Drafting a Surgical Procedure Using a Computational Anatomy Driven Approach for Precise, Robust, and Safe Vestibular Neuroprosthesis Placement-When One Size Does Not Fit All.

OBJECTIVE: To design and evaluate a new vestibular implant and surgical procedure that should reach correct electrode placement in 95% of patients in silico. DESIGN: Computational anatomy driven implant and surgery design study. SETTING: Tertiary referral center. PARTICIPANTS: The population comprised 81 patients that had undergone a CT scan of the Mastoid region in the Maastricht University Medical Center. The population was subdivided in a vestibular implant eligible group (28) and a control group (53) without known vestibular loss. INTERVENTIONS: Canal lengths and relationships between landmarks were calculated for every patient. The relationships in group-anatomy were used to model a fenestration site on all three semicircular canals. Each patient's simulated individual distance from the fenestration site to the ampulla was calculated and compared with the populations average to determine if placement would be successful. MAIN OUTCOME MEASURES: Lengths of the semicircular canals, distances from fenestration site to ampulla (intralabyrinthine electrode length), and rate of successful electrode placement (robustness). RESULTS: The canal lengths for the lateral, posterior, and superior canal were respectively 12.1 mm ±â€Š1.07, 18.8 mm ±â€Š1.62, and 17.5 mm ±â€Š1.23, the distances from electrode fenestration site to the ampulla were respectively 3.73 mm ±â€Š0.53, 9.02 mm ±â€Š0.90, and 5.31 mm ±â€Š0.73 and electrode insertions were successful for each respective semicircular canal in 92.6%, 66.7%, and 86.4% of insertions in silico. The implant electrode was subsequently revised to include two more electrodes per lead, resulting in a robustness of 100%. CONCLUSIONS: The computational anatomy approach can be used to design and test surgical procedures. With small changes in electrode design, the proposed surgical procedure's target robustness was reached.

Bilateral vestibulopathy: Diagnostic criteria Consensus document of the Classification Committee of the Bárány Society.

This paper describes the diagnostic criteria for bilateral vestibulopathy (BVP) by the Classification Committee of the Bárány Society. The diagnosis of BVP is based on the patient history, bedside examination and laboratory evaluation. Bilateral vestibulopathy is a chronic vestibular syndrome which is characterized by unsteadiness when walking or standing, which worsen in darkness and/or on uneven ground, or during head motion. Additionally, patients may describe head or body movement-induced blurred vision or oscillopsia. There are typically no symptoms while sitting or lying down under static conditions.The diagnosis of BVP requires bilaterally significantly impaired or absent function of the vestibulo-ocular reflex (VOR). This can be diagnosed for the high frequency range of the angular VOR by the head impulse test (HIT), the video-HIT (vHIT) and the scleral coil technique and for the low frequency range by caloric testing. The moderate range can be examined by the sinusoidal or step profile rotational chair test.For the diagnosis of BVP, the horizontal angular VOR gain on both sides should be <0.6 (angular velocity 150-300°/s) and/or the sum of the maximal peak velocities of the slow phase caloric-induced nystagmus for stimulation with warm and cold water on each side <6°/s and/or the horizontal angular VOR gain <0.1 upon sinusoidal stimulation on a rotatory chair (0.1 Hz, Vmax = 50°/sec) and/or a phase lead >68 degrees (time constant of <5 seconds). For the diagnosis of probable BVP the above mentioned symptoms and a bilaterally pathological bedside HIT are required.Complementary tests that may be used but are currently not included in the definition are: a) dynamic visual acuity (a decrease of ≥0.2 logMAR is considered pathological); b) Romberg (indicating a sensory deficit of the vestibular or somatosensory system and therefore not specific); and c) abnormal cervical and ocular vestibular-evoked myogenic potentials for otolith function.At present the scientific basis for further subdivisions into subtypes of BVP is not sufficient to put forward reliable or clinically meaningful definitions. Depending on the affected anatomical structure and frequency range, different subtypes may be better identified in the future: impaired canal function in the low- or high-frequency VOR range only and/or impaired otolith function only; the latter is evidently very rare.Bilateral vestibulopathy is a clinical syndrome and, if known, the etiology (e.g., due to ototoxicity, bilateral Menière's disease, bilateral vestibular schwannoma) should be added to the diagnosis. Synonyms include bilateral vestibular failure, deficiency, areflexia, hypofunction and loss.

Heterogeneity in Reported Outcome Measures after Surgery in Superior Canal Dehiscence Syndrome-A Systematic Literature Review.

BACKGROUND: Superior canal dehiscence syndrome (SCDS) can be treated surgically in patients with incapacitating symptoms. However, the ideal treatment has not been determined. OBJECTIVES: This systematic literature review aims to assess available evidence on the comparative effectiveness and risks of different surgical treatments regarding: (1) symptom improvement; (2) objectively measurable auditory and vestibular function; (3) adverse effects, and (4) length of hospitalization. SEARCH METHOD AND DATA SOURCES: A systematic database search according to PRISMA statement was conducted on Pubmed, Embase, and Cochrane library. In addition, reference lists were searched. No correspondence with the authors was established. The last search was conducted on June 9, 2017. STUDY ELIGIBILITY CRITERIA: Retrospective and prospective cohort studies were held applicable under the condition that they investigated the association between a surgical treatment method and the relief of vestibular and/or auditory symptoms. Only studies including quantitative assessment of the pre- to postoperative success rate of a surgical treatment method were included. Case reports, reviews, meta-analysis, and studies not published in English, Dutch, or German were excluded. DATA COLLECTION AND ANALYSIS: The first author searched literature and extracted data; the first and last analyzed the data. MAIN RESULTS: Seventeen studies (354 participants, 367 dehiscences) met the eligibility criteria and were grouped according to surgical approach. Seven combinations of surgical approaches and methods for addressing the dehiscence were identified: plugging, resurfacing, or a combination of both through the middle fossa (middle fossa approach); plugging, resurfacing, or a combination of both through the mastoid (transmastoid approach); round window reinforcement through the ear canal (transcanal approach). Several studies showed high internal validity, but quality was often downgraded due to study design (1). Outcome measures and timing of postsurgical assessment varied among studies, making it unfeasible to pool data to perform a meta-analysis. CONCLUSION: A standardized protocol including outcome measures and timeframes is needed to compare the effectiveness and safety SCDS treatments. It should include symptom severity assessments and changes in vestibular and auditory function before and after treatment.

The Vestibular Implant: Hearing Preservation during Intralabyrinthine Electrode Insertion-A Case Report.

OBJECTIVE: The vestibular implant seems feasible as a clinically useful device in the near future. However, hearing preservation during intralabyrinthine implantation remains a challenge. It should be preserved to be able to treat patients with bilateral vestibulopathy and (partially) intact hearing. This case study investigated the feasibility of hearing preservation during the acute phase after electrode insertion in the semicircular canals. METHODS: A 40-year-old woman with normal hearing underwent a translabyrinthine approach for a vestibular schwannoma Koos Grade IV. Hearing was monitored using auditory brainstem response audiometry (ABR). ABR signals were recorded synchronously to video recordings of the surgery. Following the principles of soft surgery, a conventional dummy electrode was inserted in the lateral semicircular canal for several minutes and subsequently removed. The same procedure was then applied for the posterior canal. Finally, the labyrinthectomy was completed, and the schwannoma was removed. RESULTS: Surgery was performed without complications. No leakage of endolymph and no significant reduction of ABR response were observed during insertion and after removal of the electrodes from the semicircular canals, indicting no damage to the peripheral auditory function. The ABR response significantly changed when the semicircular canals were completely opened during the labyrinthectomy. This was indicated by a change in the morphology and latency of peak V of the ABR signal. CONCLUSION: Electrode insertion in the semicircular canals is possible without acutely damaging the peripheral auditory function measured with ABR, as shown in this proof-of-principle clinical investigation.

Ocular Vestibular Evoked Myogenic Potentials

Introduction: Diagnostic testing of the vestibular system is an essential component of treating patients with balance dysfunction. Until recently, testing methods primarily evaluated the integrity of the horizontal semicircular canal, which is only a portion of the vestibular system. Recent advances in technology have afforded clinicians the ability to assess otolith function through vestibular evoked myogenic potential (VEMP) testing. VEMP testing from the inferior extraocular muscles of the eye has been the subject of interest of recent research. Objective: To summarize recent developments in ocular VEMP testing. Results: Recent studies suggest that the ocular VEMP is produced by otolith afferents in the superior division of the vestibular nerve. The ocular VEMP is a short latency potential, composed of extraocular myogenic responses activated by sound stimulation and registered by surface electromyography via ipsilateral otolithic and contralateral extraocular muscle activation. The inferior oblique muscle is the most superficial of the six extraocular muscles responsible for eye movement. Therefore, measurement of ocular VEMPs can be performed easily by using surface electrodes on the skin below the eyes contralateral to the stimulated side. Conclusion: This new variation of the VEMP procedure may supplement conventional testing in difficult to test populations. It may also be possible to use this technique to evaluate previously inaccessible information on the vestibular system...

Visual acuity while walking and oscillopsia severity in healthy subjects and patients with unilateral and bilateral vestibular function loss.

OBJECTIVES: To assess visual acuity (VA) while the patient is walking and to evaluate oscillopsia severity in patients with bilateral vestibulopathy (BV) and in patients with unilateral vestibular loss (UVL). DESIGN: Prospective study with a group of patients with BV, a group of patients with UVL, and a control group of healthy subjects. SETTING: Tertiary academic center. PARTICIPANTS: Thirty seven patients with BV(age range, 29-80 years), 11 patients with UVL (age range, 48-75 years), and 57 healthy subjects (age range 20-77 years). INTERVENTION: Computation of the difference between the VA measured in static conditions and in dynamic conditions while walking on a treadmill at 2, 4, and 6 km/h. Oscillopsia severity was assessed with a questionnaire that we developed. MAIN OUTCOME MEASURES: Differences in VA at 2, 4, and 6 km/h and oscillopsia severity score. RESULTS: As a group, patients with BV showed a significant increase of the VA differences compared with healthy subjects (P < .001) and patients with UVL (P < .001) for all 3 walking velocities. Normality thresholds were defined as healthy subjects' 95% CI. Sensitivity of the test was 97% for discriminating patients with BV. Moderate to extreme oscillopsia severity was found in 81% of patients with BV and in 9% of patients with UVL. Differences in VA did not correlate with oscillopsia severity scores in patients with BV (P > .05 for all comparisons). CONCLUSIONS: We designed a highly sensitive, simple, cost-effective protocol to assess dynamic VA under physiologic conditions and a questionnaire to determine oscillopsia severity. Both tools could be used for the evaluation of new treatments for BV and patients with UVL.

Potencial evocado miogênico vestibular / Vestibular evoked myogenic potential

INTRODUÇÃO: O Potencial Evocado Miogênico Vestibular (VEMP) é um teste promissor para a avaliação do sistema vestíbulo-cólico descendente. Este reflexo depende da integridade da mácula sacular, do nervo vestibular inferior, dos núcleos vestibulares, das vias vestíbulo-espinhais e do músculo efetor. OBJETIVO: Realizar revisão sistemática de literatura pertinente por meio de bases de dados (COCHRANE, MEDLINE, LILACS, CAPES). CONCLUSÃO: A aplicação clínica do VEMP expandiu-se nos últimos anos, com o objetivo de que este exame seja utilizado como complementar na avaliação otoneurológica atualmente utilizada. Porém, questões metodológicas devem ser esclarecidas. Dessa forma, este método, quando combinado com o protocolo padrão, poderá fornecer uma avaliação mais abrangente do sistema vestibular. A padronização da metodologia é fundamental critério para a replicabilidade e sensibilidade do exame.

INTRODUCTION: The Vestibular Evoked Myogenic Potential (VEMP) is a promising test for the evaluation of the cholic descending vestibular system. This reflex depends of the integrity from the saccular macula, from the inferior vestibular nerve, the vestibular nuclei, the vestibule-spinal tract and effectors muscles. OBJECTIVE: Perform a systematic review of the pertinent literature by means of database (COCHRANE, MEDLINE, LILACS, CAPES). CONCLUSION: The clinical application of the VEMP has expanded in the last years, as goal that this exam is used as complementary in the otoneurological evaluation currently used. But, methodological issues must be clarified. This way, this method when combined with the standard protocol, can provide a more widely evaluation from the vestibular system. The standardization of the methodology is fundamental criterion for the replicability and sensibility of the exam.

The modified ampullar approach for vestibular implant surgery: feasibility and its first application in a human with a long-term vestibular loss.

OBJECTIVE: To assess, for the first time in a human with a long-term vestibular loss, a modified approach to the ampullae and the feasibility of evoking a VOR by ampullar stimulation. MATERIALS AND METHODS: Peroperative stimulation of the ampullae, using the ampullar approach, was performed under full anesthesia during cochlear implantation in a 21-year-old female patient, who had experienced bilateral vestibular areflexia and sensorineural hearing loss for almost 20 years. RESULTS: The modified ampullar approach was performed successfully with as minimally invasive surgery as possible. Ampullar stimulation evoked eye movements containing vectors congruent with the stimulated canal. As expected, the preliminary electrophysiological data were influenced by the general anesthesia, which resulted in current spread and reduced maximum amplitudes of eye movement. Nevertheless, they confirm the feasibility of ampullar stimulation. CONCLUSION: The modified ampullar approach provides safe access to the ampullae using as minimally invasive surgery as possible. For the first time in a human with long-term bilateral vestibular areflexia, it is shown that the VOR can be evoked by ampullar stimulation, even when there has been no vestibular function for almost 20 years. This approach should be considered in vestibular surgery, as it provides safe access to one of the most favorable stimulus locations for development of a vestibular implant.

Double-blind clinical trial of thalamic stimulation in patients with Tourette syndrome.

Deep brain stimulation of the thalamus has been proposed as a therapeutic option in patients with Tourette syndrome who are refractory to pharmacological and psychotherapeutic treatment. Patients with intractable Tourette syndrome were invited to take part in a double-blind randomized cross-over trial assessing the efficacy and safety of stimulation of the centromedian nucleus-substantia periventricularis-nucleus ventro-oralis internus crosspoint in the thalamus. After surgery, the patients were randomly assigned to 3 months stimulation followed by 3 months OFF stimulation (Group A) or vice versa (Group B). The cross-over period was followed by 6 months ON stimulation. Assessments were performed prior to surgery and at 3, 6 months and 1 year after surgery. The primary outcome was a change in tic severity as measured by the Yale Global Tic Severity Scale and the secondary outcome was a change in associated behavioural disorders and mood. Possible cognitive side effects were studied during stimulation ON at 1 year postoperatively. Interim analysis was performed on a sample of six male patients with only one patient randomized to Group B. Tic severity during ON stimulation was significantly lower than during OFF stimulation, with substantial improvement (37%) on the Yale Global Tic Severity Scale (mean 41.1 ± 5.4 versus 25.6 ± 12.8, P = 0.046). The effect of stimulation 1 year after surgery was sustained with significant improvement (49%) on the Yale Global Tic Severity Scale (mean 42.2 ± 3.1 versus 21.5 ± 11.1, P = 0.028) when compared with preoperative assessments. Secondary outcome measures did not show any effect at a group level, either between ON and OFF stimulation or between preoperative assessment and that at 1 year postoperatively. Cognitive re-assessment at 1 year after surgery showed that patients needed more time to complete the Stroop Colour Word Card test. This test measures selective attention and response inhibition. Serious adverse events included one small haemorrhage ventral to the tip of the electrode, one infection of the pulse generator, subjective gaze disturbances and reduction of energy levels in all patients. The present preliminary findings suggest that stimulation of the centromedian nucleus-substantia periventricularis-nucleus ventro-oralis internus crosspoint may reduce tic severity in refractory Tourette syndrome, but there is the risk of adverse effects related to oculomotor function and energy levels. Further randomized controlled trials on other targets are urgently needed since the search for the optimal one is still ongoing.

Vestibulotoxicity as a consequence of systemically administered tobramycin in cystic fibrosis patients.

CONCLUSION: The reported prevalence of vestibulotoxicity (30.4%) in cystic fibrosis (CF) patients supports vestibulotoxicity screening in CF patients during or after tobramycin exposure. Prospective longitudinal investigation is required for a more specific evidence-based proposal. OBJECTIVE: To investigate the prevalence of tobramycin-induced vestibulotoxicity in CF patients, as it had not been investigated before. PATIENTS AND METHODS: In this observational cohort study, 23 CF patient volunteers from the Haga Teaching Hospital Adult CF centre who had been exposed to at least one treatment with systemically administered tobramycin were included. Subjective feelings of dizziness were measured using validated questionnaires and vestibular symptoms were assessed by physical examination. Electronystagmography (ENG) with caloric irrigation was used as the gold standard. RESULTS: Peripheral vestibular loss was found in seven patients (7/23 = 30.4%). Central vestibular loss was found in one patient. Analysis of the 19 completed questionnaires showed that 12 patients (12/19 = 63.2%) did not experience dizziness and 3 patients (3/19 = 15/8%) experienced specific vestibular symptoms. The results of the questionnaire could not predict the results of ENG with caloric irrigation. Physical examination showed no abnormalities in any patients. No age- or dose-related predictive factors were found.

Adverse patient occurrences in otorhinolaryngology: results of a systematic registry in a tertiary referral hospital.

OBJECTIVE: To identify patient groups at risk for Adverse Patient Occurrences (APOs) to improve the quality of care. STUDY DESIGN: This study was conducted using retrospective analysis. METHODS: APOs have been systematically registered from 1997 to 2006 in all patients (6,932) admitted to the otorhinolaryngology-head and neck surgery department of the University Hospital Maastricht, the Netherlands. Several characteristics such as length of stay, age, gender, season, and diagnosis were related to the incidence and type of APOs. RESULTS: Increasing age and length of stay are related to an increasing incidence of APOs. Children are found to be at high risk too and outpatient treatment (<24 h) is a risk factor for APOs. Of all APOs, 67% were organizational and 33% medical. The three diagnosis-related groups (DRGs), in which APOs occurred most, were the inner ear/cerebellopontine angle (CPA), esophagus, and head and neck oncology group. No seasonal influences on APO occurrences existed. CONCLUSIONS: Male and female patients >60 or <10 years old are at the highest risk for APOs. Their risk increases with their length of stay and is high when admitted less than 24 hours. When patients are among the three most prevalent DRGs, their risk is even higher.

Galvanic-induced body sway in vestibular schwannoma patients: evidence for stimulation of the central vestibular system.

OBJECTIVE: To investigate the various possible sites of excitation by galvanic stimulation by comparing the galvanic-induced body sway (GBS) in vestibular schwannoma (VS) patients with that in healthy subjects. MATERIAL AND METHODS: This was a prospective experimental study conducted in a tertiary referral centre. In a previous study we developed a standardized procedure for reproducible quantification of GBS using a monaural continuous 1-cosinusoidal stimulus (0.5 Hz; 2 mA). In this study, 23 VS patients were tested before and 12 VS patients were also tested after surgical intervention (extirpation of tumour with concomitant vestibular neurectomy) and the results were compared with those obtained in 47 healthy subjects. RESULTS: There were no significant differences in mean total GBS gain between VS patients and healthy subjects (p>0.05) before surgical intervention. After vestibular neurectomy a significant difference in the mean total GBS gain was observed, but GBS was still present after surgery. CONCLUSION: These results prove that galvanic vestibular stimulation excites the central vestibular system even when conduction via the vestibular nerve is hampered.