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

BACKGROUND Secondary degeneration of the pyramidal tract distal to the primary lesion after a stroke has been detected by some studies using diffusion tensor imaging (DTI) but its potential clinical significance and the degeneration of the fibre tract proximal to the primary lesion have received little attention. METHODS Twelve patients underwent DTI on the 1st, 4th and 12th week following a subcortical infarct involving the posterior limb of the internal capsule, and 12 age and sex matched controls underwent DTI once. The DTI parameters mean diffusivity and fractional anisotropy (FA), and the clinical scores before DTI examination, including the National Institutes of Health Stroke Scale (NIHSS), the Fugl-Meyer (FM) scale and the Barthel index (BI), were assessed. The relations between the per cent changes in DTI parameters and clinical scores were analysed. RESULTS From the 1st to the 12th week after stroke onset, FA values decreased (p<0.01, respectively) in the fibre tract above and below the internal capsule, and the NIHSS decreased (p<0.01) but the FM scale and BI increased (p<0.01, respectively) progressively. The per cent reductions in FA value in the fibre tract above and below the internal capsule were negatively correlated with the per cent changes in NIHSS and FM scale (p<0.05, respectively). CONCLUSIONS Secondary degeneration of the fibre tract proximal and distal to a primary lesion can be detected by DTI clearly and quantitatively and deteriorates with time progressively, which may hamper functional recovery after a subcortical cerebral infarct.