Does Catastrophizing Predict Response to Treatment in Patients With Vestibular Disorders? A Prospective Cohort Study.

OBJECTIVE: Determine levels of catastrophizing in patients with vestibular disorders and prospectively evaluate their relationship with patient-reported outcome measures. STUDY DESIGN: Prospective cohort study. SETTING: Tertiary care neurotology vestibular disorders clinic. PATIENTS: Adult patients with various vestibular disorders. INTERVENTIONS: Patients were given the Dizziness Handicap Inventory (DHI) and the Dizziness Catastrophizing Scale (DCS) at a baseline visit and follow-up visit after treatment. MAIN OUTCOME MEASURES: Correlation studies were used to determine the relationships between DHI and DCS. Multivariable linear regression was performed to determine the relationship between DCS and DHI change with treatment, accounting for demographic variables. RESULTS: Forty-six subjects completed both the DHI and the DCS before and after treatment. Patients with higher baseline DCS scores had higher baseline DHI scores ( p < 0.001). There was a significant improvement in both DHI score ( p < 0.001) and DCS ( p < 0.001) at follow-up. Patients who had reduction in DCS scores during were more likely to show reduction in DHI scores ( p < 0.001). A subset of patients had a mindfulness-based stress reduction program included in their treatment. These patients had a greater reduction in both DCS and DHI scores at follow-up compared with those who received other treatments. CONCLUSIONS: Catastrophizing is associated with higher pretreatment DHI scores and worse treatment outcomes. Addressing dizziness catastrophizing may help improve vestibular outcomes.

VM-PATHI Correlates With Cognitive Function Improvement After Successful Treatment in Patients With Vestibular Migraine.

OBJECTIVE: To assess changes in cognitive function in vestibular migraine patients undergoing treatment. STUDY DESIGN: Prospective cohort. SETTING: Single-institution tertiary-care center. PATIENTS: Thirty-four patients with vestibular migraine were included in the study. Average age at diagnosis was 47.9 years. A majority of patients (91.2%) were female. INTERVENTIONS: Vestibular therapies included pharmacologic treatment (67.6%), mindfulness-based stress reduction (58.8%), vestibular physical therapy (20.6%), and lifestyle changes only (2.9%). MAIN OUTCOME MEASURES: Pretreatment and posttreatment questionnaires were collected including the Cognitive Failures Questionnaire (CFQ), Vestibular Migraine Patient Assessment Tool and Handicap Inventory (VM-PATHI), and Dizziness Handicap Inventory. RESULTS: Median time between pretreatment and posttreatment questionnaire was 4.4 months (range, 2.8-15.6. mo). CFQ scores decreased in subjects who responded to treatment, as defined by those with a positive change in VM-PATHI score (average decrease, 6.5; p = 0.03). CFQ scores did not improve in subjects who had no improvement in their vestibular condition, as defined by no change or an increase in VM-PATHI score (average increase, 2.0; p = 0.53). Univariate linear regression showed that VM-PATHI score change was highly predictive of CFQ change ( p < 0.01, r2 = 0.36). Multivariate regression demonstrated that the VM-PATHI ( p = 0.03) and not the Dizziness Handicap Inventory ( p = 0.10) predicted changes in CFQ score. CONCLUSIONS: Self-reported cognitive dysfunction improves with successful treatment of vestibular migraine.

Acceptance and commitment therapy combined with vestibular rehabilitation for persistent postural-perceptual dizziness: A pilot study.

PURPOSE: This study investigated the feasibility of acceptance and commitment therapy for persistent postural-perceptual dizziness and preliminarily verified the long-term effectiveness of the therapy. MATERIALS AND METHODS: This study implemented the within-group pre-post comparison design. We enrolled 27 adult patients who met the criteria of persistent postural-perceptual dizziness. They underwent a treatment program including acceptance and commitment therapy combined with vestibular rehabilitation once a week for a total of six sessions. The primary outcome was changes in the Dizziness Handicap Inventory score 6 months posttreatment. RESULTS: All 27 patients completed the acceptance and commitment therapy + vestibular rehabilitation program, and 25 patients (92.6%) could be followed for 6 months posttreatment. For 27 participants, the scores from pretreatment to 6 months posttreatment significantly declined (P < .001), and the Dizziness Handicap Inventory effect size was 1.11 (95% confidence interval = 0.80-1.42). At 6 months posttreatment, 11 patients (40.7%) achieved remission (the score ≤ 14), 16 (59.3%) achieved treatment response (reduction in the score ≥ 18), and 20 (74.1%) achieved remission and/or treatment response. CONCLUSIONS: Acceptance and commitment therapy is feasible for persistent postural-perceptual dizziness and might have long-term effectiveness. However, a randomized controlled trial is warranted.

Electrical Vestibular Stimulation in Humans: A Narrative Review.

BACKGROUND: In patients with bilateral vestibulopathy, the regular treatment options, such as medication, surgery, and/or vestibular rehabilitation, do not always suffice. Therefore, the focus in this field of vestibular research shifted to electrical vestibular stimulation (EVS) and the development of a system capable of artificially restoring the vestibular function. Key Message: Currently, three approaches are being investigated: vestibular co-stimulation with a cochlear implant (CI), EVS with a vestibular implant (VI), and galvanic vestibular stimulation (GVS). All three applications show promising results but due to conceptual differences and the experimental state, a consensus on which application is the most ideal for which type of patient is still missing. SUMMARY: Vestibular co-stimulation with a CI is based on "spread of excitation," which is a phenomenon that occurs when the currents from the CI spread to the surrounding structures and stimulate them. It has been shown that CI activation can indeed result in stimulation of the vestibular structures. Therefore, the question was raised whether vestibular co-stimulation can be functionally used in patients with bilateral vestibulopathy. A more direct vestibular stimulation method can be accomplished by implantation and activation of a VI. The concept of the VI is based on the technology and principles of the CI. Different VI prototypes are currently being evaluated regarding feasibility and functionality. So far, all of them were capable of activating different types of vestibular reflexes. A third stimulation method is GVS, which requires the use of surface electrodes instead of an implanted electrode array. However, as the currents are sent through the skull from one mastoid to the other, GVS is rather unspecific. It should be mentioned though, that the reported spread of excitation in both CI and VI use also seems to induce a more unspecific stimulation. Although all three applications of EVS were shown to be effective, it has yet to be defined which option is more desirable based on applicability and efficiency. It is possible and even likely that there is a place for all three approaches, given the diversity of the patient population who serves to gain from such technologies.

External trigeminal nerve stimulation: Potential rescue treatment for acute vestibular migraine.

OBJECTIVE: Vestibular migraine (VM) is the most common neurologic cause of vertigo among adults. However, there are no specifically studied or approved rescue therapies for acute VM attacks. This study describes how external trigeminal nerve stimulation (eTNS) using the Cefaly® (CEFALY Technology, Seraing, Belgium) device relieves acute VM episodes. METHODS: Single-center, retrospective review of 19 patients with acute VM attacks (seen between May 2018 and June 2019) treated with 20-min eTNS. Prior to treatment, patients graded the severity of their vertigo/headache using a 10-point visual analog scale (VAS) with 0 representing no vertigo/headache, and 10 representing the worst imaginable vertigo/headache. After eTNS, patients graded their vertigo/headache using the same VAS 15 min. In addition, bedside neuro-otologic examination was performed before and after treatment. RESULTS: 19/19 patients reported improvement in vertigo severity. Mean vertigo severity was 6.6 (±2.1; median 7) before eTNS, and 2.7 (±2.6; median 3) following treatment; mean improvement in vertigo was 61.3% (±32.6; median 50.0%). During VM episodes, 14/19 experienced headache. Mean headache severity was 4.8 (±2.4; median 4.5) before eTNS, and was 1.4 (±2.4; median 0) following treatment; mean improvement in headache was 77.2% (±32.7; median 100.0%). Neuro-otologic examination was normal during VM attacks in all except Patient 7 who had spontaneous upbeat nystagmus which resolved after eTNS. Other improvements include improvement of eye pressure, head pressure, and chronic facial pain. No intolerable side effects were reported. CONCLUSION: This study provides preliminary evidence that eTNS is a novel, non-invasive, safe and effective treatment for acute VM attacks.

Acute vestibular migraine treatment with noninvasive vagus nerve stimulation.

OBJECTIVE: To report on the benefits of noninvasive vagus nerve stimulation (nVNS) on acute vestibular migraine (VM) treatment. METHODS: This was a retrospective chart review of patients with VM treated with nVNS in a single tertiary referral center between November 2017 and January 2019. Eighteen patients (16 women) were identified (mean age 45.7 [±14.8] years); 14 were treated for a VM attack and 4 for bothersome interictal dizziness consistent with persistent perceptual postural dizziness (PPPD). Patients graded the severity of vestibular symptoms and headache using an 11-point visual analog scale (VAS; 0 = no symptoms, 10 = worst ever symptoms) before and 15 minutes after nVNS. RESULTS: In those with acute VM, vertigo improved in 13/14 (complete resolution in 2, at least 50% improvement in 5). The mean vertigo intensity before nVNS was 5.2 (±1.6; median 6), and 3.1 (±2.2; median 3) following stimulation; mean reduction in vertigo intensity was 46.9% (±31.5; median 45%). Five experienced headache with the VM attack; all reported improvement following nVNS. Mean headache severity was 6 (±1.4; median 6) prior to treatment and 2.4 (±1.5; median 3) following nVNS; mean reduction in headache intensity was 63.3% (±21.7; median 50). All 4 treated with nVNS for interictal PPPD reported no benefit. CONCLUSION: Our study provides preliminary evidence that nVNS may provide rapid relief of vertigo and headache in acute VM, and supports further randomized, sham-controlled studies into nVNS in VM. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that for patients with acute VM, nVNS rapidly relieves vertigo and headache.

Sinusoidal Transcranial Direct Current Versus Galvanic Vestibular Stimulation for Treatment of Lateropulsion Poststroke.

OBJECTIVE: To compare the effects of Transcranial Direct Current Stimulation (tDCS) versus Galvanic Vestibular Stimulation (GVS) on Lateropulsion following stroke. METHODS: Patients with Stroke and Burke Lateropulsion Scale (BLS) scores greater than or equal to 2 gave informed consent to receive sinusoidal 1 Hz DC (0-2 mA) anodal stimulation over the affected parietal cortex versus similar GVS with ipsilesional mastoidal anode. Seated haptic center of pressure (COP-X) was measured using an AMTI analog-to-digital forceplate. An inclinometer (Biopac ) measured lateral thoracic tilt. COP-X Power Spectra were analyzed over 3 frequency intervals: 0-.3 Hz, .3-1 Hz, and 1-3 Hz. RESULTS: Six males/4 females age 66 ± 9.5 standard deviation with admission BLS scores of 5.4 ± 3.7 within 8.6 ± 8.1 days poststroke were enrolled. COP-X medial-lateral speed increased for both the tDCS and the GVS protocols compared to sham condition. Fourier Analysis of COP-X velocity for 0-.3 Hz responses showed a significant increase for tDCS stimulation. The .3-1 Hz responses for the tDCS condition were decreased from baseline. Lateral thoracic tilt showed significant improvement for tDCS compared to Sham stimulation at 10 minutes and for GVS versus Sham at 15 minutes. DISCUSSION: Anodal tDCS over the ipsilesional PIVC increases low frequency postural responses usually attributed to visual control with down regulation of median frequency vestibular responses, biasing postural control toward more dependence on visual as opposed to vestibular control. CONCLUSIONS: 2 mA sinusoidal 1 Hz anodal tDCS over the ipsi-lesional PIVC or similar ipsi-lesional anodal GVS improve Lateropulsion following stroke.

EMBalance - validation of a decision support system in the early diagnostic evaluation and management plan formulation of balance disorders in primary care: study protocol of a feasibility randomised controlled trial.

BACKGROUND: Balance problems are caused by multiple factors and often lead to falls and related fractures, bringing large socio-economic costs. The complexity of balance control mechanisms, the lack of medical expertise, and the absence of specialised equipment contribute to the delayed or incorrect diagnosis and management ofthese patients. Advances in computer science have allowed the development of computer systems that support clinical diagnosis and treatment decisions based on individualised patient data. The aim of the EMBalance decision support system (DSS) is to support doctors facing this clinical challenge, to make a definitive diagnosis and implement an effective management plan. The EMBalance study will determine the accuracy of this supportive tool when used by non-specialist doctors. This study is funded by the European Union's Seventh Framework Programme. METHODS/DESIGN: EMBalance is a proof-of-concept study designed as a non-commercial, international, multi-centre, single-blind, parallel-group randomised controlled trial to be carried out at four clinical sites in the United Kingdom, Germany, Greece and Belgium. The study is comprised of three stages: internal pilot, phase I (diagnosis) and stage II (management). For this purpose, 200 patients presenting with persistent dizziness (>3 months' duration) to primary care services will be randomised to either the intervention group (diagnostic assessment with the DSS) or a control group (diagnostic assessment without the DSS). Patients allocated to the intervention group will be assessed by a doctor with the support of the EMBalance DSS, while patients allocated to the control group will receive a visit as per standard practice. Ultimately, all patients' diagnoses and management plans will be certified by a consultant in neuro-otology. DISCUSSION: EMBalance is the first trial to test the accuracy of a DSS in both the diagnosis of and the management plan for vestibular disorders across the healthcare systems of four different countries. The EMBalance study is the result of a combined effort of engineers and physicians to develop an accurate tool to support non-specialist doctors, with no risk for the patient. This trial will provide reliable information about the benefits of implementing DSSs in primary care while supporting the feasibility of testing the EMBalance algorithms in further research. TRIAL REGISTRATION: ClinicalTrials.gov NCT02704819 . Registered 29 February 2016.

Long-term effects of electrotactile sensory substitution therapy on balance disorders.

This clinical research investigated whether a new type of rehabilitation therapy involving the use of a vestibular substitution tongue device (VSTD) is effective for severe balance disorders caused by unilateral vestibular loss. Sixteen patients with postural imbalances because of unilateral vestibular loss underwent training with VSTD. The VSTD transmits information on the head position to the brain through the tongue as substitutes for the lost vestibular information. The device's electrode array was placed on the tongue and participants were trained to maintain a centered body position by ensuring the electrical signals in the center of their tongue. All participants completed 10 min training sessions 2-3 times per day for 8 weeks. Functional gait assessments and the dizziness handicap inventory were, respectively, used to the evaluate participants' dynamic gait function and their severity of balance problems before and after the training period. All examined parameters improved after the 8-week training period. These changes were maintained for up to 2 years after the termination of the training program. Short-term training with VSTD had beneficial carry-over effects. VSTD training might represent a useful rehabilitation therapy in individuals with persistent balance disorders and might lead to long-term improvements in their balance performance and ability to perform daily and social activities.

Preclinical validation of anti-nuclear factor-kappa B therapy to inhibit human vestibular schwannoma growth.

Vestibular schwannomas (VSs), the most common tumors of the cerebellopontine angle, arise from Schwann cells lining the vestibular nerve. Pharmacotherapies against VS are almost non-existent. Although the therapeutic inhibition of inflammatory modulators has been established for other neoplasms, it has not been explored in VS. A bioinformatic network analysis of all genes reported to be differentially expressed in human VS revealed a pro-inflammatory transcription factor nuclear factor-kappa B (NF-κB) as a central molecule in VS pathobiology. Assessed at the transcriptional and translational level, canonical NF-κB complex was aberrantly activated in human VS and derived VS cultures in comparison to control nerves and Schwann cells, respectively. Cultured primary VS cells and VS-derived human cell line HEI-193 were treated with specific NF-κB siRNAs, experimental NF-κB inhibitor BAY11-7082 (BAY11) and clinically relevant NF-κB inhibitor curcumin. Healthy human control Schwann cells from the great auricular nerve were also treated with BAY11 and curcumin to assess toxicity. All three treatments significantly reduced proliferation in primary VS cultures and HEI-193 cells, with siRNA, 5 µM BAY11 and 50 µM curcumin reducing average proliferation (±standard error of mean) to 62.33% ± 10.59%, 14.3 ± 9.7%, and 23.0 ± 20.9% of control primary VS cells, respectively. These treatments also induced substantial cell death. Curcumin, unlike BAY11, also affected primary Schwann cells. This work highlights NF-κB as a key modulator in VS cell proliferation and survival and demonstrates therapeutic efficacy of directly targeting NF-κB in VS.

Proposed treatment for geriatric vestibular disease in dogs.

Sudden-onset vestibular dysfunction in the canine is a commonly seen condition in veterinary practice, with some veterinarians reporting several cases each month. However, traditional veterinary medicine has little to offer these patients other than symptomatic relief for the severe nausea that accompanies the vertigo and supportive advice for the owners. Owners of affected dogs are informed that these symptoms usually resolve within a few days. As physical therapists, we often see cases of benign paroxysmal positional vertigo in our human practice clinics, and effective protocols for diagnosis and treatment of the condition have been developed for this condition. A modified testing and repositioning postural maneuver used successfully on 12 canine patients in our canine rehabilitation clinic (The Canine Fitness Centre, Calgary, Alberta, Canada) is hereby described.

Galvanic vestibular stimulation: a novel modulatory countermeasure for vestibular-associated movement disorders.

Motion sickness or kinetosis is the result of the abnormal neural output originated by visual, proprioceptive and vestibular mismatch, which reverses once the dysfunctional sensory information becomes coherent. The space adaptation syndrome or space sickness relates to motion sickness; it is considered to be due to yaw, pith, and roll coordinates mismatch. Several behavioural and pharmacological measures have been proposed to control these vestibular-associated movement disorders with no success. Galvanic vestibular stimulation has the potential of up-regulating disturbed sensory-motor mismatch originated by kinetosis and space sickness by modulating the GABA-related ion channels neural transmission in the inner ear. It improves the signal-to-noise ratio of the afferent proprioceptive volleys, which would ultimately modulate the motor output restoring the disordered gait, balance and human locomotion due to kinetosis, as well as the spatial disorientation generated by gravity transition.

Vestibular dysfunction in patients with chronic pain or underlying neurologic disorders.

CONTEXT: Individuals with vestibular dysfunction are at increased risk for falling. In addition, vestibular dysfunction is associated with chronic pain, which could present a serious public health concern as approximately 43% of US adults have chronic pain. OBJECTIVE: To assess the incidence of vestibular dysfunction in patients receiving medication for chronic, noncancer pain or other underlying neurologic disorders and to determine associated follow-up therapeutic and diagnostic recommendations. METHODS: The authors conducted a retrospective medical record review of consecutive patients who were treated in their private neuroscience practice with medications for chronic pain or underlying neurologic disorders in 2011. All patients underwent a series of tests using videonystagmography for the assessment of vestibular function. Test results and recommendations for therapy and additional testing were obtained. RESULTS: Medical records of 124 patients (78 women, 46 men) were reviewed. Vestibular deficits were detected in 83 patients (66.9%). Patient ages ranged from 29 through 72 years, with a mean age of 50.7 years for women and 52.5 years for men. Physician-recommended therapy and follow-up testing were as follows: 32 patients (38.6%), neurologic examination and possible magnetic resonance (MR) imaging or computed tomography (CT) of the brain; 26 patients (31.3%), vestibular rehabilitation therapy only; 22 patients (26.5%), vestibular and related balance-function rehabilitation therapy, further neurologic examination, and possible MR imaging or CT; 2 patients (2.4%), balance-function rehabilitation therapy and specialized internal auditory canal high-magnification MR imaging or CT to assess for acoustic neuroma; and 1 patient (1.2%), specialized internal auditory canal high-magnification MR imaging or CT to evaluate for possible intracanalicular acoustic neuroma. CONCLUSION: Patients being treated with medications for chronic, noncancer pain or other underlying neurologic disorders may have a higher-than-average incidence of vestibular dysfunction. Baseline assessment and monitoring of the vestibular apparatus may be indicated for these patients.

Galvanic vestibular stimulation: a novel modulatory countermeasure for vestibular-associated movement disorders / Estimulacao galvanica vestibular para corrigir transtornos neurologicos associados a disfuncao vestibular

Motion sickness or kinetosis is the result of the abnormal neural output originated by visual, proprioceptive and vestibular mismatch, which reverses once the dysfunctional sensory information becomes coherent. The space adaptation syndrome or space sickness relates to motion sickness; it is considered to be due to yaw, pith, and roll coordinates mismatch. Several behavioural and pharmacological measures have been proposed to control these vestibular-associated movement disorders with no success. Galvanic vestibular stimulation has the potential of up-regulating disturbed sensory-motor mismatch originated by kinetosis and space sickness by modulating the GABA-related ion channels neural transmission in the inner ear. It improves the signal-to-noise ratio of the afferent proprioceptive volleys, which would ultimately modulate the motor output restoring the disordered gait, balance and human locomotion due to kinetosis, as well as the spatial disorientation generated by gravity transition.

A cinetose ou doença do movimento resulta de uma resposta neural anormal originada do desequilíbrio entre estímulos visuais, proprioceptivos e vestibulares, que melhora quando esse desequilíbrio é corrigido. A síndrome de adaptação espacial ou doença do espaço está relacionada à doença do movimento e é desencadeada por mudanças bruscas de direção, inclinação e rotação da cabeça. Têm sido propostas várias medidas comportamentais e farmacológicas para controlar esses transtornos do movimento associados com o sistema vestibular, mas sem sucesso. A estimulação galvânica vestibular pode regular o desequilíbrio sensitivo-motor causado pela cinetose e pela doença do espaço modulando os canais iônicos GABA, relacionados à transmissão de impulsos nervosos no ouvido interno. Essa estimulação melhora a relação sinal-ruído dos impulsos proprioceptivos que acabam modulando a resposta motora, restabelecendo o equilíbrio e a marcha, recuperando a desorientação espacial causada pelos diversos gradientes de gravidade.

Differential effect of dopa and subthalamic stimulation on vestibular activity in Parkinson's disease.

Postural disturbances in advanced Parkinson's disease are less responsive to therapy than other cardinal motor signs. The vestibulocollic reflex represents one brain-stem neuronal circuit involved in postural adjustments. The objective of this study was to investigate the vestibulocollic reflex in parkinsonian patients and the effects of subthalamic stimulation and dopa by recording vestibular-evoked myogenic potentials. After overnight withdrawal of medication, 20 patients with Parkinson's disease with (6 men, 4 women; mean age, 64.4 ± 2.2 years) or without (8 men, 2 women; mean age, 62.7 ± 3.9 years) implanted subthalamic electrodes in different treatment conditions were compared with 10 age-matched controls (5 men, 5 women; mean age, 59.6 ± 2.4 years). Vestibular-evoked myogenic potentials were recorded by electromyographic surface electrodes applied to both sternocleidomastoid muscles (band-pass filter, 8-1600 Hz; sampling rate, 5 kHz) and averaged in response to bilateral auditory tone bursts (120 dB SPL; sine waves, 7 ms; 1000 Hz) applied through earphones. Adjusted vestibular-evoked myogenic potential amplitudes were significantly smaller in parkinsonian patients than in controls, in particular in patients without surgery. Administration of dopa, but not subthalamic stimulation, significantly increased amplitudes. Onset latencies were similar for all groups and treatment conditions. Decreased vestibular-evoked myogenic potential amplitudes in parkinsonian patients suggest reduced vestibular nuclei excitability within the brain stem, which is modulated by dopa but not by subthalamic stimulation. This suggests different pathways for the action of both treatment modalities in Parkinson's disease and may explain clinical differences in terms of postural disturbances. © 2012 Movement Disorder Society.

Co-modulation of stimulus rate and current from elevated baselines expands head motion encoding range of the vestibular prosthesis.

An implantable prosthesis that stimulates vestibular nerve branches to restore sensation of head rotation and vision-stabilizing reflexes could benefit individuals disabled by bilateral loss of vestibular sensation. The normal vestibular system encodes head movement by increasing or decreasing firing rate of the vestibular afferents about a baseline firing rate in proportion to head rotation velocity. Our multichannel vestibular prosthesis emulates this encoding scheme by modulating pulse rate and pulse current amplitude above and below a baseline stimulation rate (BSR) and a baseline stimulation current. Unilateral baseline prosthetic stimulation that mimics normal vestibular afferent baseline firing results in vestibulo-ocular reflex (VOR) eye responses with a wider range of eye velocity in response to stimuli modulated above baseline (excitatory) than below baseline (inhibitory). Stimulus modulation about higher than normal baselines resulted in increased range of inhibitory eye velocity, but decreased range of excitatory eye velocity. Simultaneous modulation of rate and current (co-modulation) above all tested baselines elicited a significantly wider range of excitatory eye velocity than rate or current modulation alone. Time constants associated with the recovery of VOR excitability following adaptation to elevated BSRs implicate synaptic vesicle depletion as a possible mechanism for the small range of excitatory eye velocity elicited by rate modulation alone. These findings can be used toward selecting optimal baseline levels for vestibular stimulation that would result in large inhibitory eye responses while maintaining a wide range of excitatory eye velocity via co-modulation.

Auditory outcomes after implantation and electrical stimulation of the lateral ampullar nerve in guinea pig.

OBJECTIVE: To determine in a guinea pig model the factors of invasiveness of a bipolar electrode implanted in the horizontal semicircular canal (HSC) and to evaluate the consequences on hearing of electrical stimulation of the ampullary nerve. DESIGN: Sixteen guinea pigs divided into four groups underwent surgical opening of the HSC of one ear as follows: control (group 1), cyanoacrylate glue application on the HSC opening (group 2), electrode implantation with cyanoacrylate glue on the HSC opening (group 3), and electrode implantation with electrical stimulation (1 hr/day) for 9 days (group 4). Auditory brainstem responses were recorded before and after surgery and after electrical stimulation. The effectiveness of electrical stimulation in producing a horizontal vestibulo-ocular reflex was evaluated by recording eye movement with video-oculography. RESULTS: Group 1 animals showed hearing loss, and in group 2, sealing the HSC opening with cyanoacrylate glue preserved the hearing thresholds. After electrode implantation, seven of the eight animals showed hearing loss compared with preoperative values. Electrical stimulation did not induce additional hearing loss. CONCLUSION: Electrode implantation at the canal level entailed a risk of hearing loss in an animal model, but electrical stimulation of the horizontal ampullary nerve did not further alter hearing function.

[Perspectives in neurotology]. / Perspektiven der Gleichgewichtsdiagnostik und -therapie.

Vestibular diagnostics and therapy is the mirror of technological, scientific and socio-economics trends as are other fields of clinical medicine. These trends have led to a substantial diversification of the field of neurotology. The improvements in diagnostics have been characterized by the introduction of new receptor testing tools (e. g., VEMPs), progress in imaging (e. g., the endolymphatic hydrops) and in the description of central-vestibular neuroplasticity. The etiopathology of vestibular disorders has been updated by geneticists (e. g., the description of the COCH gene mutations), the detection of structural abnormalities (e. g., dehiscence syndromes) and related disorders (e. g. migraine-associated vertigo). The therapeutic options were extended by re-evaluation of techniques known a long time ago (e. g., saccus exposure), the development of new approaches (e. g., dehiscence repair) and the introduction of new drug therapy concepts (e. g., local drug delivery). Implantable, neuroprosthetic solutions have not yet reached experimental safety and validity and are still far away. However, externally worn neuroprosthetic solution were introduced in the rehab of vestibular disorders (e. g., VertiGuard system). These and related trends point into a medical future which is characterized by presbyvertigo as classical sign of the demographic changes ahead, by shortage of financial resources and a medico-legally over-regulated, even hostile environment for physicians in clinical medicine.

Improving balance function using vestibular stochastic resonance: optimizing stimulus characteristics.

Stochastic resonance (SR) is a phenomenon whereby the response of a non-linear system to a weak periodic input signal is optimized by the presence of a particular non-zero level of noise. Stochastic resonance using imperceptible stochastic vestibular electrical stimulation, when applied to normal young and elderly subjects, has been shown to significantly improve ocular stabilization reflexes in response to whole-body tilt; improved balance performance during postural disturbances and optimize covariance between the weak input periodic signals introduced via venous blood pressure receptors and the heart rate responses. In our study, 15 subjects stood on a compliant surface with their eyes closed. They were given low-amplitude binaural bipolar stochastic electrical stimulation of the vestibular organs in two frequency ranges of 1-2 and 0-30 Hz over the amplitude range of 0 to ±700 µA. Subjects were instructed to maintain an upright stance during 43-s trials, which consisted of baseline (zero amplitude) and stimulation (non-zero amplitude) periods. Measures of stability of the head and trunk using inertial motion unit sensors attached to these segments and the whole body using a force plate were measured and quantified in the mediolateral plane. Using a multivariate optimization criterion, our results show that the low levels of vestibular stimulation given to the vestibular organs improved balance performance in normal healthy subjects in the range of 5-26% consistent with the stochastic resonance phenomenon. In our study, 8 of 15 and 10 of 15 subjects were responsive for the 1-2- and 0-30-Hz stimulus signals, respectively. The improvement in balance performance did not differ significantly between the stimulations in the two frequency ranges. The amplitude of optimal stimulus for improving balance performance was predominantly in the range of ±100 to ±400 µA. A device based on SR stimulation of the vestibular system might be useful as either a training modality to enhance adaptability or skill acquisition, or as a miniature patch-type stimulator that may be worn by people with disabilities due to aging or disease to improve posture and locomotion function.

Effects of vestibular prosthesis electrode implantation and stimulation on hearing in rhesus monkeys.

To investigate the effects of vestibular prosthesis electrode implantation and activation on hearing in rhesus monkeys, we measured auditory brainstem responses (ABR) and distortion product otoacoustic emissions (DPOAE) in four rhesus monkeys before and after unilateral implantation of vestibular prosthesis electrodes in each of 3 left semicircular canals (SCC). Each of the 3 left SCCs were implanted with electrodes via a transmastoid approach. Right ears, which served as controls, were not surgically manipulated. Hearing tests were conducted before implantation (BI) and then 4 weeks post-implantation both without electrical stimulation (NS) and with electrical stimulation (S). During the latter condition, prosthetic electrical stimuli encoding 3 dimensions of head angular velocity were delivered to the 3 ampullary branches of the left vestibular nerve via each of 3 electrode pairs of a multichannel vestibular prosthesis. Electrical stimuli comprised charge-balanced biphasic pulses at a baseline rate of 94 pulses/s, with pulse frequency modulated from 48 to 222 pulses/s by head angular velocity. ABR hearing thresholds to clicks and tone pips at 1, 2, and 4 kHz increased by 5-10 dB from BI to NS and increased another ∼5 dB from NS to S in implanted ears. No significant change was seen in right ears. DPOAE amplitudes decreased by 2-14 dB from BI to NS in implanted ears. There was a slight but insignificant decrease of DPOAE amplitude and a corresponding increase of DPOAE/Noise floor ratio between NS and S in implanted ears. Vestibular prosthesis electrode implantation and activation have small but measurable effects on hearing in rhesus monkeys. Coupled with the clinical observation that patients with cochlear implants only rarely exhibit signs of vestibular injury or spurious vestibular nerve stimulation, these results suggest that although implantation and activation of multichannel vestibular prosthesis electrodes in human will carry a risk of hearing loss, that loss is not likely to be severe.