Transient Global Amnesia

TGA, once observed, is a remarkable condition. Its sufferers (for lack of a better word) lose the ability to form memories for up to 24 hours. They are marked by their propensity to repeat the same questions over and over again. They recover with only loss of memory for the discrete period of time in which they were impaired. The neuroimaging case cited below records bilateral hippocampal lesions that corresponded to the period of impairment. This included hyperintensity on FLAIR, restricted diffusion, and a SPECT scan showing hypoperfusion of bilateral hippocampi. Not all cases are associated with MRI changes but these studies seem to support the idea that hypoperfusion of the hippocampi without infarct causes the syndrome.

Di Filippo M, Calabresi P. Ischemic bilateral hippocampal dysfunction during transient global amnesia. Neurology 69;5:493.