Amnestic Syndrome and Bilateral Hippocampal Diffusion Abnormalities From Opioid Use

A 17 year-old man presented to the emergency department unconscious and developed anterograde amnesia without other deficits in mental status, motor function, or coordination. High-resolution mass spectrometry (but not routine immunoassays) of his urine detected the presence of fentanyl, morphine, and oxycodone. A brain MRI showed symmetric reduced diffusion in the bilateral hippocampi and globi pallidi as well as a focus of reduced diffusion in the left cerebellum (Figure 1). His anterograde amnesia gradually improved over 8 days. This case highlights the MR features of opioid-related amnestic syndrome and suggests a critical role for both brain MRI and mass spectrometry-based toxicology screening.1, 2