This, in turn, may disrupt arterial blood flow within the brain, resulting in ischemia (lack of oxygen) to memory centers or other areas of the brain. The support for this hypothesis is that increases in sympathetic nervous system activity and/or pressure within the thorax may exert pressure on the jugular veins. Some drug interactions have been known to cause other types of amnesia, although not the type associated with TGA.Īnother suggestion as a cause for TGA is that venous congestion (congested blood flow in the veins) inhibits blood flow to the thalamic or temporal regions of the brain. People who have experienced TGA are also screened for current use of medications. A well-accepted hypothesis suggests that blood is reduced to the temporal region of the brain during Valsalva, or weight-bearing movement. In some cases, there is evidence of small strokes and local evidence of minor depressions on the surface of the brain. The hypotheses that the event is triggered by a temporary loss of blood to certain regions of the brain are most popular. The causes of this disorder are not yet fully understood. However, the condition has, as one of its major triggers, the exposure to cold water as in swimming, or prolonged exposure to cold rain or snow.
For example, the connection of TGA with exposure to cold water cannot be explained in any convincing way. No definitive links to any particular pathology or reaction to medication have been discovered. The reason people in their 50s and 60s are more likely to experience TGA is not understood. About 3% of people who experience one episode of TGA will experience another episode sometime during their lifetime, but it is very rare for a person to experience more than three episodes of TGA. The most likely ages in which to experience TGA are the 50s and 60s. In addition, the occurrence of this type of amnesia rarely happens before middle age, with about 12 out of 100,000 people ever experiencing the condition before age 50. Men experience the condition more often than women. There are no race or inherited conditions associated with TGA. However, there is no report of a migraine prior to onset, nor is there any reported nausea, sensitivity to light or sound, or headache.
One of the puzzling associations with TGA is that many people who experience this disorder are also migraine headache sufferers. People experiencing TGA can register information and there is no loss of social skills and sense of identity, but their ability to retain information is severely impaired. Since that time, there have been extensive writings and studies about the condition, but its etiology (causation) is still not clearly known or understood. Transient global amnesia was first identified and described around 1960. While this hypothesis is still under review, it has been accepted as a logical explanation for a condition that currently has no generally accepted causal explanation. This loss of blood may induce the loss of memory by persons experiencing TGA. The temporal lobes are where the memories are stored. It is thought that this maneuver temporarily siphons blood from the temporal lobes of the brain.
During this maneuver, a person performs the "breathe-in-bear-down" movement that is automatically performed during strenuous exercise. The event may also be triggered by a condition called the Valsalva maneuver. Usually occurring in otherwise healthy persons, TGA triggers memory loss from external stresses such as strenuous exertion, high levels of anxiety, sexual intercourse, immersion in water, and other similar conditions. Transient global amnesia (TGA) is a temporary short-term memory loss that may result from the deactivation of the brain's temporal lobes and/or thalamus (the part of the brain that serves as a center for the relay of sensory information).
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