Multi-target repetitive transcranial magnetic stimulation (rTMS) protocol for the treatment of comorbid depression and chronic pain

Abstract

Abstract Background: Major Depressive Disorder (MDD) and chronic pain are frequently co-occurring, and the onset of either condition can either precede or follow the onset of the other. Notably, clinical outcome for pharmacological and rTMS treatment for depression is significantly worse in the presence of chronic pain symptoms. To improve clinical care for depression it is thus critical to address the comorbidity of depression and chronic pain in a unified approach rather than treating them as separate conditions. Objective: We examined whether a multi-target rTMS protocol including stimulation of the left dorsolateral prefrontal cortex (DLPFC) and primary motor cortex (M1) would improve depressive and chronic pain symptoms more than a standard single-target rTMS protocol. Methods: We treated 20 comorbid depressive and chronic pain patients with a multi-target rTMS protocol and another 20 age- and sex-matched comorbid patients that had comparable baseline depression and pain symptom severity were treated only at the left DLPFC, for a minimum of 10 sessions. We have also recorded electroencephalography (EEG) at baseline session and examined a previously reported metric of pain sensitivity, peak alpha frequency (PAF), as a possible marker of treatment outcome. Preliminary Results: The multi-target rTMS achieved on average 15% greater improvement than stimulation at left DLPFC alone. Cohen’s D effect size was D = 0.8, which represents a moderate effect. We will also present EEG data examining the associations between PAF and pain and depression treatment outcomes. Conclusions: Multi-target rTMS to DLPFC and M1 may be more effective in treating the comorbidity of depression and chronic pain than rTMS to DLPFC only. Multi-site protocols could represent a treatment augmentation strategy with significant benefit for comorbid subjects. Other potential rTMS target site should be evaluated in future studies. Keywords: Chronic Pain, Depression, EEG, TMS