The effects of augmenting traditional rehabilitation with audio biofeedback in people with persistent imbalance following mild traumatic brain injury
Campbell KR, Peterka RJ, Fino PC, et al. The effects of augmenting traditional rehabilitation with audio biofeedback in people with persistent imbalance following mild traumatic brain injury. Frontiers in Neurology. 2022;13. doi:10.3389/fneur.2022.926691Link to Original Article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9577092/
Key Points
- Chronic mild traumatic brain injury (mTBI) often leads to complaints of non-resolving imbalance, which can persist for months after the initial injury, impacting quality of life.
- Vestibular rehabilitation therapy, augmented with audio biofeedback (ABF), has shown promise in improving postural sway and static balance in individuals with chronic mTBI.
- A study involving 31 participants with chronic mTBI symptoms of self-reported imbalance compared vestibular rehabilitation with ABF to vestibular rehabilitation without ABF.
- Both groups showed similar improvements in reducing post-concussion symptoms and increasing sensory organization test (SOT) composite scores after rehabilitation.
- The group with ABF showed trends of larger effect sizes in increasing motor activation and decreasing time delay, indicating potential benefits of the addition of ABF to vestibular rehabilitation.
- While vestibular rehabilitation with or without ABF showed improvements in symptom severity and balance function, the ABF group demonstrated larger improvements in specific measures of balance control, suggesting potential benefits of ABF in enhancing vestibular rehabilitation outcomes.
Introduction
The study investigates the impact of adding audio biofeedback (ABF) to vestibular rehabilitation for individuals with chronic mild traumatic brain injury (mTBI). Persistent symptoms following mTBI, such as imbalance and dizziness, have been linked to visual and vestibular issues, suggesting central process abnormalities. Around 28% of people with mTBI complain of persistent balance deficits more than 1 year post injury. Recent evidence suggests people with persistent balance deficits as a result of mTBI have normal vestibular and oculomotor function. However, the symptoms of balance deficits are caused by abnormal central processes such as decreased sensory utilization, impaired sensory reweighting, or change in sensorimotor control properties. While vestibular rehabilitation has shown promise in alleviating mTBI-related symptoms, there is limited evidence from randomized controlled trials. Despite its name, vestibular rehabilitation does not specifically train the vestibular function. It reduces dizziness and improves balance through central sensory training and adaptations by utilizing habituation, adaptation, and substitution strategies.
A new approach to vestibular rehabilitation involves biofeedback, with recent evidence suggesting its effectiveness in improving balance in various neurological conditions. Audio biofeedback (ABF) provides concurrent measures of postural sway performance through auditory cues, and studies have shown its potential in improving postural sway and balance in different patient populations. Past studies on ABF showed promises in improving postural sway and maintaining static balance in patients with bilateral vestibular loss.
This study aims to explore the effects of adding ABF to vestibular rehabilitation for chronic mTBI and hypothesizes that ABF will enhance the effectiveness of standard vestibular rehabilitation by reducing symptoms and improving balance control. The researchers anticipate that ABF may provide an additional sensory cue to coordinate balance and improve postural sway. The potential benefits of ABF in enhancing rehabilitation for chronic mTBI warrant further investigation, and this study seeks to contribute to the understanding of the effectiveness of ABF in improving balance and reducing symptoms in this population.
Methods
Participants
The Participants section of the research paper involved individuals who provided written informed consent and were approved by the Oregon Health & Science University and Veterans Affairs Portland Health Care System joint Institutional Review Board for the recruitment procedures and experimental protocols. The study focused on individuals who had experienced a mild traumatic brain injury (mTBI) more than 3 months prior and were still experiencing imbalance, with a total of 40 participants. The participants were part of a larger study aimed at evaluating central sensorimotor impairments after mTBI. Inclusion criteria for participants consisted of being between 18 and 60 years old, having minimal-to-no cognitive deficits, as indicated by a Short Blessed Test score of ≤8, and experiencing the mTBI more than 3 months before the study. They were excluded if they had a previous or current musculoskeletal injury, surgery, medication, or neurological illness that can influence balance, a pre-existing peripheral vestibular/oculomotor disorders, have significant hearing loss, or moderate to severe substance abuse.
Intervention
In a study examining the effects of adding audio biofeedback (ABF) to vestibular rehabilitation for chronic mild traumatic brain injury (mTBI), participants were randomized into two groups: vestibular rehabilitation with ABF or vestibular rehabilitation without ABF. The rehabilitation program involved biweekly sessions for 6 weeks consisting of warm-up, static and dynamic balance exercises, with each exercise performed for 30 seconds and an additional 5-second calibration period for the ABF system. Subjects also completed a home exercise program, including gaze stabilization, saccades, visual motion sensitivity exercises, habituation exercises, and cardiovascular exercise without exacerbating mTBI symptoms. The percentage of exercises completed was calculated by the total number of exercises completed divided by the total number of exercises. This value indicated exercise tolerance. The vestibular rehabilitation exercises consisted of:
Table 2.
Exercises performed during vestibular rehabilitation sessions for with and without ABF groups
Those in the ABF intervention group wore headphones and a smartphone on their back (L4/L5 for static balance exercises and T7/T8 for dynamic balance exercises), which provided feedback on body sway acceleration as an auditory tone. Prior to the use of ABF, the participants were instructed on the use of ABF devices at each rehabilitation session and how to correct their balance and return to a balanced position if the feedback was provided. The ABF system provided feedback about mediolateral (ML) sway by changing the location of the tone and provided feedback about anteroposterior (AP) sway by changing the pitch. When the patients were standing within calibrated limits, no sound or feedback were provided to indicate stability. Feedbacks were only provided when the participant’s stance was outside its calibrated limits. For dynamic balance exercises, feedback was only provided in the ML direction. Home exercises were the same for both groups. Exercise adherence was tracked, and the percentage of exercises completed was documented during each rehabilitation session.
Protocol
The study collected baseline demographic information and conducted questionnaires on post-mTBI symptom severity and the overall impact of dizziness on daily life using the Post-Concussion Symptom Scale (PCSS) and Dizziness Handicap Inventory-DHI. Participants also underwent pre- and post-rehabilitation evaluations on the sensory organization test (SOT) and a custom Central Sensorimotor Integration (CSMI) test using the NeuroCom SMART Balance Master. The SOT assessed equilibrium scores, while the CSMI test measured parameters of a balance control model, including sensory weights, time delay, and motor activation factors. The CSMI test used frequency domain analyses to derive an experimental frequency response function (FRF) and model-predicted FRF, with the primary outcome measures being sensory weights, time delay, and motor activation factors.
Statistical analysis
The study compared the baseline demographic characteristics of individuals with chronic mild traumatic brain injury (mTBI) who underwent vestibular rehabilitation with and without audio biofeedback (ABF). The outcome measures included the Post-Concussion Symptom Scale (PCSS), Dizziness Handicap Inventory (DHI), Sensory Organization Test (SOT) composite scores, as well as model-derived parameters and sway-derived measures of balance performance from the Computerized Dynamic Posturography Sensory Organization Test (CSMI). The analysis focused on conditions evaluating vestibular weighting, specifically SS/EC and SS + VS/EO conditions. The effects of adding ABF to rehabilitation were assessed using the effect size of the change in pre- and post-rehabilitation outcomes (Hedge's G) and the number of participants who experienced a detectable change in their SOT composite score. Effect sizes were interpreted as having little to no effect (<0.19), a small effect (0.20-0.49), a medium effect (0.50-0.79), or a large effect (>0.80). The analysis was conducted using the Measures of Effect Size (MES) Toolbox in MATLAB 2021b.
Results
Participant characteristics
The participant characteristics section of the study included 40 participants who were enrolled and randomized for vestibular rehabilitation, with 31 completing the rehabilitation and post-rehabilitation assessments. Nine participants did not complete post-rehabilitation testing due to various reasons including pregnancy, musculoskeletal injury, time constraints, subject withdrawal, personal reasons, and loss to follow up.
Based on the data of 31 patients who completed the rehabilitation program, the mean age was 40.9 years with 9 to 22 male to female ratio and mean of 393 days post injury. The initial baseline PCSS score was 36.1, the initial DHI score was 43.9, and the initial SOT was 55.5.
Demographic information indicated no significant group differences on various factors between participants that completed the intervention and those included in the final analysis. The ABF group reported a significantly lower symptom severity score at prerehabilitation relative to the without ABF group. The time between pre-and post-rehabilitation evaluations was not different between the groups.
At the start of the intervention, participants in the without ABF and with ABF groups completed 29% and 32% of the exercises in the rehabilitation program, respectively. By the end of the intervention, participants in the without ABF and with ABF groups completed 65% and 60% of the exercises. Both groups progressed similarly as indicated by the change in the percentage of the exercises completed over the intervention.
Effects of augmenting vestibular rehabilitation with ABF on clinical balance performance measures
The study compared the effects of vestibular rehabilitation with and without audio biofeedback (ABF) on clinical balance performance measures in individuals with chronic mild traumatic brain injury (mTBI). Both groups showed similar medium effects in decreasing symptom severity scores, with the ABF group demonstrating a small effect on the total score of the Dizziness Handicap Inventory (DHI), while the non-ABF group showed no effect. Both groups had large effects on increasing Sensory Organization Test (SOT) composite scores, with a similar number of participants improving or maintaining their scores. In terms of the Cawthorne-Matthews Severity Inventory (CSMI) model-derived parameters and sway-derived outcomes, the non-ABF group displayed small effects on vestibular weighting, time delay decreases, and motor activation increases, while the ABF group had varying effects ranging from no effects to medium to large effects on these parameters. Additionally, the ABF group exhibited larger decreases in stimulus-evoked and remnant center of mass (CoM) sway, as well as smaller effects on decreasing internal sensory noise compared to the non-ABF group. Overall, the findings suggest that adding ABF to vestibular rehabilitation may lead to more significant improvements in clinical balance performance measures, particularly in reducing sway and enhancing sensory organization in individuals with chronic mTBI.
Discussion
The study aimed to investigate the effects of adding audio biofeedback (ABF) to traditional vestibular rehabilitation in individuals with chronic mild traumatic brain injury (mTBI). Imbalance is a common and persistent symptom following mTBI, and treatment can be challenging due to the assumption of multiple etiologies for these symptoms. The researchers found that participants in both the ABF and non-ABF groups showed decreased symptom severity and improved balance function after rehabilitation when assessed with the Sensory Organization Test (SOT), a common balance assessment tool. However, the ABF group showed larger improvements in measures related to the balance control system. Contrary to the reductions in overall mTBI symptoms, the study did not observe substantial changes in Dizziness Handicap Inventory (DHI) scores after rehabilitation. Both groups demonstrated improvements in postural stability as measured by the SOT, with larger improvements observed in the ABF group. The study also observed changes in the balance control system, with reductions in time delay and increases in motor activation and reductions in stimulus-evoked and remnant center of mass (CoM) sway. The ABF group showed larger changes in these measures compared to the non-ABF group. The findings suggest that ABF may have benefits in improving postural control and reducing symptom severity in chronic mTBI. However, the study had limitations, including a relatively low sample size, a high dropout rate, and a focus on static balance, which may not fully capture the effects on dynamic balance. Further research is needed to explore the optimal scheduling and dose-response parameters for vestibular rehabilitation in this population.
Conclusion
The study examined the effects of adding audio biofeedback (ABF) to vestibular rehabilitation for individuals with chronic mild traumatic brain injury (mTBI). It was found that both vestibular rehabilitation with and without ABF effectively reduced the severity of persistent post-mTBI symptoms, as well as improved balance function as measured by the Sensory Organization Test (SOT). However, it was observed that individuals completing vestibular rehabilitation augmented with ABF showed larger improvements in the time delay and motor activation components of balance function. These findings suggest that the addition of ABF to vestibular rehabilitation may offer additional benefits in improving balance control and reducing symptoms in individuals with chronic mTBI. As a result, the study advocates for the consideration of additional approaches such as neuromuscular training and real-time biofeedback for rehabilitation after mTBI, based on the preliminary results. These results provide valuable insights into the potential impact of ABF on postural sway and balance, as well as the overall effectiveness of vestibular rehabilitation programs for individuals with chronic mild traumatic brain injury.
