Background and purpose: By using neurorehabilitation outcome measures and functional magnetic resonance imaging (fMRI), we attempted to elucidate the effect of Wallerian degeneration (WD) in the pyramidal tract distal to a posterior capsular stroke on functional recovery.

Methods: In 18 patients with pure motor hemiparesis caused by capsular infarct, we identified the presence of WD and then tested whether it affected the rate of motor improvement and the final motor outcome. The discharge T2-weighted MRI (139 +/- 5 days on average after stroke) showed WD in 10 of 18 patients (WD-positive, n = 10; WD-negative, n = 8). All patients performed mass grasping of paretic fingers before and after inpatient neurorehabilitation for the fMRI.

Results: Demographic characteristics, rate of disability change, final motor status, and volume of lesion were comparable between the groups. On the first fMRI, patterns of fMRI activation in the sensorimotor cortex, premotor cortex (PMC), and supplementary motor area were comparable. However, on the second fMRI, considerably more patients in the WD-positive group (8 out of 10) exhibited persistent contralateral activation in PMC than in the WD-negative group (1 out of 8; P = .0044, chi-square test). Ipsilateral PMC was also more frequently activated (P = .04) in WD-positive patients than in WD-negative patients.

Conclusions: Persistent WD had no effect on the impairment or disability outcome; however, it was associated with novel regional activation on repeat fMRI after recovery. To determine whether persistent PMC activation resulted from effort or represents a general effect of WD on motor recovery will require a longer follow-up time and more precise control of functional measurement during imaging.