A group of patients in the Boston, Massachusetts area are posing a medical mystery.  They're suffering from an unusual and debilitating form of memory loss that appears linked to the scourge of opioid drug use.

The first patient was a young man who spent a night out partying in the dive bars in Boston's Back Bay neighborhood back in 2012.  He met his dealer and scored what he believed was heroin.  After shooting up and passing out on a couch, he woke up the next morning with paralysis in one leg.  But each time he tried to stand he failed to form a short term memory, leading to several attempts to stand up without remembering the previous attempts. 

Hours spent in two hospitals failed to determine what was causing his paralysis and confusion, until doctors ordered an MRI scan.  They found two bright white spherical shapes, "perfectly localized" on either side of the hippocampus, the seahorse-shaped part of the brain that encodes new memories.  The patient's rehabilitation has been slow - his university studies came to an abrupt halt, and he has trouble holding holding a job.

Since then, doctors have identified 13 more patients with similar damage to their hippocampi who could not form short term memories.  Of the 14, twelve had the commonality of opioid drug use.  But drug use alone might not be the key - after all, two patients supposedly did not use drugs while thousands more opioid abusers in eastern Massachusetts didn't lose their ability to form short-term memories.  Another possibility being considered is the cheap heroin substitute fentanyl.  It's 50 times stronger than heroin and its introduction into the drug culture seems to parallel the appearance of this specific form of memory loss.

Next week, Massachusetts public health officials will officially recognize Complete Hippocampal Ischemic Amnestic Syndrome (CHIAS) as a "reportable disease", meaning that doctors who run into new cases will alert the state just as they would for infectious diseases link Zika or Ebola.  It's hoped that researchers will learn more about the causes and effects of CHIAS as they get more data to study, as well as develop quicker diagnoses and treatment.