Hippocampal lesions in transient global amnesia

Abstract

The history of primarily anterograde amnesia, lasting several hours and characterised by an inability to lay down new memory (as evidenced by repeatedly asking the same questions), without impairment of other neurological functions and with preserved consciousness and self awareness, is typical of transient global amnesia (TGA). Episodes may follow stressful situations, physical exertion, cold immersion or as in this case, sexual intercourse. Small punctate (1–2 mm) hippocampal lesions on MRI diffusion-weighted imaging have been reported in patients with TGA. In one study, lesion detection was improved by reducing the thickness of MR slices, that is, 13% lesion detection at 5 mm slice thickness which increased up to 38% at 3 mm section thickness. An increased b-value of 2000 also improved lesion detection. With subsequent imaging, the hippocampal lesions seen on diffusion-weighted imaging are not seen on later studies. This is analogous to the reversibility of diffusion weighted imaging hyper-