Transient global amnesia is a sudden, temporary loss of memory for events during, after, and sometimes before the event that caused the amnesia.
Transient global amnesia usually occurs in people aged 50 to 70. It rarely occurs in people under 40.
What causes this amnesia is not known. Some experts wonder whether the causes could include seizures, migraines, 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 to indicate that these conditions are the usual causes.
Drinking too much alcohol, taking moderately large doses of barbiturates (as a sedative), using several illegal drugs, or sometimes taking relatively small doses of a benzodiazepine (a sedative), especially midazolam and triazolam, can impair concentration, the ability to think clearly, and probably the ability to form and store new memories. However, such cases are not usually considered 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, or a Valsalva maneuver (forcefully trying to exhale without letting air escape, as during a bowel movement). However, usually no trigger is identified.
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. They may be confused about time, place, and sometimes the identity of other people. 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).
When alcohol or a drug causes amnesia, people forget events that happened around 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.
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.
Diagnosis and Treatment
Doctors usually diagnose this amnesia based mainly on symptoms and the results of a type of magnetic resonance imaging (MRI) of the brain called diffusion-weighted MRI. MRI results are usually normal when the person has symptoms but abnormal about 48 hours after symptoms have resolved.
Doctors usually do blood tests to check for signs of excessive blood clotting, a rare cause of this amnesia. If doctors suspect that a seizure may be the cause, they do electroencephalography (EEG).
Treatment depends on the cause.
Last full review/revision October 2013 by Juebin Huang, MD, PhD