and his or her relatives. seeing a once competent and healthy partner, sibling or parent become incapable of remembering what was said only a minute ago is very distressing, and hence it is often the relatives who will require reassurance." it is unclear if episodes of tga increase the future risk of a stroke. some population based studies show no increased risk of a stroke after an episode of tga, while other population based studies show a slightly increased risk. recurrence rates of tga are variously reported, with one systematic calculation suggesting the rate is under 6% per year. fifteen percent of people who have had an episode of tga have multiple episodes, with an average interval of 2 years between episodes. tga may have multiple etiologies and prognoses. atypical presentations may masquerade as epilepsy and be more properly considered tea. in addition to such probable tea cases, some people experiencing amnestic events diverging from the diagnostic criteria articulated above may have a less benign prognosis than those with "pure" tga. recently, moreover, both imaging and neurocognitive testing studies question whether tga is as benign as has been thought. mri scans of the brain in one study showed that among people who had experienced tga, all had cavities in the hippocampus, and these cavities were far more numerous, larger, and more suggestive of pathological damage than in either healthy controls or a large control group of people with tumor or stroke. verbal and cognitive impairments have been observed days after tga attacks, of such severity that the researchers estimated the effects would be unlikely to resolve within a short time frame. a large neurocognitive study of patients more than a year after their attack has shown persistent effects consistent with amnestic mild cognitive impairment (mci-a) in a third of the people who had experienced tga. in another study, "selective cognitive dysfunctions after the clinical recovery" were observed, suggesting a prefrontal impairment. these dysfunctions may not be in memory per se but in retrieval, in which speed of access is part of the problem among people who have had tga and experience ongoing memory problems. epidemiology the estimated annual incidence of tga varies from a minimum of 2.9 cases per 100,000 population (in spain) and 5.2 per 100,000 (in the us), but among people aged over 50, the rate of tga incidence is reported to range from approximately 23 per 100,000 (in a us population) to 32 per 100,000 (in a population in scandinavia). tga is most common in people between age 56 and 75, with the average age of a person experiencing tga being approximately 62.