A 75-year-old female with a past medical history significant for osteoporosis presented with confusion. Her neighbors found her wandering around her house repeating “I’m lost.” On admission to the emergency department, vital signs were normal. On physical examination, she was awake, alert and oriented to person, place, time, but not to event. On further interview, she exhibited short-term anterograde amnesia. Urine toxicology screen was positive for cocaine and fentanyl. MRI of the brain revealed abnormal T2/FLAIR hyperintensity and restricted diffusion involving the bilateral globus pallidus and bilateral hippocampi.
Over the following week the patient showed subtle improvement with gradual recollection of events leading up to the hospitalization. Given her clinical presentation, positive urine toxicology, and otherwise negative work-up for ischemic, infectious, and metabolic etiologies, this patient was ultimately diagnosed with OAS.