Transient Global Amnesia
What causes many cases of transient global amnesia is not known, but one type is caused by drinking too much alcohol or taking certain drugs.
People with this amnesia suddenly but temporarily become unable to store new memories and to recall events that happened after the amnesia occurred.
Usually, doctors diagnose this amnesia based mainly on symptoms.
The cause of memory loss is treated if possible.
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. Excessive blood clotting is a rare cause of transient global amnesia.
The following can impair concentration, the ability to think clearly, and probably the ability to form and store new memories. A brief episode of transient global amnesia can result.
Such cases are considered a specific form of transient global amnesia.
Transient global amnesia can be triggered by
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 and place but are usually not confused about 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).
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.
Transient global amnesia that is caused by alcohol or a drug is different from that caused by other conditions. It differs 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 imaging tests such as computed tomography (CT), magnetic resonance imaging (MRI), or both to check for abnormalities.
If doctors suspect a blockage in the blood vessels to the brain, they do a type of magnetic resonance imaging (MRI) of the brain called high-resolution diffusion-weighted MRI. In most people with a blockage, MRI results are normal for 24 hours after symptoms begin, but results become abnormal after about 3 days.
Doctors usually do other tests to exclude other causes of transient global amnesia.
If doctors suspect that a seizure may be the cause, they do electroencephalography (EEG).