Beyond primary motor cortex: clinical relevance of non-primary motor areas in upper-extremity recovery after stroke-A scoping review.

Facilitating excitability of the ipsilesional primary motor cortex can help enhance upper-extremity recovery in individuals with mild motor impairments after stroke. However, results are mixed in those with moderate-to-severe motor impairments. Extensive damage to the ipsilesional primary motor cortex may require non-primary motor areas and the contralesional primary motor cortex to assume aspects of ipsilesional primary motor cortex function. Nonetheless, the role of these areas in upper-extremity recovery is unclear. Thus, this scoping review comprehensively summarized evidence on the roles of non-primary and primary motor areas in upper-extremity muscle recovery after moderate-to-severe stroke. Eleven studies met the inclusion criteria. Findings varied by corticospinal tract integrity and time since stroke. Individuals with greater corticospinal tract integrity relied primarily on ipsilesional primary motor cortex for proximal and distal muscle recovery. With greater corticospinal tract damage, recovery increasingly relied on non-primary motor areas. Proximal muscle recovery involved the contralesional dorsal premotor cortex, whereas distal recovery involved a broader network including premotor cortices, supplementary motor area, cingulate motor area, dorsolateral prefrontal cortex, and intraparietal sulcus. During the acute and subacute phases, the contralesional intraparietal sulcus showed maladaptive effects, whereas in the chronic phase, the contralesional dorsal premotor cortex supported recovery. Future trials should investigate the contributions of the contralesional intraparietal sulcus and ipsilesional and contralesional dorsal premotor cortices across recovery phases after moderate-to-severe stroke. Registration doi: 10.17605/OSF.IO/YH7E6.