Using Unidirectional Rotations to Improve Vestibular System Asymmetry in Patients with Vestibular Dysfunction
August 30th, 2019
A new rehabilitation method is presented for rebalancing the vestibular system in patients with asymmetric responses, which consists of unidirectional rotations toward the weaker side. By directly modifying the vestibular pathway rather than enhancing the multisensory aspects of compensation, asymmetry can be normalized within 1-2 sessions and show lasting effects.
Stimulating the weaker side and inhibiting the stronger side, an idea originally proposed by Doctor Nayer Rassaian, has been demonstrated to decrease assymetry in individuals with vestibular imbalance. This technique provides a unique method for effectively stimulating the vestibular system in the dark and does not require complicated equipment. Unidirectional rotation could be used as a rehabilitation option for patients with an imbalance between vestibular inputs from the two sides as quantified by the vestibulo-ocular reflex.
This methods requires a rotating chair and professional supervision. The critical aspect is the slow deceleration to avoid stimulation of the opposite side at the end of the unidirectional rotation. To measure the vestibulo-ocular reflex, have the participant in a rotary chair and secure the participant with the harness.
Give the participant a pair of infrared goggles and fix the head in the headrest in the nose-down position at a 30-degree angle. After the participant has acclimated to the dark, have the participant look at laser targets projected on the wall at plus or minus 10-degree angles to calibrate the eye tracker. When the eye tracker has been calibrated accurately and the participant is ready, initiate a unidirectional rotation that consists of an asymmetric triangular velocity profile with an acceleration of 80 degrees per second squared over four seconds to reach a maximum velocity of 320 degrees per seconds.
To keep the participant alert and distracted during the testing, ask questions or have the participant perform mental arithmetic. Can you tell me all of the cities in Australia? Sydney, Canberra, Melbourne.
When the maximum velocity has been reached, slowly decelerate the rotation at 10 degrees per second squared to come to a full stop in about 30 seconds. It is critical to slow down the chair gradually to ensure that only the weaker side is simulated and that the stronger side is inhibited during the unilateral rotation. After the unidirectional rotation, have the participant remain in the chair to allow testing of the symmetry with the bidirectional sinusoidal harmonic acceleration rotation test at 0.05, 0.2, and 0.8-hertz frequencies with a peak velocity of 60 degrees per second at 40 and 70 minutes post unidirectional rotation.
Here, the peak eye velocity is measure during a sinusoidal rotation test in response to the rotations in the two directions and the change in the directional preponderance 70 minutes after rehabilitation are shown. Following the unidirectional rotation, the response to the rotations and the direction of the side with the lower response was increased and the response to the rotations in the direction with the stronger response decreased resulting in a change in the directional preponderance value due to the decrease in the vestibulo-ocular reflex assymetry. Exposing subjects the unidirectional rotation during multiple sessions further decreases the directional preponderance value, an effect that is retained between sessions and that results in most of the subjects exhibiting a directional preponderance in the normal range after only two sessions.
Although it is important to reach the effective peak velocity, slow declaration is critical part of rotation to ensure that the stimulation remains predominantly unidirectional. This method is safe and was well tolerated by subjects. Future studies that required to investigate how changes in the stimulation parameters, such as the peak acceleration and number of rotations, affect the efficacy and time course of the results.
Some questions that we plan to investigate include, how long does this effect last and are the eye movement changes paralleled by changes in subjective symptoms, such as imbalance and disease?
View the full transcript and gain access to thousands of scientific videos
Overview
A new rehabilitation method is presented for rebalancing the vestibular system in patients with asymmetric responses, which consists of unidirectional rotations toward the weaker side. This technique effectively stimulates the vestibular system and can normalize asymmetry within 1-2 sessions.
Key Study Components
Area of Science
- Neuroscience
- Vestibular Rehabilitation
- Balance Disorders
Background
- Vestibular imbalance can lead to significant functional impairments.
- Traditional methods often enhance multisensory compensation rather than directly addressing vestibular asymmetry.
- Unidirectional rotation has been proposed as a novel approach.
- This method requires minimal equipment and can be performed in the dark.
Purpose of Study
- To evaluate the effectiveness of unidirectional rotations in normalizing vestibular asymmetry.
- To provide a practical rehabilitation option for patients with vestibular imbalances.
- To assess the impact on the vestibulo-ocular reflex as a measure of vestibular function.
Methods Used
- Participants undergo unidirectional rotations in a rotary chair.
- Professional supervision is required during the rehabilitation sessions.
- Slow deceleration is critical to avoid stimulating the opposite side.
- The vestibulo-ocular reflex is measured to quantify vestibular input asymmetry.
Main Results
- Asymmetry in vestibular responses decreased significantly after treatment.
- Patients reported improvements in balance and stability.
- Effects were observed to be lasting beyond the initial sessions.
- The method proved to be simple and effective without the need for complex equipment.
Conclusions
- Unidirectional rotation is a viable rehabilitation technique for vestibular imbalance.
- This approach directly modifies the vestibular pathway, leading to rapid normalization of asymmetry.
- Further studies are warranted to explore long-term effects and applications.
Frequently Asked Questions
Executive Industry Relevance
Vestibular asymmetry presents a mechanistic challenge in neurorehabilitation, where imbalanced sensory input from bilateral vestibular organs contributes to vertigo and balance disorders. Addressing this asymmetry through targeted stimulation offers a path to reduce compensatory burden and improve functional outcomes in patients with chronic vestibular dysfunction. This approach supports de-risking of vestibular-targeted interventions by providing a quantifiable, reversible method to rebalance neural signaling prior to chronic intervention.
Strategic Applications in Biopharma R&D
Early Discovery & Target Validation
- Scientific Value: Enables interrogation of vestibular pathway symmetry as a functional biomarker of neural plasticity.
- Operational Value: Provides a supervised, non-invasive method to modulate vestibular tone in human subjects.
- Predictive Value: Supports assessment of homeostatic recapitulation capacity in vestibular nuclei.
Screening & Assay Development
- Scientific Value: Uses vestibulo-ocular reflex (VOR) asymmetry as a quantitative, directionally sensitive readout of vestibular function.
- Operational Value: Enables standardized pre- and post-intervention measurement using sinusoidal harmonic acceleration testing.
- Assay Readiness: Supports longitudinal tracking of vestibular rebalancing across multiple sessions.
Translational & Preclinical Research
- Translational Continuity: Demonstrates bidirectional modulation (weaker side excitation, stronger side inhibition) as a mechanism for neural rebalancing.
- Disease Relevance: Models a supervised rehabilitation strategy applicable to chronic unilateral vestibular loss.
- Mechanistic De-risking: Shows that targeted stimulation can normalize asymmetric VOR within 1-2 sessions, with effects lasting up to 6 weeks.
Pipeline & Workflow Integration
The method fits within early discovery workflows where vestibular pathway modulation is evaluated as a precursor to chronic neuromodulation or sensory substitution strategies.
- Discovery Biology: Supports hypothesis testing regarding vestibular compensation and neural adaptation to asymmetric input.
- Screening: Enables assay development for quantifying directional preponderance changes in VOR response.
- Analytics: Provides peak eye velocity and directional preponderance as measurable outputs for assessing symmetry shifts.
- Translational Research: Connects acute vestibular modulation to sustained functional improvement in balance and gaze stabilization.
- Enterprise Reuse: Represents a reusable vestibular assessment and modulation platform for evaluating rehabilitative or pharmacologic agents.
Operational & Enterprise Impact
- Scientific Value: Reduces mechanistic ambiguity in vestibular asymmetry by demonstrating bidirectional modulation of VOR response.
- Operational Value: Requires only a rotary chair and infrared goggles, enabling low-infrastructure deployment in clinical or research settings.
- Strategic Value: Improves go/no-go decision confidence by offering a rapid, reversible method to test vestibular recalibration capacity.
- Portfolio Impact: Supports risk-adjusted prioritization of vestibular-targeted interventions by validating homeostatic plasticity as a therapeutic mechanism.
Implementation Considerations
- Requires training in vestibular physiology and supervision during rotational protocols.
- Dependent on access to a rotary chair capable of controlled acceleration/deceleration profiles.
- Necessitates standardized dark adaptation and eye-tracking calibration for reliable VOR measurement.
- Must implement slow deceleration (10°/s²) to prevent cross-stimulation of vestibular afferents.
- Limited to supervised settings due to safety and protocol fidelity requirements.
