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What Is Transient Global Amnesia?
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What Is Transient Global Amnesia?

Written by
Kara Rogers
Kara Rogers is the senior editor of biomedical sciences at Encyclopædia Britannica, where she oversees a range of content from medicine and genetics to microorganisms. She joined Britannica in 2006 and...
Kara Rogers
Fact-checked by
Britannica Editors
Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree....
Britannica Editors
History

Transient global amnesia (TGA) is a neurological syndrome that causes the sudden, temporary inability to form new memories while leaving consciousness, personal identity, language, and most other cognitive functions intact. Although the condition can be alarming, it is usually short-lived—lasting an average of 6 to 8 hours and resolving within 24 hours. TGA typically occurs in adults between the ages of 50 and 70, with the majority of those affected experiencing only a single episode.

The hallmark of TGA is anterograde amnesia, the inability to store new memories. Affected individuals remain awake, recognize familiar people, and perform routine tasks, yet they are unable to retain newly acquired information. They commonly ask the same questions repeatedly because they cannot remember having already received the answers. Many people also experience retrograde amnesia, temporarily losing memories of events that occurred shortly before the episode.

The exact cause of TGA remains uncertain, but evidence suggests that it results from a temporary disruption of memory-processing networks centered on the hippocampus, which is located in the medial temporal lobe of the brain and is essential for forming long-term memories. Episodes are often associated with sudden physical or emotional stress, vigorous exercise, immersion in hot or cold water, severe pain, sexual activity, and certain medical procedures. People with a history of migraine appear to have an increased risk of developing TGA.

A TGA diagnosis is based primarily on a reliable witness account confirming acute onset, the characteristic pattern of symptoms, and the exclusion of other causes of sudden memory loss, such as head injury, stroke, seizures, or alcohol or drug intoxication. Magnetic resonance imaging (MRI) may reveal small, temporary abnormalities, specifically in the memory-processing CA1 region of the hippocampus, several hours after symptom onset, but imaging findings are often normal.

As memory gradually returns, individuals usually recover fully, although they often retain a permanent gap in memory for the events that occurred during the episode. Evidence indicates that TGA does not increase the long-term risk of neurological conditions such as epilepsy or stroke, making it one of the few causes of sudden memory loss with an excellent prognosis.

Kara Rogers