Parkinson's disease (PD), the most common movement disorder, is characterized by motor symptoms including tremor, rigidity, bradykinesia, and postural instability. These symptoms substantially impair quality of life and increase the risk of falls, disability, and accidental injury, representing a major therapeutic challenge.
External trigeminal nerve stimulation (eTNS), a non-invasive neuromodulation technique, has shown promising potential in PD and other movement disorders. A clinical study published in 2017 suggested that trigeminal nerve stimulation may contribute to the alleviation of motor symptoms in patients with PD. In 2023, the U.S. Food and Drug Administration cleared the Portable Neuromodulation Stimulator (PoNS) as an adjunctive treatment for gait impairment caused by multiple sclerosis; the lingual nerve is a branch of the mandibular division of the trigeminal nerve. In the same year, experimental evidence showed that trigeminal nerve stimulation could activate intracranial dopaminergic neurons and modulate dopamine release in mice. These findings suggest substantial potential for eTNS in modulating motor dysfunction in PD, although high-level clinical evidence remains lacking.
This randomized, within-subject study will evaluate the immediate effects of eTNS at different stimulation frequencies on motor dysfunction in patients with PD. Gait parameters will be quantitatively assessed using the IDEEA gait system, together with the MDS-Unified Parkinson's Disease Rating Scale Part III (MDS-UPDRS Part III), Tinetti Gait Scale, and Hoehn and Yahr Scale.
This within-subject study comprises three 20-min stimulation conditions: 120-Hz eTNS, 40-Hz eTNS, and sham stimulation. Each patient with Parkinson's disease will complete all conditions in a single session in randomized order. Instrumented gait analysis, together with motor and gait rating scales, will be used to quantify immediate post-stimulation changes in gait and motor function relative to baseline.
Patients with idiopathic Parkinson's disease diagnosed by two neurologists, according to the Chinese diagnostic criteria for Parkinson's disease formulated in 2020 by the Chinese Parkinson's Disease and Movement Disorders Society based on the MDS Clinical Diagnostic Criteria for Parkinson's disease.
Hoehn and Yahr stage 1-5 in the medication ON state.
Mini-Mental State Examination (MMSE) score >24.
Stable antiparkinsonian medication for at least 1 month before the trial.
Secondary parkinsonism or atypical parkinsonian syndromes.
Current use of anticholinergic medications.
Contraindications to non-invasive electrical neuromodulation.
Previous eTNS treatment within the past 6 months.
Crossover
external Trigeminal Nerve Stimulation, eTNS
DeviceThe experiment will be conducted in the MED-ON state, consistently 1-2 h after administration of antiparkinsonian medication. Baseline gait and motor function assessments will first be performed, followed by three randomized eTNS stimulation sessions. Gait will be assessed after each stimulation session, and motor function scales will be reassessed after completion of all experimental conditions.
Dual-Task Cost (DTC)
This is a within-subject study. Instrumented gait parameters and clinical rating scales will be assessed at baseline, followed by eTNS stimulation in randomized order under the 120-Hz, 40-Hz, and sham conditions. After each eTNS condition, instrumented gait parameters will be collected during walking tasks. Clinical rating scales will be additionally assessed after the final stimulation condition.Dual-task cost will be calculated as: \[(single-task gait speed - dual-task gait speed) / single-task gait speed\] × 100%.DTC reflects the reduction in walking performance under dual-task conditions relative to single-task conditions. A decrease in DTC after eTNS indicates reduced dual-task interference during walking, suggesting that eTNS may reduce dual-task gait cost in patients with PD.
Mean Gait Speed（m/s）
This is a within-subject study. Instrumented gait parameters and clinical rating scales will be assessed at baseline, followed by eTNS stimulation in randomized order under the 120-Hz, 40-Hz, and sham conditions. After each eTNS condition, instrumented gait parameters will be collected during walking tasks. Clinical rating scales will be additionally assessed after the final stimulation condition. Mean gait speed will be directly obtained from the IDEEA system, which uses inertial sensors to quantitatively monitor gait during walking tasks in patients with PD.
Mean Stride Length (m)
This is a within-subject study. Instrumented gait parameters and clinical rating scales will be assessed at baseline, followed by eTNS stimulation in randomized order under the 120-Hz, 40-Hz, and sham conditions. After each eTNS condition, instrumented gait parameters will be collected during walking tasks. Clinical rating scales will be additionally assessed after the final stimulation condition. Mean stride length will be directly obtained from the IDEEA system, which uses inertial sensors to quantitatively monitor gait during walking tasks in patients with PD.
stride frequency（steps/min）
This is a within-subject study. Instrumented gait parameters and clinical rating scales will be assessed at baseline, followed by eTNS stimulation in randomized order under the 120-Hz, 40-Hz, and sham conditions. After each eTNS condition, instrumented gait parameters will be collected during walking tasks. Clinical rating scales will be additionally assessed after the final stimulation condition.Stride frequency will be recorded as directly generated by the IDEEA system.Improvement in stride frequency after eTNS suggests potential improvement in walking rhythm and gait control in patients with PD.
Double-support phase percentage（%）
This is a within-subject study. Instrumented gait parameters and clinical rating scales will be assessed at baseline, followed by eTNS stimulation in randomized order under the 120-Hz, 40-Hz, and sham conditions. After each eTNS condition, instrumented gait parameters will be collected during walking tasks. Clinical rating scales will be additionally assessed after the final stimulation condition.Double-support phase percentage will be calculated as: (double-support time / gait cycle time) × 100%. A higher Double-support phase percentage value generally indicates greater reliance on double-limb support to maintain stability, suggesting more cautious gait, impaired dynamic balance, and increased fall risk. A decrease in double-support phase percentage after eTNS suggests reduced dependence on double-limb support and potential improvement in gait stability and dynamic balance in patients with PD.
gait symmetry index（%）
This is a within-subject study. Instrumented gait parameters and clinical rating scales will be assessed at baseline, followed by eTNS stimulation in randomized order under the 120-Hz, 40-Hz, and sham conditions. After each eTNS condition, instrumented gait parameters will be collected during walking tasks. Clinical rating scales will be additionally assessed after the final stimulation condition.The symmetry index will be calculated as: \|left-side gait parameter - right-side gait parameter\| / \[0.5 × (left-side gait parameter + right-side gait parameter)\] × 100%.The symmetry index reflects the degree of difference between left- and right-side gait parameters and is used to evaluate bilateral gait symmetry. A higher value indicates greater asymmetry, whereas a lower value indicates better gait symmetry. A decrease in the symmetry index after eTNS suggests improved bilateral gait symmetry in patients with PD.
Hoehn and Yahr Scale
This is a within-subject study. Instrumented gait parameters and clinical rating scales will be assessed at baseline, followed by eTNS stimulation in randomized order under the 120-Hz, 40-Hz, and sham conditions. After each eTNS condition, instrumented gait parameters will be collected during walking tasks. Clinical rating scales will be additionally assessed after the final stimulation condition.The Hoehn and Yahr scale ranges from 1 to 5 in this study. Higher stages indicate more advanced disease and greater motor disability. It is a clinical staging system used to assess the overall severity of Parkinson's disease based on the distribution of motor symptoms, postural instability, walking ability, and functional disability. A higher stage indicates more severe disease. A decrease in Hoehn and Yahr scale after eTNS would suggest improvement in overall motor function and disease severity.
Incidence of eTNS-Related Adverse Reactions [Safety and Tolerability]
Adverse reactions related to eTNS will be recorded throughout the experimental session, including local skin numbness, tingling, itching, redness at the electrode site, headache, dizziness, or any other discomfort reported by the participant or observed by the investigator. The number and percentage of participants experiencing eTNS-related adverse reactions will be reported.
Movement Disorder Society-Unified Parkinson's Disease Rating Scale Part III
This is a within-subject study. Instrumented gait parameters and clinical rating scales will be assessed at baseline, followed by eTNS stimulation in randomized order under the 120-Hz, 40-Hz, and sham conditions. After each eTNS condition, instrumented gait parameters will be collected during walking tasks. Clinical rating scales will be additionally assessed after the final stimulation condition. Movement Disorder Society-Unified Parkinson's Disease Rating Scale Part III(MDS-UPDRS III) is a clinician-rated motor examination scale used to assess the severity of motor signs in Parkinson's disease, including rigidity, bradykinesia, tremor, gait, posture, and postural stability. The score ranges from 0 to 132, with each item rated from 0 to 4. Higher scores indicate more severe motor impairment.A decrease in the MDS-UPDRS Part III score after eTNS indicates improvement in motor function.
Tinetti Gait Assessment
This is a within-subject study. Instrumented gait parameters and clinical rating scales will be assessed at baseline, followed by eTNS stimulation in randomized order under the 120-Hz, 40-Hz, and sham conditions. After each eTNS condition, instrumented gait parameters will be collected during walking tasks. Clinical rating scales will be additionally assessed after the final stimulation condition.The Tinetti Gait Assessment score ranges from 0 to 12. Higher scores indicate better gait performance and stability.The Tinetti Gait Assessment evaluates gait performance during walking, including gait initiation, step length and height, step symmetry, step continuity, walking path, trunk stability, and walking stance. A lower score indicates poorer gait function and greater gait instability, whereas a higher score indicates better gait function. An increase in the Tinetti Gait Assessment score after eTNS suggests improvement in gait function in patients with PD.
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Zhengli Di
Lead sponsor
Xi'an Central Hospital
Sponsor institution
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