Continuous, and not intermittent, theta-burst stimulation of the unlesioned hemisphere improved brain and hand function in chronic stroke: A case study

Abstract

In chronic stroke, transcranial magnetic stimulation is used to investigate if the primary motor cortex (M1) of the unlesioned hemisphere (UH) optimizes or hampers the functional gains. Continuous and intermittent theta-burst stimulation (cTBS, iTBS) were used to decrease and increase UH-M1 excitability, respectively. However, the effects of these protocols were never compared in the same patients and studies remain controversial. Therefore, the present study first compared the two protocols in the same patient, a 60-yo male at a chronic stage post-stroke, then tested in the long-term the protocol with the largest after-effects. To this end, experiment 1 compared the after-effects of iTBS, cTBS, and sham over UH-M1 (one session each, one week apart): data showed that the paretic hand motricity and M1 excitability of the lesioned hemisphere (LH) were improved after cTBS only. cTBS was then administrated over 10 sessions in experiment 2 and the outcomes were tested at different timepoints: M1 excitability was improved in both hemispheres and the functional gains obtained during cTBS sessions were still present three months after the end of stimulation. In conclusion, our chronic case study showed that UH inhibition, and not activation, promoted the function in a patient with spared corticospinal control from LH. Group studies in chronic stroke should reproduce our experiments and determine if, to optimize the gains, UH should be inhibited in patients with spared LH function (our case) or activated in patients with lost LH function, as already hypothesized. This is of major interest in neurorehabilitation using TMS protocols.