Amnesia case baffles even neurologists

A man lives the same day over and over again and forgets everything after 90 minutes

Enigmatic amnesia: After 90 minutes, the patient has forgotten everything before © Anilakkus / Thinkstock
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Such a case was even unknown to researchers: a 38-year-old man developed after a normal root canal treatment a memory disorder that makes him forget everything experienced after 90 minutes. And not only that: he has been waking up every morning for ten years, believing that it is the day of his appointment as a dentist. What reminds me of movies like "And every day greets the marmot" is a sad reality for the man.

Cases of people who can not remember anything new, especially after brain damage more often. For example, if the hippocampus is damaged, those affected can no longer transfer memories to long-term memory. After a few seconds to minutes they forget everything again. However, cases in which such memory disorder occurs without manifested brain damage are extremely rare.

"We've never seen anything like it before"

Gerald Burgess of the University of Leicester now presents such a case - in the hope of finding out from colleagues or possible other victims about similar cases and their possible causes. "We've never seen anything like this before and we just do not know what to do, " says the neurologist.

The story begins ten years ago: the 38-year-old man went to an appointment with the dentist for a root canal treatment. He got a local anesthetic and after an hour the treatment was finished. But the patient was pale, dizzy, could not get up himself and spoke slowly and washed out. He was admitted to the hospital, but there was no evidence of any physical or brain abnormality.

It's over after 90 minutes

After a few hours it became apparent that the man is suffering from anterograde amnesia: he has been able to remember things for only about 90 minutes since then. "He can learn new things, but if that information is not recapitulated within that time, he loses it forever, " Burgess explains. "Since then, the patient has only been coping with his everyday life with the help of constant checking in an electronic diary and notes." Display

In cases of similar amnesia, the hippocampus is often damaged or destroyed - not so in this patient. public domain

The strange thing is that this time span is actually too long. Because if the transfer of information from the work memory to the long-term memory does not work, the memory span should last only a few seconds to minutes. In addition, patients with such memory disturbances can not normally remember any explicit information, but they may well learn new movement patterns and other implicit skills, but not this patient.

Always caught in the same day

Strange too: The man seems caught in a time warp, every night everything that he has experienced the day before is wiped out. "Every morning he thinks it's the day of his dentist appointment, " reports Burgess. "He knows who he is and knows his family members, but he expects everyone to have the same age as he did in March 2005."

It is striking, however, that the patient was able to remember things in two exceptional cases: he knows that his father died, although this happened shortly after the start of his amnesia. And he was able to remember the birth of the child of a close relative for at least 24 hours before he forgot that again.

Cause mysterious

The neurologists are mystified because neither in the brain of the man nor in his history can be found evidence of a physical or psychological cause of this amnesia. "Without bilateral damage to the hippocampus or the diencephalon, which usually causes such severe amnesia, we can only speculate on the causes of this case."

Although scientists can not rule out a connection with root canal treatment and local anesthesia, they consider it very unlikely. "To blame the treatment would be unethical and a baseless fear-mongering - there is simply not enough evidence, " Burgess points out. "I think the real reason lies elsewhere."

A possible explanation would be an error in the synthesis of the proteins needed for the remodeling of the synapses in the brain and thus for the permanent storage of memories in the long-term memory, "The 90-minute period in this patient agrees well with the time this protein synthesis takes place, " says Burgess. "In addition, such an error would interfere with both episodic and procedural memory, and that is the case with this patient."

But even that is not much more than a hypothesis, as the researchers emphasize. They now hope that people will report on this case to people who know similar cases or colleagues who can contribute to the clarification of this mysterious case. (Neurocase: The Neural Basis of Cognition, 2015; doi: 10.1080 / 13554794.2015.1046885)

(University of Leicester, 15.07.2015 - NPO)