Transient global amnesia causes a sudden inability to form new memories, often with repeated questions, while a person remains awake and can usually recognize who they are. The episode clears within 24 hours, commonly after several hours, but you cannot safely identify it at home: stroke, seizure and other urgent problems can also cause sudden confusion or memory loss. New, unexplained memory loss needs immediate medical assessment.
What transient global amnesia causes—and what remains unknown
Despite the name, the cause of transient global amnesia (TGA) is not established. Researchers have proposed several possibilities, including changes in blood flow, migraine-related mechanisms and seizure activity, but no single explanation accounts for the syndrome. Physical exertion, emotional stress, pain or straining have been reported before some episodes; a preceding activity does not prove what caused one.
TGA is seen most often between ages 50 and 70. During a typical episode, the person repeatedly asks about the time or what is happening because new information does not stick. They may be confused about recent events, but alertness and other abilities are generally preserved, without a new weakness, speech problem or other focal neurological sign. Memory usually returns, though a gap for the episode itself commonly remains.
How clinicians distinguish TGA from an emergency
Clinicians rely first on the history, a neurological examination and information from someone who witnessed the episode. They look for the pattern of memory loss, how long it lasts, whether the person stayed alert, and whether other symptoms or a seizure were present. Blood tests may check for metabolic problems or other explanations. A CT scan may be used early in an emergency evaluation, but a normal CT does not by itself establish TGA.
Stroke can overlap with TGA, so sudden memory loss is not something to watch at home while waiting to see if it passes. Weakness, numbness, trouble speaking, vision changes or difficulty walking make urgent stroke assessment especially important; their absence does not rule out every serious cause. Read more about why TIA symptoms that go away still need urgent assessment.
Seizure is another consideration, particularly when memory episodes are brief and recur. An EEG, which records electrical activity in the brain, may help clinicians assess possible epileptic amnesia. A normal EEG does not necessarily exclude it. The German Society of Neurology’s 2023 guideline, developed jointly with neurological societies in Austria and Switzerland, advises prompt further testing when the presentation is atypical or another diagnosis is suspected. It also says TGA is rare under age 50, making a search for other causes particularly important in younger people.
What an MRI can show—and why timing matters
MRI is useful both to look for other causes and, in some cases, to support TGA. Diffusion-weighted imaging (DWI) may show tiny spots in the hippocampus, a brain area involved in memory, often in a region called CA1. These findings are not visible in every person with TGA, and an MRI taken very early can be normal.
A 2025 case series by Saeedur Rahman and colleagues at Darent Valley Hospital in Kent, UK, described three patients assessed for TGA. In one case, an MRI taken four hours after symptoms began showed no definite abnormality; a repeat scan at 24 hours showed small hippocampal changes. The German, Austrian and Swiss guideline likewise notes that MRI is more sensitive when performed 24–72 hours after onset. So an early normal scan does not settle the question; clinicians decide whether later imaging or other tests are needed based on the whole presentation.
Recovery and the chance of another episode
By definition, a TGA episode resolves within 24 hours, and most people return to their usual level of memory and thinking. The memory gap for the episode may persist. The German Society of Neurology guideline reports no evidence that TGA causes chronic memory impairment, dementia or increased risk of cerebral ischaemia. That is reassuring at a group level, but it does not replace assessment of the individual episode or management of other health risks.
TGA can recur, although most people do not have repeated episodes. The guideline puts recurrence estimates at 12–27%; estimates vary across research, so this range cannot predict an individual’s chances. There is no evidence-based treatment or prevention plan specific to TGA because its mechanism remains uncertain. If another episode occurs—or memory loss does not resolve within 24 hours—seek urgent medical care rather than assuming it is the same condition. A clinician can assess what happened and whether follow-up is appropriate.
