspartate aminotransferase (488 U/L [8.15 μkat/L]; normal reference range, 3–44 U/L [0.05–0.74 μkat/L]) levels were elevated. Polymerase chain reaction results were negative for HIV-1, HIV-2, syphilis treponemal, and COVID-19 antibodies. The remaining routine laboratory work-up findings were within normal limits. Urine drug screening was positive for cocaine, marijuana, fentanyl, and benzodiazepines. Naloxone was administered, but the patient remained unresponsive. Intubation was performed for airway protection. Noncontrast and contrast-enhanced CT of the head and CT angiography were performed in the emergency department to rule out an acute intracranial abnormality. Multisequence MRI of the brain with administration of intravenous contrast material was ordered for further assessment. CT of the abdomen and pelvis was unremarkable (images not shown).