The impact of left prefrontal repetitive transcranial magnetic stimulation on depression in Parkinson's disease: a randomized, double-blind, placebo-controlled study

Abstract

Based on several open-label and case studies, repetitive transcranial magnetic stimulation (rTMS) seems to have an antidepressive effect on patients with Parkinson's disease (PD). However, this hypothesis requires further confirmation. We conducted a randomized, double-blind placebo-controlled study to evaluate the effect of rTMS over the left dorsolateral prefrontal cortex (DLPFC) on depression and various motor and nonmotor features of PD. Twenty-two PD patients with mild or moderate depressive episodes were assigned into two groups, one receiving real-rTMS (90% of resting motor threshold, 5 Hz, 600 pulses-a-day for 10 days) over the left DLPFC, and another group receiving sham-rTMS. An investigator blinded to the treatment performed three video-taped examinations on each patient: before stimulation (baseline), 1 day (short term), and 30 days after treatment session ended (long-term effect). Mini-Mental State Examination, Unified Parkinson's Disease Rating Scale (UPDRS), Hoehn-Yahr, Epworth Sleepiness, Visual Analog and Montgomery-Asberg Depression Rating Scales (MADRS), Beck Depression Inventory (BDI), and Trail making and Stroop tests were applied. In the actively treated group, not only depression rating scales showed significant improvement 30 days after treatment ended (BDI by 44.4% and MADRS by 26.1%), but also the accuracy of Stroop test (by 16%). We could also demonstrate an insignificant improvement in UPDRS-III by 7.5 points (31.9%, P = 0.06). In the sham-treated group none of the examined tests and scales improved significantly after sham stimulation. Our study demonstrated the beneficial effect of the left DLPFC rTMS on depression in PD lasting at least 30 days after treatment. However, this result should be confirmed in patients with severe depression by further clinical trials.