What remains after transient global amnesia (TGA)? An ultra-high field 7T magnetic resonance imaging study of the hippocampus.

To study whether ultra-high-field 7T MRI can demonstrate chronic focal defects in the hippocampus corresponding to the former acute DWI lesions and to assess chronic T2-hyperintense hippocampal lesion load in transient global amnesia (TGA) patients.Follow-up 7T MRI of the hippocampus was performed in 13 patients with documented hippocampal DWI lesions (detected via 3T MRI) after acute TGA. The location of DWI lesions was transformed to 7T T2 images after data co-registration. Additionally, the T2-hyperintense lesion load was estimated in each patient and compared with that of 13 healthy controls.7T MRI was performed after a median of four months. No structural abnormality at the site of the previous TGA lesion was observed in any case. None of the controls showed DWI lesions. There was no significant difference between patients and controls concerning the number (p=0.67) or volume (p=0.45) of T2-hyperintense hippocampal lesions.DWI lesions in patients with TGA do not provoke any visible sequelae and do not result in hippocampal cavities. The occurrence of incidental hippocampal T2 lesions after TGA is not more frequent than in controls.