Sensorimotor modulation by botulinum toxin A in post-stroke arm spasticity: Passive hand movement

• Patients with upper limb post-stroke spasticity were treated with botulinum toxin.
• Central effects of spasticity treatment were studied using functional MRI.
• Brain activation pattern was assessed during passive hand movements.
• BoNT-induced spasticity relief is associated with changes in sensorimotor network.

IntroductionIn post-stroke spasticity, functional imaging may uncover modulation in the central sensorimotor networks associated with botulinum toxin type A (BoNT) therapy. Investigations were performed to localize brain activation changes in stroke patients treated with BoNT for upper limb spasticity using functional magnetic resonance imaging (fMRI).MethodsSeven ischemic stroke patients (4 females; mean age 58.86) with severe hand paralysis and notable spasticity were studied. Spasticity was scored according to the modified Ashworth scale (MAS). fMRI examination was performed 3 times: before (W0) and 4 (W4) and 11 weeks (W11) after BoNT. The whole-brain fMRI data were acquired during paced repetitive passive movements of the plegic hand (flexion/extension at the wrist) alternating with rest. Voxel-by-voxel statistical analysis using the General Linear Model (GLM) implemented in FSL (v6.00)/FEAT yielded group session-wise statistical maps and paired between-session contrasts, thresholded at the corrected cluster-wise significance level of p < 0.05.ResultsAs expected, BoNT transiently lowered MAS scores at W4. Across all the sessions, fMRI activation of the ipsilesional sensorimotor cortex (M1, S1, and SMA) dominated. At W4, additional clusters transiently emerged bilaterally in the cerebellum, in the contralesional sensorimotor cortex, and in the contralesional occipital cortex. Paired contrasts demonstrated significant differences W4 > W0 (bilateral cerebellum and contralesional occipital cortex) and W4 > W11 (ipsilesional cerebellum and SMA). The remaining paired contrast (W0 > W11) showed activation decreases mainly in the ipsilesional sensorimotor cortex (M1, S1, and SMA).ConclusionsThe present study confirms the feasibility of using passive hand movements to map the cerebral sensorimotor networks in patients with post-stroke arm spasticity and demonstrates that BoNT-induced spasticity relief is associated with changes in task-induced central sensorimotor activation, likely mediated by an altered afferent drive from the spasticity-affected muscles.