To describe resting-­state (rs) cerebral networks using functional MRI (fMRI) in chronic stroke patients with hemiparesis both with and without post­-stroke spasticity (PSS) and to explore the relationship between functional connectivity and spasticity.

The neurological disorder of PSS hampers effective rehabilitation of the paretic arm and lowers the quality of life. Even though models of spasticity development exist, the cerebral networks involved have not been well characterized.

Fourteen chronic stroke patients (3 women, mean age 63.6 years, SD 9.8) with upper limb weakness and PSS (the PSS group) and 9 patients (3 women, mean age 62.4 years, SD 8.2) with comparable weakness but no PSS (the control group, CG) underwent clinical and spasticity evaluation and fMRI examinations. 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 8­min BOLD sequence. Pre­processed data were analyzed using the CONN toolbox to extract fractional amplitude of low-frequency fluctuations (fALFF). Differences in fALFF between groups were evaluated using parametric tests and Gaussian random field theory. Results were thresholded using voxel threshold at p < 0.001 uncorrected and cluster size threshold at the false discovery rate (FDR)-corrected p < 0.05.

Mean global MAS in the PSS group (2.28 +/- 0.44 (SD)) was significantly higher than in the CG (0.22 +/- 0.44), P<0.05. Analysis comparing the resting-state networks in the PSS group and the control group revealed significantly lower fALFF in the PSS group in 4 frontal regions of the lesioned hemisphere, including the orbitofrontal cortex/frontal operculum, precentral gyrus/inferior frontal gyrus, central opercular cortex and the superior frontal gyrus.

Post-stroke spasticity is associated with resting-state connectivity changes in the lesioned frontal lobe, ranging from primary and secondary motor cortex to multimodal cortical areas.

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