Effects of Repetitive Transcranial Magnetic Stimulation on the Excitability of the Motor Cortex in Parkinson′s Disease
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Aim:To investigate the effects of low frequency repetitive transcranial magnetic stimulation (rTMS) on the excitability of the motor cortex in Parkinson′s disease (PD) and to study mechanism of PD from the eletrophysiology. Methods:30 patients with PD were performed by 1Hz rTMS therapy to 10 days, 15 patients were performed sham stimulation, 15 normal volunteers were enrolled as control. Excitability of the motor cortex were assessed by rest threshold (RT), central motor conduction time (CMCT), central silent period (CSP) and amplitude of motor evoked potential(MEP). Results:①Patients with PD were treated by rTMS, the results of RT, CMCT and CSP decreased or shortened significantly compared with control, but MEP amplitudes were not changed. In the treatment group, RT increased, CMCT and CSP prolonged, they were closed to normal subjects after treatment, but these changes were not observed in sham group. ②The four indexes were not different in patients with marked tremor or marked rigidity. ③ Patients were divided into mild, moderate and grievous groups by Unified Parkinson′s Disease Rating Scale (UPDRS). The results of the three groups were not significant different by comparing the four indexes. Conclusion An increased motor cortical excitability in PD was observed in our study. Low frequency rTMS may to some extent inhibit the enhanced cortical excitability. But rTMS is not so sensible to detect the excitability of early PD,and more work needs to be done.Keywords:
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AIM: To explore the characteristics of motor evoked potential(MEP) and cortical excitability in Parkinson's disease by transcranial magnetic stimulation(TMS).METHODS: 20 normal volunteers were enrolled as control(group A),with the average age of(62.3±16.7) year old ranged from 52 to 79 years including 12 males and 8 females.MEP were assessed and compared separately between left and right hemispheres.21 patients with Parkinson's disease(PD) in asymmetry symptoms were performed in this study(group B),with the average age of(63.3±16.7) year old ranged from 46 to 80 years including 12 males and 9 females.UPDRS motor scores(UPDRSⅢ) were assessed before the check of cortical excitability(MEP).Motor evoked potentials(MEP) was assessed and compared separately on the minor and the serious bodyside,compared to control group.RESULTS: The indexes of MEP from both sides of normal control had no significant diversity.Amp was increased and both rest motor threshold(RMT) and cortical latency(CL) were also decreased significantly in PD patient compared to the normal control.On the serious side of PD,RMT decreased significantly compared to the minor side.Amp,CL and central motor conduct time(CMCT) changed without significant diversity between minor and serious bodyside.CONCLUSION: The motor cortical excitability is increased in PD patients.The excitability is higher with the more serious symptom side.The character of MEP in PD patients may be helpful to make a diagnosis and evaluate the severity of symptoms.
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OBJECTIVE To investigate changes in various sensory functions after low-frequency repetitive transcranial magnetic stimulation (rTMS) in healthy subjects. METHODS A Neurometer® CPT/C was used to measure current perception threshold (CPT) values at frequencies of 2000, 250, and 5 Hz in the left index finger to assess the tactile sense, fast pain, and slow pain, respectively. Somatosensory evoked potentials (SEPs) elicited by left median nerve stimulation at the wrist were used to assess excitability in the primary sensory cortex (S1). These were investigated before and after rTMS (0.9 Hz, 0.9 AEresting motor threshold, 500 pulses) or sham rTMS over the right primary motor cortex (M1). RESULTS All CPT values increased significantly and the P25-N33 of SEP amplitude decreased significantly after real rTMS, but not after sham rTMS; however, no correlations between the changes were observed. CONCLUSIONS Low-frequency rTMS over the M1 provides global anesthetic effects and inhibits excitability in S1. The lack of correlation between these changes suggests that the anesthetic effects may not always relate to the excitability of S1; thus, the mechanisms responsible for the changes remain unclear. Nevertheless, these findings suggest that rTMS may be a useful strategy for treating intractable pain in rehabilitation medicine.
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Background: Recently, high-frequency repetitive transcranial magnetic stimulation (rTMS) is reported to evaluating the corticospinal pathway and improving both cortical excitability and motor function significantly in subjects. According to some previous reports, the maximum voluntary muscle contraction (MVC) of target muscle can reinforce the influence by rTMS. The aim of this study was to confirm 5 Hz rTMS with MVC in healthy individuals is an effective method to facilitate motor neuron excitability and the efficiency can last at least 30min post stimulation. Objective: To compare the motor evoked potentials (MEPs) elicited by 5Hz rTMS and 5Hz rTMS combined with MVC. Methods: In this randomized, controlled, assessor-blinded, crossover trial, 40 healthy right-handed subjects were divided into group A (n=20) and group B (n=20). All subjects received rTMS over the primary motor cortex area (M1) in the left hemisphere. The parameters of rTMS were 5 Hz, 90of the resting motor threshold (RMT), for a total of 500 pulses in100 trains (1-sec inter-stimulus and 8- sec inter-interval). Method 1: All subjects received rTMS over the hand area of left M1. Method 2: All subjects received rTMS at the same stimulated point, combined with maximum voluntary hand griping in each 10 trains. Test 1: group A underwent method 1, while group B underwent method 2. Test 2: A week later, group B underwent method 1, while group A underwent method 2. In each test, the MEP amplitude and latency was measured before (P-rTMS), 5min after (Post 1) and 30min after (Post 2) the rTMS intervention. Results: MEP amplitude increased significantly from baseline at 5 minutes post intervention under both treatment regimes. However for both sequences, it decreased towards baseline under the rTMS intervention at 30 minutes post intervention but remained relatively high when rTMS was combined with MVC. MEP latency decreased significantly from baseline at 5 minutes post intervention under both treatment regimes. For both sequences, it then increased again towards baseline under both treatment regimes at 30 minutes post intervention. Although there was a trend for a less pronounced increase under the combined treatment, this effect was not significant. Conclusion: Both 5Hz rTMS and 5Hz rTMS combined with MVC facilitate motor cortical excitability, but the enhancement in rTMS with MVC is more pronounced and maintained longer than simple rTMS. Keywords: Repetitive transcranial magnetic stimulation; motor evoked potentials; maximum voluntary muscle contraction; primary motor cortex area.
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Repetitive transcranial magnetic stimulation (rTMS) has been applied for modulating cortical excitability and treating spasticity in neurological lesions. However, it is unclear which rTMS frequency is most effective in modulating cortical and spinal excitability in incomplete spinal cord injury (SCI).To evaluate electrophysiological and clinical repercussions of rTMS compared to sham stimulation when applied to the primary motor cortex (M1) in individuals with incomplete SCI.A total of 11 subjects (35±12 years) underwent three experimental sessions of rTMS (10 Hz, 1 Hz and sham stimulation) in a randomized order at 90%intensity of the resting motor threshold and interspersed by a seven-day interval between sessions. The following outcome measures were evaluated: M1 and spinal cord excitability and spasticity in the moments before (baseline), immediately after (T0), 30 (T30) and 60 (T60) minutes after rTMS. M1 excitability was obtained through the motor evoked potential (MEP); spinal cord excitability by the Hoffman reflex (H-reflex) and homosynaptic depression (HD); and spasticity by the modified Ashworth scale (MAS).A significant increase in cortical excitability was observed in subjects submitted to 10 Hz rTMS at the T0 moment when compared to sham stimulation (p = 0.008); this increase was also significant at T0 (p = 0.009), T30 (p = 0.005) and T60 (p = 0.005) moments when compared to the baseline condition. No significant differences were observed after the 10 Hz rTMS on spinal excitability or on spasticity. No inter-group differences were detected, or in the time after application of 1 Hz rTMS, or after sham stimulation for any of the assessed outcomes.High-frequency rTMS applied to M1 was able to promote increased cortical excitability in individuals with incomplete SCI for at least 60 minutes; however, it did not modify spinal excitability or spasticity.
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Objective To investigate the effects of low frequency repetitive transcranial magnetic stimulation (rTMS) on motor function and excitability of motor cortex in Parkinson's disease (PD) patients and to study the mechanism of PD from the electrophysiology. Methods Twenty-eight patients with PD received 1 Hz rTMS therapy for 15 d. Thirty normal volunteers were enrolled as controls. Unified Parkinson's Disease Rating Scale (UPDRS) and motor evoked potential (MEP) were adopted as assessment indicators. The excitability of motor cortex was assessed by rest motor threshold (RMT), central motor conduction time (CMCT) and the amplitude of MEP. Results The initial RMTs and CMCTs of PD patients were significantly lower than those of the controls, but MEP amplitudes were not significantly different. After rTMS treatment, motor function of PD patients improved, RMTs increased and CMCTs prolonged. Conclusion In PD patients, motor function disorder and increased motor cortical excitability were observed. Low frequency rTMS may inhibit these changes to some extent.
Key words:
Parkinson's disease; Motor function; Excitability of motor cortex; Low frequency repetitive transcranial magnetic stimulation
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