Transient global amnesia

Transient global amnesia is an episode of confusion that comes on suddenly in a person who is otherwise alert. This confused state isn't caused by a more common neurological condition, such as epilepsy or stroke.

During an episode of transient global amnesia, a person is unable to create new memory, so the memory of recent events disappears. You can't remember where you are or how you got there. You may not remember anything about what's happening right now. 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 get better slowly over a few hours. During recovery, you may begin to remember events and circumstances. Transient global amnesia isn't serious, but it can still be frightening.

The main symptom of transient global amnesia is being unable to create new memories and remember the recent past. Once that symptom is confirmed, ruling out other possible causes of amnesia is important.

You must have these signs and symptoms to be diagnosed with transient global amnesia:

• Sudden onset of confusion that includes memory loss, seen by a witness
• Being awake and alert and knowing who you are, despite memory loss
• Normal cognition, such as the ability to recognize and name familiar objects and follow simple directions
• No signs of damage to a particular area of the brain, such as being unable to move an arm or leg, movements you can't control, or problems understanding words

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

• Symptoms lasting no more than 24 hours and generally shorter
• Gradual return of memory
• No recent head injury
• No signs of seizures during the period of amnesia
• No history of active epilepsy

Another common sign of transient global amnesia due to the inability to create new memories includes repetitive questioning, usually of the same question — for example, "What am I doing here?" or "How did we get here?"

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.

Transient global amnesia isn't dangerous. But there's no easy way to tell the difference between transient global amnesia and the life-threatening illnesses that can also cause sudden memory loss.

The underlying cause of transient global amnesia is unknown. There may be a link between transient global amnesia and a history of migraines. But experts don't understand the factors that contribute to both conditions. Another possible cause is the overfilling of veins with blood due to some sort of blockage or other problem 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
• Being emotionally upset, perhaps by bad news, conflict or overwork

Interestingly, many studies have found that 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.
• History of migraines. If you have migraines, your risk of transient global amnesia is significantly higher than that of someone without migraines.

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.

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.