BACKGROUND AND PURPOSE: Botulinum toxin (BoNT) treatment relieves focal arm spasticity after stroke, likely acting at several hierarchical levels of the motor system. The central correlate of BoNT-induced spasticity relief may be detected using repeated functional MRI (fMRI) during motor task. METHODS: Five patients (4 males, 1 female, mean age 67 years) with hemiparesis and distal arm spasticity after chronic ischemic stroke were studied. FMRI was performed while moving the paretic hand in three sessions: before and 4 and 11 weeks after BoNT treatment. RESULTS: Arm spasticity significantly decreased following BoNT treatment across the group (mean modified Ashworth scale change .6). FMRI prior to BoNT treatment showed extensive bilateral active networks, whereas post-BoNT activation was limited to midline and contralateral sensorimotor cortices, and the third examination, when the toxin effect has worn off, again showed extensive activation similar to pre-BoNT examination. Post-BoNT session 2 compared to sessions 1 and 3 demonstrated a significantly less activation in contralateral frontoparietal areas including inferior frontal, postcentral, and middle frontal gyri as well as transient crossed cerebellar activation. CONCLUSION: Relief of post-stroke arm spasticity may be associated with changes at several hierarchical levels of the cortical sensorimotor system, including the prefrontal cortex.

Department of Neurology Faculty of Medicine and Dentistry Palacký University and University Hospital Olomouc Czech Republic

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