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.
With transient global amnesia, you do remember who you are, and recognize the people you know well. But that doesn't make your memory loss less disturbing.
Fortunately, transient global amnesia is rare, seemingly harmless and unlikely to happen again. Episodes are usually short-lived, and afterward your memory is fine.
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.
Necessary symptoms for diagnosis
Health care professionals base a diagnosis of transient global amnesia on the following signs and symptoms:
- 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 on which a diagnosis for transient global amnesia is based:
- Duration of no more than 24 hours and generally shorter
- Gradual return of memory
- 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 disoriented 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. In fact, sudden amnesia is much more likely to be caused by a stroke or a seizure than by transient global amnesia. A medical evaluation is the only way to determine the cause of sudden memory loss.
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.
Some commonly reported events that may trigger transient global amnesia 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
Interestingly, high blood pressure and high cholesterol — which are closely linked to strokes — are not risk factors for transient global amnesia. 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, but it can cause emotional distress. If you have an episode, the gap in your memory can be unsettling, and you're likely to worry about a recurrence.
Also, a symptom as dramatic as memory loss often indicates a serious underlying disease. Transient global amnesia is an exception, but it can be hard to let go of the fear that you have a tumor or had a stroke.
If you need reassurance, ask your doctor to go over the results of your neurological exam and diagnostic tests with you. A counselor or psychotherapist can help you deal with persistent anxiety. Importantly, transient global amnesia is not a risk factor for stroke.
Because the cause of transient global amnesia is unknown and the rate of recurrence is low, no standard approaches for preventing the condition exist. If your episode of transient global amnesia followed a particular activity, such as a strenuous workout or a swim in a chilly lake, talk with your doctor about limiting or avoiding the activity that seemed to trigger your memory loss.