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.
Keywords: Stroke; arm spasticity; botulinum toxin; finger movement; functional magnetic resonance imaging.
Copyright © 2011 by the American Society of Neuroimaging.