Leen Maes

The vestibular evoked myogenic potential: A test–retest reliability study

OBJECTIVE The purpose of this study was to evaluate the reliability of the vestibular evoked myogenic potential (VEMP) response in a clinical setting when only a feedback mechanism is available for monitoring background EMG. METHODS Sixty-one healthy subjects participated in the investigation of the within-session reliability, whereas fourteen of them were retested after one week for examination of the between-session reliability. VEMPs were recorded using 500 Hz tone bursts with the subjects in a sitting position and their heads turned away from the test ear to the contralateral shoulder, thereby pushing their chin against the inflatable cuff of a blood pressure manometer, serving as feedback method. RESULTS The feedback method revealed latency and amplitude values comparable to other data in the literature where different test conditions were applied. Excellent reliability with ICC values ranging from 0.78 to 0.96 and CV(ME) values ranging from 4% to 36%, was achieved for P1 and N1 latency, threshold and interpeak amplitude. Good reliability with ICC values of 0.65 and 0.68 and CV(ME) values of 170% and 189%, was obtained for the asymmetry ratio. CONCLUSIONS A unilateral muscle contraction controlled by a feedback mechanism resulted in reliable response parameters, comparable right to left and corresponding to literature data obtained in different test conditions. SIGNIFICANCE The use of a blood pressure manometer as feedback mechanism combined with a meticulously controlled positioning of the head and contraction of the SCM muscle provides a reliable alternative in clinical settings, when the background muscle contraction cannot be measured or software related correction algorithms are not accessible.

Impact of newborn hearing screening: comparing outcomes in pediatric cochlear implant users.

To evaluate the impact of a newborn hearing screening program on the management and outcome of deaf children and to identify underlying factors that may be responsible for the differences between high and low performing implanted children.

The influence of a vestibular dysfunction on the motor development of hearing-impaired children.

To identify the predictive ability of vestibular function test results on motor performance among hearing‐impaired children.

Transient-evoked and distortion product otoacoustic emissions: A short-term test-retest reliability study

Abstract Knowledge regarding the variability of transient-evoked otoacoustic emissions (TEOAEs) and distortion product otoacoustic emissions (DPOAEs) is essential in clinical settings and improves their utility in monitoring hearing status over time. In the current study, TEOAEs and DPOAEs were measured with commercially available OAE-equipment in 56 normally-hearing ears during three sessions. Reliability was analysed for the retest measurement without probe-refitting, the immediate retest measurement with probe-refitting, and retest measurements after one hour and one week. The highest reliability was obtained in the retest measurement without probe-refitting, and decreased with increasing time-interval between measurements. For TEOAEs, the lowest reliability was seen at half-octave frequency bands 1.0 and 1.4 kHz; whereas for DPOAEs half-octave frequency band 8.0 kHz had also poor reliability. Higher primary tone level combination for DPOAEs yielded to a better reliability of DPOAE amplitudes. External environmental noise seemed to be the dominating noise source in normal-hearing subjects, decreasing the reliability of emission amplitudes especially in the low-frequency region. Sumario Es esencial conocer la variabilidad de las emisiones otoacústicas evocadas por transitorios (TEOAEs) y por productos de distorsión (DPOAEs) en ambientes clínicos para mejorar su utilidad en el monitoreo de la condición auditiva en el tiempo. En este estudio se midieron TEOAEs y DPOAEs con equipo de OAE comercialmente disponible en 56 oídos normales durante tres sesiones. La confiabilidad se analizó en el retest sin re-colocar la sonda, en el retest inmediato con recolocación de la sonda y con mediciones después de una hora y una semana. La mayor confiabilidad se obtuvo en el retest sin recolocación de la sonda y disminuyó a aumentar el intervalo entre mediciones. Con TEOAEs la confiabilidad más baja se observó en bandas de frecuencia en 1.0 y 1.4 kHz mien-tras que para las DPOAEs también la banda de frecuencia de media octava de 8 kHz tuvo también confiabilidad pobre. La combinación de niveles tonales primarios superiores con DPOAEs, llevó a una mejor confiabilidad de las amplitudes de las DPOAEs. El ruido ambiental externo parece ser la fuente de ruido dominante en sujetos normales, disminuyendo la confiabilidad de las amplitudes de la emisión, especialmente en la región de las frecuencias graves.

Auditory steady-state responses in normal hearing adults: a test-retest reliability study.

The test-retest reliability of the auditory steady-state response (ASSR) has received limited attention. Therefore, the aim was to assess the test-retest reliability of an 80-Hz multiple-ASSR system in normal-hearing subjects by a comprehensive set of statistical methods. Twenty-nine participants (15 females) aged between 18 and 30 years contributed to two sessions (test-retest), and the ASSR thresholds were determined with a descending search protocol using a 10-dB precision. The test-retest reliability was assessed by a three-layered approach which consisted of Pearson product-moment correlation, analysis of variance (ANOVA), and standard error of measurement (SEM). The correlations for ASSR thresholds ranged from poor (0.34) for 500 Hz CF to moderate (0.55) for 1000, 2000, and 4000 Hz CF. A two-way ANOVA of the difference scores (ASSR threshold minus behavioral threshold) demonstrated no significant difference between test and retest. The SEM determined the normal tolerance for clinical error of repeated thresholds and the ASSR SEM values fell well within ±10 dB HL. This investigation shows that the multiple ASSR-technique produces a clinically acceptable test-retest reliability for normal-hearing adults.

Rotatory and collic vestibular evoked myogenic potential testing in normal-hearing and hearing-impaired children

Objectives: Vertigo and imbalance are often underestimated in the pediatric population, due to limited communication abilities, atypical symptoms, and relatively quick adaptation and compensation in children. Moreover, examination and interpretation of vestibular tests are very challenging, because of difficulties with cooperation and maintenance of alertness, and because of the sometimes nauseatic reactions. Therefore, it is of great importance for each vestibular laboratory to implement a child-friendly test protocol with age-appropriate normative data. Because of the often masked appearance of vestibular problems in young children, the vestibular organ should be routinely examined in high-risk pediatric groups, such as children with a hearing impairment. Purposes of the present study were (1) to determine age-appropriate normative data for two child-friendly vestibular laboratory techniques (rotatory and collic vestibular evoked myogenic potential [cVEMP] test) in a group of children without auditory or vestibular complaints, and (2) to examine vestibular function in a group of children presenting with bilateral hearing impairment. Design: Forty-eight typically developing children (mean age 8 years 0 months; range: 4 years 1 month to 12 years 11 months) without any auditory or vestibular complaints as well as 39 children (mean age 7 years 8 months; range: 3 years 8 months to 12 years 10 months) with a bilateral sensorineural hearing loss were included in this study. All children underwent three sinusoidal rotations (0.01, 0.05, and 0.1 Hz at 50 degrees/s) and bilateral cVEMP testing. Results: No significant age differences were found for the rotatory test, whereas a significant increase of N1 latency and a significant threshold decrease was noticeable for the cVEMP, resulting in age-appropriate normative data. Hearing-impaired children demonstrated significantly lower gain values at the 0.01 Hz rotation and a larger percentage of absent cVEMP responses compared with normal-hearing children. Seventy-four percent of hearing-impaired children showed some type of vestibular abnormality when examined with a combination of rotatory and cVEMP testing, in contrast to an abnormality rate of 60% with cVEMP and a rate of 49% with rotatory testing alone. Conclusions: The observed pediatric age correlations underscore the necessity of age-appropriate normative data to guarantee accurate interpretation of test results. The high percentages of abnormal vestibular test results in hearing-impaired children emphasize the importance of vestibular assessment in these children because the integrity of the vestibular system is a critical factor for motor and psychological development.

Cobalt toxicity in humans—a review of the potential sources and systemic health effects

Cobalt (Co) and its compounds are widely distributed in nature and are part of numerous anthropogenic activities. Although cobalt has a biologically necessary role as metal constituent of vitamin B12, excessive exposure has been shown to induce various adverse health effects. This review provides an extended overview of the possible Co sources and related intake routes, the detection and quantification methods for Co intake and the interpretation thereof, and the reported health effects. The Co sources were allocated to four exposure settings: occupational, environmental, dietary and medical exposure. Oral intake of Co supplements and internal exposure through metal-on-metal (MoM) hip implants deliver the highest systemic Co concentrations. The systemic health effects are characterized by a complex clinical syndrome, mainly including neurological (e.g. hearing and visual impairment), cardiovascular and endocrine deficits. Recently, a biokinetic model has been proposed to characterize the dose-response relationship and effects of chronic exposure. According to the model, health effects are unlikely to occur at blood Co concentrations under 300μg/l (100μg/l respecting a safety factor of 3) in healthy individuals, hematological and endocrine dysfunctions are the primary health endpoints, and chronic exposure to acceptable doses is not expected to pose considerable health hazards. However, toxic reactions at lower doses have been described in several cases of malfunctioning MoM hip implants, which may be explained by certain underlying pathologies that increase the individual susceptibility for Co-induced systemic toxicity. This may be associated with a decrease in Co bound to serum proteins and an increase in free ionic Co2+. As the latter is believed to be the primary toxic form, monitoring of the free fraction of Co2+ might be advisable for future risk assessment. Furthermore, future research should focus on longitudinal studies in the clinical setting of MoM hip implant patients to further elucidate the dose-response discrepancies.

Effectiveness of hearing protector devices in impulse noise verified with transiently evoked and distortion product otoacoustic emissions

This study aimed to evaluate the effect of impulse noise on otoacoustic emissions (OAEs) while a passive non-linear earplug or an active level-dependent earmuff was worn. Since none of the standardized attenuation measurement techniques, REAT (real ear at threshold), ATF (acoustic test fixture), or MIRE (microphone in real ear), is designed to test both types in real-wearing condition, OAEs, suitable for detecting subtle changes in the functional integrity of the cochlear outer hair cells, are used. First, DPOAEs (distortion product) and TEOAEs (transiently evoked) of 24 subjects were compared before, immediately after gunfire practice, and after one hour of non-exposure. Secondly, both types of OAEs were evaluated in 31 subjects before and after exposure during a five-day military practice. Significant differences existed between the ears in most cases; the emissions from the right ear had a tendency to be more robust. There were no significant changes in OAEs either before and after exposure, or in the second experiment over multiple days. These findings suggest that the HPDs are able to prevent cochlear damage.

Mal de debarquement syndrome: a systematic review

Mal de debarquement (MdD) is a subjective perception of self-motion after exposure to passive motion, in most cases sea travel, hence the name. Mal de debarquement occurs quite frequently in otherwise healthy individuals for a short period of time (several hours). However, in some people symptoms remain for a longer period of time or even persist and this is then called mal de debarquement syndrome (MdDS). The underlying pathogenesis is poorly understood and therefore, treatment options are limited. In general, limited studies have focused on the topic, but the past few years more and more interest has been attributed to MdDS and its facets, which is reflected by an increasing number of papers. Till date, some interesting reviews on the topic have been published, but a systematic review of the literature is lacking and could help to address the shortcomings and flaws of the current literature. We here present a systematic review of MdD(S) based on a systematic search of medical databases employing predefined criteria, using the terms “mal de debarquement” and “sea legs”. Based on this, we suggest a list of criteria that could aid healthcare professionals in the diagnosis of MdDS. Further research needs to address the blank gaps by addressing how prevalent MdD(S) really is, by digging deeper into the underlying pathophysiology and setting up prospective, randomized placebo-controlled studies to evaluate the effectiveness of possible treatment strategies.

Examining the impact of cochlear implantation on the early gross motor development of children with a hearing loss

Objective: As deaf children are now implanted at a very early age, the influence of a cochlear implant (CI) on the early motor development of children with a hearing loss becomes relevant. Design: Forty-eight children with a hearing loss were included in this controlled prospective follow-up study and were subdivided into a CI group (n = 23) receiving a CI during the follow-up period and a control group (n = 25) receiving no CI during the follow-up period. All children were assessed around the ages of 6 (T1), 12 (T2), 18 (T3), and 24 (T4) months with a motor test battery consisting of the Peabody Developmental Motor Scales-2 (PDMS-2), Alberta Infant Motor Scales (AIMS) (only at T1 and T2), and Ghent Developmental Balance Test (GDBT) (only at T3 and T4). In addition, collic vestibular-evoked myogenic potential testing was performed in all children. Group differences in PDMS-2 Gross Motor Quotient (GMQ), Fine Motor Quotient, AIMS z score, and GDBT z score were analyzed using Linear Mixed Model (LMM) analysis for repeated measures. Results: For PDMS-2 GMQ, the LMM revealed significant effects for group (p = 0.04), test moment (p < 0.001), and for the interaction between these two factors (p = 0.035). Contrasts indicated that the CI group showed a greater deterioration in PDMS-2 GMQ between T2 and T3 compared with that showed by the control group (p = 0.002). The LMM for PDMS-2 Fine Motor Quotient and AIMS z score showed no significant effects. For GDBT z score, the LMM pointed out significant effects for group (p = 0.013) and test moment (p < 0.001), but no significant interaction between these two factors. Contrasts indicated that the CI group performed significantly weaker than the control group at both test moments (T3 and T4; all p < 0.012) and that both groups showed a significant recovery in GDBTz scores between T3 and T4 (all p < 0.012). Conclusions: This study shows that the trajectory of gross motor development can be changed in children with a hearing loss after a cochlear implantation. Implanted children show a drop in their gross motor performance within the age range of 6 to 18 months, at which period the majority of the implantations took place, with a tendency of recovery toward the age of 2 years. However, longer follow-up will be necessary to trace whether the implanted children catch up their motor delay in comparison with nonimplanted children with a hearing loss at later age.