Transient Global Amnesia TGA

This is a rare syndrome in which a person has a short-lived episode of amnesia, usually lasting just a few hours and no longer ,121

than one day. The cause of TGA is unknown; it is not associated with any neurological signs or obvious neuropsychological deficit.

TGA is a transient inability to form new memories, as well as to recall memories from the days, weeks, or years prior to the onset. The person behaves normally and can talk, reason, and carry out other cognitive functions without obvious problem, but he or she can't remember anything that occurred during the episode. As the TGA resolves, the person recovers most memory function but has a persisting amnesia for events that occurred during the episode.

TGA typically occurs in people ages fifty and older. Although migraine, temporal lobe seizures, and transient ischemic attacks have been cited as possible causes, compelling evidence is lacking. Certain medicines have also been implicated, including sleeping medications and sedative hypnotics. One provocative causal hypothesis concerns transient reduction of blood flow to the medial temporal lobes or thalamus, structures critical for memory function. This type of reduced perfusion can occur with physical and emotional stress, when normal blood flow is partially diverted to other areas of the body. Reported trigger events include pain, physical exertion, cold water exposure, severe emotional stress, and sexual intercourse.

In a 2004 study published in Neurology, researchers studied thirty-one consecutive cases of TGA and found punctate (tiny) lesions in the hippocampus in twenty-six cases. They point out that although only two patients had MRI abnormalities in the acute phase of the episode, lesions were visible in all twenty-six cases on MRIs obtained between twenty-four and forty-eight hours after onset. This finding provides very strong support for an ischemic etiology in TGA.

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