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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

• Sudden immersion in cold or hot water

• Physical exertion

• Emotional or psychologic stress

• Pain

• Medical procedures

• Sexual intercourse

• A Valsalva maneuver (forcefully trying to exhale without letting air escape, as during a bowel movement)

However, usually no trigger can be identified.

The following can cause symptoms that resemble those of transient global amnesia:

• Drinking too much alcohol

• Taking moderately large doses of certain sedatives (such as a barbiturate)

• Using any of several illicit drugs

• Sometimes taking relatively small doses of a benzodiazepine (a sedative), especially midazolam and triazolam

People with transient global amnesia suddenly but temporarily lose the ability to recall events that happened after or before the amnesia occurred and to store new memories. 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.

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.

• A doctor's evaluation

• Magnetic resonance imaging

Doctors usually diagnose transient global amnesia based mainly on symptoms. They also do tests to check for other causes of sudden amnesia:

• A complete blood count to check for other possible disorders of the amnesia

• Blood tests for alcohol and clotting disorders

• Urine tests for illicit drugs

• Magnetic resonance imaging (MRI) of the brain

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.

A more extensive evaluation may be done if the transient amnestic episodes recur.

• Treatment of the cause if identified

There is no specific treatment for transient global amnesia. It has no lasting effects and only rarely recurs.

If identified, the cause of transient global amnesia is treated. For example, if seizures are the cause, antiseizure drugs are used.