Patients with vestibular impairment often suffer from postural instability. This could be compensated by other sensory systems such as the auditory system. The aim of this study was to investigate whether auditory input improves postural stability in patients with abnormal subjective haptic vertical (SHV). Participants (n = 13) with normal hearing and vision, but abnormal SHV participated. Participants performed standing on firm ground and foam support (eyes open/closed) and Tandem Romberg test (eyes closed) in quiet (reference), noise and with plugged ears. All tasks were conducted in a soundproofed and reverberant room. Postural stability was recorded close to the body's center of gravity. Reference conditions were compared with a control group. In only two tasks sway increased significantly when noise was presented during challenging tasks in the soundproofed room. Sway of the reference conditions did not differ significantly between control and study group. This study shows no influence of applied auditory stimulation on posture in participants with abnormal SHV in a reverberant room, but an adverse effect on balance during difficult tasks in the soundproofed room. Noise possibly masked auditory information that was helpful in improving posture in the quiet condition. Futhermore, noise might have distracted participants from maintaining balance.

Persistent postural-perceptual dizziness (PPPD) is worsened in a standing posture, or by body movement, or visual stimulation. We aimed to evaluate postural stability in PPPD patients using foam posturography and to investigate the dependence on visual and somatosensory input in the standing posture. Foam posturography was performed on 53 PPPD patients, and data from the PPPD patients were compared with the data from an age- and sex-matched healthy controls. The PPPD patients were divided into four groups based on the findings of vestibular function tests and the effect of vestibular function on posturographic data was examined. Romberg's ratios were significantly higher in PPPD patients than in controls. The median Romberg's ratios in PPPD patients with normal vestibular function were also higher than those in controls. However, foam ratio was significantly lower in PPPD patients than in controls. The median foam ratios in PPPD patients with vestibular dysfunction were also lower than those in controls. In a standing posture, PPPD patients may be more dependent on visual input and less dependent on somatosensory input than healthy subjects. Higher dependence on visual and lower dependence on somatosensory input in PPPD may be a feature unaffected by vestibular function.

The computerized rotational head impulse test (crHIT) uses a computer-controlled rotational chair to deliver whole-body rotational impulses to assess the semicircular canals. The crHIT has only been described for horizontal head plane rotations. The purpose of this study was to describe the crHIT for vertical head plane rotations. In this preliminary study, we assessed four patients with surgically confirmed unilateral peripheral vestibular abnormalities and two control subjects. Results indicated that the crHIT was well-tolerated for both horizontal head plane and vertical head plane stimuli. The crHIT successfully assessed each of the six semicircular canals. This study suggests that the crHIT has the potential to become a new laboratory-based vestibular test for both the horizontal and vertical semicircular canals.

Vestibular rehabilitation therapy (VRT) is effective for most patients with dizziness and imbalance. Home exercise programs are widely used. It is unknown, however, how specific the instructions for exercises have to be. To evaluate the effects of expert assessment and instructions in a booklet-based home VRT program for patients with chronic dizziness. Randomized controlled study on 74 participants with disabling dizziness for >3 months. All study participants received a booklet-based VRT for training at home. Participants were prescribed 20 minutes of exercise, twice a day. The intervention group (n = 37) received specific instructions (expert physiotherapist). The control group (n = 37) practiced without specific instructions. Primary outcome was the total score of the Dizziness Handicap Inventory (DHI-G). All outcomes were assessed at baseline, after 4 weeks, and at follow up 4 weeks later. Both groups improved (DHI-G 43.94±18.89 at inclusion to 33.06±19.67 at follow-up in controls and 42.82±16.60 to 22.65±19.12 in the intervention group). The intervention group, however, improved more (p = 0.014). We show a significant effect of expert physiotherapy guidance in home-based VRT. This strengthens the role of the physiotherapist in VRT: Tailored, personalized instructions are needed to get the best effect of VRT.

There have been no comprehensive studies on the incidence of peripheral vestibular disorders based on population-based data for a long-term period. We investigated the incidence of peripheral vestibular disorders using population-based data representing the whole population of South Korea. This study used the National Health Insurance Service data in Korea from 2008 to 2020. Peripheral vestibular disorders such as benign paroxysmal positional vertigo (BPPV), vestibular neuritis (VN), and Meniere's disease (MD) were defined with diagnostic, treatment, or audiovestibular test codes. The annual incidence in total and according to sex, age, and residence was analyzed. The annual incidence of BPPV, VN, and MD per 100,000 was 51.4, 22.7, and 12.4 in 2008 and 181.1, 62.9, and 50.5 in 2020, respectively. The incidence of each was significantly different by sex (p < 0.001), age (p < 0.001), and residence (p < 0.001), with the highest value in female, people aged 60 years or older, and people who resided in metropolitan cities. The annual incidence of BPPV, VN, and MD had increasing trends from 2008 through 2020 in South Korea, and all were significantly higher in female, people aged 60 years or older, and people who resided in metropolitan cities.

Hypoxia influences standing balance and vestibular function. The purpose here was to investigate the effect of hypoxia on the vestibular control of balance. Twenty participants (10 males; 10 females) were tested over two days (normobaric hypoxia and normoxia). Participants stood on a force plate (head rotated leftward) and experienced random, continuous electrical vestibular stimulation (EVS) during trials of eyes open (EO) and closed (EC) at baseline (BL), after 5 (H1), 30 (H2) and 55-min (H3) of hypoxia, and 10-min into normoxic recovery (NR). Vestibular-evoked balance responses were quantified using cumulant density, coherence, and gain functions between EVS and anteroposterior forces. Oxyhemoglobin saturation, end-tidal oxygen and carbon dioxide decreased for H1-3 compared to BL; however, end-tidal carbon dioxide remained reduced at NR with EC (p≤0.003). EVS-AP force peak-to-peak amplitude was lower at H3 and NR than at BL (p≤0.01). At multiple frequencies, EVS-AP force coherence and gain estimates were lower at H3 and NR than BL for females; however, this was only observed for coherence for males. Overall, vestibular-evoked balance responses are blunted following normobaric hypoxia >30 min, which persists into NR and may contribute to the reported increases in postural sway.

The vestibular system provides a comprehensive estimate of self-motion in 3D space. Widely used to artificially stimulate the vestibular system, binaural-bipolar square-wave Galvanic Vestibular Stimulation (GVS) elicits a virtual sensation of roll rotation. Postural responses to GVS have been clearly delineated, however quantifying the perceived virtual rotation vector has not been fully realised. We aimed to quantify the perceived virtual roll rotation vector elicited by GVS using a psychophysical approach on a 3D turntable. Participants were placed supine on the 3D turntable and rotated around the naso-occipital axis while supine and received square-wave binaural-bipolar GVS or sham stimulation. GVS amplitudes and intensities were systematically manipulated. The turntable motion profile consisted of a velocity step of 20°/s2 until the trial velocity between 0-20°/s was reached, followed by a 1°/s ramp until the end of the trial. In a psychophysical adaptive staircase procedure, we systematically varied the roll velocity to identify the exact velocity that cancelled the perceived roll sensation induced by GVS. Participants perceived a virtual roll rotation towards the cathode of approximately 2°/s velocity for 1 mA GVS and 6°/s velocity for 2.5 mA GVS. The observed values were stable across repetitions. Our results quantify for the first time the perceived virtual roll rotations induced by binaural-bipolar square-wave GVS. Importantly, estimates were based on perceptual judgements, in the absence of motor or postural responses and in a head orientation where the GVS-induced roll sensation did not interact with the perceived direction of gravity. This is an important step towards applications of GVS in different settings, including sensory substitution or Virtual Reality.

The Gaze Stabilization Test (GST) assesses vestibulo-ocular reflex (VOR) function by determining the maximum head velocity at which an individual can accurately perceive a fixed-size visual target. There is limited information about gaze stability performance in youth athletes. The purpose of this study is to describe baseline performance of athletes ages 17 years and under on a computerized GST and explore the influence of demographic characteristics on performance. Baseline GST and demographic data were acquired via retrospective chart review. The sample included 106 athletes aged 8 to 17 years (mean 13.9 years±1.79; 78% male). The median values for baseline GST function were 180 (IQR: 150-210) degrees per second (d/sec) in the leftward direction, and 190 d/sec (IQR: 160-220) in the rightward direction. There were no significant effects of sex/gender or concussion history on GST performance. The GST is one of many tools available for clinicians to use in a multi-modal approach to concussion management. Understanding how healthy young athletes perform can assist clinicians in determining vestibular impairment, formulating the exercise prescription, and estimating physiologic recovery.

To evaluate the benefit of vestibular rehabilitation therapy (VRT) in the management of patients with idiopathic cerebellar ataxia with bilateral vestibulopathy (iCABV). iCABV is a hindbrain degenerative disorder with impairment of both central and peripheral vestibular pathways. There is combined failure of four compensatory eye movement systems including the vestibulo-ocular reflex (VOR), optokinetic reflex, smooth pursuit and the visually enhanced vestibulo-ocular reflex (VVOR). Phenotypic presentation includes postural and gait instability, oscillopsia and dizziness with active head movement. The benefit of VRT in iCABV patients has not been established. A retrospective review was performed on a cohort of twelve patients diagnosed with iCABV in a multidisciplinary neuro-otology clinic. All participated in VRT and completed their suggested course of VRT. The following clinical measures were assessed before starting and after finishing VRT: 1) Dizziness Handicap Inventory (DHI), 2) Activities-Specific Balance Confidence (ABC) Scale, 3) Catastrophization scale, 4) Positive Affective Negative Affective Score (PANAS), 5) Dynamic Gait Index (DGI) and 6) Modified Clinical Test of Sensory Interaction in Balance (mCTSIB). The number of falls historically was recorded in addition to gait speed (ft./sec). Following VRT, patients were found to have improved balance on mCTSIB (condition 4 : 7 vs 18 seconds, P = 0.04) and a better postural stability with a reduced number of falls (p = 0.01). No statistically significant improvement was seen in the DHI, ABC, Catastrophization scale, DGI, PANAS and gait speed (p > 0.05). iCABV patients who underwent VRT were found to have a better postural stability and reduced risk of falls. VRT was not found to significantly improve patients' overall subjective perception of their symptoms or their psychological status.