How safe is repetitive Transcranial Magnetic Stimulation?

To the Editor

There is considerable support for the efficacy of repetitive Transcranial Magnetic Stimulation (rTMS) in the treatment of depression (Gaynes et al., 2014). However, there is less literature available regarding its safety in clinical use. We report data from an rTMS clinical service operating since August 2008 (see Galletly et al., 2010). In seven years of operation, both bilateral and unilateral treatment protocols were used. In unilateral treatments, continuous low frequency (1Hz) rTMS was applied to the right dorsolateral prefrontal corte (DLPFC) for 15 minutes, whilst bilateral treatments also included intermittent high frequency rTMS (10Hz) applied to the left DLPFC for 15 minutes. All treatment intensities were delivered at 110% of the motor threshold using a MagPro R30 machine and MCF B65 figure-of-eight coil (MagVenture A/S, Denmark). In acute courses, either 18 or 20 treatments were administered over six or four weeks respectively, whilst maintenance treatments were delivered every one to four weeks. Patients were offered earplugs, or listened to relaxation or mindfulness recordings, during treatment.

Two hundred and five individual patients have been treated, 45 more than once (262 courses in total). There have been a total of 6,155 rTMS treatments; 5,008 (81.4%) acute course treatments, and 1,147 (18.6%) maintenance treatments. There were no serious adverse events – in particular, there have been no seizures and no manic episodes associated with rTMS.

More than two thirds of patients (69.4%) indicated that they experienced no side-effects. Only 4.3% reported side-effects that were severe enough to interfere with functioning, with just one patient indicating that the therapeutic benefit was outweighed by the side-effects experienced. The remaining patients said they were aware of side-effects but that these did not interfere with functioning.

Consistent with the literature (Rossi et al., 2009), the side-effects commonly reported were mild, mostly localised discomfort at the site of stimulation and headaches. Some patients also reported tiredness following treatment sessions. Discomfort at the site was addressed by reducing the intensity of the stimulus. Overall, only 8.0% of patients dropped out before completing their course, often because of side-effects or lack of efficacy. One patient cited nausea and dizziness as the reason.

Patients were referred by their treating psychiatrists, and people with comorbid medical conditions (except epilepsy) were not excluded. People with psychiatric comorbidities, other than drug and alcohol use disorders, were also accepted for treatment. The present report therefore provides naturalistic Australian data about the safety of rTMS, in a clinical setting. Drop-out rates and incidences of troublesome side-effects were low, and treatment was generally well accepted.