A Perplexing Neurologic Condition: Transient Global Amnesia

Transcript generated from video captions. You may have heard that Katie Couric recently experienced an episode of a perplexing neurological condition, transient global amnesia. While neurologists will see patients with transient global amnesia in their training or throughout their career, most people outside of medicine are unfamiliar with the condition. Hello and welcome on behalf of Medscape. I am Dr Kathrin LaFaver, a neurologist in Saratoga Springs, New York.Family Friend and TGAI was recently reminded of this when a family friend reached out to me because of a scary episode her husband went through. My friend and her husband, Mike, were just returning from an international trip the day before and were having dinner at home when Mike became suddenly confused. He started asking strange questions, like where he was and how he had gotten there.He asked the same questions over and over again and didn't seem to recall the answers my friend was giving him just moments before. Scared, my friend convinced Mike to go to the ER for an evaluation. In the hospital, he continued to ask what was going on. He was seen by a neurologist and underwent several tests, including an MRI of the brain, which showed no stroke or other concerning findings.He was kept for observation overnight and by the next morning felt back to himself, although he did not remember why he was in the hospital or what had happened during the time of his confusion. He was eventually given a diagnosis of transient global amnesia, or TGA. So, what is TGA? The defining features are anterograde amnesia, which means the inability to form new memories.That's why Mike kept asking the same questions repeatedly. The answers simply don't stick. He also experienced retrograde amnesia, which is the loss of memories from the recent past, typically only hours or days before the event. During an episode, a person with TGA is alert and can communicate normally.Their cognitive functions, other than memory, are preserved. They can perform complex tasks they already know, like driving or cooking, though they won't remember doing them later. Importantly, the person's identity and long-term memories remain intact. They know who they are, and they recognize close family members.The episode is always temporary. By definition, TGA resolves completely within 24 hours, and often much sooner — typically within 4-8 hours. Once it is over, the person is back to normal functioning, except for a permanent memory gap for the duration of the episode itself. Of course, other causes of amnesia, such as seizures, stroke, or the effects of alcohol and drugs, have to be considered, especially in cases of an atypical presentation, such as a focal neurological deficit or delirium.Amnesia, including the loss of personal identity — a popular theme in movies and pop culture — is typically due to a functional or psychogenic etiology. Who gets TGA and what triggers it? According to a review in The New England Journal of Medicine in 2023, by Dr Allan Ropper, between three to five out of 100,000 people per year will have an episode of transient global amnesia.TGA typically occurs in people over the age of 50. Triggers may include a stressful life event, strenuous activity, sexual intercourse, a medical procedure, or severe pain, but many cases have no clear precipitating factor. What makes the condition so mysterious is that no clear pathophysiology has been identified.I reached out to a few colleagues specialized in cognitive and behavioral neurology to ask about their opinions about TGA. Dr Marissa Natelson Love is a dementia expert at the University of Alabama. She felt the phenomenon may be linked to migraines, as she frequently sees a migraine history in people presenting with this condition.Dr Khushboo Verma, from University of [Texas at Tyler], felt that low blood supply to brain regions involved in memory formation was the best explanation for TGA episodes. Brain imaging studies are typically normal in acute settings.Benign, Self-Limiting ConditionHowever, there often is delayed appearance of small ischemic lesions on MRI in the hippocampus formation. Fortunately, despite our limits in understanding TGA, we can reassure our patients and their family members that the outlook is good. TGA is considered a benign, self-limiting condition.Although this can be frustrating to hear that no specific treatment is available and that the memory gap will remain, the risk of recurrence is fortunately very low. Mike and my friend were most concerned about his future risk for memory loss, but having a single episode of TGA is not associated with an increased risk of stroke or future dementia.To sum it up, while an episode of transient global amnesia is deeply unsettling for both the affected individual and their family, it is a temporary stage of forgetting, not a sign of permanent brain damage. A few weeks have passed for Mike since his TGA episode, and it almost seems like a bad dream to him now as he is back to living his usual life.It certainly is a powerful reminder that there is still much to be understood about the intricate workings of our memory system. On behalf of Medscape, thank you for listening and have a great rest of your day.