Induction of seizures by TMS/rTMS

The induction of seizures by magnetic stimulation of the cortex is the primary negative effect of TMS, and most prevalent with rTMS usage.1 The rate of incidence among subjects undergoing TMS or rTMS is 1-2% among populations excluding subjects with epilepsy or depression. Short term EEG changes have been observed for this phenomenon, more specifically postictal slowing, but EEG changes resolve within 2 days. Thus, long-term clinical sequellæ has not been observed.1 Headaches, facial muscle twitching, and tinnitus have also been implicated as adverse side effects in TMS/rTMS usage.2 Safety guidelines and contraindications for TMS/rTMS have been established. Absolute contraindications include metal in cranium, intracardiac lines, and increased intracranial pressure. Relative contraindications include pregnancy, childhood, heart disease, cardiac pacemaker, implanted medication pump, tricyclic antidepressants, neuroleptics, and a history of epilepsy.1 Adherence to these guidelines may partially be responsible for the recent lack of seizures in studies that use TMS/rTMS.2