P1-27. Influence of stimulus direction on the efficacy of continuous theta burst stimulation

Publication date: September 2017
Source:Clinical Neurophysiology, Volume 128, Issue 9
Author(s): Takuya Sasaki, Masashi Hamada, Shin-ichi Tokushige, Satomi Inomata-Terada, Yasuo Terao, Yoshikazu Ugawa
Continuous theta burst stimulation (cTBS) is a method commonly used to induce long term depression (LTD)-like plasticity in human motor cortex. However, its after-effects are likely to be highly variable between individuals. In this study, we hypothesized that the direction of stimulus current may have a role in the efficacy of cTBS, as cTBS is usually applied using a biphasic stimulus pulse which preferentially induces anterior-to-posterior (AP) current in the second depolarizing phase in the brain. To test this, we investigated changes of motor evoked potentials (MEPs) after cTBS carried out with rotating the stimulation coil 45° clockwise from the conventional position, which preferentially induces medial-to-lateral current in the brain. Nine healthy volunteers participated in the study and transcranial magnetic stimulation (TMS) was given to the M1 representation of the right first dorsal interosseous muscle. We found that the modified cTBS with rotated coil tented to show better responder rate compared with the conventional cTBS (66.7% vs. 33.3%) though there were no statistical differences. We concluded that the after-effects of cTBS were highly variable irrespective of direction of stimulus current.



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