Detecting poststroke cortical motor maps with biphasic single- and monophasic paired-pulse TMS

BackgroundResidual corticospinal connections are the precondition for poststroke motor recovery and necessary for targeted interventions. In severely affected patients, standard transcranial magnetic stimulation (TMS) may lead to false negative findings.ObjectiveDetecting the cortical representation of paralyzed forearm muscles by applying different stimulation techniques and maps beyond the hotspot.MethodsIn seventeen chronic stroke patients with severe motor deficits, navigated biphasic single (SP) and monophasic paired-pulse (PP) TMS was applied at 100% stimulator output to an extended cortical area in the ipsilesional hemisphere, while recording surface EMG of the extensor carpi radialis muscle.ResultsIn eleven patients, residual connectivity to the paralyzed forearm was detected with either mapping technique (five SP and PP, four PP only, two SP only). In five patients, connections originated from non-primary motor areas.ConclusionThese results could be instrumental for identifying candidates and stimulation targets for novel neuromodulation interventions in the context of neurorehabilitation.