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Objective: To investigate the effect of daily use of subconscious vibrotactile stimulation in bilateral vestibulopathy (BVP) patients, who judged the effect of vestibular rehabilitation as insufficient. Methods: BVP patients were asked to wear a subconscious vibrotactile stimulation belt for 2 h. Patients who reported benefit after 2 h of use, were instructed to wear a subconscious vibrotactile stimulation belt in daily life, for up to more than 2 years. Follow-up consultations (mostly by telephone calls) were scheduled after 2 weeks, 2 months, 1 year, and 2 years of use. During these consultations, adherence and the self-reported overall Balance and Mobility Score (BMS) were evaluated. Results: One hundred twenty-one BVP patients were included. Regarding adherence, 74% of patients (n = 89) wanted to proceed with daily use at home after 2 h of try out. Of these patients, 90% (n = 80) was still wearing the belt daily after 2 months, and at least 81% (n = 72) after 1 year and 73% (n = 65) after 2 years. It should be noted that lack of adherence after 1 and 2 years resulted from a loss to follow-up. All patients responding to telephone consultations in the 2 years follow up were wearing a subconscious vibrotactile stimulation belt daily. The median BMS score significantly improved within 2 h of use, from 4 to 6 points (p < 0.0001). Compared to baseline, the median BMS score significantly improved with >=3 points after 2 weeks, 2 months, 1 year, and 2 years of daily use (p < 0.0001). Long-term adherence was high in patients who experienced an increase of two or more points on the BMS, after 2 weeks of daily use. Conclusion: The Subconscious vibrotactile stimulation improves self-reported balance andmobility in a subgroup of motivated BVP patients in which vestibular rehabilitation is insufficient. [ABSTRACT FROM AUTHOR]

ObjectiveTo investigate the effect of daily use of subconscious vibrotactile stimulation in bilateral vestibulopathy (BVP) patients, who judged the effect of vestibular rehabilitation as insufficient.MethodsBVP patients were asked to wear a subconscious vibrotactile stimulation belt for 2 h. Patients who reported benefit after 2 h of use, were instructed to wear a subconscious vibrotactile stimulation belt in daily life, for up to more than 2 years. Follow-up consultations (mostly by telephone calls) were scheduled after 2 weeks, 2 months, 1 year, and 2 years of use. During these consultations, adherence and the self-reported overall Balance and Mobility Score (BMS) were evaluated.ResultsOne hundred twenty-one BVP patients were included. Regarding adherence, 74% of patients (n = 89) wanted to proceed with daily use at home after 2 h of try out. Of these patients, 90% (n = 80) was still wearing the belt daily after 2 months, and at least 81% (n = 72) after 1 year and 73% (n = 65) after 2 years. It should be noted that lack of adherence after 1 and 2 years resulted from a loss to follow-up. All patients responding to telephone consultations in the 2 years follow up were wearing a subconscious vibrotactile stimulation belt daily. The median BMS score significantly improved within 2 h of use, from 4 to 6 points (p < 0.0001). Compared to baseline, the median BMS score significantly improved with >=3 points after 2 weeks, 2 months, 1 year, and 2 years of daily use (p < 0.0001). Long-term adherence was high in patients who experienced an increase of two or more points on the BMS, after 2 weeks of daily use.ConclusionThe Subconscious vibrotactile stimulation improves self-reported balance and mobility in a subgroup of motivated BVP patients in which vestibular rehabilitation is insufficient.

Introduction: This study compares the balance control and cognitive responses of subjects with bilateral vestibulopathy (BVP) to those of astronauts immediately after they return from long-duration spaceflight on board the International Space Station. Methods: Twenty-eight astronauts and thirty subjects with BVP performed five tests using the same procedures: sit-to-stand, walk-and-turn, tandem walk, duration judgment, and reaction time. Results: Compared to the astronauts' preflight responses, the BVP subjects' responses were impaired in all five tests. However, the BVP subjects' performance during the walk-and-turn and the tandem walk tests were comparable to the astronauts' performance on the day they returned from space. Moreover, the BVP subjects' time perception and reaction time were comparable to those of the astronauts during spaceflight. The BVP subjects performed the sit-to-stand test at a level that fell between the astronauts' performance on the day of landing and 1 day later. Discussion: These results indicate that the alterations in dynamic balance control, time perception, and reaction time that astronauts experience after spaceflight are likely driven by central vestibular adaptations. Vestibular and somatosensory training in orbit and vestibular rehabilitation after spaceflight could be effective countermeasures for mitigating these post-flight performance decrements. [ABSTRACT FROM AUTHOR]

IntroductionThis study compares the balance control and cognitive responses of subjects with bilateral vestibulopathy (BVP) to those of astronauts immediately after they return from long-duration spaceflight on board the International Space Station.MethodsTwenty-eight astronauts and thirty subjects with BVP performed five tests using the same procedures: sit-to-stand, walk-and-turn, tandem walk, duration judgment, and reaction time.ResultsCompared to the astronauts' preflight responses, the BVP subjects' responses were impaired in all five tests. However, the BVP subjects' performance during the walk-and-turn and the tandem walk tests were comparable to the astronauts' performance on the day they returned from space. Moreover, the BVP subjects' time perception and reaction time were comparable to those of the astronauts during spaceflight. The BVP subjects performed the sit-to-stand test at a level that fell between the astronauts' performance on the day of landing and 1 day later.DiscussionThese results indicate that the alterations in dynamic balance control, time perception, and reaction time that astronauts experience after spaceflight are likely driven by central vestibular adaptations. Vestibular and somatosensory training in orbit and vestibular rehabilitation after spaceflight could be effective countermeasures for mitigating these post-flight performance decrements.

A few years after their bilateral vestibular loss, patients usually show a motor repertoire that is almost back to normal. This recovery is thought to involve an upregulation of the visual and proprioceptive information that compensates for the lack of vestibular information. Here, we investigated whether plantar tactile inputs, which provide body information relative to the ground and to the Earth vertical, contribute to this compensation. More specifically, we tested the hypothesis that somatosensory cortex response to electric stimulation of the plantar sole in standing adults will be greater in humans (n = 10) with bilateral vestibular hypofunction (VH) than in an age-matched healthy group (n = 10). Showing significantly greater somatosensory evoked potentials (i.e., P1N1) in VH than in control subjects, the electroencephalographic recordings supported this hypothesis. Furthermore, we found evidence that increasing the differential pressure between both feet, by adding a 1-kg mass at each pendant wrist, enhanced the internal representation of body orientation and motion relative to a gravitational reference frame. The large decrease in alpha power in the right posterior parietal cortex (and not in the left) is in line with this assumption. Finally, behavioral analyses showed that trunk oscillations were smaller than head oscillations in VH and showed a reverse pattern for healthy participants. These findings are consistent with a tactile-based postural control strategy in the absence of vestibular input and a vestibular-based control strategy in healthy participants where the head serves as a reference for balance control. [ABSTRACT FROM AUTHOR]

Vestibular implant (VI) is a prosthesis that aims to restore bilaterally damaged peripheral vestibular function. VI fundamentally consists of three key components. (1) Gyroscopes and/or accelerometers, (2) An external processor, and (3) implanted stimulator. VI is applied to patients with bilateral vestibulopathy (BVP). In order to restore peripheral vestibular function, a new artificial (electrical) baseline stimulation needs to be created as the peripheral vestibular physiology is bilaterally damaged in patients with BVP. After adjusting the new artificial baseline stimulation with the vestibular implant, motion modulations are applied in order to adapt the individuals to the new electrical stimulation. VI research-based implantation criteria basically consist of 2 main processes: Bilaterally reduced or absent peripheral vestibular function as a result of the caloric test, rotational chair test (video) head impulse test and (2) the presence of severe vestibular function with the chronic symptoms such as imbalance and oscillopsia. However, one should pay attention to the existence of extra criteria. Regarding VI surgery, two different types of surgical approaches, intralabyrinthine and extralabyrinthine, can be used. Although both approaches have pros and cons, the most preferred approach is the intralabyrinthine approach. Intraoperative measurements are also performed during the surgery in order to assess the integrity of the implant and the appropriateness of the placement of the electrodes. The VI started with animal experiments and has been currently continuing with research based on humans. The aim of this review is to address fundamental knowledge and convey the scientific results on vestibular implants. [ABSTRACT FROM AUTHOR]

Loss of vestibular function is known to cause spatial memory deficits and hippocampal dysfunction, in terms of impaired place cell firing and abnormal theta rhythm. Based on these results, it has been of interest to determine whether vestibular loss also affects the development and maintenance of long-term potentiation (LTP) in the hippocampus. This article summarizes and critically reviews the studies of hippocampal LTP following a vestibular loss and its relationship to NMDA receptor expression, that have been published to date. Although the available in vitro studies indicate that unilateral vestibular loss (UVL) results in reduced hippocampal field potentials in CA1 and the dentate gyrus (DG), the in vivo studies involving bilateral vestibular loss (BVL) do not. This may be due to the differences between UVL and BVL or it could be a result of in vitro/in vivo differences. One in vitro study reported a decrease in LTP in hippocampal slices following UVL; however, the two available in vivo studies have reported different results: either no effect or an increase in EPSP/Population Spike (ES) potentiation. This discrepancy may be due to the different high-frequency stimulation (HFS) paradigms used to induce LTP. The increased ES potentiation following BVL may be related to an increase in synaptic NMDA receptors, possibly increasing the flow of vestibular input coming into CA1, with a loss of selectivity. This might cause increased excitability and synaptic noise, which might lead to a degradation of spatial learning and memory.

Loss of vestibular function is known to cause spatial memory deficits and hippocampal dysfunction, in terms of impaired place cell firing and abnormal theta rhythm. Based on these results, it has been of interest to determine whether vestibular loss also affects the development and maintenance of long-term potentiation (LTP) in the hippocampus. This article summarizes and critically reviews the studies of hippocampal LTP following a vestibular loss and its relationship to NMDA receptor expression, that have been published to date. Although the available in vitro studies indicate that unilateral vestibular loss (UVL) results in reduced hippocampal field potentials in CA1 and the dentate gyrus (DG), the in vivo studies involving bilateral vestibular loss (BVL) do not. This may be due to the differences between UVL and BVL or it could be a result of in vitro/in vivo differences. One in vitro study reported a decrease in LTP in hippocampal slices following UVL; however, the two available in vivo studies have reported different results: either no effect or an increase in EPSP/Population Spike (ES) potentiation. This discrepancy may be due to the different high-frequency stimulation (HFS) paradigms used to induce LTP. The increased ES potentiation following BVL may be related to an increase in synaptic NMDA receptors, possibly increasing the flow of vestibular input coming into CA1, with a loss of selectivity. This might cause increased excitability and synaptic noise, which might lead to a degradation of spatial learning and memory. [ABSTRACT FROM AUTHOR]

This opinion statement proposes a set of candidacy criteria for vestibular implantation of adult patients with bilateral vestibulopathy (BVP) in a research setting. The criteria include disabling chronic symptoms like postural imbalance, unsteadiness of gait and/or head movement-induced oscillopsia, combined with objective signs of reduced or absent vestibular function in both ears. These signs include abnormal test results recorded during head impulses (video head impulse test or scleral coil technique), bithermal caloric testing and rotatory chair testing (sinusoidal stimulation of 0.1 Hz). Vestibular implant (VI) implantation criteria are not the same as diagnostic criteria for bilateral vestibulopathy. The major difference between VI-implantation criteria and the approved diagnostic criteria for BVP are that all included vestibular tests of semicircular canal function (head impulse test, caloric test, and rotatory chair test) need to show significant impairments of vestibular function in the implantation criteria. For this, a two-step paradigm was developed. First, at least one of the vestibular tests needs to fulfill stringent criteria, close to those for BVP. If this is applicable, then the other vestibular tests have to fulfill a second set of criteria which are less stringent than the original criteria for BVP. If the VI-implantation is intended to excite the utricle and/or saccule (otolith stimulation), responses to cervical and ocular vestibular evoked myogenic potentials must be absent in addition to the above mentioned abnormalities of semicircular canal function. Finally, requirements for safe and potentially effective stimulation should be met, including implanting patients with BVP of peripheral origin only, and assessing possible medical and psychiatric contraindications. [ABSTRACT FROM AUTHOR]

Background: A battery of stance and gait tasks can be used to quantify functional deficits and track improvement in balance control following peripheral vestibular loss. An improvement could be due to at least 3 processes: partial peripheral recovery of sensory responses eliciting canal or otolith driven vestibular reflexes; central compensation of vestibular reflex gains, including substitution of intact otolith responses for pathological canal responses; or sensory substitution of visual and proprioceptive inputs for vestibular contributions to balance control.Results: We describe the presumed action of all 3 processes observed for a case of sudden incapacitating acute bilateral peripheral loss probably due to vestibular neuritis. Otolith responses were largely unaffected. However, pathological decreases in all canal-driven vestibular ocular reflex (VOR) gains were observed. After 3 months of vestibular rehabilitation, balance control was normal but VOR gains remained low.Conclusions: This case illustrates the difficulty in predicting balance control improvements from tests of the 10 vestibular end organs and emphasizes the need to test balance control function directly in order to determine if balance control has improved and is normal again despite remaining vestibular sensory deficits. This case also illustrates that the presence of residual otolithic function may be crucial for balance control improvement in cases of bilateral vestibular hypofunction.

The review of the literature on RSCI and PubMed databases presents methods of electrical vestibular stimulation to improve vestibular function in patients with bilateral vestibulopathy. The variants of stimulation of peripheral vestibular structures, such as vestibular implantation, noise galvanic vestibular stimulation are described. The perspectives of development of this direction, advantages of application of electrical stimulation in the future, as well as current limitations that do not currently allow to use these methods in clinical practice are shown.

The functional significance of vestibular information for the generation of gaze shifts is controversial and less well established than the vestibular contribution to gaze stability. In this study, we asked seven bilaterally avestibular patients to execute voluntary, whole body pivot turns to visual targets up to 180° while standing. In these conditions, not only are the demands imposed on gaze transfer mechanisms more challenging, but also neck proprioceptive input represents an inadequate source of head-in-space motion information. Patients' body segment was slower and jerky. In the absence of visual feedback, gaze advanced in small steps, closely resembling normal multiple-step gaze-shift patterns, but as a consequence of the slow head motion, target acquisition was delayed. In ~25% of trials, however, patients moved faster but the velocity of prematurely emerging slow-phase compensatory eye movements remained lower than head-in-space velocity due to vestibuloocular failure. During these trials, therefore, gaze advanced toward the target without interruption but, again, taking longer than when normal controls use single-step gaze transfers. That is, even when patients attempted faster gaze shifts, exposing themselves to gaze instability, they acquired distant targets significantly later than controls. Thus, while patients are upright, loss of vestibular information disrupts not only gaze stability but also gaze transfers. The slow and ataxic head and trunk movements introduce significant foveation delays. These deficits explain patients' symptoms during upright activities and show, for the first time, the clinical significance of losing the so-called "anticompensatory" (gaze shifting) function of the vestibuloocular reflex. NEW & NOTEWORTHY Previous studies in sitting avestibular patients concluded that gaze transfers are not substantially compromised. Still, clinicians know that patients are impeded (e.g., looking side to side before crossing a road). We show that during large gaze transfers while standing, vestibularly derived head velocity signals are critical for the mechanisms governing reorientation to distant targets and multisegmental coordination. Our findings go beyond the traditional role of the vestibular system in gaze stability, extending it to gaze transfers, as well. [ABSTRACT FROM AUTHOR]

This study assessed cardiovascular control during head-down neck flexion (HDNF) in a group of patients suffering from total bilateral idiopathic vestibular loss (BVL) for 7 ± 2 yr. Nine adult patients (age 54 ± 6 yr) with BVL were recruited. Calf blood flow (CBF), mean arterial pressure (MAP), and heart rate (HR) were measured with subjects' eyes closed in two lying body positions: ventral prone (VP) and lateral (LP) on the left side. Vascular resistance (CVR) was calculated as MAP/CBF. The HDNF protocol consisted in passively changing the head position: head up (HU)- head down (HD)-HU. Measurements were taken twice at each head position. In VP CBF significantly decreased in HD (3.65 ± 0.65 mL·min-1·100 mL-1) vs. HU (4.64 ± 0.71 mL·min-1·100 mL-1) (P = 0.002), whereas CVR in VP significantly rose in HD (31.87 ± 6.93 arbitrary units) vs. HU (25.61 ± 6.36 arbitrary units) (P = 0.01). In LP no change in CBF or CVR was found between the two head positions. MAP and HR presented no difference between HU and HD in both body positions. Age of patients did not significantly affect the results. The decrease in CBF of the BVL patients was similar to the decrease observed with the same HDNF protocol in normal subjects. This suggests a sensory compensation for the lost vestibular inputs that could originate from the integration of inputs from trunk graviceptors and proprioceptive and cutaneous receptors. Another possibility is that the HDNF vascular effect is evoked mostly by nonlabyrinthine sensors. [ABSTRACT FROM AUTHOR]

Introduction: Although it is recommended to perform cochlear implantation in both ears at the same time for management of profound hearing loss in children, many centers prefer to perform sequential implantation. There are many reasons as to why a simultaneous bilateral implantation is not commonly accepted and performed. The major risk is the possibility of bilateral vestibular organ impairment. However, it is beyond doubt that children who received the first implant should be given a chance for binaural hearing and associated benefits. In the literature, there are no homogenous criteria for bilateral implantation, and it is hard to find uniform and convincing algorithms for second cochlear implantation. The aim of this study is an attempt to identify a safe way of qualifying for second cochlear implantation in children. Material and methods: Forty children with one cochlear implant were qualified for the second implantation. During qualification, the following were taken into account: time of the first implantation, audiometry results, use of the hearing aid in the ear without an implant and benefit of the device, speech and hearing development, and vestibular organ function. Results: Fifteen out of forty children (38%) were qualified for the second implantation. In 35% of children, the decision was delayed with possible second implantation in the future. Eleven children (27%) were disqualified from the second surgery. Discussion: During evaluation according to the protocol presented in our study, 38% of children with a single cochlear implant were qualified for the second implantation with a chance for an optimal development and effective use of the second cochlear implant. We are convinced that sequential implantation with a short interval between surgeries and with an examination of the vestibular organ, hearing and speech development as well as an assessment of potential benefits from the second implant (bimodal stimulation) before the second implantation is the safest and most beneficial solution for children with severe hearing loss. [ABSTRACT FROM AUTHOR]

The impact of vibrotactile feedback of the gravity vector, provided by a "balance" belt worn around the waist, was evaluated in 39 patients with a severe bilateral vestibular loss, confirmed by extensive laboratory testing and suffering from a low quality of life, mainly due to imbalance. The mobility and balance score (MBS) of all patients prior to the use of the belt was equal or less than 5 out of a scale of 10. Thirty-one out of the 39 patients experienced the effect of the belt on their balance and mobility as positive in a preselection trial of 2 h in the hospital. The 31 positive responders then used the belt for 1 month in daily life. The average MBS increased significantly from 4.2 to 7.9 (paired T test, T = 9.82, p < 0.00001). Twenty-three out of 31 patients reported a benefit ranging from an improvement of 60–200% in their MBS. Eight patients did not experience any benefit. In summary, 23 out of 39 patients with a severe imbalance due to a bilateral vestibular loss experienced a clear benefit of vibrotactile feed = back in daily life. We conclude that vibrotactile feedback via the waist can serve as an effective prothesis for patients with severe bilateral vestibular loss to improve the quality of life. [ABSTRACT FROM AUTHOR]

Background: A battery of stance and gait tasks can be used to quantify functional deficits and track improvement in balance control following peripheral vestibular loss. An improvement could be due to at least 3 processes: partial peripheral recovery of sensory responses eliciting canal or otolith driven vestibular reflexes; central compensation of vestibular reflex gains, including substitution of intact otolith responses for pathological canal responses; or sensory substitution of visual and proprioceptive inputs for vestibular contributions to balance control. Results: We describe the presumed action of all 3 processes observed for a case of sudden incapacitating acute bilateral peripheral loss probably due to vestibular neuritis. Otolith responses were largely unaffected. However, pathological decreases in all canal-driven vestibular ocular reflex (VOR) gains were observed. After 3 months of vestibular rehabilitation, balance control was normal but VOR gains remained low. Conclusions: This case illustrates the difficulty in predicting balance control improvements from tests of the 10 vestibular end organs and emphasizes the need to test balance control function directly in order to determine if balance control has improved and is normal again despite remaining vestibular sensory deficits. This case also illustrates that the presence of residual otolithic function may be crucial for balance control improvement in cases of bilateral vestibular hypofunction. [ABSTRACT FROM AUTHOR]

Patients with inner ear damage associated with bilateral vestibular impairment often ask “how much damage do I have.” Although there are presently three clinical methods of measuring semicircular canal vestibular function; electronystagmography (ENG or VENG), rotatory chair and video head-impulse (VHIT) testing; none of these methods provides a method of measuring total vestibular output. Theory suggests that the slow cumulative eye position can be derived from the rotatory chair test by multiplying the high frequency gain by the time constant, or the “GainTc product.” In this retrospective study, we compared the GainTc in three groups, 30 normal subjects, 25 patients with surgically induced unilateral vestibular loss, and 24 patients with absent or nearly absent vestibular responses due to gentamicin exposure. We found that the GainTc product correlated better with remaining vestibular function than either the gain or the time constant alone. The fraction of remaining vestibular function was predicted by the equation R = (GainTc/11.3) – 0.6. We suggest that the GainTc product answers the question “how much damage do I have,” and is a better measure than other clinical tests of vestibular function.

There is evidence that vestibular sensory processing affects, and is affected by, higher cognitive processes. This is highly relevant from a clinical perspective, where there is evidence for cognitive impairments in patients with peripheral vestibular deficits. The vestibular system performs complex probabilistic computations, and we claim that understanding these is important for investigating interactions between vestibular processing and cognition. Furthermore, this will aid our understanding of patients’ self-motion perception and will provide useful information for clinical interventions. We propose that cognitive training is a promising way to alleviate the debilitating symptoms of patients with complete bilateral vestibular loss (BVP), who often fail to show improvement when relying solely on conventional treatment methods. We present a probabilistic model capable of processing vestibular sensory data during both passive and active self-motion. Crucially, in our model, knowledge from multiple sources, including higher-level cognition, can be used to predict head motion. This is the entry point for cognitive interventions. Despite the loss of sensory input, the processing circuitry in BVP patients is still intact, and they can still perceive self-motion when the movement is self-generated. We provide computer simulations illustrating self-motion perception of BVP patients. Cognitive training may lead to more accurate and confident predictions, which result in decreased weighting of sensory input, and thus improved self-motion perception. Using our model, we show the possible impact of cognitive interventions to help vestibular rehabilitation in patients with BVP.

Patients with inner ear damage associated with bilateral vestibular impairment often ask "how much damage do I have." Although there are presently three clinical methods of measuring semicircular canal vestibular function; electronystagmography (ENG or VENG), rotatory chair and video head-impulse (VHIT) testing; none of these methods provides a method of measuring total vestibular output. Theory suggests that the slow cumulative eye position can be derived from the rotatory chair test by multiplying the high frequency gain by the time constant, or the "GainTc product." In this retrospective study, we compared the GainTc in three groups, 30 normal subjects, 25 patients with surgically induced unilateral vestibular loss, and 24 patients with absent or nearly absent vestibular responses due to gentamicin exposure. We found that the GainTc product correlated better with remaining vestibular function than either the gain or the time constant alone. The fraction of remaining vestibular function was predicted by the equation R = (GainTc/11.3) - 0.6. We suggest that the GainTc product answers the question "how much damage do I have," and is a better measure than other clinical tests of vestibular function. [ABSTRACT FROM AUTHOR]

Objective Gait imbalance in patients with bilateral-vestibular-deficiency (BVD) was linked to increased variability in perceived direction of gravity while upright. We hypothesized this to be true also when roll-tilted. Moreover, as utricular input is essential for spatial orientation, we predicted the variability of perceived vertical to correlate inversely with utricular function. Methods Subjective visual vertical (SVV) and haptic vertical (SHV) were measured in various roll-orientations (0°/±45°/±90°) and postural adjustments along earth-vertical/earth-horizontal were collected in patients with partial BVD ( n  = 10) and healthy controls ( n  = 11). Patients with bilaterally-absent bone-conducted ocular vestibular-evoked myogenic-potentials (oVEMPs) were compared to those with (partially) preserved oVEMPs. Results For the SVV ( p  < 0.001) and SHV ( p  = 0.004) variability was larger in patients than controls. Compared to those with (partially) preserved oVEMPs, patients with bilaterally-absent oVEMPs had higher SVV ( p  = 0.024) and SHV ( p  = 0.006) variability. Self-positioning along earth-horizontal was more variable in BVD-patients compared to controls ( p  < 0.001). Again, variability was higher in those with bilaterally-absent oVEMPs ( p  = 0.032). SVV/SHV-variability was correlated ( R 2  = 0.61, slope = 1.06 [95%-CI = 0.80–1.54]) in BVD-patients. Conclusion With variability correlating amongst the different paradigms and with oVEMP-responses, this emphasizes the role of bilaterally intact utricular input for precise perception of gravity. Significance In BVD-patients with bilaterally-absent oVEMPs intensified vestibular rehabilitation should be considered. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate whether it is possible to restore the high-frequency angular vestibulo-ocular reflex (aVOR) in patients suffering from a severe bilateral vestibulopathy (BV) and implanted with a vestibular implant prototype. Three patients (S1–3) participated in the study. They received a prototype vestibular implant with one to three electrode branches implanted in the proximity of the ampullary branches of the vestibular nerve. Five electrodes were available for electrical stimulation: one implanted in proximity of the left posterior ampullary nerve in S1, one in the left lateral and another one in the superior ampullary nerves in S2, and one in the right lateral and another one in the superior ampullary nerves in S3. The high-frequency aVOR was assessed using the video head impulse test (EyeSeeCam; EyeSeeTec, Munich, Germany), while motion-modulated electrical stimulation was delivered via one of the implanted vestibular electrodes at a time. aVOR gains were compared to control measurements obtained in the same patients when the device was not activated. In three out of the five tested electrodes the aVOR gain increased monotonically with increased stimulation strength when head impulses were delivered in the plane of the implanted canal. In these cases, gains ranging from 0.4 to values above 1 were measured. A “reversed” aVOR could also be generated when inversed stimulation paradigms were used. In most cases, the gain for excitatory head impulses was superior to that recorded for inhibitory head impulses, consistent with unilateral vestibular stimulation. Improvements of aVOR gain were generally accompanied by a concomitant decrease of corrective saccades, providing additional evidence of an effective aVOR. High inter-electrode and inter-subject variability were observed. These results, together with previous research, demonstrate that it is possible to restore the aVOR in a broad frequency range using motion-modulated electrical stimulation of the vestibular afferents. This provides additional encouraging evidence of the possibility of achieving a useful rehabilitation alternative for patients with BV in the near future.

The peripheral vestibular system is critical for the execution of activities of daily life as it provides movement and orientation information to motor and sensory systems. Patients with bilateral vestibular hypofunction experience a significant decrease in quality of life and have currently no viable treatment option. Vestibular implants could eventually restore vestibular function. Most vestibular implant prototypes to date are modified cochlear implants to fast-track development. These use various objective measurements, such as the electrically evoked compound action potential (eCAP), to supplement behavioral information. We investigated whether eCAPs could be recorded in patients with a vestibulo-cochlear implant. Specifically, eCAPs were successfully recorded for cochlear and vestibular setups, as well as for mixed cochlear-vestibular setups. Similarities and slight differences were found for the recordings of the three setups. These findings demonstrated the feasibility of eCAP recording with a vestibulo-cochlear implant. They could be used in the short term to reduce current spread and avoid activation of non-targeted neurons. More research is warranted to better understand the neural origin of vestibular eCAPs and to utilize them for clinical applications.

ObjectiveWe examined the eye movement response patterns of a group of patients with bilateral vestibular loss (BVL) during suppression head impulse testing. Some showed a new saccadic strategy that may have potential for explaining how patients use saccades to recover from vestibular loss.MethodsEight patients with severe BVL [vestibulo-ocular reflex (VOR) gains less than 0.35 and absent otolithic function] were tested. All patients were given the Dizziness Handicap Inventory and questioned about oscillopsia during abrupt head movements. Two paradigms of video head impulse testing of the horizontal VOR were used: (1) the classical head impulse paradigm [called head impulse test (HIMPs)]—fixating an earth-fixed target during the head impulse and (2) the new complementary test paradigm—fixating a head-fixed target during the head impulse (called SHIMPs). The VOR gain of HIMPs was quantified by two algorithms.ResultsDuring SHIMPs testing, some BVL patients consistently generated an inappropriate covert compensatory saccade during the head impulse that required a corresponding large anti-compensatory saccade at the end of the head impulse in order to obey the instructions to maintain gaze on the head-fixed target. By contrast, other BVL patients did not generate this inappropriate covert saccade and did not exhibit a corresponding anti-compensatory saccade. The latencies of the covert saccade in SHIMPs and HIMPs were similar.ConclusionThe pattern of covert saccades during SHIMPs appears to be related to the reduction of oscillopsia during abrupt head movements. BVL patients who did not report oscillopsia showed this unusual saccadic pattern, whereas BVL patients who reported oscillopsia did not show this pattern. This inappropriate covert SHIMPs saccade may be an objective indicator of how some patients with vestibular loss have learned to trigger covert saccades during head movements in everyday life.

The peripheral vestibular system is critical for the execution of activities of daily life as it provides movement and orientation information to motor and sensory systems. Patients with bilateral vestibular hypofunction experience a significant decrease in quality of life and have currently no viable treatment option. Vestibular implants could eventually restore vestibular function. Most vestibular implant prototypes to date are modified cochlear implants to fast-track development. These use various objective measurements, such as the electrically evoked compound action potential (eCAP), to supplement behavioral information. We investigated whether eCAPs could be recorded in patients with a vestibulo-cochlear implant. Specifically, eCAPs were successfully recorded for cochlear and vestibular setups, as well as for mixed cochlear-vestibular setups. Similarities and slight differences were found for the recordings of the three setups. These findings demonstrated the feasibility of eCAP recording with a vestibulo-cochlear implant. They could be used in the short term to reduce current spread and avoid activation of non-targeted neurons. More research is warranted to better understand the neural origin of vestibular eCAPs and to utilize them for clinical applications. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate whether it is possible to restore the highfrequency angular vestibulo-ocular reflex (aVOR) in patients suffering from a severe bilateral vestibulopathy (BV) and implanted with a vestibular implant prototype. Three patients (S1-3) participated in the study. They received a prototype vestibular implant with one to three electrode branches implanted in the proximity of the ampullary branches of the vestibular nerve. Five electrodes were available for electrical stimulation: one implanted in proximity of the left posterior ampullary nerve in S1, one in the left lateral and another one in the superior ampullary nerves in S2, and one in the right lateral and another one in the superior ampullary nerves in S3. The high-frequency aVOR was assessed using the video head impulse test (EyeSeeCam; EyeSeeTec, Munich, Germany), while motion-modulated electrical stimulation was delivered via one of the implanted vestibular electrodes at a time. aVOR gains were compared to control measurements obtained in the same patients when the device was not activated. In three out of the five tested electrodes the aVOR gain increased monotonically with increased stimulation strength when head impulses were delivered in the plane of the implanted canal. In these cases, gains ranging from 0.4 to values above 1 were measured. A "reversed" aVOR could also be generated when inversed stimulation paradigms were used. In most cases, the gain for excitatory head impulses was superior to that recorded for inhibitory head impulses, consistent with unilateral vestibular stimulation. Improvements of aVOR gain were generally accompanied by a concomitant decrease of corrective saccades, providing additional evidence of an effective aVOR. High inter-electrode and inter-subject variability were observed. These results, together with previous research, demonstrate that it is possible to restore the aVOR in a broad frequency range using motion-modulated electrical stimulation of the vestibular afferents. This provides additional encouraging evidence of the possibility of achieving a useful rehabilitation alternative for patients with BV in the near future. [ABSTRACT FROM AUTHOR]

Objective: We examined the eye movement response patterns of a group of patients with bilateral vestibular loss (BVL) during suppression head impulse testing. Some showed a new saccadic strategy that may have potential for explaining how patients use saccades to recover from vestibular loss. Methods: Eight patients with severe BVL [vestibulo-ocular reflex (VOR) gains less than 0.35 and absent otolithic function] were tested. All patients were given the Dizziness Handicap Inventory and questioned about oscillopsia during abrupt head movements. Two paradigms of video head impulse testing of the horizontal VOR were used: (1) the classical head impulse paradigm [called head impulse test (HIMPs)]--fixating an earthfixed target during the head impulse and (2) the new complementary test paradigm--fixating a head-fixed target during the head impulse (called SHIMPs). The VOR gain of HIMPs was quantified by two algorithms. Results: During SHIMPs testing, some BVL patients consistently generated an inappropriate covert compensatory saccade during the head impulse that required a corresponding large anti-compensatory saccade at the end of the head impulse in order to obey the instructions to maintain gaze on the head-fixed target. By contrast, other BVL patients did not generate this inappropriate covert saccade and did not exhibit a corresponding anti-compensatory saccade. The latencies of the covert saccade in SHIMPs and HIMPs were similar. Conclusion: The pattern of covert saccades during SHIMPs appears to be related to the reduction of oscillopsia during abrupt head movements. BVL patients who did not report oscillopsia showed this unusual saccadic pattern, whereas BVL patients who reported oscillopsia did not show this pattern. This inappropriate covert SHIMPs saccade may be an objective indicator of how some patients with vestibular loss have learned to trigger covert saccades during head movements in everyday life. [ABSTRACT FROM AUTHOR]

Both parabolic flight, i.e. a condition of altered gravity, and loss of vestibular function, have been suggested to affect spatial learning and memory, which is known to be influenced by neurogenesis in the hippocampus. In this study we investigated whether short alternated micro- and hyper-gravity stimulations during parabolic flight and/or loss of vestibular function, would alter cell proliferation in the hippocampal dentate gyrus of rats, by measuring the number of bromodeoxyuridine (BrdU)-incorporated cells. Rats were randomly allocated to the following experimental groups: (1) sham transtympanic saline injection only (n = 5); (2) bilateral vestibular deafferentation (BVD) by sodium arsanilate transtympanic injection only (n = 5); (3) sham treatment and parabolic flight (n = 5); (4) BVD and parabolic flight (n = 6). Forty-two days following transtympanic injection, the animals were subjected to parabolic flight in an awake restrained condition after habituation. A modified Airbus A300 aircraft was flown on a parabolic path, creating 20 s of 1.8 G during both climbing and descending and 22 s of 0 G at the apex of each parabola. The no flight animals were subjected to the same housing for the same duration. Immediately after the parabolic flight or control ground condition, animals were injected with BrdU (300 mg/kg, i.p). Twenty-four hs after BrdU injection, rats were sacrificed. BrdU immunolabelling was performed and the number of BrdU +ve cells in the dentate gyrus of the hippocampus was quantified using a modified fractionator method. BVD caused a large and significant reduction in the number of BrdU-positive cells compared to sham animals (P ≤ 0.0001); however, flight and all interactions were non-significant. These results indicate that BVD significantly decreased cell proliferation irrespective of the short exposure to altered/modified gravity. [ABSTRACT FROM AUTHOR]

The primary goal of the vestibular implant is to restore the vestibular function in patients with a disabling bilateral vestibular loss for whom there is currently no available treatment. The prototype developed by our team is a hybrid system consisting of a modified cochlear implant incorporating additional vestibular electrodes. Therefore, in addition of delivering sound information it is also capable of delivering motion information to the central nervous system using electrical stimulation. To date, thirteen patients have been implanted with such vestibular implant prototypes. For ethical reasons, only deaf ears were implanted and all patients experienced a clinical benefit from the hearing rehabilitation. The recent demonstration of partial restoration of the vestibulo-ocular and the vestibulo-collic reflexes in implanted patients suggests that gaze stabilization and postural control, fundamental functions of the balance system, can be artificially restored using a vestibular implant. This allows us to glimpse a useful clinical application in a near future. In parallel, we show how the vestibular implant provides a unique opportunity to explore the integration of the vestibular sensory input into the multisensory, multimodal balance system in humans, since it is able to selectively stimulate the vestibular system. [ABSTRACT FROM AUTHOR]

Vestibular implants are devices designed to rehabilitate patients with a bilateral vestibular loss (BVL). These patients lack a properly functioning vestibulo-ocular reflex (VOR), which impairs gaze stabilization abilities and results in an abnormal loss of visual acuity (VA) in dynamic situations (i.e., severely limiting the patient's ability to read signs or recognize faces while walking).We previously demonstrated that the VOR can be artificially restored in a group of BVL patients fitted with a prototype vestibular implant. This study was designed to investigate whether these promising results could be translated to a close-to-reality task, significantly improving VA abilities while walking. Six BVL patients previously implanted with a vestibular implant prototype participated in the experiments. VA was determined using Sloan letters displayed on a computer screen, in four conditions: (1) with the patient standing still without moving (static), (2) while the patient was walking on a treadmill at constant speed with the vestibular implant prototype turned off (systemOFF), (3) while the patient was walking on a treadmill at constant speed with the vestibular implant prototype turned on providing coherent motion information (systemONmotion), and (4) a "placebo" condition where the patient was walking on a treadmill at constant speed with the vestibular implant prototype turned on providing reversed motion information (systemONsham). The analysis (one-way repeated measures analysis of variance) revealed a statistically significant effect of the test condition [F(3, 12) = 30.5, p < 0.001]. Significant decreases in VA were observed with the systemOFF condition when compared to the static condition (Tukey post-hoc p < 0.001). When the vestibular implant was turned on, delivering pertinent motion information (systemONmotion) the VA improved to close to normal values. The improvement disappeared in the placebo condition (systemONsham) and VA-values also dropped significantly in this condition (Tukey post-hoc p < 0.001). These results are a significant step forward in the field, demonstrating for the first time in humans that gaze stabilization abilities can be restored with a vestibular implant prototype. The vestibular implant shows considerable promise of being the first-ever effective therapeutic alternative for patients with a BVL in the near future. [ABSTRACT FROM AUTHOR]

Objective Bilateral vestibular loss (BVL) is often diagnosed with great delay and an underlying cause is only identified in 50–80%. We measured horizontal and vertical semicircular canal function using the video-head-impulse test (vHIT) and hypothesized that specific vHIT-patterns may be linked to certain etiologies. Methods We retrospectively analyzed 109 BVL-patients linked to aminoglycoside vestibulotoxicity ( n = 16), Menière’s disease ( n = 10), infectious inner-ear disorders ( n = 11), sensorineural hearing-loss ( n = 11), cerebellar-ataxia-neuropathy-vestibular-areflexia-syndrome (CANVAS, n = 5), other causes ( n = 19) as well as those with unknown origin ( n = 47). Vestibulo-ocular reflex gains and cumulative saccade amplitudes were measured with vHIT, and the functional integrity of all semicircular canals was rated. Results Overall, anterior canal hypofunction ( n = 86/218) was identified significantly ( p < 0.001) less often than horizontal ( n = 186/218) and posterior ( n = 194/218) hypofunction. Preserved anterior canal function was associated with aminoglycoside vestibulotoxicity, Menière’s disease and BVL of unknown origin, while no such sparing was found for inner-ear infections, CANVAS and sensorineural hearing loss. Conclusions Semicircular canal function in BVL shows disease-specific dissociations, potentially related to reduced vulnerability or superior recovery of the anterior canals. Significance In patients with suspected BVL we recommend quantifying vHIT gains and saccade amplitudes for all semicircular canals as the pattern of canal hypofunction may help identifying the underlying disorder. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the different etiologies and clinical subtypes of bilateral vestibular hypofunction (BVH) and the value of diagnostic tools in the diagnostic process of BVH. Materials and methods: A retrospective case review was performed on 154 patients diagnosed with BVH in a tertiary referral center, between 2013 and 2015. Inclusion criteria comprised (1) imbalance and/or oscillopsia during locomotion and (2) summated slow phase velocity of nystagmus of less than 20°/s during bithermal caloric tests. results: The definite etiology of BVH was determined in 47% of the cases and the probable etiology in 22%. In 31%, the etiology of BVH remained idiopathic. BVH resulted from more than 20 different etiologies. In the idiopathic group, the percentage of migraine was significantly higher compared to the non-idiopathic group (50 versus 11%, p < 0.001). Among all patients, 23.4% were known with autoimmune disorders in their medical history. All four clinical subtypes (recurrent vertigo with BVH, rapidly progressive BVH, slowly progressive BVH, and slowly progressive BVH with ataxia) were found in this population. Slowly progressive BVH with ataxia comprised only 4.5% of the cases. The head impulse test was abnormal in 94% of the cases. The torsion swing test was abnormal in 66%. Bilateral normal hearing to moderate hearing loss was found in 49%. Blood tests did not often contribute to the determination of the etiology of the disease. Abnormal cerebral imaging was found in 21 patients. conclusion: BVH is a heterogeneous condition with various etiologies and clinical characteristics. Migraine seems to play a significant role in idiopathic BVH and autoimmunity could be a modulating factor in the development of BVH. The distribution of etiologies of BVH probably depends on the clinical setting. In the diagnostic process of BVH, the routine use of some blood tests can be reconsidered and a low-threshold use of audiometry and cerebral imaging is advised. The torsion swing test is not the "gold standard" for diagnosing BVH due to its lack of sensitivity. Future diagnostic criteria of BVH should consist of standardized vestibular tests combined with a history that is congruent with the vestibular findings. [ABSTRACT FROM AUTHOR]

Bilateral vestibular hypofunction (BVH) probably represents a heterogeneous disorder with different types of clinical pictures, with and without vertigo. In spite of increasingly sophisticated electrophysiological testing, still many challenges are met when establishing a diagnosis of BVH. Here, we review the main challenges, which are a reflection of its often difficult clinical presentation and the lack of diagnostic standards regarding the implementation and interpretation of vestibular tests. These challenges show that there is an urgent need for standardization. The resulting decisions should be used for the development of uniform diagnostic criteria for BVH, which are, at present, not yet available. [ABSTRACT FROM AUTHOR]

Background: The concept of the vestibular implant is primarily to artificially restore the vestibular function in patients with a bilateral vestibular loss (BVL) by providing the central nervous system with motion information using electrical stimulation of the vestibular nerve. Our group initiated human trials about 10 years ago.Methods: Between 2007 and 2013, 11 patients with a BVL received a vestibular implant prototype providing electrodes to stimulate the ampullary branches of the vestibular nerve. Eye movements were recorded and analyzed to assess the effects of the electrical stimulation. Perception induced by electrical stimulation was documented.Results: Smooth, controlled eye movements were obtained in all patients showing that electrical stimulation successfully activated the vestibulo-ocular pathway. However, both the electrical dynamic range and the amplitude of the eye movements were variable from patient to patient. The axis of the response was consistent with the stimulated nerve branch in 17 out of the 24 tested electrodes. Furthermore, in at least 1 case, the elicited eye movements showed characteristics similar to those of compensatory eye movements observed during natural activities such as walking. Finally, diverse percepts were reported upon electrical stimulation (i.e., rotatory sensations, sound, tickling or pressure) with intensity increasing as the stimulation current increased.Conclusions: These results demonstrate that electrical stimulation is a safe and effective means to activate the vestibular system, even in a heterogeneous patient population with very different etiologies and disease durations. Successful tuning of this information could turn this vestibular implant prototype into a successful artificial balance organ. [ABSTRACT FROM AUTHOR]

A unilateral sudden loss of function generates intense and frightening symptoms urging patients to see a doctor. Generally, the symptoms and signs of the deficit are so obvious that doctors make the diagnosis quickly. The situation is quite different if the deficit is gradual and affects both sides. To better understand the difficulties faced by patients suffering from total bilateral vestibular loss, 19 subjects were interviewed in a semistructured talk. The discussion focused on five main topics: (1) symptoms, (2) the medical trajectory from the earliest symptoms to the diagnosis, (3) the prescribed treatments, (4) the impact of the disease on work, and (5) the impact on social functioning and recreational activities. The symptoms reported by patients are insidious, and they may suggest a neurological deficit or a cardiocirculatory or psychiatric disorder. The diagnosis is often made after several consultations with several doctors from different specialties. When the diagnosis is made, all kinds of treatment are undertaken, in particular vestibular rehabilitation. Indeed, most physicians believe that it can promote central compensation processes, even though it has been demonstrated that vestibular exercises are ineffective in most of these patients. Two thirds of our subjects were obliged to modify or even stop their professional activities due the bilateral vestibular loss. In some patients, the disability is such that they almost constantly require the presence of their spouse. In conclusion, the symptoms of bilateral vestibular loss are sometimes misleading. They are often not recognized by doctors. The deficit has an obvious impact on patients' social functioning and professional activities. [ABSTRACT FROM AUTHOR]

Background/hypothesis: The video Head Impulse Test (vHIT) is now widely used to test the function of each of the six semicircular canals individually by measuring the eye rotation response to an abrupt head rotation in the plane of the canal. The main measure of canal adequacy is the ratio of the eye movement response to the head movement stimulus, i.e., the gain of the vestibulo-ocular reflex (VOR). However, there is a need for normative data about how VOR gain is affected by age and also by head velocity, to allow the response of any particular patient to be compared to the responses of healthy subjects in their age range. In this study, we determined for all six semicircular canals, normative values of VOR gain, for each canal across a range of head velocities, for healthy subjects in each decade of life. Study design: The VOR gain was measured for all canals across a range of head velocities for at least 10 healthy subjects in decade age bands: 10-19, 20-29, 30-39, 40-49, 50-59, 60-69, 70-79, 80-89. Methods: The compensatory eye movement response to a small, unpredictable, abrupt head rotation (head impulse) was measured by the ICS impulse prototype system. The same operator delivered every impulse to every subject. Results: Vestibulo-ocular reflex gain decreased at high head velocities, but was largely unaffected by age into the 80- to 89-year age group. There were some small but systematic differences between the two directions of head rotation, which appear to be largely due to the fact that in this study only the right eye was measured. The results are considered in relation to recent evidence about the effect of age on VOR performance.Conclusion: These normative values allow the results of any particular patient to be compared to the values of healthy people in their age range and so allow, for example, detection of whether a patient has a bilateral vestibular loss. VOR gain, as measured directly by the eye movement response to head rotation, seems largely unaffected by aging. [ABSTRACT FROM AUTHOR]

BACKGROUND: The aim of his study was to evaluate the reliability and validity of the Expanded Timed Get-up-and-Go (ETGUG) test in patients with bilateral vestibular loss (BVL). METHODS: 21 BVL patients (58 ± 14 years) were recruited and measured twice by two raters. After a one hour break ETGUG was repeated by the first rater. 21 age matched controls (CON; 58 ± 14 years) were measured once by the first rater. All time scores of the ETGUG for the separate tasks and gait speed calculated from tasks 3 and 5 were analysed to determine relative and absolute reliability, smallest detectable change (SDC) and discriminatory capabilities. RESULTS: The ETGUG scores showed good to excellent inter-rater (ICC2,1 = 0.85-0.97) and test-retest reliability (ICC3,1 = 0.86-0.98) following log-transformation for tasks 2-6. Task1 scored fair r = 0.46-0.68. The SDCs were small (SDC = 0.05-0.21 seconds). Bland-Altman plots demonstrated good agreement between the measurements. There were significant differences between BVL and CON in ETGUG scores for tasks 1, 3, 4, 5, 6 & overall time. Task 2 showed no difference between the groups. BVL patients walked slower compared to the age-matched controls. DISCUSSION: Good reliability of the ETGUG in BVL and an indication for the discriminatory capabilities for the separate tasks suggest that the ETGUG could facilitate the study of functional deficits in BVL patients. Good reliability, small measurement error and values of SDC warrant the further utilisation of the ETGUG for the evaluation of physical functioning in BVL patients. [ABSTRACT FROM AUTHOR]

Background Disorders affecting the vestibular organs (semicircular canals, utriculus, sacculus), may result in distinct patterns of peripheral-vestibular loss that may facilitate the diagnostic assessment. When neuropathological tests of these sensors are available, it is possible to classify responses as being due to different deficit types. Objective To provide a topical review and to summarize recent advances in pattern-recognition of unilateral and bilateral vestibular disease by use of hierarchical cluster analysis (HCA) as published by the authors. Hypothesis We propose that certain patterns of peripheral-vestibular loss are associated with specific underlying disorders and that HCA is a suitable approach to identify such patterns. Discussion In the studies reviewed, disease-specific patterns could be recognized in different patient cohorts, with anterior-canal sparing being a hallmark feature in aminoglycoside-related bilateral vestibulopathy, Menière's disease and vestibular Schwannoma. The reasons for such anterior-canal sparing remain subject to debate, but potential explanations include reduced toxic exposure, faster recovery and lower vulnerability of the anterior canals. The pattern observed in acute superior-branch vestibular neuropathy, i.e., involvement of the horizontal and anterior canal and the utricle, matches neural inner-ear physiology. The broadly varying extent of damage to the different vestibular sensors even within given disorders underlines the necessity for detailed vestibular-testing. Conclusion HCA significantly facilitates pattern-identification in unilateral and bilateral vestibulopathies and underlines the extensive range of vestibular end-organ damage in the different study populations and subgroups. The large number of existing clustering algorithms with distinct strengths and weaknesses emphasizes the need for careful selection of the most suitable algorithm. • Hierarchical cluster analysis successfully identifies distinct patterns of peripheral-vestibular loss. • The pattern of vestibular impairment critically depends on the underlying disorder. • Within a given disorder, the extent of vestibular damage may vary significantly. • Varying exposure and vulnerability to aminoglycosides likely contribute to anterior-canal sparing. [ABSTRACT FROM AUTHOR]

Disorders of gait and balance are common in medicine and often lead to referral for neurologic evaluation. Because the maintenance of balance and normal gait are mediated by complex neurologic pathways as well as musculoskeletal, metabolic, and behavioral considerations, the list of possible contributing causes is very large. Much of the time, the history and neurologic examination reveal the underlying cause or causes. There are instances, however, when there are limited neurologic findings, as well as no structural abnormalities on brain or spine magnetic resonance imaging studies to explain the imbalance or gait difficulty. In this article, selected disorders that may be overlooked in the neurologic examination and imaging studies are reviewed. Possible causes of imbalance include occult drug-induced ataxia, autoimmune ataxia, ataxia associated with tremor, bilateral vestibular hypofunction, and spastic or dystonic gait disorders with normal imaging. [ABSTRACT FROM AUTHOR]

Abstract: Vestibular dysfunction in animals and humans is associated with a variety of cognitive and anxiety disorders, and it has been difficult to determine how the different symptoms may be related to one another. The aim of this study was to determine the extent to which the spatial memory deficits that occur following bilateral vestibular deafferentation (BVD) in rats can be attributed to other behavioural symptoms. Spatial memory was measured using a spatial T maze alternation task (STM), while locomotor activity and anxiety were measured using open field, elevated plus and T mazes, respectively. Using multiple linear and random forest regression, we determined that the best predictors of performance in the STM were whether the animals had received a BVD or sham lesion, and the duration of rearing. Using linear discriminant analysis, random forest classification, support vector machines and cluster analysis, we found that BVD animals could be clearly distinguished from sham controls by their behavioural syndrome, in particular their decreased duration of rearing in the open field maze (suggesting reduced exploration), decreased time spent in the outer zone of the open field maze (‘reduced thigmotaxis’, suggesting increased risk taking), and spatial memory deficits in the STM. These results suggest that the poor performance of rats with BVD in spatial memory tasks is largely due to spatial memory deficits themselves rather than a result of other changes in locomotor activity or anxiety. [Copyright &y& Elsevier]

Bilateral vestibular loss (BVL) may present with or without vertigo and hearing loss. Amongst the causes of BVL are vestibulotoxic antibiotics, autoimmune ear diseases, Menière’s disease and meningitis. Clinical diagnosis of BVL is based on the result of three simple bedside tests: a positive head impulse test, reduced dynamic visual acuity and a positive Romberg test on foam rubber. With these signs, diagnosis of severe BVL is usually straightforward to establish. [ABSTRACT FROM PUBLISHER]