Low-frequency repetitive TMS plus anodal transcranial DCS prevents transient decline in bimanual movement induced by contralesional inhibitory rTMS after stroke.

BACKGROUND: Low-frequency repetitive transcranial magnetic stimulation (rTMS) over the unaffected motor cortex may improve motor function of the paretic hand after stroke. However, low-frequency rTMS might adversely affect bimanual movement by decreasing transcallosal function. OBJECTIVE: The authors investigated whether combined administration of rTMS and transcranial direct current stimulation (tDCS) prevents deterioration of bimanual movement induced by low-frequency rTMS over the unaffected hemisphere. METHODS: A total of 27 participants with chronic subcortical stroke were randomly assigned to receive either 1 Hz rTMS over the unaffected hemisphere, anodal tDCS over the affected hemisphere, or a combination of rTMS and tDCS. All patients performed a pinching motor-training task after stimulation. Bimanual movement and transcallosal inhibition (TCI) were evaluated after stimulation. RESULTS: rTMS and rTMS-tDCS enhanced the motor training effect on the paretic hand. rTMS decreased bimanual coordination and reduced TCI from the unaffected to the affected hemisphere (TCI(unaff-aff)). rTMS-tDCS changed TCI balance of both hemispheres but did not affect bimanual coordination or TCI(unaff-aff). The change in bimanual coordination was negatively correlated with TCI(unaff-aff). Following stimulation, improvement in the pinch force in the paretic hand was negatively correlated with TCI balance. CONCLUSIONS: Inhibitory rTMS over the unaffected hemisphere transiently caused deterioration of bimanual movements for the current task in stroke patients. This short-term decline was prevented by combined administration of low-frequency rTMS over the unaffected hemisphere and anodal tDCS over the affected hemisphere. These responses to bihemispheric stimulation suggest possible caution and opportunities for the rehabilitation of hand function after stroke.

Correlation of motor function with transcallosal and intracortical inhibition after stroke.

OBJECTIVE: The inhibitory role of neuronal networks in motor recovery after stroke remains to be elucidated. We examined the influence of transcallosal inhibition and short intracortical inhibition on motor recovery after stroke. We also investigated the correlation between transcallosal inhibition and mirror activity. DESIGN: A cross-sectional study. SUBJECTS: Thirty-eight chronic stroke patients. METHODS: Transcallosal inhibition was evaluated using single transcranial magnetic stimulation, and short intracortical inhibition was assessed using paired-pulse transcranial magnetic stimulation. Mirror activity was measured during tonic contraction of the contralateral hand. RESULTS: Transcallosal inhibition from the contralesional to the ipsilesional motor cortex correlated positively with motor function of the paretic hand; in contrast, transcallosal inhibition to the ipsilesional motor cortex correlated negatively with mirror activity of the paretic hand in both cortical and subcortical stroke patients. Short intracortical inhibition of the ipsilesional motor cortex correlated negatively with motor function of the paretic hand in only the subcortical stroke patients. CONCLUSION: Transcallosal inhibition from the contralesional to the ipsilesional motor cortex may inhibit mirror movements in stroke patients with good motor function. The weak transcallosal inhibition in patients after stroke with poor motor function may be ineffective for inhibiting mirror movement; however, it may have the advantage of facilitating motor recovery.

Repetitive transcranial magnetic stimulation over bilateral hemispheres enhances motor function and training effect of paretic hand in patients after stroke.

OBJECTIVE: The interhemispheric competition model proposes that the functional recovery of motor deficits in patients after stroke can be achieved by increasing the excitability of the affected hemisphere or decreasing the excitability of the unaffected hemisphere. We investigated whether bilateral repetitive transcranial magnetic stimulation might improve the paretic hand in patients after stroke. DESIGN: A double-blind study. PATIENTS: Thirty patients with chronic subcortical stroke. METHODS: The patients were randomly assigned to receive 1 Hz repetitive transcranial magnetic stimulation over the unaffected hemisphere, 10 Hz repetitive transcranial magnetic stimulation over the affected hemisphere, or bilateral repetitive transcranial magnetic stimulation comprising both the 1 Hz and 10 Hz repetitive transcranial magnetic stimulation. All patients underwent motor training following repetitive transcranial magnetic stimulation. RESULTS: Bilateral repetitive transcranial magnetic stimulation and 1 Hz repetitive transcranial magnetic stimulation immediately improved acceleration in the paretic hand. Compared with 1 Hz repetitive transcranial magnetic stimulation, bilateral repetitive transcranial magnetic stimulation decreased the inhibitory function of the affected motor cortex and enhanced the effect of motor training on pinch force. Moreover, this effect of motor training lasted for one week. On the other hand, 10 Hz repetitive transcranial magnetic stimulation had no effect on the motor function. CONCLUSION: Bilateral repetitive transcranial magnetic stimulation improved the motor training effect on the paretic hand of patients after stroke more than unilateral stimulation in pinch force; this might indicate a new neurorehabilitative strategy for stroke.

Inhibition of the unaffected motor cortex by 1 Hz repetitive transcranical magnetic stimulation enhances motor performance and training effect of the paretic hand in patients with chronic stroke.

OBJECTIVE: Recent reports demonstrated that low-frequency repetitive transcranial magnetic stimulation (rTMS) over the unaffected hemisphere improved the affected hand function in chronic stroke patients. We investigated whether 1 Hz rTMS improved the motor learning of the affected hand in patients after stroke. DESIGN: A double-blind study. PATIENTS: Twenty patients with chronic subcortical stroke. METHODS: The patients were randomly assigned to receive either a sub-threshold rTMS over the unaffected hemisphere (1 Hz, 25 minutes) or sham stimulation, and all patients performed a pinching task after stimulation. We evaluated the motor function of the affected hand and the excitatory and inhibitory function of the affected motor cortex by transcranial magnetic stimulation. RESULTS: Compared with sham stimulation, rTMS induced an increase in the excitability of the affected motor cortex(p < 0.001) and an improvement in acceleration of the affected hand (p = 0.006). Moreover, the effect of motor training on pinch force was enhanced by rTMS (p < 0.001). These improvement in the motor function lasted for one week after rTMS and motor training (p < 0.001). CONCLUSION: rTMS improved the motor learning of the affected hand in patients after stroke; thus, it can apply as anew rehabilitation strategy for patients after stroke.

Disinhibition of the premotor cortex contributes to a maladaptive change in the affected hand after stroke.

BACKGROUND AND PURPOSE: The mechanism of reorganization after stroke remains uncertain. Several studies that have measured reaction time (RT) delay by transcranial magnetic stimulation (TMS) have revealed some substrates responsible for the reorganization of motor recovery. In this study, we evaluated the RT delay and inhibitory functions by examining the silent period (SP) in the primary motor cortex (M1) and premotor cortex (PMC) of the affected hemisphere. Using these data, we investigated whether a change in the inhibitory system might influence motor recovery. METHODS: This study was performed in 20 patients with chronic subcortical stroke. To evaluate the RT delay, TMS was applied to the affected hemisphere 100 ms after showing the cue that indicated paretic finger movement. The SP was induced by TMS over the affected hemisphere during voluntary contraction of the paretic hand. RESULTS: The RT delays of the PMC were more prominent in patients with greater disability. The ratio of SP duration to RT delay in the PMC decreased with the decline in motor function. Moreover, upper arm function was better than hand function in patients with a decreased SP in the PMC. CONCLUSIONS: The inhibitory function of the PMC was disturbed in patients with poor motor function. Stroke patients with poor motor ability appeared to depend not only on the motor pathway from M1 but also on other parallel motor circuits to move the paretic side. However, this brain reorganization might result in the sacrifice of function of the affected hand.