Auricular Vagus Nerve Stimulation Combined With Rehabilitation in Parkinson's Disease

The Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) was used to assess motor and non-motor symptom severity in individuals with Parkinson's disease. The MDS-UPDRS is a validated, comprehensive clinical rating scale consisting of four parts: non-motor experiences of daily living (Part I), motor experiences of daily living (Part II), motor examination (Part III), and motor complications (Part IV). Higher scores indicate greater symptom severity. The scale has demonstrated excellent reliability, validity, and sensitivity to change in clinical trials and is widely recommended as a primary outcome measure in Parkinson's disease research.

The force platform, considered the gold standard for the quantitative assessment of postural stability, is a valid and reliable method that enables objective evaluation of balance. In this study, postural stability during quiet standing will be assessed using a force platform. Participants will stand on the platform in a standardized foot position, with their arms at their sides and their gaze fixed forward. Measurements will be performed under eyes-open and eyes-closed conditions. For each condition, trials of fixed duration will be recorded, and center of pressure (CoP) parameter will be calculated. Higher CoP value will indicate reduced postural stability. Measurements will be repeated according to a standardized protocol, and the average values will be used for analysis.

Spatiotemporal gait characteristics will be evaluated using a gait analysis system. Participants will walk across the walkway six times at their self-selected comfortable speed. Temporal and spatial parameters (step length, stride length, step time, stride time, double support time) of gait, as well as variability measures, will be calculated.

Functional walking capacity will be assessed using the 6-Minute Walk Test (6MWT). Participants will be instructed to walk as far as possible within six minutes along a standardized walkway. The total distance covered will be recorded in meters. In individuals with Parkinson's disease, the minimal clinically important difference has been reported as 82 meters.

Functional balance will be assessed using the Berg Balance Scale (BBS), a widely used and validated clinical scale for the evaluation of balance performance in individuals with neurological conditions. The BBS consists of 14 functional tasks, including sitting, standing, transfers, reaching, turning, and single-leg stance. Each item is scored on a 5-point ordinal scale ranging from 0 to 4, with a maximum total score of 56 points. Higher scores indicate better balance performance. The BBS has demonstrated high reliability, validity, and sensitivity to change in individuals with Parkinson's disease and other neurological populations.

Balance confidence will be assessed using the Activities-specific Balance Confidence Scale (ABC). The ABC is a self-reported questionnaire designed to evaluate an individual's confidence in maintaining balance during various daily activities. It consists of 16 items, each scored from 0% (no confidence) to 100% (complete confidence). The overall score is calculated as the average of all item scores, with higher values indicating greater balance confidence. The ABC has demonstrated good reliability, validity, and responsiveness in individuals with Parkinson's disease and other neurological populations.

Functional mobility will be assessed using the Timed Up and Go Test (TUG). In this test, participants are instructed to stand up from a chair on the command "go," walk 3 meters, turn around, walk back, and sit down again. The test is performed on a flat, unobstructed 3-meter walkway. Timing begins at the command "go" and stops when the participant sits back in the chair. A chair with armrests will be used (seat height: 50 cm, seat depth: 47 cm, seat width: 50 cm, armrest height: 65 cm). One practice trial will be performed, followed by two recorded trials, and the final measurement will be used for analysis.

The Trail Making Test (TMT) is used to assess executive functions, task-switching ability, attention, visual scanning speed, visuomotor processing, planning, organization, abstract thinking, and response inhibition. The test consists of two parts: Part A (TMT-A) and Part B (TMT-B). In Part A, participants are asked to connect numbered circles in sequential order from 1 to 25, and the completion time is recorded. In Part B, participants are required to alternate between numbers and letters in sequence (e.g., 1-A-2-B-3-C), and the completion time is recorded.

The Stroop Test is a cognitive assessment that evaluates executive functions, particularly selective attention, cognitive flexibility, and the ability to inhibit automatic responses under interference conditions. In this study, the Stroop Test-Basic Sciences Research Group Form (ST-BSRG) will be used. This form is a combined version of the original Stroop Test and the Victoria version. The test is administered in five sections using four different cards. Each card contains six rows, with each row consisting of four items arranged in sequence. The completion time and errors are recorded for analysis.

Quality of life will be evaluated using the Parkinson's Disease Questionnaire-8 (PDQ-8). The PDQ-8 is a short-form, disease-specific questionnaire that assesses the impact of Parkinson's disease on quality of life. The items evaluate the individual's experiences over the previous month and are scored on a scale from 0 (never) to 4 (always). The total score is converted to a 0-100 scale, with higher scores indicating poorer quality of life. The Turkish version of the PDQ-8 has been shown to be valid and reliable, with excellent test-retest reliability (ICC = 0.97) as reported by Kahraman and colleagues.

Subjective fatigue will be evaluated using the Parkinson Fatigue Scale (PFS). The PFS consists of 16 items and is rated on a five-point Likert scale. It was specifically developed to assess fatigue related to Parkinson's disease. Each item is scored from "strongly disagree" to "strongly agree," with higher scores indicating greater fatigue severity. The Turkish version of the scale has been shown to be valid and reliable.