BoNT treatment was effective in reducing arm spasticity. Mean MAS score were: at W0, 2.40 (SD 0.49), at W4, 1.49 (SD 0.51) and at W11, 2.15 (SD 0.52). FMRI during movement imagery before treatment (W0) demonstrated extensive activation of bilateral frontoparietal sensorimotor cortex, cerebellum and contralesional basal ganglia and thalamus, where peak activation localized to the supplementary motor area, cortex lining the intraparietal sulcus bilaterally (IPS), contralesional ventrolateral premotor cortex and Ipsilesional cerebellar hemisphere. After treatment (W4), the activation pattern showed clear reduction, mostly in the bilateral parietal cortex and cerebellum. After disappearance of the local BoNT effect (W11), activation extent returned to almost the original size. Specific contrast revealed a localized significant BoNT-A effect, manifested as a transient activation decrease in the ipsilesional IPS and superior parietal lobule.