What is it about?
In a patient who presented with acute onset amnesia after a reported fentanyl overdose, brain imaging showed abnormal signal in the memory circuits and on follow-up imaging at 4 months, there was an approximate 10% reduction in hippocampal volume and persistent neuropsychological deficits in episodic memory.
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Why is it important?
Serial MRIs of the brain in a patient with an acute, opioid-related amnestic syndrome reveals both transient and residual changes in the hippocampi, providing quantifiable structural data to support the persistent cognitive impairments observed in this case.
Perspectives
The pattern of hippocampal volume loss across sub-fields provides clues about mechanism-of-injury. In combination with excitotoxic and hypermetabolic effects, hypoxia from opioid-induced respiratory depression might also play a role in accentuating hippocampal susceptibility to neuronal dysfunction.
Monroe Butler
University of California San Francisco
Read the Original
This page is a summary of: An Opioid-Related Amnestic Syndrome With Persistent Effects on Hippocampal Structure and Function, Journal of Neuropsychiatry, October 2019, American Psychiatric Association,
DOI: 10.1176/appi.neuropsych.19010017.
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Resources
Complete, bilateral hippocampal ischemia: a case series
Acute and complete ischemia of the hippocampi represents a rare cause of amnesia. This paper describes the features of four such cases presenting to a single tertiary care center over a 3-year period. Interestingly, in three instances, toxicology screening was positive for opioids at the time of presentation, while in the fourth, there was a known, reportedly remote, history of heroin use. Taken together with the known literature on the topic, complete hippocampal ischemia appears at least highly suggestive of a toxic exposure. Further case finding is necessary to better understand the etiology, nature, and prevalence of this unusual clinico-radiologic entity.
Cluster of an Unusual Amnestic Syndrome — Massachusetts, 2012–2016
A unique cluster of 14 cases of sudden onset amnesia with acute, complete, and bilateral ischemia of the hippocampus was identified in Massachusetts during 2012–2016. No clear etiology exists, but at time of initial evaluation, 13 of 14 tested positive for opioids or had opioid use recorded in their medical history.
Acute Amnestic Syndrome Associated with Fentanyl Overdose
Additional case of opioid-related amnestic syndrome
An Unusual Amnestic Syndrome Associated With Combined Fentanyl and Cocaine Use
Another case of opioid-related amnesia
Connecting the dots: an association between opioids and acute hippocampal injury
Acute hippocampal injury represents a relatively rare cause of amnesia. Interestingly however, between 2012 and 2017, 18 patients were reported at hospitals in Massachusetts with sudden-onset amnesia in the setting of complete diffusion-weighted hyperintensity of both hippocampi on magnetic resonance imaging. Notably, 17 of the 18 patients tested positive for opioids or had a recorded history of opioid use. This observation suggests an association between opioids and acute hippocampal injury. With particular attention to the Massachusetts cluster and data on fentanyl and its congeners, the epidemiological and pathophysiological evidence that supports this hypothesis is presented, as are potential underlying mechanisms.
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