In 2012, a 22-year-old boy was taken to a hospital in Massachusetts, suffering from leg problems and what was initially considered a high level of confusion. He was constantly repeating the same phrases and asking the same questions. After passing several tests, it soon became clear that what was considered to be confusion was in fact severe amnesia .

This had appeared suddenly, being associated with the consumption, the night before the admission, of what the young man believed to be heroin. Since then, about 16 similar cases of what has come to be considered a new amnesic syndrome, associated with the use of opioids, have been detected.

What is this syndrome?

The complete ischemic hippocampal amnesia syndrome , as it has been called for the moment by the doctors who discovered its existence, is characterised by the presence of the sudden appearance of anterograde amnesia, often shortly after the consumption or after surviving an overdose of some type of opiate (the most frequent being heroin and/or fentanyl).

This means that patients lose the ability to record new information and store it in memory. Beyond the memory problems, those who suffer from this syndrome may have other alterations, but they are not definitive of this syndrome. In some cases there has been an improvement over time (as occurred with the first of the known cases), largely recovering the memory capacity to record new information.

At a neuropsychological level, the existence of brain damage has been observed in a very specific area , being this aspect what is most striking (since they do not tend to have large brain injuries in other areas): the greatest damage and the most characteristic of this evident syndrome is the presence of a very important injury in both seahorses, being the injury bilateral.

Amnesia due to damage to the hippocampus or different areas is not so unusual, and it is also known that hypoxia and strokes affect the hippocampus to a greater extent than other regions but it is not so simple that damage occurs in both hippocampuses at the same time in such a sudden way and without any trauma that also damages other areas.

Cause?

The causes of the appearance of massive lesions in both seahorses and the occurrence of this type of amnesia are largely unknown. However, the immediate cause, the trigger, seems to be associated with the above-mentioned consumption of opioids. In many of the cases, the patients had a history of opiate use (mainly heroin), suffering from a substance abuse disorder, and in some other cases, other drugs such as cocaine, marijuana, amphetamines, hallucinogens or medicines such as benzodiazepines have been observed by analysis.

Another element to be taken into account is that we are mostly dealing with more or less young patients (between twenty and fifty mostly), of which about half of the known cases suffer from some vascular disorder such as hypertension or diabetes. The vascular alterations could facilitate the appearance of ischaemias that cause hippocampal damage, but how they are really related is little known.

Having a substance use dependence or disorder, in addition to being one of the possible causes or triggers, can have different health implications that can complicate your recovery if you continue to use after the amnestic episode.

A little-known amnesia syndrome

Not much is known about this syndrome, but it has been observed that it is undergoing some expansion: since the first case was observed in 2012 until now, a total of 16 cases have been identified in the United States that have the same characteristics.

However, we must take into account that it is possible that there are more, since there is the possibility that people without resources have not gone to the hospital (these 14 cases have been observed in the United States), or that previous cases have been associated with other disorders.

But other than the findings mentioned above, little is known about this syndrome. Much more research is needed to determine the causes of this disorder and to establish protocols for action and treatment more appropriate to this problem.

Bibliographic references:

  • Barash, J.A.; Somerville, N. & DeMaria, A. (2017). Cluster of an unusual amnestic syndrome – Massachusetts, 2012-2016. MMWR: 66(3); 76-79.
  • Duru, U.B.; Pawat, G.; Barash, J.A.; Miller, L.E.; Thiruselvam, I.K. & Haut, M.W. (2018). An Unusual Amnestic Syndrome Associated With Combined Fentanyl and Cocaine Use. Annals of Internal Medicine. American College of Physicians
  • Lim, C.; Alexander, M.P.; LaFleche, G.; Schnyer, D.M.; Verfaellie, M. (2004). The neurological and cognitive sequelae of cardiac arrest. Neurology, 63 (10): 1774-1778.