Safety and tolerability of repetitive transcranial magnetic stimulation: an analysis of over 1200 sessions

Transcranial magnetic stimulation (TMS) is increasingly used in research and clinical practice, therefore, the issues of its safety and tolerability are especially important. Currently, serious adverse reactions (ARs) are extremely rare. The more common mild ARs that can develop during and after stimulation remain less well understood but may affect procedure tolerance and treatment adherence.Objective: to study the tolerability and safety of TMS in patients and healthy volunteers.Material and methods. In a retrospective cohort study using standardized questionnaires, ARs were assessed during and within 24 hours after TMS in patients (n=103) and healthy volunteers (n=74).Results. In total, the data of 1246 sessions were analyzed. ARs were observed during 56.8% of the analyzed sessions and within 24 hours after in 21.5% of the sessions. In most cases, they were mild and did not affect the intent to continue stimulation. TMS withdrawal due to ARs was reported in six cases (3.3% of participants), three of which experienced severe headache (HA) after stimulation. During stimulation, sleepiness (32.4%) and pain in the stimulation area (20.3%) were most often recorded. The most frequent AR within 24 hours after TMS was HA (13.3% of sessions), its characteristics are described and possible diagnostic criteria are proposed.Conclusion. ARs can occur during and after a TMS session and are mild in most cases. TMS-induced HA, which is the most common AR within 24 hours after TMS, can be considered a distinct type of secondary HA, the pathogenesis of which requires further study.