Residual dizziness after BPPV management: exploring pathophysiology and treatment beyond canalith repositioning maneuvers.

Despite the high success rate of canalith repositioning maneuvers (CRMs) in the treatment of benign paroxysmal positional vertigo (BPPV), a growing number of patients report residual dizziness symptoms that may last for a significant time. Although the majority of BPPV cases can be explained by canalolithiasis, the etiology is complex. Consideration of the individual patient's history and underlying pathophysiology of BPPV may offer the potential for treatment approaches supplementary to CRMs, as well as a promising alternative for patients in whom CRMs are contraindicated. This article provides a summary of the possible underlying causes of BPPV and residual dizziness, along with suggestions for potential management options that may be considered to relieve the burden of residual symptoms.

Large Variability of Head Angulation During the Epley Maneuver: Use of a Head-Mounted Guidance System with Visual Feedback to Improve Outcomes.

BACKGROUND: The aim of this study was to show the variability in head angulation during the canalolith repositioning maneuvers to treat benign paroxysmal positional vertigo and to describe a head-mounted benign paroxysmal positional vertigo guidance system to measure the head orientation. METHODS: A guidance system for benign paroxysmal positional vertigo was developed by NeuroEquilibrium Diagnostic Systems to measure head orientation and provide visual feedback and instructions to examiners during various maneuvers for benign paroxysmal positional vertigo. Twenty-five experienced examiners and 25 healthy volunteers (aged 21-35 years) were recruited. Each examiner applied the Epley maneuver twice in 1 volunteer: without and with the use visual feedback from a guidance system. Head orientation in both procedures was measured and compared. RESULTS: The trained examiners demonstrated a large variability in head orientation during the Epley maneuver, which was reduced by using the benign paroxysmal positional vertigo guidance system. There was a variability of 39-65° in head orientation measured without the guidance system. The use of the guidance system reduced the variation range to a sixfold decrease in variability. CONCLUSION: There is a large variability in head orientation when performing repositioning maneuvers, which could compromise the efficacy of benign paroxysmal positional vertigo treatment. Treatment for benign paroxysmal positional vertigo can be optimized by reducing this variability with a benign paroxysmal positional vertigo guidance system. It might also be a useful tool for teaching.

Comparison of EOG and VOG obtained eye movements during horizontal head impulse testing.

Introduction: Video head impulse testing is frequently used to evaluate the vestibular function. During this test, eye movement responses are recorded with video-oculography (VOG). However, the use of VOG can sometimes be challenging, especially due to pupil detection problems (e.g., blinking, droopy eyelids, etc.). Therefore, this study investigated whether electro-oculography (EOG), a technique that does not depend on pupil tracking but on the orientation of the corneoretinal potential, might be an alternative to VOG for quantifying eye movement responses during head impulse testing. Subjects and methods: Head impulse testing was performed in 19 healthy subjects without a prior history of vestibular symptoms. Horizontal eye movements were recorded simultaneously with EOG (using an EOG system) and VOG (using a VHIT system: ICS Impulse). The eye movement responses to each side of both techniques were compared using a concordance correlation coefficient (r c ), t-testing, and Bayes Factor (BF) paired t-testing. Results: EOG and VOG obtained eye movement traces that correlated well with each other during head impulse testing (average r c = 0.89). Average VOR gains obtained with EOG and VOG were not significantly different from each other for all subjects during left head impulses. However, VOG gains differed between both techniques regarding right head impulses. VOG showed significant VOR gain asymmetry (5% to the right), whereas EOG showed no significant asymmetry (1% to the right). Conclusion: This study demonstrated the use of EOG to record eye movements during head impulse testing for the first time. EOG and VOG obtained eye movement traces that correlated well with each other during horizontal head impulse testing. In addition, EOG showed smaller VOR gain asymmetry in healthy individuals, in contrast to VOG. These findings indicate that EOG might potentially be applicable as an alternative to VOG for collecting eye movement responses during head impulse testing. Trial registration number: 10192021-38 dated 19.10.21.

Optimized Signal Analysis to Quantify the Non-Linear Behaviour of the Electrically Evoked Vestibulo-Ocular Reflex in Patients with a Vestibular Implant.

INTRODUCTION: Different eye movement analysis algorithms are used in vestibular implant research to quantify the electrically evoked vestibulo-ocular reflex (eVOR). Often, standard techniques are used as applied for quantification of the natural VOR in healthy subjects and patients with vestibular loss. However, in previous research, it was observed that the morphology of the VOR and eVOR may differ substantially. In this study, it was investigated if the analysis techniques for eVOR need to be adapted to optimize a truthful quantification of the eVOR (VOR gain, orientation of the VOR axis, asymmetry, and phase shift). METHODS: "Natural" VOR responses were obtained in six age-matched healthy subjects, and eVOR responses were obtained in eight bilateral-vestibulopathy patients fitted with a vestibular implant. Three conditions were tested: "nVOR" 1-Hz sinusoidal whole-body rotations of healthy subjects in a rotatory chair, "eVOR" 1-Hz sinusoidal electrical vestibular implant stimulation without whole-body rotations in bilateral-vestibulopathy patients, and "dVOR" 1-Hz sinusoidal whole-body rotations in bilateral-vestibulopathy patients using the chair-mounted gyroscope output to drive the electrical vestibular implant stimulation (therefore also in sync 1 Hz sinusoidal). VOR outcomes were determined from the obtained VOR responses, using three different eye movement analysis paradigms: (1) peak eye velocity detection using the raw eye traces; (2) peak eye velocity detection using full-cycle sine fitting of eye traces; (3) peak eye velocity detection using half-cycle sine fitting of eye traces. RESULTS: The type of eye movement analysis algorithm significantly influenced VOR outcomes, especially regarding the VOR gain and asymmetry of the eVOR in bilateral-vestibulopathy patients fitted with a vestibular implant. Full-cycle fitting lowered VOR gain in the eVOR condition (mean difference: 0.14 ± 0.06 95% CI, p = 0.018). Half-cycle fitting lowered VOR gain in the dVOR condition (mean difference: 0.08 ± 0.04 95% CI, p = 0.009). In the eVOR condition, half-cycle fitting was able to demonstrate the asymmetry between the excitatory and inhibitory phases of stimulation in comparison with the full-cycle fitting (mean difference: 0.19 ± 0.12 95% CI, p = 0.024). The VOR axis and phase shift did not differ significantly between eye movement analysis algorithms. In healthy subjects, no clinically significant effect of eye movement analysis algorithms on VOR outcomes was observed. CONCLUSION: For the analysis of the eVOR, the excitatory and inhibitory phases of stimulation should be analysed separately due to the inherent asymmetry of the eVOR. A half-cycle fitting method can be used as a more accurate alternative for the analysis of the full-cycle traces.

Modified Interpretations of the Supine Roll Test in Horizontal Canal BPPV Based on Simulations: How the Initial Position of the Debris in the Canal and the Sequence of Testing Affects the Direction of the Nystagmus and the Diagnosis.

Background and Objectives: The aim of this study was to show with three-dimensional simulations how the diagnostic supine roll test (SRT) is affected by the initial position of the debris within the horizontal canal (hc) and study the nystagmus patterns on changing the sequence of testing and its impact on the diagnosis of the side of involvement in hc-BPPV. Methods: A 3D dynamic simulation model was developed and applied based on reconstructed MRI images and fluid dynamics. Each semicircular canal was linked to the respective extraocular muscles to visualize nystagmus generated on stimulation of the canal. Results: The simulations of hc-canalithiasis showed that the nystagmus pattern seen with the SRT is changed by the initial position of the otolith debris within the canal and the sequence of testing. The debris changes position during SRT so that sequential steps do not start at the initial position as previously assumed. The sequence of performing the SRT steps from the right or left side influences the nystagmus pattern generated: bilateral direction-changing, bilateral direction-fixed, and unilateral nystagmus can be seen in different test conditions. The SRT itself may even reposition the debris out of the canal. Conclusions and Clinical Implications: Simulations provide a dynamic tool to study the diagnostic SRT in hc-canalithiasis. Starting the SRT from right or left has a major impact on the test outcome (unlike the Dix-Hallpike maneuver). The findings provide a new interpretation for the results of the SRT. The simulations explain the phenomenon of direction-fixed nystagmus as a logical consequence of starting the SRT with the head turned toward the non-affected side in hc-canalithiasis with debris in the ampullary arm. They also show that unilateral nystagmus seen on SRT indicates canalithiasis of the non-ampullary arm of the side opposite to the side of nystagmus. The generation of bilateral direction-changing, bilateral direction-fixed, and unilateral nystagmus can be the cause of misdiagnoses in terms of the affected side and underlying mechanisms. Finally, a recommendation for a standardized protocol for the sequence of positional tests should be established to ensure uniform interpretation of test results.

Suppression Head Impulse Test (SHIMP) versus Head Impulse Test (HIMP) When Diagnosing Bilateral Vestibulopathy.

The Suppression Head Impulse (SHIMP) test was introduced as an alternative to the Head Impulse Paradigm (HIMP) to overcome challenges in VOR gain calculation due to the interference of covert saccades. The objectives of this study were (1) to determine if SHIMP, compared to HIMP, reduces covert saccades in BV patients and (2) to define the agreement on diagnosing BV between SHIMP and HIMP. First, the number of covert saccades was compared between SHIMP and HIMP. Secondly, VOR gain was compared between SHIMP and HIMP. Lastly, the agreement between SHIMP and HIMP on identifying BV (horizontal VOR gain <0.6) was evaluated. A total of 98 BV patients were included. To our knowledge, this is the largest study population on SHIMP testing in BV patients. Covert saccades were significantly reduced, and a lower VOR gain was found during SHIMP compared to HIMP (p < 0.001). However, the clinical relevance of these statistically significant differences is small. In 93% of the patients, an agreement was found between the two paradigms regarding the diagnosis of BV, and both paradigms detect BV in the vast majority of patients.

Bilateral vestibulopathy decreases self-motion perception.

OBJECTIVE: Current diagnostic criteria for bilateral vestibulopathy (BV) primarily involve measurements of vestibular reflexes. Perceptual self-motion thresholds however, are not routinely measured and their clinical value in this specific population is not yet fully determined. Objectives of this study were (1) to compare perceptual self-motion thresholds between BV patients and control subjects, and (2) to explore patterns of self-motion perception performance and vestibular function in BV patients. METHODS: Thirty-seven BV patients and 34 control subjects were included in this study. Perceptual self-motion thresholds were measured in both groups using a CAREN platform (Motek Medical BV, Amsterdam, The Netherlands). Vestibular function was evaluated (only in BV patients) by the caloric test, torsion swing test, video head impulse test of all semicircular canals, and cervical- and ocular vestibular-evoked myogenic potentials. Differences in thresholds between both groups were analyzed. Hierarchical cluster analysis was performed to visualize patterns between self-motion perception and vestibular function within the group of BV patients. RESULTS: Perceptual self-motion thresholds were significantly higher in BV patients compared to control subjects, regarding nearly all rotations and translations (depending on the age group) (p ≤ 0.001). Cluster analysis showed that within the group of BV patients, higher perceptual self-motion thresholds were generally associated with lower vestibular test results (significant for yaw rotation, caloric test, torsion swing test, and video head impulse test (p ≤ 0.001)). CONCLUSION: Self-motion perception is significantly decreased in BV patients compared to control subjects regarding nearly all rotations and translations. Furthermore, decreased self-motion perception is generally associated with lower residual vestibular function in BV patients. TRIAL REGISTRATION: Trial registration number NL52768.068.15/METC.

Bilateral vestibulopathy patients' perspectives on vestibular implant treatment: a qualitative study.

OBJECTIVES: The aim of this study was to explore expectations of patients with bilateral vestibulopathy regarding vestibular implant treatment. This could advance the definition of recommendations for future core outcome sets of vestibular implantation and help to determine on which characteristics of bilateral vestibulopathy future vestibular implant research should focus. METHODS: Semi-structured interviews were conducted with 50 patients diagnosed with bilateral vestibulopathy at Maastricht UMC + . Interviews followed a semi-structured interview guide and were recorded and transcribed. Transcripts were analyzed thematically by two independent researchers. A consensus meeting took place to produce a joint interpretation for greater dimensionality and to confirm key themes. RESULTS: Overall, patient expectations centralized around three key themes: (physical) symptom reduction, functions and activities, and quality of life. These themes appeared to be interrelated. Patient expectations focused on the activity walking (in a straight line), reducing the symptom oscillopsia and being able to live the life they had before bilateral vestibulopathy developed. In general, patients indicated to be satisfied with small improvements. CONCLUSION: This study demonstrated that patient expectations regarding a vestibular implant focus on three key themes: symptom reduction, functions and activities, and quality of life. These themes closely match the functional improvements shown in recent vestibular implantation research. The results of this study provide a clear guideline from the patient perspective on which characteristics of bilateral vestibulopathy, future vestibular implant research should focus. TRIAL REGISTRATION: NL52768.068.15/METC.

DISCOHAT: An Acronym to Describe the Spectrum of Symptoms Related to Bilateral Vestibulopathy.

Objective: To assess the prevalence of each symptom listed in the acronym DISCOHAT (worsening of symptoms in Darkness and/or uneven ground, Imbalance, Supermarket effect, Cognitive complaints, Oscillopsia, Head movements worsen symptoms, Autonomic complaints, and Tiredness) in patients with bilateral vestibulopathy (BVP), compared to patients with unilateral vestibulopathy (UVP). Methods: A descriptive case-control study was performed on BVP and UVP patients who were evaluated for their vestibular symptoms by two of the authors (RvdB, MCG) at a tertiary referral center, between 2017 and 2020. During history taking, the presence of each DISCOHAT symptom was checked and included in the electronic health record. Presence of a symptom was categorized into: "present," "not present," and "missing." Results: Sixty-six BVP patients and 144 UVP patients were included in this study. Prevalence of single DISCOHAT symptoms varied from 52 to 92% in BVP patients and 18-75% in UVP patients. Patients with BVP reported "worsening of symptoms in darkness," "imbalance," "oscillopsia," and "worsening of symptoms with fast head movements" significantly more than UVP patients (p ≤ 0.004). Conclusion: The DISCOHAT acronym is able to capture a wide spectrum of symptoms related to vestibulopathy, while it is easy and quickly to use in clinic. Application of this acronym might facilitate a more thorough and uniform assessment of bilateral vestibulopathy, within and between vestibular clinics worldwide.

History Taking in Non-Acute Vestibular Symptoms: A 4-Step Approach.

History taking is crucial in the diagnostic process for vestibular disorders. To facilitate the process, systems such as TiTrATE, SO STONED, and DISCOHAT have been used to describe the different paradigms; together, they address the most important aspects of history taking, viz. time course, triggers, and accompanying symptoms. However, multiple (vestibular) disorders may co-occur in the same patient. This complicates history taking, since the time course, triggers, and accompanying symptoms can vary, depending on the disorder. History taking can, therefore, be improved by addressing the important aspects of each co-occurring vestibular disorder separately. The aim of this document is to describe a 4-step approach for improving history taking in patients with non-acute vestibular symptoms, by guiding the clinician and the patient through the history taking process. It involves a systematic approach that explicitly identifies all co-occurring vestibular disorders in the same patient, and which addresses each of these vestibular disorders separately. The four steps are: (1) describing any attack(s) of vertigo and/or dizziness; (2) describing any chronic vestibular symptoms; (3) screening for functional, psychological, and psychiatric co-morbidity; (4) establishing a comprehensive diagnosis, including all possible co-occurring (vestibular) disorders. In addition, pearls and pitfalls will be discussed separately for each step.

The Effect of Different Head Movement Paradigms on Vestibulo-Ocular Reflex Gain and Saccadic Eye Responses in the Suppression Head Impulse Test in Healthy Adult Volunteers.

Objective: This study aimed to identify differences in vestibulo-ocular reflex gain (VOR gain) and saccadic response in the suppression head impulse paradigm (SHIMP) between predictable and less predictable head movements, in a group of healthy subjects. It was hypothesized that higher prediction could lead to a lower VOR gain, a shorter saccadic latency, and higher grouping of saccades. Methods: Sixty-two healthy subjects were tested using the video head impulse test and SHIMPs in four conditions: active and passive head movements for both inward and outward directions. VOR gain, latency of the first saccade, and the level of saccade grouping (PR-score) were compared among conditions. Inward and active head movements were considered to be more predictable than outward and passive head movements. Results: After validation, results of 57 tested subjects were analyzed. Mean VOR gain was significantly lower for inward passive compared with outward passive head impulses (p < 0.001), and it was higher for active compared with passive head impulses (both inward and outward) (p ≤ 0.024). Mean latency of the first saccade was significantly shorter for inward active compared with inward passive (p ≤ 0.001) and for inward passive compared with outward passive head impulses (p = 0.012). Mean PR-score was only significantly higher in active outward than in active inward head impulses (p = 0.004). Conclusion: For SHIMP, a higher predictability in head movements lowered gain only in passive impulses and shortened latencies of compensatory saccades overall. For active impulses, gain calculation was affected by short-latency compensatory saccades, hindering reliable comparison with gains of passive impulses. Predictability did not substantially influence grouping of compensatory saccades.

Diagnostic and Therapeutic Maneuvers for Anterior Canal BPPV Canalithiasis: Three-Dimensional Simulations.

Background and Objectives: Anterior canal BPPV is a rare BPPV variant. Various diagnostic and therapeutic maneuvers have been described for its management. The aim of this study was to use three-dimensional simulation models to visualize otoconial debris movement within the anterior canal during diagnostic tests and different liberatory maneuvers. This can help to optimize existing treatment maneuvers and help in the development of better management protocols. Methods: Based on reconstructed MRI images and fluid dynamics, a 3D dynamic simulation model (as a function of time) was developed and applied. Simulations of the supine head-hanging test for diagnosis of ac-BPPV were studied. Three repositioning maneuvers were simulated: 1) the Yacovino maneuver and its modifications, 2) the reverse Epley maneuver and 3) the short canal repositioning (CRP) maneuver. Results: The simulation showed that the supine head-hanging test is a good test for diagnosis of ac-BPPV affecting both labyrinths and demonstrated why there is no inversion of nystagmus on sitting up. The Yacovino maneuver was seen to be an effective treatment option for ac-BPPV without having to determine the side involved. However, simulations showed that the classical Yacovino maneuver carried a risk of canal switch to the posterior canal. To overcome this risk, a modified Yacovino maneuver is suggested. The reverse Epley maneuver was not an effective treatment. Short CRP is useful in ac-BPPV treatment; however, it requires determination of side of involvement. Conclusion: The 3D simulator of the movement of the otoconial debris presented here can be used to test the mechanism of action and the theoretical efficacy of existing diagnostic tests and maneuvers as well as to develop new treatment maneuvers to optimize BPPV treatment.

Three-dimensional simulations of six treatment maneuvers for horizontal canal benign paroxysmal positional vertigo canalithiasis.

BACKGROUND AND PURPOSE: Horizontal canal benign paroxysmal positional vertigo (BPPV) is the second most common variant of BPPV after posterior canal BPPV. Various liberatory maneuvers are recommended for the treatment of horizontal canal BPPV canalithiasis (hc-BPPV-ca). The aim of this study was to show how three-dimensional (3D) dynamic simulation models visualize the movement of the clot of otoconia within the canal for a better understanding of the theoretical efficacy. METHODS: Based on reconstructed magnetic resonance imaging and fluid dynamics, a 3D dynamic simulation model (as a function of time) was developed and applied. Thereby, six treatment maneuvers for hc-BPPV-ca were simulated: two types of the roll maneuver (the original 270° and the modified 360°) as well as two Gufoni and Zuma maneuvers (for geotropic and apogeotropic nystagmus). RESULTS: The simulations showed that the 360° roll maneuver and Zuma maneuver are effective treatment options for hc-BPPV-ca for debris in all locations within the canal. However, the original 270° roll maneuver will not be effective if the clot is in the ampullary arm of the horizontal canal. The Gufoni maneuver for geotropic hc-BPPV-ca is effective, whereas for apogeotropic hc-BPPV-ca there is a risk of treatment failure due to insufficient repositioning of the debris. CONCLUSIONS: The 3D simulations for movement of the otoconia clots can be used to test the mechanism of action and the theoretical efficacy of existing maneuvers for the different BPPV variants. For hc-BPPV-ca, the modified 360° roll maneuver and Zuma maneuver are theoretically efficient for all subtypes, whereas Gufoni maneuver is effective for geotropic nystagmus only.

BPPV Simulation: A Powerful Tool to Understand and Optimize the Diagnostics and Treatment of all Possible Variants of BPPV.

BPPV is a mechanical disorder caused by the displacement of otolith debris into the semicircular canals. The treatment involves different repositioning maneuvers to bring the debris back into the utricle. This study aims to show how dynamic simulation models based on fluid dynamics and MRI, can help to visualize and understand the movement of the debris within the canals during head movement in 3D as a function of time. The user can define the rotation angle and plane at each step of the maneuver and then the model visualizes the canal and the otoconial movement in 3D. The simulation developed also allows alteration of various parameters like the rotational head acceleration, the duration of each step of the maneuver, the initial position of the otoconial debris in the canal, the size and the number of the particles and fluid dynamics of endolymph. The clod movement is visualized in such a way that it allows a better understanding of the impact and efficacy of various liberation maneuvers and why certain maneuvers might fail when not applied properly in the clinic. The model allows simulation of multi-canal BPPV. In this paper we demonstrate the power of the model applied on the maneuvers of Semont and Yacovino when executed in different ways. The model aims to provide a visual explanation for the need of specific maneuvers for each type of BPPV. The simulator presented here can be used to test the efficacy of existing maneuvers and help in the development of new maneuvers to treat different BPPV variants.

Diagnosing vestibular hypofunction: an update.

Unilateral or bilateral vestibular hypofunction presents most commonly with symptoms of dizziness or postural imbalance and affects a large population. However, it is often missed because no quantitative testing of vestibular function is performed, or misdiagnosed due to a lack of standardization of vestibular testing. Therefore, this article reviews the current status of the most frequently used vestibular tests for canal and otolith function. This information can also be used to reach a consensus about the systematic diagnosis of vestibular hypofunction.

Worldwide survey on laboratory testing of vestibular function.

BACKGROUND: The function of the peripheral vestibular system can nowadays be quantified. The video head impulse test (vHIT) and caloric irrigation are used for the semicircular canals, cervical vestibular evoked myogenic potentials (cVEMP) for the sacculus, and ocular vestibular evoked myogenic potentials (oVEMP) for the utriculus. Because there is no agreement on normal and pathologic values, we performed a worldwide survey. METHODS: A web-based standardized survey questionnaire was used to collect data on "reference values" and "cutoff" values. Thirty-eight centers from all continents (except Africa) replied. RESULTS: "Reference values": vHIT: mean for the vestibulo-ocular reflex gain of the left horizontal canal 0.91 (range: 0.7-1.01) and of the left horizontal canal 0.92 (0.7-1.05); side difference 0.15 (0.25-0.3). Caloric irrigation: mean peak slow phase velocity of caloric-induced nystagmus for warm (44°C) water 18.65°/s (12-30°/s); cold (30°C) water 18.21°/s (10-25°/s). cVEMP: P13-N23 amplitude mean for the lower limit 28.67 µV (16-50 µV); upper limit 200 µV (50-350 µV). "Cutoff values": vHIT: side difference 0.26 (0.1-0.4), bilateral vestibulopathy <0.61 (0.3-0.8); unilateral vestibulopathy (UVP) <0.68 (0.4-0.8). Caloric irrigation pathologic side difference mean 25.93% (17.7%-40%) or 12°/sec (5-30°/s); side difference UVP 26.73% (20%-40%) or 29.8°/s (5-100°/s). cVEMP: P13/N23 amplitude mean lower cutoff 32.5 µV (15-50 µV), mean upper cutoff 125 µV (50-200 µV), asymmetry 36.08 µV (20-50 µV). CONCLUSION: This worldwide survey showed a large variability in terms of reference and pathologic cutoff values in the 38 centers included. Therefore, standardization of how to achieve these values and agreement on which values should be used is highly warranted to guarantee a high quality of vestibular testing and interpretation of clinical and scientific results.

Self-assessment of unilateral and bimodal cochlear implant experiences in daily life.

OBJECTIVE: The subjective experiences were assessed of cochlear implant (CI) users either wearing or not wearing a hearing aid (HA) at the contralateral ear. DESIGN: Unilateral CI-recipients were asked to fill out a set of daily-life questionnaires on bimodal HA use, hearing disability, hearing handicap and general quality of life. STUDY SAMPLE: Twenty-six CI-recipients who regularly use a contralateral HA (bimodal group) and twenty-two CI-recipients who do not use a HA in the contralateral ear (unilateral group). RESULTS: Comparisons between both groups (bimodal versus unilateral) showed no difference in self-rated disability, hearing handicap or general quality of life. However within the group of bimodal listeners, participants did report a benefit of bimodal hearing ability in various daily life listening situations. CONCLUSIONS: Bimodal benefit in daily life can consistently be experienced and reported within the group of bimodal users.

Simultaneous activation of multiple vestibular pathways upon electrical stimulation of semicircular canal afferents.

BACKGROUND AND PURPOSE: Vestibular implants seem to be a promising treatment for patients suffering from severe bilateral vestibulopathy. To optimize outcomes, we need to investigate how, and to which extent, the different vestibular pathways are activated. Here we characterized the simultaneous responses to electrical stimuli of three different vestibular pathways. METHODS: Three vestibular implant recipients were included. First, activation thresholds and amplitude growth functions of electrically evoked vestibulo-ocular reflexes (eVOR), cervical myogenic potentials (ecVEMPs) and vestibular percepts (vestibulo-thalamo-cortical, VTC) were recorded upon stimulation with single, biphasic current pulses (200 µs/phase) delivered through five different vestibular electrodes. Latencies of eVOR and ecVEMPs were also characterized. Then we compared the amplitude growth functions of the three pathways using different stimulation profiles (1-pulse, 200 µs/phase; 1-pulse, 50 µs/phase; 4-pulses, 50 µs/phase, 1600 pulses-per-second) in one patient (two electrodes). RESULTS: The median latencies of the eVOR and ecVEMPs were 8 ms (8-9 ms) and 10.2 ms (9.6-11.8 ms), respectively. While the amplitude of eVOR and ecVEMP responses increased with increasing stimulation current, the VTC pathway showed a different, step-like behavior. In this study, the 200 µs/phase paradigm appeared to give the best balance to enhance responses at lower stimulation currents. CONCLUSIONS: This study is a first attempt to evaluate the simultaneous activation of different vestibular pathways. However, this issue deserves further and more detailed investigation to determine the actual possibility of selective stimulation of a given pathway, as well as the functional impact of the contribution of each pathway to the overall rehabilitation process.