Lack of significant changes on magnetic resonance scans before and after 2 weeks of daily left prefrontal repetitive transcranial magnetic stimulation for depression

Repetitive transcranial magnetic stimulation (rTMS) is a new technology for exploring brain function. With this method, a small electromagnet is placed on the scalp; by activating and deactivating it, nerve cells in the underlying superficial cortex are depolarized. Several studies have found that prefrontal rTMS has potential efficacy in treating depression, and this technology, in addition to being a research tool, may soon play a role in psychiatric practice. Thus, establishing the safety of this technology is important and has been studied insufficiently. The authors performed T1-weighted three-dimensional volumetric magnetic resonance (MR) imaging on 22 depressed adults (15 active, 7 control) before and after they participated in a 2-week double-blinded, placebo-controlled trial of daily left prefrontal rTMS for the treatment of depression (a total of 16,000 stimuli). Seventeen patients also had paired T2-weighted scans. In a blinded manner, MR scans were qualitatively and quantitatively assessed for structural changes. No qualitative structural differences were observed before and after treatment. In addition, volumetric analysis of the prefrontal lobe showed no changes in the 2 weeks of the study. In conclusion, 10 days of daily prefrontal rTMS at these intensities and frequencies does not cause observable structural changes on MR scans in depressed adults.