The Video Head Impulse Test (vHIT) is a clinical test used to assess the vestibulo-ocular reflex (VOR) by measuring eye movement responses to head rotations. This test evaluates the function of the three semicircular canals, providing insight into vestibular physiology. During the test, participants wear video goggles that record eye movements while the head is gently rotated to either side at a velocity of ~150°/s, consistent with standardized vHIT protocols. The primary outcome measure is VOR gain (eye velocity/head velocity), with lower gain values potentially indicating vestibular dysfunction.

The Dynamic Visual Acuity (DVA) test is a validated clinical measure used to assess the ability to maintain clear vision during head movements. The test evaluates the vestibulo-ocular reflex (VOR) by comparing static visual acuity (head stationary) with visual acuity during dynamic head rotations in the horizontal and vertical planes (e.g., head movements right, left, up, and down). Participants are seated 2 meters from the testing screen, and head rotation speeds must reach a minimum of 80°/s to generate the randomized optotype. The primary measure is logMAR (logarithm of the minimum angle of resolution) scores, where higher logMAR values indicate worse visual acuity during movement.

The Functional Gait Assessment (FGA) is a clinical tool used to evaluate gait performance in individuals during different walking tasks. It consists of 10 tasks, including walking while changing speeds, walking with head turns, walking backward, stepping over obstacles, and walking in tandem. Each task is scored on a 0-3 scale, with a total score range of 0-30 indicating optimal performance, and lower scores reflecting greater balance impairments and reduced gait functionality. The FGA is validated for identifying fall risk. Scores below 22/30 indicate fall risk in older adults.

The Timed Up and Go (TUG) test is a validated tool for assessing functional mobility and fall risk. Participants are instructed to rise from a seated position, walk 3 meters, turn 180°, walk back, and return to a seated position. The time taken to complete the sequence is recorded as the primary outcome. Faster times indicate normal functional mobility, while slower times (>13.5 seconds for older adults) are indicative of increased fall risk, particularly in individuals with vestibular disorders.

The Timed Up and Go Dual Task test is a dual-task modified version of the traditional TUG protocol, which further assesses the impact of cognitive load on mobility and balance. Participants perform the same tasks as the TUG test (stand, walk 3 meters, turn, and return to sit) while simultaneously counting backwards from 100 by threes (or another similar cognitive challenge). Timings exceeding 15 seconds in elderly individuals are associated with increased fall risk.

Gait velocity will be measured using the 10-Meter Walk Test (10MWT), a validated assessment tool for evaluating walking speed during a self-selected comfortable pace over a short distance. Participants will be instructed to walk 10 meters while gait speed is recorded, with or without an assistive device as appropriate. The average speed (meters/second) is calculated and will be used as the primary outcome measure.

The Adaptation Test assesses participants' ability to maintain stability and adapt to unexpected changes in surface tilt. Testing is conducted using a rotating force plate, which provides controlled motion stimuli in two directions: toes-up and toes-down. Participants will stand on the force plate while wearing the Virtualis Motion (VR) headset, which provides immersive visual environments to simulate balance challenges and enhance sensorimotor engagement. Postural stability is evaluated by measuring sway energy, which quantifies force and the extent of anterior-posterior sway, as well as sway over time, which measures center of pressure (COP) movement across the duration of the trials. These measures provide insight into a participant's balance control and adaptive strategies during repeated tilt trials.

The Falls Efficacy Scale - International (FES-I) is a widely validated self-reported questionnaire designed to assess a participant's concern about falling during a variety of daily physical and social activities. It consists of 16 items covering tasks performed both inside and outside the home, such as cleaning, shopping, and walking. Each item is rated on a 4-point Likert scale ranging from "Not at all concerned" (1) to "Very concerned" (4), resulting in a total score range of 16-64, with higher scores indicating greater concerns about falling.

The EQ-5D-5L is a standardized instrument for measuring health-related quality of life. It evaluates five dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Each dimension is scored on five levels ranging from "no problems" to "extreme problems," creating a profile of a participant's health status. Additionally, participants complete a Visual Analog Scale (VAS) to rate overall health from 0 ("worst imaginable health") to 100 ("best imaginable health").

The Vestibular Evoked Myogenic Potential (VEMP) test is a clinical measure used to assess the function of the vestibular system, focusing specifically on the otolith organs (utricle and saccule). VEMP includes two types: cervical VEMP (cVEMP), which assesses saccular function through responses from the sternocleidomastoid neck muscle, and ocular VEMP (oVEMP), which evaluates utricular function through responses from the orbicularis oculi eye muscles. Participants are positioned reclined and equipped with electrodes over the relevant muscles. Auditory stimuli, such as clicks or tone bursts, are delivered via earphones to each ear individually, and participants are asked to lift the head (cVEMP) or look upward (oVEMP) to optimize muscle activation. Test results include latency and amplitude of evoked potential responses, with reduced or absent responses indicating possible vestibular dysfunction.

The Vestibular Nystagmogram (VNG) is a standard clinical test used to evaluate the function of the vestibular system, particularly the horizontal semicircular canal. It involves recording participants' eye movements while wearing video goggles designed to track nystagmus (involuntary eye movements) in response to various stimuli. Participants follow an infrared light with the eyes during certain conditions, and nystagmus responses are evaluated after exposure to both cold air and warm air stimuli administered into the ear canal.

The Scale for Ocular Motor Disorders in Ataxia (SODA) is a clinical rating tool designed to quantify and characterize ocular motor dysfunction in patients with cerebellar ataxia and related disorders. SODA systematically evaluates a range of oculomotor deficits, including gaze-holding and smooth pursuit abnormalities, saccadic dysmetria (hypometria and hypermetria), saccade velocity and restriction, gaze-evoked and spontaneous nystagmus (horizontal and vertical), saccadic oscillations, and abnormalities in the vestibulo-ocular reflex (VOR). Each domain is scored based on the observed severity and type of deficit. Higher SODA scores correspond to more severe ocular motor dysfunction.

The Dynamic Gait Index (DGI) is a validated clinical tool used to assess gait, balance, and fall risk during dynamic walking tasks. The DGI includes 8 tasks, such as walking while changing speeds, turning the head, stepping over obstacles, and pivoting. Each task is scored on a 0-3 scale, with a total maximum score of 24 indicating optimal performance, and lower scores reflecting greater gait and balance impairments. A score below 19/24 indicates a significantly increased risk of falls (2.58 times greater likelihood of falling within the previous 6 months).

The Scale for the Assessment and Rating of Ataxia (SARA) is a validated clinical tool designed to quantify the severity of ataxia symptoms. SARA consists of 8 tasks that evaluate various aspects of motor function, including gait, stance, sitting, and limb coordination (such as finger chase, nose-finger tests, and heel-shin tests). Each task is rated on a 0-4 scale, with total scores ranging from 0 (no ataxia) to 40 (most severe ataxia). Lower scores reflect minimal impairment, while higher scores indicate greater dysfunction.