TABLE 2. Selected characteristics of 14 patients with sudden-onset amnesia and complete hippocampal ischemia of unclear etiology, by onset year — Massachusetts, June 2012–July 2016

Abbreviations: F = female; LSD = lysergic acid diethylamide; M = male; MDMA = 3,4-methylenedioxymethamphetamine; MRI = magnetic resonance imaging; PCP = phencyclidine.
* Patient had oxycodone/acetaminophen prescribed.
^† Patient had butalbital/acetaminophen/caffeine prescribed.

A history of substance use disorder was documented in 13 of 14 patients; the remaining patient tested positive for opiates and cocaine at the time of initial evaluation. The other patient, who tested positive for cocaine, also tested positive for opiates, amphetamines, and benzodiazepines, none of which were being prescribed at the time. Overall, 12 of 14 patients had a history of opioid use, and eight tested positive for opiates on routine toxicology screening, including one whose medication list included oxycodone-acetaminophen and another who had not reportedly filled a prescription for buprenorphine/naloxone in approximately two months. Among the six patients with a history of benzodiazepine use, four had lorazepam or clonazepam on their medication list, and two tested positive for benzodiazepines. Tobacco and alcohol histories were incompletely documented for multiple patients, although no patient tested positive for alcohol on routine screening. One of the two patients with negative toxicology results upon routine testing had reported heroin use in the days preceding the event, and the other had a history of opioid use, but further details were unavailable. Marijuana, lysergic acid diethylamide (LSD), 3,4-methylenedioxymethamphetamine (MDMA, commonly known as Ecstasy), mushrooms, and phencyclidine (PCP) were among other substances reported to have been used (see Table 2). Neither of the patients with a history of dextroamphetamine/amphetamine use had amphetamines listed as a prescribed medication. Among four patients with gabapentin on their active medication list, one reportedly had evidence of gabapentin overdose at the time of evaluation. Routine clinical toxicology screening in that patient also revealed the presence of opiates, cannabinoids, and salicylates.