Vestibular Rehabilitation and Otolith Dysfunction
Condition: Dizziness
MeSH terms: Vertigo; Dizziness
Study type: Interventional

Summary: 
      Recent studies suggest that otolith dysfunction is a common finding in individuals with a
      history of head trauma/blast exposure and/or noise-induced hearing loss. Therefore, otolith
      dysfunction may be a significant health concern for the Veteran population, and determining
      optimal intervention strategies for otolith dysfunction is important for VA healthcare. The
      purpose of this project is to identify optimum stimulus parameters of a novel treatment,
      off-axis rotation (centrifugation) for otolith dysfunction, in healthy participants.
    

Detailed description: 
      The primary function of the vestibular (inner ear balance) system is to maintain gaze and
      postural stability. The vestibular system is comprised of two types of sensory organs
      (semicircular canals and otolith organs) each with unique contributions to balance.

      Vestibular Rehabilitation (VR) is the treatment of choice for patients experiencing
      dizziness, imbalance, and mobility impairments related to vestibular dysfunction. VR
      typically includes gaze stability exercises, gait and balance training, and general
      conditioning. Gaze stability exercises were developed based on the concepts of adaptation and
      substitution with the goal of improving gaze stability by facilitating vestibular
      compensation of the semicircular canal-mediated vestibulo-ocular reflex (VOR).

      Many factors that might influence recovery, such as the involvement of different vestibular
      sensory organs (semicircular canals versus otolith organs) have not been examined to
      determine their impact on recovery. Most studies examining the effectiveness of VR have used
      only tests of VOR function (caloric and rotational tests) that measure horizontal
      semicircular canal to determine vestibular loss. Thus, little is known about interventions to
      facilitate vestibular compensation of the otolith organs.

      Recent studies have demonstrated adaptation following otolith organ stimulation using
      centrifugation (or linear acceleration), but there is no data regarding optimum stimulus
      parameters. The concept of using centrifugation for otolith adaptation may be similar to
      using gaze stability exercises for VOR adaptation. Healthy control subjects (n = 5 per
      experiment) will participate in three separate experiments to determine: (1) the optimum
      off-axis distance of the rotary chair, (2) the optimum duration of off-axis rotation (OAR),
      and (3) the optimum OAR stimulation/training schedule.
    

Intervention name(s): Centrifugation Distance; Centrifugation Duration; Centrifugation Schedule
Intervention type(s): Behavioral; Behavioral; Behavioral
Intervention description(s): To determine optimal distance off-axis, participants were rotated in a darkened rotary chair booth with 1 ear positioned 3.5 cm off-axis and the other ear positioned on-axis for 1 minute. Participants received 5 sessions in a 1-week period. Following a 2-week washout period, participants were rotated in a darkened rotary chair booth with 1 ear positioned 7.0 cm off-axis and the other ear positioned on-axis for 1 minute. Participants received 5 sessions in a 1-week period.; To determine optimal duration, after a two week washout period, participants were rotated off-axis at 3.5 cm (determined to be optimal in Exp 1) for 3 minutes. Participants received 5 sessions in a 1-week period.; To determine optimal schedule, after a two week washout period, participants were rotated off-axis at 3.5 cm (determined to be optimal in Exp 1) for 3 minutes (determined to be optimal in Exp 2). Participants received biweekly sessions for a total of 5 sessions.
Intervention model: Sequential Assignment
Intervention model description: To determine optimal stimulus parameters for off-axis rotation (OAR), participants progressed through the study starting with off-axis distance (3.5 vs 7.0 cm), off-axis duration (1 vs 3 minutes) and finally training schedule (daily vs biweekly). SVV was measured immediately before and after training.
To determine optimal distance, OAR was first performed at 3.5 cm and then 7.0 cm off-axis for 1 minute and the change in SVV compared. Participants trained daily for 5 consecutive days at 3.5 cm followed by a washout period of two weeks, then trained at 7.0 cm.
To determine optimal duration, participants were rotated at 3.5 cm off-axis (determined to be optimal) for 3 minutes and the change in SVV was compared to 3.5 cm off-axis for 1 minute.
To determine optimal training schedule, participants were rotated at 3.5 cm off-axis for 3 minutes (determined to be optimal) on a biweekly schedule for a total of 5 sessions and change in SVV was compared to the daily training schedule.
Masking: None (Open Label)
Primary purpose: Other
Keywords: dizziness; postural balance; rehabilitation