Advancement of Vestibular Intervention Via Portable Electrical Stimulator (VIPES)

The VIPES system that delivers sGVS is a small wearable device that administers stimulation aiming to improve the function of a vestibular system that has been adversely affected by mild TBI, concussion. In particular VIPES is designed to provide stimulus comprising random noise in a low frequency band (0 to 5Hz maximum) below the level of perception by the subject. The VIPES system consists of the four electrodes (two behind each ear). The stimulator can deliver the stimulation in multiple directions and receive information about the amplitude delivered accounting for skin impedance. The Bertec Portable Essential's dual-balance plate balance system and the APDM Opal V2R sensor are used as reference measurement tools for assessing clinical performance.

The study to be completed is an N=32 single-arm clinical investigation, comprised of a within-subject crossover study designed to evaluate whether electrical stimulation delivered by a wearable vestibular system can improve functional performance on clinical balance and mobility assessments. All participants will complete both Timed Up and Go (TUG) and mCTSIB + COBALT performance tests under a series of stimulation conditions.

Each test session begins with a Baseline (no stimulation) trial, followed by four additional trials under different stimulation levels: 0mA (sham), 0.33mA, 0.67mA, and 1.0mA. The stimulation sequence is randomized after Baseline. Participants are blinded to stimulation level during all trials.

Participants will be recruited from the pool of patients treated at the University of Michigan - NeuroSport Clinic for mTBI. Upon passing pre-screening through chart review and via phone, interested individuals will be scheduled for a study visit that begins with obtained informed consent. Prior to beginning the testing procedures, enrolled participants will provide demographic information (age, sex/gender, race, ethnicity), have height measured, weight measured, and provide a detailed medical history, history of present illness, a list of current medications, as well as complete a post-concussion symptoms questionnaire.

The performance tests to be completed:

1. Modified Clinical Test of Sensory Integration on Balance (mCTSIB):

Tool: Bertec Portable Essential's dual-balance plate balance system

Rationale: mCTSIB is a balance test commonly used to evaluate individuals of all ages post-concussion. This test protocol assesses how well an individual uses sensory input when one or more sensory systems are compromised. This protocol is commonly used to evaluate individuals post-concussion to describe static balance ability.

The test will be performed for each sGVS amplitudes from 0mA (sham \& baseline) to 1 mA at 0.33 mA increments. Two trials for each of the following conditions: * Standard (eyes open on firm surface) * Proprioception (eyes closed on firm surface) * Vision (eyes open on foam surface) * Vestibular (eye closed on foam surface) 2. COBALT Balance Test:

Tool: Bertec Portable Essential's dual-balance plate balance system

Rationale: COBALT is a balance test commonly used to evaluate individuals post-concussion. This test protocol places high demand on the visual and vestibular systems that is not provided by traditional balance tests. These higher demand conditions improve sensitivity in detecting balance dysfunction in those post-concussion.

The test will be performed for each sGVS currents from 0mA (sham \& baseline) to 1 mA at 0.33 mA increments. Two trials for each of the following conditions/surfaces:

On Firm Surface: * Head Shake - Standing on firm surface with feet apart, head movement\*

* Normal stance with headshake and eyes closed. The subject will be instructed to stand still, with hands on hips and then asked to adjust head positioning approximately 30 degrees from a center position in sync with a metronome set at 120 beats/min. * Participant will practice with eyes open and when ready close eyes. * Visual Motion Sensitivity - Visual motion sensitivity condition on firm surface.

* The subject is instructed to stand at the center of the balance plate with feet together and both arms extended out in front with hands clasped together and the thumbs straight up. The subject is to focus on the thumbs held in front while rotating approximately 30 degrees right and left, for a total excursion of 60 degrees, in sync with the metronome set at 40 beats/min.

On Foam Surface: * Head Shake - Standing on foam with feet apart, head movement\*

o Normal stance with head shake and eyes closed on foam. Performed with the foam pad placed on the balance plate with the same procedure and parameters as HS on firm surface described above. * Visual Motion Sensitivity - Visual motion sensitivity condition on foam. o Performed with the foam pad placed on the balance plate with the same procedure and parameters as VMS condition on firm surface described above. 3. Timed up and go (TUG):

Tool: Opal V2R Sensor

Rationale: TUG is a test used to assess an individual's functional balance. It requires appropriate static and dynamic balance system integration. TUG provides a measure of functional balance integration not provided from standing balance tasks.

The test will be performed for each GVS amplitudes from 0mA (sham \& baseline) to 1 mA at 0.33 mA increments.

* The subject starts in a seated position * The subject stands up upon research staff command: walks 3 meters, turns around, walks back to the chair and sits down. * The time stops when the patient is seated.

Participants take a break following the testing prior to repeating. Following completion of the study, participants are asked to completed a short System Usability Scale Questionnaire. The entire study visit is estimated to take about 120 minutes.

The overall aim of the study is to determine whether performance improves under active stimulation conditions when compared to sham trials. Results may inform optimal parameter selection for future efficacy-focused studies.