Complete Bilateral Hippocampal Diffusion Restriction and Reversible Amnesia Following Opiate, Cocaine, and Benzodiazepine Abuse

Abstract

The hippocampus is a crucial component of the circuits involved in memory formation and recall. Bilateral hippocampal lesions can lead to profound anterograde amnesia. As a highly vascularized structure, the hippocampus is susceptible to ischemia from hypoxic and toxic insults. Infarction of bilateral hippocampi as a result of cocaine use, while rare, is well described in the literature. Combined opiate and stimulant abuse also cause dysfunction of this structure. We present a case of complete bilateral hippocampal diffusion restriction and anterograde amnesia after heroin, cocaine, and benzodiazepine abuse, consistent with opioid-associated amnestic syndrome, as well as a remarkable resolution of amnesia months later.

Bilateral Acute Hippocampal Ischemia in Two Patients Abusing Cocaine: What is the Outcome?

“…In those patients, cognitive deficits persisted for weeks to months following the initial insult, and the duration of follow up in those patients was highly variable (Table 2). However, it is unknown in these cases whether the patients discontinued illicit substance use [2][3][4][5][6][7][8][9]. Huang and Lukas (2021) reported a case of a 30-year-old male patient who presented with acute anterograde amnesia and bilateral acute hippocampal ischemia, who showed no improvement at one month, but improved to his baseline 10 months after the initial insult [9].…”

“…However, it is unknown in these cases whether the patients discontinued illicit substance use [2][3][4][5][6][7][8][9]. Huang and Lukas (2021) reported a case of a 30-year-old male patient who presented with acute anterograde amnesia and bilateral acute hippocampal ischemia, who showed no improvement at one month, but improved to his baseline 10 months after the initial insult [9]. The clinical course of the patient in case 2 suggests that better clinical outcomes may be achieved with complete discontinuation of illicit substance use.…”

“…Vascular supply stems primarily from the collateral branches of the posterior cerebral artery (PCA) and the anterior choroidal artery [1]. In recent years, cases of patients developing anterograde amnesia with notable MRI abnormality of bilateral hippocampal ischemia in the setting of substance abuse, most notably with opioids and to a lesser extent cocaine, have been reported [2][3][4][5][6][7][8][9]. Bilateral hippocampal ischemia is a rare complication of cocaine abuse [3].…”

Opioid-Associated Amnestic Syndrome

“…Due to the novelty and low incidence of OAS, the long-term effects are not entirely clear. Some reports indicate that amnesic symptoms completely resolved for patients months after OAS diagnosis, while for other patients, severe symptoms persisted [ 9 ]. OAS is a rare diagnosis and patients with OAS may be misdiagnosed, especially when patients are using opioids that are undetectable on UDS.…”

Opioid-Associated Nervous System Injuries

“…The amnesia in OAS may be wholly reversible with time, although some patients may have residual short-term memory deficits. 22,26 Cerebellar Hippocampal and Basal Nuclei Transient Edema with Restricted Diffusion Cerebellar Hippocampal and Basal Nuclei Transient Edema with Restricted diffusion (CHANTER) syndrome is a clinicoradiographic syndrome first described by Jasne et al in 2019. 27 CHANTER is characterized by altered mental status, bilateral diffusion restriction affecting the cerebellar cortex, basal ganglia, hippocampi, and the possibility of obstructive hydrocephalus secondary to cerebellar edema (see Case 1).…”