ADC and Diffusion Anisotropy Indices in Wallerian Degeneration

We compared the sensitivity of diffusion MRI to T2SI for early detection of Wallerian degeneration secondary to cerebral infarction. Serial full tensor DWI of 15 acute stroke patients with B=1221. ROI analysis of ADC, T2, DWI, eigenvalues, and anisotropy indices in bilateral intracerebral corticospinal tracts. 5/16 patients developed DWI hyperintensity and/or ADC/FA reduction, prior to T2 prolongation, during initial two weeks in ipsilateral corticospinal tracts. Mean FA and ADC reductions were 12% and 24% respectively. All were subsequently confirmed to be Wallerian degeneration on follow up MRI. Another 6/15 patients without observable DWI signal changes demonstrated ipsilateral ADC and FA reductions at one or more levels in CS tracts without subsequent demonstration of Wallerian. Antegrade thalamic transneuronal degeneration was noted in 2/15. Changes in diffusion parameters precede T2 signal abnormalities in the evolution of Wallerian degeneration.