Human Vestibulo-Ocular Reflex Adaptation Reduces when Training Demand Variability Increases

Influence of Visual Feedback on Roll Tilt Perceptual Training

HYPOTHESIS

We hypothesized that the addition of visual feedback during roll tilt perceptual training would yield a significant reduction in vestibular perceptual thresholds relative to a control group.

BACKGROUND

We previously showed that roll tilt vestibular thresholds could be improved through a perceptual training protocol that used a simple auditory cue. Variability in training outcomes within the treatment group suggested that an auditory cue alone may be suboptimal for improving self-motion perception.

METHODS

In 10 healthy adults, roll tilt vestibular thresholds, quantifying the smallest motion that can be reliably perceived, were measured before ("pretraining") and after ("posttraining") a training protocol designed to improve roll tilt perception. The protocol included 1,300 trials of 0.5 Hz whole-body roll tilt over 5 days, with participants being given both an auditory cue ("correct' vs. "incorrect') and visual feedback (viewing a stationary visual scene) after indicating their perceived direction of tilt. A control group (N = 10) underwent only the "pretraining" and "posttraining" assessments.

RESULTS

The training group showed an average decrease in roll tilt vestibular thresholds of 1.7% ± 56%, with training outcomes varying widely. Three individuals showed an average increase in roll tilt thresholds of 69.7%, whereas the remaining seven adults showed an average decrease in thresholds of 32.3%.

CONCLUSION

These data show that visual feedback during roll tilt perceptual training leads to heterogenous outcomes, but in a subset of individuals, it may lead to improvements in perceptual precision. Additional work is needed to define the optimal training parameters, including feedback schema, before investigating potential clinical applications.

Comparison between caloric and video-head impulse tests in Ménière's disease and vestibular neuritis

OBJECTIVE

To compare the diagnostic accuracies of air caloric testing with electronystagmography and the vHIT (video-head impulse test).

DESIGN

Prospective, controlled study.

STUDY SAMPLE

MD (Ménière's disease), 26; vestibular neuritis, 27; control, 56.

RESULTS

In MD, CP (canal paresis) was pathological in 88.5%, the GA (gain asymmetry) on vHIT was pathological in 65.3%, and the gain was abnormal in only one patient. The GA and CP, were significantly higher in the MD group than in the control group, indicating hypofunction of the horizontal canals in MD, whereas a hyperfunction may also occur. No correlation was observed between the results of the two tests for evaluating MD, suggesting that pathological outcomes of one test do not guarantee abnormalities on the other test. For vestibular neuritis, significantly higher CP (96.3%), GA (81.5%), and gain (51.9%) values were detected. A correlation was identified between the two tests for vestibular neuritis, indicating a similar diagnostic efficiency. The higher percentage of pathological GA versus pathological gain values indicates that the asymmetry may be more informative.

CONCLUSIONS

The vHIT showed a higher specificity, whereas the caloric test a higher sensitivity. No correlation between the two methods was observed; therefore, the tests appear to provide complementary information.

Comparison of Incremental Vestibulo-ocular Reflex Adaptation Training Versus x1 Training in Patients With Chronic Peripheral Vestibular Hypofunction: A Two-Year Randomized Controlled Trial

BACKGROUND AND PURPOSE

A crossover, double-blinded randomized controlled trial to investigate once-daily incremental vestibulo-ocular reflex (VOR) adaptation (IVA) training over 2 years in people with stable and chronic peripheral vestibular hypofunction.

METHODS

Twenty-one patients with peripheral vestibular hypofunction were randomly assigned to intervention-then-control (n = 12) or control-then-intervention (n = 9) groups. The task consisted of either x1 (control) or IVA training, once daily every day for 15 minutes over 6-months, followed by a 6-month washout, then repeated for arm 2 of the crossover. Primary outcome: vestibulo-ocular reflex gain. Secondary outcomes: compensatory saccades, dynamic visual acuity, static balance, gait, and subjective symptoms. Multiple imputation was used for missing data. Between-group differences were analyzed using a linear mixed model with repeated measures.

RESULTS

On average patients trained once daily 4 days per week. IVA training resulted in significantly larger VOR gain increase (active: 20.6% ± 12.08%, P = 0.006; passive: 30.6% ± 25.45%, P = 0.016) compared with x1 training (active: -2.4% ± 12.88%, P = 0.99; passive: -0.6% ± 15.31%, P = 0.68) (P < 0.001). The increased IVA gain did not significantly reduce with approximately 27% persisting over the washout period. x1 training resulted in greater reduction of compensatory saccade latency (P = 0.04) and increase in amplitude (P = 0.02) compared with IVA training. There was no difference between groups in gait and balance measures; however, only the IVA group had improved total Dizziness Handicap Inventory (P = 0.006).

DISCUSSION AND CONCLUSIONS

Our results suggest IVA improves VOR gain and reduces perception of disability more than conventional x1 training. We suggest at least 4 weeks of once-daily 4 days-per-week IVA training should be part of a comprehensive vestibular rehabilitation program.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A356).