LEICESTER, England, July 16 (UPI) -- Doctors have been baffled by a man who was brought to the hospital in 2005 after a root canal with tinnitus, or ringing in the ears, and an ability to remember things for 10 minutes after they occurred before the memories would disappear forever.
The memory problem, called anterograde amnesia, has been seen before in people with structural damage to their brain. In this case, however, the man had not experienced trauma that would harm the hippocampus, which makes new memories.
"I remember getting into the chair and the dentist inserting the local anesthetic," the man, whose identity has been withheld to protect his privacy, told the BBC. But after that, he has no memory of anything that has happened in the 10 years since.
A member of the British armed forces, the man was stationed in Germany when he went for the root canal. The dentist completed the procedure and noticed his patient looked pale and faint, could not get out of the chair and appeared "vacant" with "slow speech," according to a case study published in Neurocase: The Neural Basis of Cognition.
Once brought to the hospital, doctors found that in addition to experiencing tinnitus, the man could not remember anything that happened after the root canal for more than 10 minutes. This eventually improved during his stay at the hospital to holding onto memories for about 90 minutes, but his ability to make new memories has not gotten better.
Dr. Gerald H. Burgess, a clinical psychologist at the University of Leicester, said in a press release that the man's condition is similar to to what characters in the movies Groundhog Day and Momento experience: He starts his day by reading a file on his smartphone called "First thing -- read this" to remind himself of where he is and what has happened because he has no memories of any of it.
The "million-pound question," Burgess said, is how a root canal could cause this form of amnesia. In the study, Burgess and co-author Bhanu Chadalavada, a consultant psychiatrist at Northamptonshire Healthcare Foundation, compared the man's case with five similar ones.
Like the other patients, nothing in his medical history shows the risk factors for anterograde amnesia, and it was brought on without brain damage. Burgess said amnesia can be brought on by stress, however his life appeared to be in good shape, aside from the death of his father, which he witnessed, a few days before the root canal.
Burgess thinks it is possible that the man, and the others, have some type of genetic disposition for the condition and something is triggered preventing synapses in the brain from reforming and solidifying memories permanently. The man is the only one whose condition was triggered by a trip to the dentist, the others experienced some sort of physical stress during a medical emergency.
"I don't have an answer," said Burgess, who has been working with the man since he was referred to the doctor a decade ago. The study, he said, will hopefully bring professionals or people with knowledge of someone that has experienced amnesia in this way forward to expand knowledge and evidence to treat it.