Therapeutic Effect Of Repetitive Transcranial Magnetic Stimulation On Parkinson's Disease

Objective This research aims to evaluate the effect of low-frequency repetitive transcranial magnetic stimulation (rTMS) of the motor cortex on motor functions in patients with Parkinson's disease, to optimize the protocol of rTMS, and to inquire into the time effect of low-frequency rTMS. Besides, by conducting in vitro experiments, it is expected to reveal, from the perspective of molecular biology, the mechanism for repetitive magnetic stimulation to protect dopaminergic neurons.Methods1. 18 patients with PD were observed in this study. Patients were examined 12h after an overnight withdrawal of anti-parkinsonian medication. First, motor performance was assessed clinically, motor evoked potentials (MEP), N30 component of somatosensory evoked potentials (SEP) and event-related potentials (ERP) were measured. Second, one of the 4 interventions, i.e. Madopar intake, 0.5Hz rTMS over the hand representation of the primary motor cortex (M1_Hand) and premotor cortex (PMC) contralateral to the (more) affected side, or sham rTMS was performed. Finally, clinical scores, MEP, N30 component of SEP and ERP were measured again after the intervention. The order of the 4 interventions was randomized across patients, and each session were separated by at least 2 weeks.2. 38 patients with PD were included in this study. For seven consecutive days, we applied 1800 stimuli at 100%RMT intensity and 0.5Hz frequency overthe M1Hand contralateral to the (more) affected side once a day using a figure-of -eight coil. The Unified Parkinson's disease rating scale (UPDRS), Hoehn & Yahr stage, Schwab & England activities of daily living score (ADL), ballistic task, walking test and the motor evoked potentials were assessed for each patient before rTMS and 1h, 1w, and 1m after the 7th session. ANOVA for repeated measurements analysis for variance was used for statistical analysis.3. PC 12 cells differentiated by nerve growth factor (NGF) as dopaminergic neurons were treated by different frequency of repetitive magnetic stimulation (1, 5, 10, and 20 Hz), 400 stimuli per day for 5 consecutive days. The intensity of magnetic stimulation was set at 40% of maximum of the stimulator. Cells were harvested 4h after the last session. RT-PCR and Western blot analysis were done to assess the expression of TH, DAT, kf-1, c-fos and c-jun gene after different frequency of repetitive magnetic stimulation on mRNA and protein level respectively.Results1. (DA significant variation among the conditions was found for all the clinical parameters. Post-hoc paired t test disclosed significant effect for each type of intervation: Madopar administration decreased the UPDRSII1 (P=0.001), reduced rigidity (P=0.001) and bradykinesia (P<0.001) subscores, and improved timed motor tasks;rTMS over the MlHand reduced UPDRSIII (P=0.015) and rigidity subscores (P=0.010);rTMS over the PMC decreased UPDRSIII (P=0.046). (2)MEP amplitude was reduced by Madopar (P=0.002), and rTMS over the PMC (P=0.004);cortical silent period (CSP) duration was prolonged by Madopar, and rTMS over the MlHand (P =0.015). Whereas, no significant variation was found in relaxed motor threshold (RMT), and cortical latency. (3) A significant variation among the conditions was found for the frontal P2O-N3O peak-to-peak amplitude (P=0.041). Post-hoc paired t test disclosed that theamplitude was increased in the Madopar group (P<0.05). There was no difference among the conditions in the latency of the frontal N30 and the parietal N20, the peak-to-peak amplitude of frontal N30-P40, and the P14-N20/P20-N30 amplitude ratio. ?Reaction time was reduced by Madopar and rTMS over the MlHand (PO.05). However, no significant variation was found in the P300 latency (P=0.089).2. ?Compared with the control side, the amplitude of MEP120 were found to be significantly larger and the CSP shorter on the (more) affected side of patients with PD. However, no significant variation was found in RMT and central motor conduction time (CMCT). (2)AN0VA for repeated measurements revealed a significant time effect for the global UPDRS and its motor section, Webster scale, ADL, rigidity and bradykinesia subscores, and the timed motor tasks during the course of the study (PO.001). Whereas, no significant changes were observed in the Hoehn & Yahr stage (P=0.173), and the tremor subscore (P=0.110). There was also a significant time effect for the CSP duration (PO.001), while no significant changes were found for the RMT, MEP120, and CMCT (P>0.05). The PD patients' clinical motor function was improved to the highest level within one week after the 7th intervention, which was paralleled by the changes of CSP.3. Significant changes were found in the expression of TH, DAT, kf-1, c-fos and c-jun genes among the groups ( P value being 0.003, 0.017, 0.019, 0.029, and 0.042 respectively). Compared with the control group, the expression of TH (P = 0.003) and DAT (P = 0.020) gene increased significantly after 5Hz repetitive magnetic stimulation, while the mRNA level of kf-1, c-fos and c-jun (P value being 0.013, 0.003, and 0.005 respectively) was increased following 20Hz stimulation. No change was observed in TH protein levels measured by Western blot analysis among the conditions (P=0.273).ConclusionsLow-frequency rTMS over the hand representation of the primary motor cortex can modulate the excitability of the motor cortex and thus improve the motor functions in patients with PD. A 7-day course of rTMS results in statistically significant long-term improvement of the motor functions, which is paralleled by the changes in the excitability of the motor cortex. Chronic repetitive magnetic stimulation can up-regulate the expression of tyrosine hydroxylase and dopamine transporter gene, whose biological effect may occur at the transcription level.