Diffusion tensor imaging study of subcortical gray matter in CADASIL

Background and Purpose-In cerebral autosomal dominant arteriopathy with sub cortical. infarcts and leukoencephalopathy (CADASIL), water diffusion chang es suggestive of microstructural tissue alterations have been recently repo rted in abnormal- and normal-appearing white matter as seen on T2-weighted images. In the subcortical gray matter, typical lacunar infarcts are repeat edly observed. Whether microstructural tissue changes are also present outs ide these lesions within the putamen or thalamus remains unknown. Methods-We used diffusion tensor imaging, an MRI method highly sensitive to cerebral microstructure, in 20 CADASIL patients and 12 controls. Both the trace of the diffusion tensor [Tr(D)] and an anisotropic diffusion index (v olume ratio) of diffusion were measured within the putamen and thalamus out side typical lacunar infarcts as detected on both T1- and T2-weighted image s. Results-A significant increase in Tr(D) and a decrease in anisotropy were o bserved in the putamen and thalamus in patients. The right/left indices of Tr(D) in the thalamus, but not in the putamen, were strongly correlated wit h the corresponding indices calculated in the white matter of the centrum. semiovale. In addition, the diffusion increase in the thalamus was positive ly correlated with Tr(D) and with the load of small deep infarcts within th e white matter and negatively correlated with the Mini-Mental State Examina tion score. Conclusions-Our results suggest that microstructural tissue alterations are present in the putamen and thalamus, outside the typical lacunar infarcts in CADASIL. In the thalamus, these microstructural changes appear constant and are even observed in asymptomatic subjects. Some of these thalamic chan ges appear to result from degeneration of thalamocortical pathways secondar y to ischemic white matter damage. The importance of this degenerative phen omenon in the pathophysiology of CADASIL requires further investigation.