Acute Anterograde Amnesia with Bilateral Hippocampal and Globus Pallidus Lesions
Objective:
To present a case of opioid-associated amnestic syndrome (OAS).
Background:
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.
Conclusions:
There has been an increase in the number of cases of OAS reported in recent years coinciding with the increase in opioid use. Notably, there were a cluster of 18 patients in Boston who presented with this syndrome, and since then a total of approximately 40 cases have been recognized across the United States. This case underlines the importance of considering opioid intoxication in patients with acute anterograde amnesia. Diagnostic criteria proposed by Barash et al. requires a positive screen for opioids and evidence of bilateral hippocampal injury on imaging. This syndrome is likely underdiagnosed, and increased recognition is necessary for identification of the incidence, prognosis and risk factors that predispose patients to developing OAS. Opioid prescribers should counsel patients and family appropriately, and monitor patients for OAS over the course of treatment. Treatment of OAS is supportive, and the timeline of recovery of deficits is variable. Cognitive evaluation with subsequent rehabilitation therapy may be useful.