Witnessing loss of consciousness during TMS – Syncope in contrast to seizure

Abstract Objective Transient loss of consciousness (T-LOC) can occur during transcranial magnetic stimulation (TMS). T-LOC during TMS can be caused by syncope or seizure. TMS operators explicitly screen participants and are also able to witness clinical manifestations of T-LOC during stimulation. Therefore they have direct access to information necessary to tell the two etiologies apart, if they are well trained on the clinical differences and not only sensitive to the potential risk of seizure induction. We here present a typical case of vasovagal syncope during TMS to contrast its clinical manifestations to that of seizures. Method We describe an event of T-LOC in a 21year old healthy woman during single-pulse TMS. Screening, setting, clinical manifestations and advanced diagnostics are reported. Discussion Based on the detailed description of the case, we discuss why syncope is the most parsimonious etiology for the clinical picture observed in this participant. We provide information on typical clinical features of seizure that were particularly not observed. We also address potential benefits of further diagnostic tools. Additionally, we go into more parameters that can be useful to distinguish syncope from seizure. Conclusion TMS operators should be well aware of the differentiation of T-LOC in syncopal or ictal in etiology, because they witness T-LOC during TMS. By presenting a typical case of vasovagal syncope during TMS the report in hand provides necessary information and literature to do so.