Sequential activation brain mapping after subcortical stroke: changes in hemispheric balance and recovery.

We prospectively studied 5 patients while they were recovering from left-sided subcortical stroke affecting the cortico-spinal tract, and examined them twice with H(2)(15)O-PET over several months while performing an identical task with the affected hand. Concomitant motor recovery was assessed by measuring the number of thumb-to-index tappings performed in 15 s at each PET session. Across patients, the hemispheric activation balance tended to shift over time toward the unaffected hemisphere, but the magnitude of this shift was highly variable from patient to patient and significantly correlated with recovery. Thus, in subcortical stroke, a shift of activation balance towards the unaffected hemisphere appears associated with lesser initial recovery and, conversely, the more this physiological balance is maintained over time the better the recovery.