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Ischemic Hypocampal Ischemic Syndrome Complete: a recently discovered type of amnesia

Ischemic Hypocampal Ischemic Syndrome Complete: a recently discovered type of amnesia

July 29, 2022

In 2012, a 22-year-old boy was taken to a hospital in Massachusetts, suffering from problems in one leg and what at first was considered a high level of confusion. He constantly repeated the same phrases and asked the same questions. After passing several tests, it was soon evident that what was considered confusion was a reality a severe amnesia .

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

  • Related article: "The different types of amnesia (and its characteristics)"

What is this syndrome?

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

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 happened with the first of the known cases), recovering to a large extent the memory capacity to record new information.

On a neuropsychological level, the existence of brain damage has been observed in a very specific area , being this aspect what is more striking (since they do not tend to have large brain lesions in other areas): the biggest and most characteristic damage of this evident syndrome is the presence of a lesion of great importance in both hippocampus, being the bilateral injury.

The suffering of an amnesia due to damage to the hippocampus or in different areas is not so unusual, and it is also known that hypoxia and strokes affect the hippocampus to a greater extent that to other regions but it is not so simple that the damages occur in both hippocampus at the same time in such a sudden way and without any kind of trauma that also damages other areas.


The causes of the appearance of massive lesions in both hippocampus and the appearance of this type of amnesia are largely unknown. Despite this, the immediate cause, the trigger, seems to be associated with the aforementioned opioid use. In many of the cases, patients had a history of opioid use (especially heroin), suffering from a substance abuse disorder, and in some other cases have been observed by analysis the presence of other drugs such as cocaine, marijuana, amphetamines, hallucinogens or drugs such as benzodiazepines.

Another element to be taken into account is that most of the patients are younger or younger (between the age of 20 and 50), of which around half of known cases suffer from vascular disorders such as hypertension or diabetes. Vascular alterations may facilitate the appearance of ischemia that cause hippocampal damage, but how they are really related is something little known.

The suffering of a dependence or disorder due to substance use, besides being one of the possible causes or triggers, can have different repercussions for your health that can complicate your recovery if you continue consuming after the amnestic episode.

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A little-known amnestic 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, a total of 16 cases identified in the United States have been detected that meet the same characteristics.

However, we must bear in mind that there may be more, since there is a possibility that people without resources have not come to the hospital (These 14 cases have been observed in the United States), or that previous cases have been associated with other alterations.

But except for the aforementioned findings, little is known about this syndrome. Much more research is needed to determine the causes of this disorder and establish protocols for action and treatment that are 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.

Hippocampus (July 2022).

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