Transient global amnesia is scary, but a benign condition. What to do when it happens

Dr. Jeff Hersh
·4 min read

A reader's friend had an episode where she seemed confused as to where she was and how she got there. They took her to the emergency room, where the doctor said she had an otherwise completely normal neurological exam, and her MRI was normal. They diagnosed her with "transient global amnesia," and it was resolved overnight. What is this condition?

Transient global amnesia (TGA) is an uncommon condition affecting about 1 in every 20,000 Americans, although as many as 1 of every 4,000 over age 50. Many TGA patients have a precipitating factor such as physical exertion, emotional stress, pain, cold-water exposure or sexual activity.

Dr. Jeff Hersh
Dr. Jeff Hersh

What are the symptoms of transient global amnesia?

The classic symptom of TGA is the acute loss of the ability to acquire new memories (anterograde memory loss). There is also often the loss of, or impaired ability to access, recent past memories (retrograde amnesia). Retrograde amnesia is typically patchy, and may affect the hours, days, months or even occasionally years prior to the TGA episode and is often subtle. Memory of things that happened in the more distant past is typically intact.

During an attack of TGA, the patient speaks and thinks normally, although the memory issues may make it seem like they are confused. They may repetitively ask the same simple questions, such as "Where am I?" or "How did I get here?" because they are not able to form a new memory of the answers they receive.

What are the criteria for an event to be considered TGA?

Criteria for a diagnosis of TGA include:

  • A reliable observer can provide a history of what happened;

  • Anterograde memory is affected;

  • There is no clouding of consciousness, no impairment of functioning and no focal neurological symptoms (such as speech problems, vision problems, weakness of the face or body, change in sensation or other symptoms that would suggest a stroke);

  • There is nothing to suggest the patient had a seizure, and no history of seizures for at least the previous two years;

  • There are no intoxicating substances (such as alcohol or benzodiazepines) in the patient’s system;

  • There was no recent head trauma (somewhat similar symptoms can occur from a concussion);

  • The symptoms last fewer than 24 hours; most commonly they last two to eight hours.

The cause of TGA is unknown. It has been theorized that a decrease in blood flow to the areas of the brain responsible for memory may be the cause; however, there is no increased risk of stroke for people who have had TGA, and it is not felt that any loss of blood flow is due to a blockage of an artery like that seen in mini-strokes (transient ischemic attacks or TIAs). Some authors theorize that TGA may be an atypical migraine. However, even though there is an increased incidence of TGA in patients with either a personal or family history of migraines, most TGA patients do not have either of these risk factors.

How doe patients recover?

Patients with TGA typically have a fast and complete recovery, although 25% will have a recurrence in their lifetimes, with about 3% to 5% having one within a year. However, less than 3% of TGA patients will have more than three episodes in their lifetime, so this is usually not a chronic condition.

The evaluation of TGA focuses on ruling out other conditions that can cause memory loss:

  • An imaging study (CT or MRI) may be done since (rarely) a bleed into the brain or even a brain tumor can cause memory problems (if they affect the parts of the brain associated with memory acquisition).

  • Atypical seizures (or even the phase after a typical seizure where a patient can seem confused, called a post-ictal phase) may be evaluated. If there is suspicion of a seizure, an electroencephalogram (EEG) may be indicated.

  • Toxic or metabolic causes (for example, due to drugs or other issues) are typically ruled out by blood and/or urine tests.

  • Alcoholics can develop a syndrome in which they develop memory problems; however, symptoms from this are not usually acute in onset.

If you or a loved one develops acute memory issues, you should go to the nearest emergency room to be evaluated. Although a TGA is scary for both patients and their families, transient global amnesia is a benign condition with an excellent prognosis.

Jeff Hersh, Ph.D., M.D., can be reached at DrHersh@juno.com.

This article originally appeared on MetroWest Daily News: Transient global amnesia inability to acquire new memories