A Slip of Memory: Transient Global Amnesia

Search the internet for drugs that cause memory problems and you will immediately become familiar with a fascinating syndrome called transient global amnesia (TGA). A website at the top of the list of results opens with these words: My personal introduction to the incredible world of transient global amnesia (TGA) occurred six weeks after Lipitor was started during my annual astronaut physical at Johnson Space Center.  TGA is not listed as an adverse effect associated with cholesterol lowering drugs, but with 12 million Americans now consuming these products, recognition of this peculiar syndrome by patients and doctors becomes important.  Beyond the tightly controlled world of pre-market drug approval studies, unexpected symptoms need to be noted.

Transient global amnesia is a short–lived problem, over in less than 24 hours. It involves all aspects of new memory formation. Nothing gets recorded during the event and the sufferer fails to remember anything from the event after it is over. To appreciate the disconcerting nature of the syndrome, imagine suddenly losing your ability to put any information into your memory. In addition, you lose access to a few hours or days or even years of past memory, but not to information about yourself. You look around but cannot identify why you are where you are. Depending on how much access to the past you’ve lost, your current situation might be totally unknown to you. With great urgency you question the people around you. “What am I doing here?” How did we get here?” What’s going on?” Someone answers and for about 30 seconds you can hold on to the information. But your ability to put that information into memory has gone offline. You forget that you just asked the question. You ask again, and again, and again, with obvious anxiety. All your other mental capacities work. You can speak, read, write – even drive and problem solve. Except for your anxiety, you are the same person as always. Then the confusion ebbs. You start to encode information again. Your past gradually returns, in chronological order. Once again you are tethered to time and place, but you will not ever remember what went on while you were cut loose and for a little while you might complain of a little headache.

The first descriptions of this odd set of symptoms appeared in an obscure medical journal in 1956. More cases came to light, and by the early 1990s there were a few epidemiological studies that suggested that TGA occurs in about 10/100,000 people, or as many as 25-32/100,00 in the peak age group of 50-80. Far from being a harbinger of impending stroke or evidence of seizures, these episodes seemed to have no correlation with any problems other than a history of migraine and left no problems in their wake. They recurred in somewhere between 5 and 25% of the cases, with one patient having over a dozen recurrences. No definite cause has ever been found, though many physicians have associated them with immediately preceding, physically or emotionally strenuous events.

Very rarely, underlying brain problems like tumors involving the deep middle and frontal areas, where memory formation takes place, turn up in TGA cases, but careful examination of these cases inevitably reveals some deviation from the typical clinical symptoms, or some type of abnormality on neurological examination. TGA research studies, using sophisticated scanning and EEG techniques, suggest that there is decreased activity in areas of the brain involved in memory formation, but give no clue about the mechanisms involved.

In 1990, criteria for diagnosis of the syndrome were published (listed below), and when a diagnosis of TGA strictly adheres to these criteria, it is almost always safe to predict that there is no underlying neurologic or vascular problem. Nevertheless, when a patient appears in an emergency room with TGA symptoms, good practice still requires a CT or MRI scan and an EEG at some point to rule out the remote possibility of an underlying tumor, hemorrhage or seizure disorder.

Reports like those of Dr. Duane Graveline, the astronaut/physician author, are considered anecdotal and not of the same value as information gleaned from statistical analysis of controlled studies .  The cholesterol lowering drugs are in widespread use and considered very safe by most physicians. However, there have been cases of muscle and nerve problems, as well as cases of decline in cognitive function attributable to the drugs, possibly mediated by damage to mitochondria, the power houses of all cells in the body. Since the drugs are viewed as valuable additions to the battle against heart disease and are likely to be used over long periods by increasing numbers of people, it is important to understand and catalogue their unintended consequences.  Once drugs reach large populations outside medical studies, more problems emerge, sometimes beginning as odd, single cases.  In the meantime Dr. Graveline has died after a progressive illness which resembled Lou Gehrig’s Disease (progressive loss of muscular strength and bulk). His memory, however, remained good.

Diagnostic Criteria for Transient Global Amnesia

  1. A witness must be present to describe what happened.
  2. The patient must be unable to form new memories of any kind (anterograde amnesia).
  3. The patient must have full knowledge of his identity and an unclouded state of consciousness.
  4. All other mental functions are normal, including speech.
  5. There are no other neurological symptoms or signs.
  6. There are no signs of a seizure.
  7. There is no history of seizures within the last 2 years, or of recent head injury.
  8. The patient is back to normal within 24 hours.

 

 

 

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