Stroke subtype and motor impairment influence contralesional excitability

Objective: The nonlesioned motor cortex (M1 NL) is thought to be hyperexcitable in patients with subacute or chronic stroke and offers a promising therapeutic target. However, whether M1 NL excitability behaves the same for subcortical and cortical strokes is unknown. The aim of the present study was to determine whether cortical, or purely subcortical, strokes have a different effect on M1 NL excitability. Methods: We looked for correlations between the Fugl-Meyer (FM) score and M1 NL resting motor threshold (RMT NL) in 34 stroke survivors classified according to lesion location (cortico-subcortical or purely subcortical). In addition to the FM, the Wolf Motor Score and motor power were measured. Results: FM correlated with RMT NL for subcortical (r 0.82; p 0.001) but not for cortical strokes (r 0.11; p 0.62). Likewise, Wolf Motor Score (r -0.62; p 0.03) and motor power (r 0.64; p 0.023) were correlated with RMT NL for the subcortical group, but not for the cortical group. Conclusion: We show that the impact on M1 NL depends on lesion location and conclude that protocols aimed at reducing M1 NL cortical excitability may be worth exploring for subcortical but not for cortical stroke.