R. Vanspauwen

Validity of a new feedback method for the VEMP test.

Conclusions. We used a feedback method, based on a blood pressure manometer with inflatable cuff, to control the sternocleidomastoid muscle (SCM) contraction. To obtain comparable left-right VEMP responses, it is necessary (1) to determine which cuff pressures on both sides yield identical mean rectified voltage (MRV) values of the SCM contraction and (2) to apply these cuff pressures during the VEMP test. Objective. To investigate the ffect of the SCM muscle contraction variability on the VEMP variables when applying the feedback method. Materials and methods. Subjects pushed with their jaw against the hand-held inflated cuff to generate cuff pressures of subsequently 30, 40 and 50 mmHg during a MRV and VEMP measurement. Results. When analyzing the relationship between the applied cuff pressures and the MRV values/VEMP amplitudes, we showed that (1) there was a linear relationship, (2) there was no side effect and (3) there was an interaction effect between ‘side’ and ‘subject’. There was neither a side effect, nor an effect of the applied cuff pressure when considering the p13 latencies. As for the n23 values, there was no side effect but there was a significant difference when comparing the n23 latencies at cuff pressures of 30 vs 40 mmHg/50 mmHg.

Meniett therapy: rescue treatment in severe drug-resistant Ménière's disease?

Conclusion. Our data indicate that Meniett therapy is unlikely to be helpful in the long-term treatment of patients with severe, drug-resistant Ménières disease (MD) in whom injection of intratympanic gentamicin (ITG) or another destructive procedure would otherwise be performed. Objective. To investigate the value of Meniett therapy in patients with drug-resistant MD referred for injection of ITG. Material and methods. Twelve patients referred for ITG treatment were followed during a 2-month period of Meniett therapy. Symptoms, functional level and hearing status were evaluated using a standardized staging system. Disease-specific quality-of-life measures were obtained before and after Meniett therapy. At the end of the study period, patients were followed for a mean of 37 months, thus providing long-term outcome data. Results. In two patients, Meniett treatment was interrupted after 1 month because of persistent severe vertigo. In the remaining 10 subjects, we found a significant decrease in the median number of vertigo spells from 10.0/month (25th–75th percentile 4.0–19.0) prior to treatment to 3.0/month (25th–75th percentile 1.5–4.5) after treatment (p=0.02). There was, however, no improvement in hearing status, tinnitus, functional level or self-perceived dizziness handicap. Long-term (>1 year) follow-up data revealed that only 2 subjects preferred to continue Meniett therapy and that ablative surgery had to be performed in 6/12 study patients.

A New Model for Utricular Function Testing Using a Sinusoidal Translation Profile during Unilateral Centrifugation

The utricle plays an important role in orientation with respect to gravity. The unilateral centrifugation test allows a side-by-side investigation of both utricles. During this test, the subject is rotated about an earth-vertical axis at high rotation speeds (e.g. 400°/s) and translated along an interaural axis to consecutively align the axis of rotation with the left and the right utricle. A simple sinusoidal translation profile (0.013 Hz; amplitude = 4 cm) was chosen. The combined rotation and translation induces ocular counter rolling (OCR), which is measured using 3-D video-oculography. This OCR is the sum of the reflexes generated by both the semicircular canals and the utricles. In this paper, we present a new physiological model that decomposes this total OCR into a canal and a utricular contribution, modelled by a second-order transfer function and a combination of 2 sine functions, respectively. This model yields parameters such as canal gain, cupular and adaptation time constants and a velocity storage component for the canals. Utricular gain, bias, phase and the asymmetry between the left and the right utricle are characteristic parameters generated by the model for the utricles. The model is presented along with the results of 10 healthy subjects and 2 patients with a unilateral vestibular loss due to acoustic neuroma surgery to illustrate the effectiveness of the model.

A re-investigation of the role of utricular asymmetries in space motion sickness

During the first days of spaceflight, about 50-70% of the astronauts experience symptoms of Space Motion Sickness (SMS). It has been proposed that an asymmetry between the left and right otolith organs contributes to an astronauts individual susceptibility. A recently developed test to measure unilateral utricular function enabled us to re-investigate this so-called otolith asymmetry hypothesis, while using the paradigm of sustained centrifugation as a ground based model for SMS. This latter paradigm has been shown to elicit symptoms similar to those of SMS and is referred to as Sickness Induced by Centrifugation (SIC). In 15 healthy subjects unilateral utricular function was assessed by recording ocular counter rolling during a unilateral centrifugation paradigm. In addition, saccular function was assessed by recording Vestibular Evoked Myogenic Potentials (VEMPs), and horizontal semicircular canal function was assessed using bithermal caloric stimulation. SIC-susceptible subjects showed a marginally higher degree of utricular asymmetry, utricular sensitivity and semicircular canal sensitivity (p < 0.1) than the non-susceptible group. Interestingly, a logistic regression model using both utricular and semicircular canal parameters led to a correct classification of 91% of the subjects. As such, these results suggest that otolith asymmetry is at most one factor - and not present in all susceptible subjects - in defining susceptibility to SMS and SIC. Both the utricular and the canal system might be involved as well.

Vestibular evoked myogenic potentials: test-retest reliability and normative values obtained with a feedback method for the sternocleidomastoid muscle contraction

OBJECTIVE To determine normal limits and to analyse the test-retest reliability of the vestibular evoked myogenic potentials (VEMPs) parameters. METHODS The VEMP procedure was repeated on different test days to analyze test-retest differences. We calculated several reliability parameters: intraclass reliability coefficient (ICC), method error (ME), coefficient of variation of the method error (CV(ME)), standard error of measurement (SEM) and minimal difference (MD) for test-retest measurements. Normal values for left-right differences, based on the interaural ratio (IAR), were determined. RESULTS For each VEMP parameter, the ICC values indicated excellent reliability, except for p13 and corrected amplitude (fair to good reliability). The CV(ME)) values were less than 7% for p13, n23, threshold, MRV(females) and MRV(males). For the parameters corrected amplitude and raw amplitude, the CV(ME)) values exceeded 15%. The 95% IAR prediction intervals (PIs) were also largest for the parameters raw amplitude and corrected amplitude. CONCLUSION In order to evaluate a VEMP outcome in a patient, the VEMP parameters and IAR values can be compared with the 95% PI of the normal values. When successive measurements are performed within the same subjects, the minimal difference (MD) serves as a tool to decide whether these differences are clinically relevant or not.

Respiratory sinus arrhythmia on the ESA-short-arm human centrifuge

In this article, we investigated the hypothesis that the effects of hypergravity on respiratory sinus arrhythmia (RSA) can mimic the effects observed after spaceflight cardiovascular deconditioning. Artificial gravity along the head-to-feet axis on a short-arm centrifuge induces gravity gradients. This physiological condition of significantly higher g at the feet than at the heart level is specific and likely induces blood sequestration in the lower limbs. After spaceflight, astronauts are in a condition of cardiovascular deconditioning, where blood pooling in the lower part of the body and autonomic adaptation are factors contributing to orthostatic intolerance and changes in heart-rate variability (HRV). ECG and respiration were recorded during imposed and controlled breathing (ICB) protocols, which were repeated at different levels of artificial gravity as well as during supine and standing control conditions, and the changes were analyzed.

Baclofen affects the semicircular canals but not the otoliths in humans.

Abstract Conclusion: This study showed that GABAB agonist baclofen (10 mg) affects the semicircular canals (SCCs), both centrally and peripherally, but does not influence the otolithic function. Objectives: The aim of the study was to identify the effects of baclofen on the complete vestibular system, i.e. semicircular canals, saccules and utricles. Methods: The study had a double-blind, placebo-controlled, repeated measures design and was conducted on healthy male volunteers. With electronystagmography (ENG), the SCC function was evaluated, whereas utricular function was determined by means of unilateral centrifugation (UC). Cervical vestibular evoked myogenic potentials (cVEMPs) tested saccular integrity. Results: Baclofen caused a significant increase of the vestibulo-ocular reflex (VOR) phase and a significant decrease of the total caloric response (TCR), both measured during ENG. The drug also decreased the maximal contribution of the SCCs to ocular counter-rolling (OCR) evaluated during UC. No effects on saccules and utricules were observed.

Wireless Vestibular Evoked Myogenic Potentials System

Existing commercial vestibular evoked myogenic potentials (VEMP) testing systems are cabled systems, which impede certain experiments, particularly those that involve motion and rotation of the patient. This paper presents an autonomous wireless system to record VEMPs. The system uses IMECs 60 muW 60 nV/VHz biopotential readout front-end to extract the electromyogram (EMG). It uses IMECs low power processing and wireless platform to perform all signal processing locally, significantly reducing the amount of wireless data transmission. The system also implements a low power audio synthesizer and an amplifier to create the necessary audio or vibration stimuli that are applied to the patient. The system can perform 1000 measurements on 2 AA batteries.

Reliability of utricular function testing using a sinusoidal translation profile during unilateral centrifugation

The unilateral centrifugation test is one of the few vestibular tests that evaluate the utricles side by side. During this test, a subject is rotated about an earth vertical axis at high rotation speeds (e.g. 400 °/s) and translated sideways along the interaural axis to align the axis of rotation consecutively with the right and the left utricle. The combined rotation and translation induces ocular counter rolling (OCR), which is measured using three-dimensional video-oculography. Recently, a new model has been proposed to analyse the OCR. The model is based on contributions from both the semicircular canals and the utricles. Concomitant with the new model a new stimulation profile using a sinusoidal translation profile during the unilateral centrifugation has been introduced [1]. The current study presents the test-retest reliability as well as the robustness of the new stimulation method, based on data of 67 healthy subjects. Test-retest reliability was based on repeated measurements of a group of subjects. To test the robustness of the new sinusoidal translation paradigm, we investigated the effect of a different amplitude of the sinusoidal translation (6 cm instead of 4 cm) and of an offset in translation (from −3 to +5 cm, instead of from −4 to +4 cm) on the parameters. Several statistical measures were used to reflect the reliability: intraclass correlation coefficient (ICC), the “coefficient of variation of the method error” and the “minimal difference” (MD). All relevant variables from the physiological model for the OCR induced by unilateral centrifugation show a good to excellent reliability during the test-retest study and the relevant parameters remain unaffected by the changes applied to the translation profile (p > 0.05) as predicted by the model. Additionally, all observed differences are smaller than the MD values calculated in the test-retest part of the study.

Contents Vol. 15, 2010

Maurizio Barbara, Rome Olivier Bertrand, Bron F. Owen Black, Portland Th omas Brandt, München Barbara Canlon, Stockholm John P. Carey, Baltimore Douglas A. Cotanche, Boston Cor W.R.J. Cremers, Nijmegen Norbert Dillier, Zürich Robert Dobie, Sacramento Manuel Don, Los Angeles Jill B. Firszt, St. Louis Andrew Forge, London Bernard Fraysse, Toulouse Rick Friedman, Los Angeles Bruce J. Gantz, Iowa City Pablo Gil-Loyzaga, Madrid Anthony W. Gummer, Tübingen James W. Hall III, Gainesville Joseph W. Hall III, Chapel Hill Michael Halmagyi, Camperdown Rudolf Häusler, Bern Vicente Honrubia, Los Angeles Gary D. Housley, Auckland Karl-Bernd Hüttenbrink, Köln Pawel J. Jastreboff , Atlanta Margaret A. Kenna, Boston Philippe P. Lefebvre, Liège Bernd Lütkenhöner, Münster Linda L. Luxon, London Geoff rey A. Manley, Oldenburg Alessandro Martini, Ferrara Jennifer R. Melcher, Boston Saumil N. Merchant, Boston Brian C.J. Moore, Cambridge David R. Moore, Nottingham Cynthia C. Morton, Boston Donata Oertel, Madison Kaoru Ogawa, Tokyo Stephen J. O’Leary, Parkville Alan R. Palmer, Nottingham Lorne S. Parnes, London, Ont. Jean-Luc Puel, Montpellier Ramesh Rajan, Monash Yehoash Raphael, Ann Arbor J. Th omas Roland, New York John J. Rosowski, Boston Rudolf Rübsamen, Leipzig Mario A. Ruggero, Evanston Leonard P. Rybak, Springfi eld Richard J. Salvi, Buff alo Robert V. Shannon, Los Angeles Guido F. Smoorenburg, Besse sur Issole Haim Sohmer, Jerusalem Olivier Sterkers, Clichy Istvan Sziklai, Debrecen Peter R. Th orne, Auckland Shin-ichi Usami, Matsumoto P. Ashley Wackym, Portland Tatsuya Yamasoba, Tokyo Fan-Gang Zeng, Irvine The Science of Hearing and Balance