What causes transient global amnesia is not known, but a similar, temporary loss of memory can result from drinking too much alcohol or taking certain drugs.
People with transient global amnesia suddenly but temporarily become unable to store new memories or to recall events that occurred during the episode.
Doctors diagnose this amnesia based mainly on symptoms and certain MRI findings..
Transient global amnesia has no lasting effects and requires no treatment.
Transient global amnesia usually occurs in people aged 50 to 70. It rarely occurs in people under 40.
What causes transient global amnesia is not known. Some experts wonder whether the causes could include seizures, migraines, problems with blood flow in the veins, or temporary blockage of the arteries that supply blood to the temporal lobe (for example, by a blood clot), and/or psychologic factors. However, there is no strong evidence that any of these conditions cause transient global amnesia.
Transient global amnesia can be triggered by
However, usually no trigger is identified.
The following can cause symptoms that resemble those of transient global amnesia:
People with transient global amnesia suddenly but temporarily lose the ability to store new memories and to recall events that happened after the amnesia occurred. They are alert and anxious and often repeat the same question or phrase because they cannot remember it. They may be confused about time and place but are usually not confused about the identity of other people. They can provide coherent answers to questions that do not depend on memory. People sometimes also forget some of the things that happened before the amnesia occurred.
Memory loss usually lasts 1 to 8 hours but may last 30 minutes up to 24 hours (rarely).
Most people with transient global amnesia have only one episode in a lifetime, unless the cause is seizures or migraines. About 5 to 25% have repeated episodes.
After an episode, the confusion usually clears quickly, and total recovery is the rule, although people may not remember what happened during the episode.
Temporary amnesia caused by alcohol or a drug, like transient global amnesia, can impair concentration, the ability to think clearly, and the ability to form and store new memories. However, it differs from transient global amnesia in the following ways:
People forget only the events that happened just before and/or during the time they were affected by alcohol or the drug.
These people are confused only as long as they are under the influence of alcohol or the drug.
Usually, amnesia recurs only if they drink the same amount of alcohol or take the same amount of the drug.
Doctors usually diagnose transient global amnesia based mainly on symptoms. They also do tests to check for other causes of sudden amnesia:
Because a seizure in the temporal lobe can temporarily impair memory, doctors may do electroencephalography (EEG) to check for abnormal electrical activity in the brain that suggests a seizure.
When transient global amnesia first occurs, MRI does not show specific abnormalities. However, after a few days, MRI may show tiny dots in an area of the brain that is important in forming and retrieving memories (the hippocampus). The spots may represent small areas where blood flow is decreased, suggesting a possible cause of the amnesia.