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Could certain opioids lead to amnesia?

An account published Thursday by the US Centers for Disease Control and Prevention raises the possibility a new syndrome is emerging.AP/File

Dr. Jed A. Barash, a neurologist, was the first to notice something puzzling was going on. Four patients over the course of three years came to Lahey Hospital & Medical Center with mysterious cases of short-term memory loss.

They were all relatively young, and none of them had disorders that can lead to memory loss. But all four shared this: They had used opioids.

In the months since, 10 more unusual amnesia cases have been discovered in Massachusetts, according to an account published Thursday by the US Centers for Disease Control and Prevention that raises the possibility a new syndrome is emerging.

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“We don’t know what we’ve found, and we think it’s worth investigating further,” said Dr. Alfred DeMaria, one of the article’s authors and the Massachusetts state epidemiologist. If more cases are identified, it may be possible to track down the cause, he said.

Thirteen of the 14 people — who developed symptoms between 2012 and 2016 — had a documented history of substance abuse, and the 14th tested positive for opioids and cocaine when brought in for medical care. Twelve had used opioids. Most of the patients had taken other drugs as well, including tranquilizers, marijuana, cocaine, and amphetamines. They ranged in age from 19 to 52 years; four were women.

DeMaria said it’s possible that a new contaminant in the drugs caused the damage. It’s also possible the syndrome is not new, just never before noticed.

Until the Massachusetts cases, it was very rare to see this combination of memory loss and the type of brain damage seen on MRIs, which showed reduced blood flow to the hippocampus, the part of the brain that turns information into memory.

Such damage has been associated with a few isolated cases of cocaine use, influenza, and carbon monoxide poisoning. One case involving heroin inhalation occurred in France in 2013.

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The fact that so many cases occurred in a short period of time, in a limited geographical area, suggests that a new syndrome could be emerging.

The article appeared in the CDC’s Morbidity and Mortality Weekly Report, a journal with wide circulation among public health officials. Many of the cases emerged after the Massachusetts Department of Public Health sent an alert to neurologists, radiologists, and emergency doctors statewide.

DeMaria said he hopes that, as a result of the publication, when patients come to the emergency room after overdosing, doctors will conduct a memory test and follow up with an MRI if they show symptoms.

“If you don’t notice it early, you can’t ask the questions that are necessary to figure out what happened,” he said.

Nine of the Massachusetts patients were unconscious when they came to medical attention. When they woke up, they could not remember what had happened to them. “These patients were saying, ‘Where am I? How did I get here?’ ” DeMaria said.

The other five were brought to the emergency department by friends or relatives who noticed sudden, severe memory loss.

The patients were able to remember past events, but new information slipped away quickly, DeMaria explained. They failed a memory test in which they were shown three commonplace objects and asked to recall them 10 minutes later.

At home, they could remember how to get to familiar places, but could not recall directions to someplace new. They could understand the rules for a new card game, but then could not remember how to play.

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Some also had problems with attention and decision-making.

It’s not known what ultimately happened to most of the patients. The youngest, who was 19 when the syndrome started, regained his memory after five months, but was left with a persistent seizure disorder.

Some of the others improved but continued to have problems, which DeMaria described as not disabling. “They’re able to function,” he said. “There are remarkably few things you have to remember.”

DeMaria said he and his colleagues had considered whether the memory loss might be a consequence of an overdose, which depresses breathing and means less oxygen gets to the brain.

But he said that even though clinicians saw some wider damage on the brain imaging, the effect was so focused in the hippocampus that something beyond an overdose was probably occurring.

But other researchers not involved with the report said they surmised the amnesia could still have been caused by an overdose.

“I don’t really know if there’s any other plausible explanation,” said Dr. Gary Franklin, a research professor at the University of Washington and fellow of the American Academy of Neurology.

Still, Franklin called the report both shocking because it showed some people dealing with memory issues years later and, at the same time, not all that surprising. Researchers are uncovering new ways opioid use can harm someone, and this finding might just be the latest addition.

Franklin also said the report suggested that it was worth assessing people who recover or are revived from an overdose for damage to their brains.

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“This would prompt me to want to study that,” he said.


Andrew Joseph of STAT contributed to this report. Felice J. Freyer can be reached at felice.freyer@globe.com. Follow her on Twitter @felicejfreyer