Opioid-Associated Amnestic Syndrome

Abstract

Opioid-associated amnestic syndrome (OAS) is a relatively new condition that is associated with opioid abuse and has increased in prevalence since the notable rise in opioid-related deaths and opioid-related hospitalizations of the opioid crisis. Patients often present with acute anterograde amnesia and current opioid abuse, most commonly fentanyl. OAS is frequently diagnosed when other potentially infectious or metabolic conditions such as encephalitis and seizures are ruled out, as these conditions can also present similarly to OAS. This case highlights the signs, symptoms, and hallmark characteristics of OAS, including bilateral hippocampal edema and anterograde amnesia.

Keywords: amnesia; hippocampal edema; opioid crisis; opioid-associated amnestic syndrome; substance abuse.

Figure 1. Symmetrical edema in bilateral hippocampi (red circles) in an otherwise unremarkable CT head (axial view) without contrast.

Figure 2. Axial views; T2-weighted (A), and FLAIR (B) demonstrate hyperintensity in the bilateral hippocampi region (white hollow arrows). On ADC (C), there is decreased signal intensity in the same hippocampi region (white solid arrows) along with corresponding increased signal intensity in DWI (D) which are suggestive of a diffusion restriction.

ADC: Apparent diffusion coefficient; DWI: Diffusion-weighted imaging.