To describe resting-state (rs) cerebral networks using functional MRI (fMRI) in stroke patients with post-stroke spasticity (PSS) and to test for functional connectivity (FC) changes associated with comprehensive (intramuscular botulinum toxin type A (BoNT-A) plus physiotherapy) treatment of PSS.

The clinical improvement of PSS by BoNT-A and physiotherapy is likely mediated by changes at the central nervous system level. Study of cerebral rs-fMRI networks may improve our understanding of the pathophysiological correlates of spasticity and the mechanisms of PSS treatment.

Ten chronic stroke patients (2 women, mean age 61 years, SD 9.7) with PSS of an upper limb underwent three sessions of spasticity evaluation and fMRI: before BoNT-A injection (W0), 4 (W4) and 11 weeks (W11) later. PSS was assessed with the modified Ashworth scale (MAS). The rs-fMRI scans were obtained using a 1.5 T Siemens MRI scanner and an 8-min eyes-closed rest. Resting-state networks were detected using independent component analysis (FSL MELODIC). Changes in connectivity over time were evaluated using dual regression and non-parametric permutation testing. Results were thresholded at the corrected p < 0.05.

BoNT-A treatment effectively alleviated upper limb PSS: The median global MAS at W0 was 2.25 (SD 0.44), at W4, 1.75 (0.71), and at W11, 2.25 (0.64). Significant changes of FC were shown in the contralesional sensorimotor and bilateral parietal cortex (W0-W11) and in the default mode network (W4-W11). rs-MRI did not reveal any significant changes of FC specific for the transient BoNT-A effect (W0-W4 or W4-W0).

Longitudinal changes in functional connectivity in the frontoparietal areas likely reflect the gradual effect of physiotherapy, as seen in our previous research. The absence of additional transient BoNT-A-related changes might be attributed to the relatively small sample size and limited statistical power to detect smaller treatment effects.

Supported by Czech Health Research Council grant NV17-29452A.