Quantitative assessment of pain threshold induced by a single-pulse transcranial magnetic stimulation

Abstract

ObjectiveTranscranial magnetic stimulation (TMS) is commonly used in basic research to evaluate human brain function. Although scalp pain is a side effect, no studies have quantitatively assessed the TMS intensity threshold for inducing pain and whether sensitivity to TMS-induced pain differs between sexes. MethodsWe measured pain thresholds when single-pulse TMS was applied over either Brocas area (BA) or left primary motor cortex (M1). We compared these thresholds with motor threshold for inducing motor evoked potential (MEP) through M1 stimulation. We also compared pain thresholds for BA and M1 between males and females. ResultsPain thresholds for both sites were significantly lower than motor threshold. Further, the pain threshold for BA was much lower than that for M1. No significant difference was observed between sexes. ConclusionThe results suggest that TMS at an intensity equivalent to motor thresholds, which is often used in experimental or clinical studies, causes slight scalp pain. SignificanceExperimental designs using TMS to evaluate functional relationships between brain and behaviors should consider scalp pain and reduce its likelihood as much as possible. HighlightsO_LIWe investigated pain thresholds induced by a single-pulse TMS over the head. C_LIO_LIPain thresholds for TMS over Brocas area (BA) and primary motor cortex (M1) were much lower than motor threshold. C_LIO_LINo significant differences in the pain thresholds were observed between sexes. C_LI