34. Modulation of cortical activity by botulinum toxin type a in patients with post-stroke arm spasticity

Abstract

There is growing evidence of remote effects of botulinum toxin. We aimed to use functional MRI (fMRI) to localize brain activation changes in stroke patients treated by botulinum toxin A (BoNT) for arm spasticity. 14 ischemic stroke patients with hand weakness and spasticity were studied. Spasticity was scored by modified Ashworth scale (MAS). FMRI was performed 3 times: before (W0) and 4 (W4) and 11 weeks (W11) after BoNT. Group A: 7 patients with hand plegia, who imagined moving fingers. Group B: 7 age-matched patients able to perform sequential finger movement. Difficulty was scored with visual analog scale. Statistical analysis (FSL) yielded group session-wise statistic maps and paired between-session contrasts. BoNT-A transiently lowered MAS in W4 in both groups. Performance difficulty did not change. In group A, activation of frontal premotor cortex dominated (as in healthy). At W4, ipsilateral cerebellum engaged as well, and persisted at W11. Paired contrasts showed activation decrease in bilateral occipital cortex W0 > W4 and left-sided occipitoparietal increase W4 < W11. These can be attributed to occipital deactivation (also precuneus and medial orbitofrontal cortex) at W4.Group B additionally activated contralateral motor and parietal cortex and bilateral cerebellum. From W0 to W4, activation was markedly reduced, which persisted at W11. Paired contrasts confirmed differences W0 > W4 (extensive ipsilateral parietal, occipital and premotor) and W0 > W11 (occipitoparietal). The effect of deactivation at was limited. Study of 2 age-matched groups with mild and severe weakness demonstrated different effect of BoNT-lowered spasticity on motor system engagement. Group A during movement imagery at maximum BoNT effect manifested deactivation of visual and default mode system, perhaps a change from visual to kinesthetic imagery, with cerebellum participating. Group B during movement also manifested motor pattern normalization, especially reduced activation extent. Supported by IGA MZ CR NT13575.