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.

To diagnose transient global amnesia, your health care provider must first rule out more-serious conditions. This can include stroke, seizure or head injury, for example. These conditions can cause the same type of memory loss.

Physical exam

This begins with a neurological exam, checking reflexes, muscle tone, muscle strength, sensory function, gait, posture, coordination and balance. The doctor may also ask questions to test thinking, judgment and memory.

Brain and imaging tests

The next step is testing to look for abnormalities in the brain's electrical activity and blood flow. Your health care provider might order one or a combination of these tests:

• Computerized tomography (CT). Using special X-ray equipment, your doctor obtains images from many different angles and joins them together to show cross-sectional images of the brain and skull. CT scans can reveal abnormalities in brain structure, including narrowed, overstretched or broken blood vessels and past strokes.
• Magnetic resonance imaging (MRI). This technique uses a magnetic field and radio waves to create detailed, cross-sectional images of the brain. The MRI machine can combine these slices to produce 3D images that may be viewed from many different angles. An MRI may not be needed if you had a CT scan at the time of the episode, and the CT didn't show any problems in the brain.
• Electroencephalogram (EEG). An EEG records the brain's electrical activity via electrodes attached to the scalp. People with epilepsy often have changes in their brain waves, even when they're not having a seizure. This test is usually ordered if you've had more than one episode of transient global amnesia or if your doctor suspects that you're having seizures.

No treatment is needed for transient global amnesia. It gets better without treatment and has no known lasting effects.

Anyone who experiences sudden loss of memory for all events leading up to the present needs emergency medical care. Call 911 or your local emergency number immediately.

If a friend or family member develops these symptoms in your presence, go with him or her to the hospital. Because he or she doesn't remember recent events, you'll need to provide important information to the doctor.

What you can do

• Stay with the person through the full medical evaluation. Sudden memory loss may indicate a serious health problem. Take an active role in noting all the information the doctor provides and in helping to make decisions about next steps.
• Share with medical staff physically or emotionally stressful events that preceded the memory loss. Important details include conflict or anxiety at work or at home, strenuous physical activity, or sudden immersion in hot or cold water — anything that may have caused the person alarm or strain.
• Note any accompanying signs or symptoms, such as numbness, weakness or trembling.
• Relay key medical information, including any other conditions with which the person has been diagnosed. Also include all medications he or she is taking.

• Write down questions to ask the doctor. Prepare a list of questions to ask the doctor on the person's behalf. Although people experiencing transient global amnesia can think and speak, it's likely that they will be feeling severe distress. For transient global amnesia, some basic questions include:

  • What is most likely causing the symptoms?
  • What are the other possible causes for these symptoms?
  • What kinds of tests do you recommend?
  • Is any treatment needed now?
  • What signs or symptoms should I be watching for at home?
  • What signs or symptoms should prompt calling 911 or emergency medical help?
  • How soon do you expect the symptoms to improve?
  • Do you expect a full recovery?
  • Are there any steps to take to prevent a recurrence of this problem?
  • What is the risk of long-term complications from this condition?

  In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions as they occur to you during the appointment.

What to expect from your doctor

The doctor is likely to ask both you and the person experiencing amnesia a number of questions about symptoms and about the period leading up to the memory loss.

The doctor may ask your loved one:

• What is the last thing you remember?
• Do you know who you are?
• Do you know the person who came with you?
• Do you have any symptoms other than memory loss?
• Are you dizzy?
• Are you having problems with balance or coordination?
• Do you feel weakness or numbness on either side of your body?
• Are you having any vision problems?
• Do your symptoms include headache?

To determine the extent of memory loss, the doctor may check your loved one's knowledge of general information — such as the name of the current president — and assess his or her ability to recall a random list of words.

The doctor may ask you:

• When did the person's memory loss begin?
• Did the memory loss come on gradually or suddenly?
• Has anything like this ever happened before?
• What happened just before the memory loss?
• Did they experience an accident that may have injured their head?
• Have they recently experienced significant stress, conflict or loss?
• Have they had a seizure since symptoms began?
• Have they been diagnosed with any other medical conditions?
• Do they have a history of migraines?
• Have they recently undergone any medical procedures or surgery?
• What medications are they taking, including prescription drugs, over-the-counter medications, herbs and supplements?