Overview

Transient global amnesia is a sudden, temporary episode of memory loss that can't be attributed to a more common neurological condition, such as epilepsy or stroke.

During an episode of transient global amnesia, your recall of recent events simply vanishes, so you can't remember where you are or how you got there. In addition, you may not remember anything about what's happening in the here and now. Consequently, you may keep repeating the same questions because you don't remember the answers you've just been given. You may also draw a blank when asked to remember things that happened a day, a month or even a year ago.

The condition most often affects people in middle or older age. With transient global amnesia, you do remember who you are, and you recognize the people you know well. Episodes of transient global amnesia always improve gradually over a few hours. During recovery, you may slowly begin to remember events and circumstances. Transient global amnesia isn't serious, but it can still be frightening.

Symptoms

Transient global amnesia is identified by its main symptom, which is the inability to form new memories and to recall the recent past. Once that symptom is confirmed, ruling out other possible causes of amnesia is important.

These signs and symptoms must be present to diagnose transient global amnesia:

Sudden onset of memory loss, verified by a witness

Retention of personal identity despite memory loss

Normal cognition, such as the ability to recognize and name familiar objects and follow simple directions

Absence of signs indicating damage to a particular area of the brain, such as limb paralysis, involuntary movement or impaired word recognition

Additional symptoms and history that may help diagnose transient global amnesia:

Duration of no more than 24 hours and generally shorter

Gradual return of memory

No recent head injury

No evidence of seizures during the period of amnesia

No history of active epilepsy

Along with these signs and symptoms, a common feature of transient global amnesia includes repetitive questioning, usually of the same question — for example, "What am I doing here?" or "How did we get here?"

When to see a doctor

Seek immediate medical attention for anyone who quickly goes from normal awareness of present reality to confusion about what just happened. If the person experiencing memory loss is too confused to call an ambulance, call one yourself.

Although transient global amnesia isn't harmful, there's no easy way to distinguish the condition from the life-threatening illnesses that can also cause sudden memory loss.

Causes

The underlying cause of transient global amnesia is unknown. There appears to be a link between transient global amnesia and a history of migraines, though the underlying factors that contribute to both conditions aren't fully understood. Another possible cause is the overfilling of veins with blood due to some sort of blockage or other abnormality with the flow of blood (venous congestion).

While the likelihood of transient global amnesia after these events is very low, some commonly reported events that may trigger it include:

Sudden immersion in cold or hot water

Strenuous physical activity

Sexual intercourse

Medical procedures, such as angiography or endoscopy

Mild head trauma

Acute emotional distress, as might be provoked by bad news, conflict or overwork

Risk factors

Interestingly, high blood pressure and high cholesterol — which are closely linked to strokes —are not risk factors for transient global amnesia. This is probably because transient global amnesia doesn't represent blood vessel diseases of aging. Your sex doesn't seem to affect your risk, either.

The clearest risk factors are:

Age. People age 50 and older have a higher risk of transient global amnesia than do younger people.

People age 50 and older have a higher risk of transient global amnesia than do younger people. History of migraines. If you have migraines, your risk of transient global amnesia is significantly higher than that of someone without migraines.

Complications

Transient global amnesia has no direct complications. It's not a risk factor for stroke or epilepsy. It's possible to have a second episode of transient global amnesia, but it's extremely rare to have more than two.

But, even temporary memory loss can cause emotional distress. If you need reassurance, ask your doctor to go over the results of your neurological exam and diagnostic tests with you.

Prevention

Because the cause of transient global amnesia is unknown and the rate of recurrence is low, there's no real way to prevent the condition.