Acute Effects Of Transcranial Direct Current Stimulation On Motor Function And Motor Cortex Excitability In Patients With Parkinson’s Disease

Research Background: Parkinson disease(PD)is a progressive,neurodegenerative disorder that is characterized by debilitating non-motor and motor symptoms,including rigidity,bradykinesia,tremor,gait and balance dysfunction.Motor deficits will eventually respond less to dopaminergic therapy and thus pose a challenge for treatment.In addition,deep brain stimulation has proven efficacy,but carries risks,and only a few patients are eligible for surgery.Transcranial direct current stimulation(tDCS)is a noninvasive brain stimulation that modulates cortical excitability and has shown promising results and may provide a therapeutic alternative.Objective: To investigate the immediate effects of tDCS with different targets motor function and motor cortex excitability in patients with PD,and to screen more efficient tDCS protocol.Methods: 60 patients with idiopathic Parkinson’s disease who met the inclusion criteria were recruited from department of Neurology and Department of Rehabilitation Medicine,Huashan Hospital Fudan University.They were randomly allocated to sham group,the primary motor cortex(M1)group,the left dorsolateral prefrontal cortex(DLPFC)group,the M1+DLPFC group.In sham group(only 30 seconds of stimulation was provided at the beginning),in real stimulation groups,each patient received one session of low intensity direct electrical current(1.5 m A each electrode)for 20 min per session.The anode electrode of M1 group was placed on M1 of more affected side.The anode electrode of DLPFC group was placed on left DLPFC.In M1+DLPFC group,the anode electrode was placed on M1 of more affected side for 10 minutes and then placed on left DLPFC for 10 minutes.Cathode electrodes were placed over left or right supraorbital area.The patients underwent Berg Balance Scale(BBS),Five times sit-tostand test,FTSTS),Timed up and Go test(TUG)and cortex indexes evaluation.Results: 55 subjects completed the intervention without any adverse events.(1)Balance function: compared with the baseline,BBS scores in the four groups showed no significant difference after intervention.(2)FTSTS: compared with the baseline,the speed of FTSTS in M1 group was significantly increased by 8.0%(P=0.001,Cohen’s d=1.40),the speed of FTSTS in DLPFC group was significantly increased by 10.1%(P=0.001,Cohen’s d=0.95),the speed of FTSTS in M1+DLPFC group was significantly increased by 9.0%(P=0.010,Cohen’s d=1.16),while there was no significant difference in sham group(P=0.263,Cohen’s d=0.28).The inter-group comparison showed that the improvement degree of FTSTS in M1 group,DLPFC group and M1+DLPFC group was significantly better than sham group,while there was no inter-group difference between real stimulation groups(P>0.05).(3)TUG: compared with the baseline,the speed of TUG in M1 group was significantly increased by 9.0%(P=0.001,Cohen’s d=1.13),the speed of TUG in DLPFC group was significantly increased by 8.0%(P=0.004,Cohen’s d=1.10),the speed of TUG in M1+DLPFC group was significantly increased by 6.3%(P=0.038,Cohen’s d=0.61),while there was no significant difference in sham group(P=0.263,Cohen’s d=0.29).The inter-group comparison showed that the improvement degree of TUG of M1 group,DLPFC group and M1+DLPFC group was significantly better than sham group,while there was no inter-group difference between real stimulation groups(P>0.05).(4)Motor cortex excitability: Rest motor threshold(RMT)was decreased significantly compared with the baseline in M1 group and M1+DLPFC group(P=0.027,P=0.01)(Cohen’s d=0.64,Cohen’s d=0.80),while there was no significant difference in DLPFC group and sham group(P=0.064,P=0.334)(Cohen’s d=0.61,Cohen’s d=0.25).The inter-group comparison showed that the improvement degree of RMT of M1 group was significantly better than sham group,while there was no inter-group difference between other groups(P>0.05).The amplitude of motor evoked potentials(MEP)was increased was significantly higher than of baseline after intervention in M1 group and M1+DLPFC group(P=0.007,Cohen’s d=0.81)(P=0.004,Cohen’s d=0.82),while there was no significant difference in DLPFC group and sham group(P=0.119,P=0.296)(Cohen’s d=0.51,Cohen’s d=0.12).The inter-group comparison showed that the improvement degree of MEP in M1 group and M1+DLPFC group was significantly better than sham group,while there was no inter-group difference between M1 group and M1+DLPFC group(P >0.05).Pearson correlation analysis showed that there was no correlation between the change of MEP amplitude and the improvement of motor function.Conclusion: This preliminary study found that single session tDCS showed an acute positive effect on mobility and walking in patients with PD.Anodal tDCS increased motor cortex excitability immediately,but there was no effect on balance function.In addition,comparison of immediate effects cannot screen out a better tDCS protocol.