Long-term sequelae of hippocampal lesions in patients with transient global amnesia: A multiparametric MRI study.

BACKGROUND

MRI signal diffusion-weighted imaging (DWI) hyperintensity in the hippocampus in patients with transient global amnesia (TGA) are resolved within several days after the onset of TGA.

PURPOSE: To use multiparametric MRI to unravel the sequelae of TGA.

STUDY TYPE: A prospective longitudinal study.

POPULATION: Eight TGA patients.

FIELD STRENGTH/SEQUENCE: A 3.0T Siemens Tim Trio MRI scanner with T1 -weighted MPRAGE, diffusion-weighted echo planar imaging, and multiecho gradient-recalled echo sequences.

ASSESSMENT: Brain MRI scanned within 72 hours, 2 weeks, and 3 months after onset of TGA, respectively. T1 image hippocampus was first segmented into 12 subregions using FreeSurfer and registered to DWI to locate DWI lesion. Then a T1 image with segmented hippocampus was registered to its corresponding apparent diffusion coefficient (ADC) map, fractional anisotropy (FA) map, and quantitative susceptibility map, respectively. Finally, the volume, water diffusion and anisotropy, and magnetic susceptibility of DWI lesion were analyzed.

STATISTICAL TESTS: A paired samples t-test was performed to detect measurement differences between three tests. Pearson correlation was used to assess the correlations between all measurements.

RESULTS

Hyperintensity was detected in the head, body, and caudate of CA1 and hippocampal tail. No significant changes existed in CA1/unit volume across the three timepoint measurements (all, P > 0.480). In Test 1, ratio ADC (DWI lesion / adjacent healthy, rADC) and ratio FA (rFA) decreased below, while ratio susceptibility increased above 1.0. In Test 2, all the episodes normalized around 1.0. In Test 3, rADC remained normalization, but rFA decreased and ratio susceptibility increased again. In Test 1 and Test 3 (vs. Test 2), decreased FA values were accompanied with lower axial diffusivity and/or higher radial diffusivity (all, P < 0.001). Moreover, rFA significantly correlated with ratio susceptibility in Test 3 (r = -0.665, P = 0.039).

DATA

CONCLUSION

Microstructural sequelae in hippocampus were demonstrated, which indicates that ischemic lesions may be associated with TGA.

LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:1350-1358.