When Katie recently experienced an episode of transient global amnesia (TGA), it left her (and everyone around her) pretty shaken. As she shared in her essay about the episode, the sudden inability to recall what had happened for several hours was alarming, confusing, and raised plenty of questions. While TGA is dramatic to witness, it's also a condition that many people have never heard of — until it happens to them or someone they love.
To help explain what transient global amnesia is, why it happens, and what to do if you ever encounter it, we turned to board-certified neurologist and bestselling author David Perlmutter, M.D., FACN, an internationally recognized expert on brain health (and whose book Brain Defenders comes out 8/18). Here, he answers the most common questions about TGA — from how it differs from a stroke to whether it has any lasting effects.
KCM: What exactly is transient global amnesia, and what does it look like in real life?
Dr. Perlmutter: TGA is a sudden, temporary loss of the ability to form new memories. A person is awake, alert, knows who they are, recognizes family members, and can carry on a conversation, but they can't remember what just happened a few minutes ago. They often ask the same questions repeatedly, such as, "Where are we?" or "How did I get here?" because each answer is quickly forgotten. In fact, this constant repetition of the same question is a symptom I have observed in every patient with this disorder I have ever treated.
It can be frightening to witness because it appears as though the person's memory has suddenly "shut off." Fortunately, despite how dramatic it looks, TGA is usually a benign condition. The episode typically lasts several hours and almost always resolves completely within 24 hours, leaving only a gap in memory for everything that occurred during the event itself.
If someone suddenly can't remember what's happening, how can you tell whether it's transient global amnesia or a stroke?
This is one situation where you should never try to make the diagnosis yourself. A stroke can sometimes present with unusual symptoms, and any sudden change in brain function deserves immediate medical evaluation.
That said, there are some important differences. People with transient global amnesia typically have isolated memory loss. They can speak normally, move both sides of their body normally, recognize loved ones, and remain fully conscious. In contrast, a stroke often causes additional symptoms such as weakness, numbness, difficulty speaking, vision changes, or problems with balance.
But to be clear, the distinction isn't always obvious, so it's best to call emergency medical services or go to the nearest emergency department so a stroke, seizure, and other serious conditions can be ruled out.
What causes transient global amnesia — are there common triggers?
Simple answer: We don’t know, but the evidence suggests that the brain's memory center, the hippocampus, temporarily stops functioning normally. The good news is that this generally appears to be reversible, with no permanent damage in the vast majority of people.
Episodes are often preceded by a sudden physical or emotional stress. Common triggers include vigorous exercise, heavy lifting, emotional shock, pain, sexual activity, coughing, or straining.
One particularly interesting trigger is sudden immersion in cold water. Neurologists have recognized for years that diving into very cold water or experiencing an abrupt temperature change can occasionally precipitate an episode of transient global amnesia. As cold plunges and ice baths become increasingly popular, we may begin seeing this condition more often. It's still uncommon, and I don't think this should discourage people from cold-water therapy altogether, but it is another reminder that abrupt physiological stress can have unexpected effects on the brain in susceptible individuals.
Does having transient global amnesia mean you're at higher risk for dementia, stroke, or another serious brain problem later?
Fortunately, the answer is generally no.
The overwhelming majority of people recover completely and do not go on to develop dementia because of the episode. Likewise, most studies have not found that transient global amnesia increases the long-term risk of stroke.
That's reassuring because the event is understandably terrifying for patients and their families. While the experience feels dramatic, the long-term outlook is excellent. Most people have only a single episode during their lifetime, although a small percentage may experience another one.
If this happens to you — or to someone you're with — what should you do in the moment?
The most important step is to treat it as a medical emergency until proven otherwise. Yes, I’ve described this as a benign event, but that’s after the diagnosis has been confirmed. Call emergency medical services or seek immediate medical attention so physicians can rule out a stroke, seizure, or other potentially serious causes of sudden memory loss.
While you're waiting for help, stay calm and reassure the person. They may ask the same questions over and over again because they simply can't retain the answers. That’s actually a good thing because it helps confirm the diagnosis. And don't expect them to remember what you've just told them.
Once they've been properly evaluated and transient global amnesia is confirmed, the prognosis is usually excellent. Although the episode can be frightening, it's one of those neurological conditions that looks much worse than it usually turns out to be. Most people quickly return to their normal baseline, with the only lasting effect being that they never remember the hours during which the episode occurred.
