Safety and feasibility of accelerated low-frequency repetitive navigated transcranial magnetic stimulation (rnTMS)

Abstract

Abstract Low frequency repetitive transcranial magnetic stimulation (rTMS) is capable of inducing changes in functional organization of underlying brain regions, however often at the cost of long stimulation protocols over several weeks. As these protocols can be difficult to implement in clinical settings, the aim of the present study was to show the feasibility and safety of an accelerated low-frequency rTMS protocol applying multiple sessions daily. To this purpose, nine healthy subjects (mean age 25.4 years; 1 female) received 14 sessions of rTMS (1 Hz, 30 minutes, 110% RMT) to the hand motor hotspot. Subjects received stimulation for either 14 days once daily (classical rTMS; c-rTMS), 7 days twice-daily (accelerated rTMS; a-rTMS) or sham stimulation for 14 days once-daily (s-rTMS). Daily stimulation sessions in the a-rTMS group were delivered with a 90-minute break in between. In total, 74% of rTMS sessions in the c-rTMS group, 89% in the a-rTMS group and 98% in the s-rTMS group were free of any side effects. Subjects reported occurrence of brief headaches in 14% of sessions in the c-rTMS group, 2% in the a-rTMS group and 0% in the s-rTMS group. Dizziness during stimulation was reported in 5% of sessions in the c-rTMS group, 2% in the a-rTMS group and 0% in the s-rTMS. Subjects reported a feeling of fatigue in the stimulated hand muscles in 2% of all sessions in the c-rTMS group, 7% in the a-rTMS group and 0% in the s-rTMS group. All side effects were reported to be at maximum mild and of short duration. Thus, accelerated low-frequency rTMS of the motor cortex is a safe and feasible method, previously shown to induce a functional reorganisation of the motor system. By shortening treatment duration in days, this approach can potentially make rTMS protocols more accessible to a wider range of patients. Keywords: rTMS, neuromodulation, plasticity, safety