A prospective study of secondary degeneration following subcortical infarction using diffusion tensor imaging

Abstract

Background: Diffusion tensor imaging (DTI) has detected secondary degeneration of the pyramidal tract distal (but not proximal) to, the primary lesion after a stroke. This finding and its potential clinical significance have received little attention.

Methods: Twelve patients underwent DTI within the first week (W1), at 4 weeks (W4), and at 12 weeks (W12) following an isolated subcortical infarct. Twelve age- and gender-matched controls underwent DTI at baseline, and mean diffusivity (MD) and fractional anisotropy (FA) were measured. Two hours before each DTI examination, every patient¡¯s neurological deficit (NIH Stroke Scale ), motor deficit (Fugl-Meyer scale) and life independence (Barthel index) were assessed.

Results: Reduced signal in FA images was visible in the infarct regions and in sites located above and below the infarct in ipsilateral side. FA values decreased significantly from W1 to W12 in all regions above the internal capsule (derived from the mean FA value of the corona radiata and the centrum semiovale) , in the internal capsule and in all regions below the internal capsule (derived from the mean FA value of the cerebral peduncle, pons, and medulla) (,P©,0.01, respectively). However, the NIH Stroke Scale decreased and Fugl-Meyer scale and Barthel index increased significantly (P<0.01, respectively) from W1 to W12 after stroke onset.

Conclusions: Secondary fibre tract degeneration detected by DTI occurs both proximal and distal to a subcortical cerebral infarct and progresses with the time course. However, the impact of the changes on the process of neurological recovery from stroke is not well understood.