Cortical activity modulation by botulinum toxin type A in patients with post-stroke arm spasticity: real and imagined hand movement.

BACKGROUND: Our aim was to use functional magnetic resonance imaging (fMRI) to compare brain activation changes due to botulinum toxin A (BoNT) application between two chronic stroke patient groups with different degree of weakness treated for upper limb spasticity.
METHODS: Fourteen 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 application. Group A: 7 patients (2 males, 5 females; mean age 59.14 years) with hand plegia, who imagined moving fingers. Group B: 7 age-matched patients (6 males, 1 female; mean age 59.57 years) able to perform sequential finger movement.
RESULTS: BoNT transiently lowered MAS in W4 in both groups. In group A, activation of the frontal premotor cortex dominated and persisted for all three fMRI sessions whereas the ipsilesional cerebellum and cortex bordering bilateral intraparietal sulcus activation changed over time. Between-session contrasts showed treatment-related activation decreases in the mesial occipitoparietal and lateral occipital cortex. In group B, brain activation was markedly reduced after BoNT (W4). Whereas some of these areas manifested only transient reduction and expanded again at W11, in others the reduction persisted.
CONCLUSION: Study of two age-matched groups with mild and severe weakness demonstrated different effects of BoNT-lowered spasticity on sensorimotor networks. Group A performing movement imagery manifested BoNT-induced reduction of activation in structures associated with visual imagery. Group B performing movement manifested reduced activation extent and reduced activation of structures outside classical motor system, suggestive of motor network normalization.