Safety, ethical considerations, and application guidelines for the use of transcranial magnetic stimulation in clinical practice and research

Abstract

This article is based on a consensus conference, which took place in Certosa di Pontignano, Siena (Italy) on March 7-9, 2008, intended to update the previous safety guidelines for the application of transcranial magnetic stimulation (TMS) in research and clinical settings. Over the past decade the scientific and medical community has had the opportunity to evaluate the safety record of research studies and clinical applications of TMS and repetitive TMS (rTMS). In these years the number of applications of conventional TMS has grown impressively, new paradigms of stimulation have been developed (e.g., patterned repetitive TMS) and technical advances have led to new device designs and to the real-time integration of TMS with electroencephalography (EEG), positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). Thousands of healthy subjects and patients with various neurological and psychiatric diseases have undergone TMS allowing a better assessment of relative risks. The occurrence of seizures (i.e., the most serious TMS-related acute adverse effect) has been extremely rare, with most of the few new cases receiving rTMS exceeding previous guidelines, often in patients under treatment with drugs which potentially lower the seizure threshold. The present updated guidelines review issues of risk and safety of conventional TMS protocols, address the undesired effects and risks of emerging TMS interventions, the applications of TMS in patients with implanted electrodes in the central nervous system, and safety aspects of TMS in neuroimaging environments. We cover recommended limits of stimulation parameters and other important precautions, monitoring of subjects, expertise of the rTMS team, and ethical issues. While all the recommendations here are expert based, they utilize published data to the extent possible.

Fig. 1

Number of published papers per/year on Transcranial Magnetic Stimulation. Medline search updated to December 2008. Key words used are “Transcranial magnetic stimulation” (left bars) and “repetitive TMS” (right bars).

Fig. 2

Left panel (Conventional rTMS). From the top: examples of 10 s of rTMS at 1 Hz (first trace) and at 5 Hz (second trace); 1 s of rTMS at 10 Hz and a typical exampleof 20 Hz application for therapeutic purposes (trains of 2 s interleaved by a pause of 28 s). Right panel (Patterned rTMS). From the top: 20 s of continuous theta burst (first trace); intermittent theta burst (second trace) and intermediate theta burst (third trace). The fourth trace represents protocols of quadripulse stimulations (QPS).