CDC: MRI helps identify cluster of amnesia in Mass.

Physicians in Massachusetts have used MRI to help identify a cluster of amnesia cases that may be linked to opioid abuse, according to the U.S. Centers for Disease Control and Prevention (CDC). The CDC has issued an alert to healthcare providers to scan some adults presenting with sudden-onset amnesia.

In a January 27 update in the CDC's Morbidity and Mortality Weekly Report, the agency reported on a series of four cases of "an uncommon amnestic syndrome" that were encountered by a Boston neuroradiologist in November 2015. MRI scans of the patients revealed acute and complete ischemia of both hippocampi.

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After state authorities distributed an email alert in February 2016, 10 more cases were discovered that had occurred between 2012 and 2016. The 14 patients had a median and mean age of 35, had records of substance abuse, and were seen at hospitals in eastern Massachusetts.

Nine of the individuals were unconscious when they received medical attention, and five required endotracheal intubation. All nine of these patients reported experiencing amnesia after regaining consciousness; regarding the other five, family members or friends reported them as having severe memory loss and brought them to the emergency room for evaluation.

Other clinical symptoms besides amnesia included deficits of orientation and attention, as well as problems with executive function. Clinical follow-up was not available for most of the patients, although one reported resolution at five months while two others reported milder symptoms.

MRI scans were performed within five days of initial evaluation for 13 patients and within eight days for the remaining individual. The MR images demonstrated bilateral hippocampal ischemia in all patients, while nine patients showed ischemic changes in one or more areas outside the hippocampus, mostly in the subcortical and posterior areas.

Ischemia of the hippocampus is a known cause of memory loss; it has previously been associated with toxic exposure, but only rarely and in isolated cases, noted lead author Dr. Jed Barash from Lahey Hospital and Medical Center and colleagues. The unique particulars of this cluster of cases indicate that further investigation is needed, they wrote.

"Extensive substance use associated with this group of patients suggests broader surveillance is needed to determine whether this represents an emerging syndrome related to substance abuse or other causes, including introduction of a toxic substance," the authors wrote.

One factor that complicates further investigation is that MRI is often not performed in the workup of these types of cases. MRI of the head, toxicology screening, and neurologic consultation should be considered in adults 18 years and older who present with sudden-onset amnesia, particularly if they have altered consciousness. More advanced testing could clarify whether there is an association with substance abuse, they concluded.

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