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Transient Global Amnesia
Transient global amnesia is a sudden, temporary loss of memory for events during, after, and sometimes before the event that caused the 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.
Drinking too much alcohol, taking moderately large doses of barbiturates (such 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. Such cases are considered a specific form of 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 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).
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.
Doctors usually diagnose this amnesia based mainly on symptoms. They also do imaging tests such as computed tomography (CT), magnetic resonance imaging (MRI), or both.
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 are abnormal after about 3 days.
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).
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