A sequence investigation on degeneration of pyramidal tract after cerebral infarction with diffusion tensor imaging.

Objective To investigate the secondary degeneration after cerebral infarct as well as its potential significance for clinical practice.Methods Eighteen patients with a recently isolated MCA infarct underwent Diffusion Tensor Imaging (DTI) examinations and evaluations with the NIH Stroke Scale (NIHSS), the Fugl-Meyer motor scale (FM) and the barthel index (BI) at the first week (W1), the end of the fourth week (W4) and the twelfth week (W12) respectively. Eighteen age and gender matched health volunteers underwent DTI as controls. Mean diffusivity (MD) and fractional anisotropy (FA) measured on bilateral sides at internal capsule, cerebral peduncle, pons and medulla were analyzed. Results The FA values of pyramidal tract in brain stem (derived from the mean value of cerebral peduncle, pons and medulla) in patients significantly decreased from W1 to W12 (P0.01 respectively), but its MD showed no significant change (P0.05, respectively). The percent reduction of brain stem FA value in patient group correlated to the percent reduction of NIHSS (r=-0.46,P0.05) and to the percent increase of FM (r=-0.61,P0.05), but not to the percent change of BI (P0.05). Conclusions After a focal cerebral infarct, the secondary degeneration in pyramidal tract distal to the primary lesion will persist at least 3 months, and may hamper the neurological recovery.