Transient global amnesia: Diffusion MRI findings

Aim of this study is to identify and describe the MRI findings in patients with Transient Global Amnesia (TGA), specifically on Diffusion Weighted Imaging (DWI) sequence.

MRI findings in 12 patients with clinical diagnosis of TGA were retrospectively analysed. MRI brain was performed with a 3T scanner on 11 patients and 1.5T scanner on 1 patient. DWI were acquired at B value of 1000 s/mm² in 4 patients, 2000 s/mm² in 2 patients and both 1000 and 2000 s/mm² in 6 patients.

There were 7 female and 5 male patients. The mean age was 65.67 years (range 61-74 years). The median time interval between the onset of symptom and MRI scan was 47.5 hours, range 25-114 hours. 11 of the 12 patients showed punctate foci of restricted diffusion in hippocampus (mean size 3.7 mm (range 2-6.5 mm). 10 patients showed foci in left hippocampus. Nine patients showed a single focus, 1 patient showed three foci and 1 patient showed four foci. In 6 patients who had DWI MRI at both B values, scans at B value of 1000 s/mm² revealed abnormality in 4 patients, while higher B value imaging improved sensitivity in one patient and one patient had a negative scan at both B values.

We have highlighted the MRI finding of typical punctate foci of bright signal in hippocampus seen on DWI in patients diagnosed with TGA. Detection on a routine stroke MRI protocol can avoid need for dedicated TGA protocols or repeat scan, improving the workflow.