Quantitative microstructural deficits in chronic phase of stroke with small volume infarcts: A Diffusion Tensor 3-D Tractographic Analysis

Abstract

BACKGROUND: Non-infarct zone white matter wallerian degeneration is well-documented in large volume territorial infarctions. However to what extent these abnormalities exist in small volume infarction is not known, particularly since routine T2/FLAIR MR images show minimal changes in such cases. We therefore utilized DTI based quantitative 3D tractography for quantitative assessment of white matter integrity in chronic phase of small volume anterior circulation infarcts. METHODS: Eleven chronic stroke subjects with small anterior circulation large vessel infarcts ( < /=10 cc volume of primary infarct) were compared with 8 age matched controls. These infarcts had negligible to mild gliosis and encephalomalacia in the primary infarct territory without obvious wallerian degeneration on conventional MRI. Quantitative Diffusion Tensor 3-D tractography was performed for CST, genu and splenium of corpus callosum. Tract based Trace and fractional anisotropy (FA) was compared with age matched controls. RESULTS: On univariate analysis, Chronic stroke subjects had significant elevation in Trace measurement in genu of corpus callosum (GCC), ipsilesional and contralesional CST, (p < 0.05), compared to controls. After adjusting for smoking, hypertension (HTN) and non-specific white matter hyperintensities, (WMHs), there was significant elevation in trace within the ipsilesional CST (p=0.05). Contralesional CST FA correlated significantly with walking speed, r=0.67, p=0.03. CONCLUSIONS: Stroke subjects with small volume infarcts demonstrate significant quantitative microstructural white matter abnormalities in chronic phase, which are otherwise subthreshold for detection on routine imaging. Ability to quantify these changes provides an important marker for assessing non-infarct zone neuroaxonal integrity in the chronic phase even in the setting of small infarction.