Transient global amnesia and focal diffusion weighted imaging lesions in mesiotemporal region: A ten-year experience

Objective: To determine prevalence and characteristics of mesiotemporal diffusion weighted imaging (DWI) lesions in transient global amnesia (TGA), and to determine prevalence of "missed" DWI lesions on routine radiological reporting. Methods: This is a retrospective study of patients with TGA admitted to a tertiary care hospital over ten years. Patients with TGA, who underwent magnetic resonance imaging (MRI) of the brain within one week of index event, were included in this study. MRI's were reviewed by two independent raters. Clinical data and other investigations were collated. Results: Of the 55 patients of TGA, 19 (35 %) had hyperintense DWI lesions with concordant apparent diffusion coefficient (ADC) hypointensity in the mesiotemporal region. Fifteen out of 19 (79 %) had unilateral lesions (6 left, 9 right). Twelve out of 19 DWI lesions were reported at the time of index scan. The false negative reporting rate was 36.8 %. DWI slice thickness (5 mm versus 3 mm), MRI machine strength (1.5 versus 3 T) and time interval from symptom onset to MRI brain (> 24 h versus <= 24 h) were not significantly different between patients with or without DWI lesions and as well between patients with DWI lesions missed and initially reported at the time of index scan. Conclusion: Punctuate DWI mesiotemporal lesions in TGA are prone to under-reporting. These lesions need to be categorically searched for at the time of reporting MRI Brain.