Case Study: Amnestic Syndrome After Combined Cocaine, Fentanyl Use

Fornix, hippocampus and mammilary body color tractography.
Fornix, hippocampus and mammilary body color tractography.
A case of new-onset amnesia occurring after cocaine use and possible fentanyl use was described.

Researchers described a case of new-onset amnesia occurring after cocaine use and possible fentanyl use in a case study published in Annals of Internal Medicine.1 The incident may be related to a cluster of amnesia cases reported in Massachusetts, in which 14 people with a history of substance use developed unusual amnestic syndrome.2

In May 2017, a 30-year-old man with a history of heroin use presented with new-onset anterograde amnesia. Bilateral, symmetrical hypodensities in the hippocampi and basal ganglia were identified with computed tomography.

Diffusion-weighted hyperintensities involving both hippocampi and the fornices, mamillary bodies, and globus pallidus were revealed by magnetic resonance imaging.

Serum toxicology screen identified cocaine in the patient’s system, but urine toxicology screen results were negative. Confirmatory urine testing was negative for fentanyl but positive for norfentanyl, a metabolite of fentanyl. The patient did not have a known history of fentanyl use.

According to the researchers, this patient, along with a man from Virginia who presented with a similar syndrome, represent the first cluster of this amnestic syndrome documented outside of Massachusetts. Although 15 of the 16 reported patients with this syndrome had tested positive for opioids, this case was the first one to associate the amnestic syndrome with fentanyl.1,2

Fentanyl has been shown to cause acute neuronal degeneration in the hippocampus and affiliated limbic structure in rats.3 The researchers suggested that “fentanyl and cocaine together potentiate the underlying mechanism of injury, including the potential for both excitotoxic and hypoxic–ischemic processes.”

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“[C]linicians who encounter patients with new-onset amnesia, particularly in the setting of substance use, should consider including in their evaluation diffusion-weighted magnetic resonance imaging of the head, routine toxicology screening, and neurologic consultation,” concluded the authors.

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  1. Duru UB, Pawar G, Barash JA, Miller LE, Thiruselvam IK, Haut MW. An unusual amnestic syndrome associated with combined fentanyl and cocaine use [published online January 30, 2018]. Ann Intern Med. doi: 10.7326/L17-0575
  2. Barash JA, Somerville N, DeMaria A Jr. Cluster of an unusual amnestic syndrome—Massachusetts, 2012-2016. MMWR Morb Mortal Wkly Rep. 2017;66(3):76-79.
  3. Kofke WA, Garman RH, Stiller RL, Rose ME, Garman R. Opioid neurotoxicity: fentanyl dose-response effects in rats. Anesth Analg. 1996;83(6):1298-1306.