Motor cortex excitability in stroke before and after constraint-induced movement therapy

Objective: To investigate motor cortex excitability in stroke patients and explore excitability changes induced by an intense physiotherapy. Methods: We studied 12 chronic stroke patients (6 cortical, 6 subcortical lesions) before and after participation in 12 days of constraint-induced movement therapy. Transcranial magnetic Stimulation was applied to test intracortical inhibition (10), intracortical facilitation, silent periods, amplitudes of motor evoked potentials, and motor thresholds. Motor function was assessed by the Motor Activity Log, the Wolf Motor Function Test, and the Modified Ashworth Scale for spasticity. Results: Motor evoked potential amplitudes and motor thresholds were inversely correlated, indicating that both parameters reflect the function of corticospinal pathways. Before therapy, a motor cortex disinhibition was found in the affected hemisphere. This disinhibition was stronger in patients with cortical lesions. The amount of disinhibition was correlated with the degree of spasticity. After therapy, ICI changes were more pronounced in the affected hemisphere compared with the unaffected side. Both ICI decreases and increases were observed. Motor function tests indicated an improvement in all patients. Conclusions: Motor cortical disinhibition is present in chronic stroke patients. Therapy-associated changes of motor cortex excitability mainly occur in the lesioned hemisphere by upregulation or down-regulation of ICT. We replicate that constraint-induced movement therapy improves motor functions in the chronic stage after stroke.