Opioid-Associated Amnestic Syndrome.

A 31-year-old male with a history significant for obesity, attention deficit hyperactivity disorder, methamphetamine use, and IV drug use was evaluated for unexplained global amnesia greater than 24 h. The patient had been in recovery for opioid use disorder for about a year, but he relapsed on IV fentanyl in the week prior to presentation. On exam, he was alert and fully oriented but had no spontaneous recall of three objects after five minutes. General medical and neurological examinations were otherwise unrevealing. Urine fentanyl and norfentanyl were positive. CT and MRI imaging demonstrated isolated bilateral hippocampal injury. Given the totality of his presentation and the contributing variables, his medical team considered this to be a case of the newly characterized opioid-associated amnestic syndrome (OAS). This case is significant because of the relative absence of potentially confounding variables on presentation, including antecedent cardiorespiratory failure. Further reporting of these cases may have implications for understanding opioid toxicity and clarifying the functional role of the hippocampus.