Controle postural na doença de Menière / Postural control in Menière's disease

RESUMO Objetivo Avaliar o controle postural na doença de Menière. Métodos 34 pacientes com doença de Menière definida (grupo experimental) e 34 indivíduos hígidos (grupo controle), homogêneos quanto à idade e ao gênero, foram submetidos à posturografia do Tetrax Interactive Balance System (Tetrax IBS TM) em oito condições sensoriais. Índice de estabilidade, índice de distribuição de peso, índice de sincronização da oscilação postural direita/esquerda e dedos/calcanhar, frequência de oscilação postural e índice de risco de queda foram analisados. Resultados O índice de estabilidade foi maior no grupo experimental, com diferença significativa entre os grupos, em todas as condições sensoriais testadas. O risco de queda foi maior no grupo experimental do que no grupo controle. A oscilação postural foi maior no grupo experimental em todas as faixas de frequência, com diferença significativa em algumas delas. Não houve diferença significativa entre os grupos nos índices de distribuição de peso e de sincronização, nas oito condições sensoriais avaliadas. Conclusão Pacientes com doença de Menière apresentam comprometimento do controle postural, caracterizado por alterações do índice de estabilidade, em frequências de oscilação postural e no índice de risco de queda.

ABSTRACT Purpose To evaluate postural control in Menière's disease. Methods 34 patients with Menière's disease (experimental group) and 34 healthy individuals (control group) were submitted to Tetrax Interactive Balance System posturography under eight sensory conditions. Stability, weight distribution, synchronization, risk of falling and postural oscillation frequency were analyzed. Results Stability index was higher in the experimental group with significant difference between the groups in all sensory conditions. Risk of falling was higher in the experimental group than in the control. Postural oscillation was higher in the experimental group in all frequency ranges, with significant difference in some of them. There was no significant difference between the groups in the weight distribution and synchronization indexes. Conclusion In this study, Menière's disease patients presented impaired postural control, characterized by postural instability and oscillation and risk of falling.

Superior Canal Dehiscence Syndrome: Relating Clinical Findings With Vestibular Neural Responses From a Guinea Pig Model.

HYPOTHESIS: In superior canal dehiscence (SCD), fluid displacement of the endolymph activates type I vestibular hair cells in the crista of the affected canal and thus irregular superior canal (SC) neurons in Scarpa's ganglion, which provides the neurophysiological basis for the clinical presentation of SCD. BACKGROUND: Patients with SCD display sound- and vibration-induced vertigo/nystagmus and increased amplitudes of vestibular evoked myogenic potentials. METHODS: Extracellular recordings from n = 25 primary vestibular neurons of 16 female guinea pigs were analyzed. We recorded from the same vestibular neuron before, during and after creating the dehiscence and after closing the dehiscence. Neurobiotin labeling was employed in n = 11 neurons. RESULTS: After SCD, previously unresponsive irregular SC neurons displayed a stimulus-locked increase in discharge during application of air-conducted sound (ACS) or bone-conducted vibration (BCV) for a broad range of frequencies (ACS: 200-4000 Hz; BCV: 500-1500 Hz). This typical response was only observed for irregular SC neurons (n = 19), but not regular SC neurons, or irregular/regular horizontal canal neurons (n = 2 each), and was abolished after closing the dehiscence. Eleven irregular SC neurons responsive to ACS and/or BCV were traced back to calyx synapses in the central crista of the affected superior canal by neurobiotin labeling. CONCLUSIONS: Stimulus-locked activation of irregular SC neurons by ACS and BCV is the neurophysiological basis for sound- and vibration-induced vertigo/nystagmus and increased VEMP amplitudes in SCD. The results of the present study help to improve vestibular diagnostics in patients with suspected SCD.

Air-Conducted Vestibular Evoked Myogenic Potential Testing in Children, Adolescents, and Young Adults: Thresholds, Frequency Tuning, and Effects of Sound Exposure.

OBJECTIVES: Pediatric vestibular evaluations incorporate cervical and ocular vestibular evoked myogenic potential (c- and oVEMP, respectively) testing; however, in children, c- and oVEMP thresholds have been minimally investigated and frequency tuning is unknown. Children are also at risk for unsafe sound exposure secondary to VEMP. While it is unknown if VEMP threshold testing leads to cochlear changes, it is possible that this risk increases due to the increased number of trials needed to obtain a threshold. Obtaining VEMP thresholds at various frequencies in children provides further information for pediatric normative VEMP data. Assessing for cochlear changes after VEMP threshold testing would provide information on the safety of threshold VEMP testing in children. The objectives of this study were to (1) characterize c- and oVEMP thresholds in children, adolescents, and young adults with normal hearing using 500 and 750 Hz tone burst (TB) stimuli, (2) compare frequency tuning of 500 and 750 Hz TB, and (3) assess whether cochlear changes exist after VEMP threshold testing. It is hypothesized that children, adolescents, and young adults would not show age-related changes to the vestibular system. Therefore, reliable VEMP thresholds would be seen below maximum acoustical stimulation levels (e.g., <125 dB SPL) and frequency tuning will be similar for 500 and 750 Hz TB stimuli. DESIGN: Ten children (age 4-9), 10 adolescents (age 10-19), and 10 young adults (age 20-29) with normal hearing and tympanometry participated. All subjects received c- and oVEMP testing at maximum stimulation and threshold. To address frequency tuning, but not exceed recommended sound exposure allowance, subjects received a 500 Hz TB stimulus in one ear and a 750 Hz TB stimulus in the other ear. Subjects completed tympanometry pre-VEMP, and audiometric threshold testing, distortion product otoacoustic emission testing, and subjective questionnaire pre- and post-VEMP to study the effect of VEMP exposure on cochlear function for each stimulus frequency. RESULTS: (1) cVEMP thresholds were determined for both stimulus frequencies for children (500 Hz = 106 dB SPL; 750 Hz = 106 dB SPL), adolescents (500 Hz = 107.5 dB SPL; 750 Hz = 109.5 dB SPL), and young adults (500 Hz = 111.5 dB SPL; 750 Hz = 112 dB SPL). oVEMP thresholds were also obtained in response to both stimulus frequencies for children (500 Hz = 111.1 dB SPL; 750 Hz = 112.2 dB SPL), adolescents (500 Hz = 112.5 dB SPL; 750 Hz = 114.5 dB SPL), and young adults (500 Hz = 116 dB SPL; 750 Hz = 117 dB SPL). Similar thresholds were found between groups except for children who had significantly lower thresholds compared with adults for cVEMP (500 Hz: p = 0.002; 750 Hz: p = 0.004) and oVEMP (500 Hz: p = 0.01; 750 Hz: p = 0.02). In addition, equivalent ear-canal volume and VEMP thresholds were linearly correlated. (2) There was no significant effect of stimulus frequency on VEMP response rates, latencies, peak to peak amplitudes, or thresholds, suggesting similar frequency tuning for 500 and 750 Hz. (3) There were no significant effects of VEMP threshold testing on cochlear function for either stimulus frequency. CONCLUSIONS: Children, adolescents, and young adults show VEMP thresholds below high stimulation levels and had similar frequency tuning between 500 and 750 Hz. Use of 750 Hz could be regarded as the safer stimuli due to its shorter duration and thus reduced sound exposure. Children with smaller ear-canal volume had present responses at maximum stimulation and lower thresholds, suggesting that VEMP testing could be initiated at lower acoustic levels to minimize sound exposure and optimize testing.

Inter-frequency amplitude ratio of oVEMP for differentiating Meniere's disease from BPPV: clinical validation using a double-blind approach.

OBJECTIVE: The study aimed at examining the usefulness of inter-frequency amplitude ratio (IFAR) of ocular vestibular evoked myogenic potential (oVEMP) in identifying Meniere's disease (MD) and differentiating it from benign paroxysmal positional vertigo (BPPV). DESIGN: A case-control design was used with a double blind approach. Phase 1 included 70 healthy individuals and 36 individuals each with MD and BPPV and Phase 2 included 20 individuals each with MD and BPPV. The age range of the participants in both phases was 15-50 years. All participants underwent oVEMP testing using 500 and 1000 Hz tone bursts and IFAR was obtained. RESULTS: The results in phase 1 revealed significantly higher IFARs in Meniere's disease than BPPV and healthy individuals (p < 0.001). An optimum criterion point of IFAR ≥1.11 for diagnosing MD was found which yielded 80% sensitivity and 98% specificity. The results in phase 2 demonstrated 85% correct identification of MD and 95% correct rejection of BPPV as non-MD. CONCLUSIONS: IFAR of oVEMP appears highly sensitive and specific parameter for identifying MD and a clinically valid tool for differentiating MD from BPPV.

Simultaneous recording of cervical and ocular vestibular-evoked myogenic potentials.

OBJECTIVE: To increase clinical application of vestibular-evoked myogenic potentials (VEMPs) by reducing the testing time by evaluating whether a simultaneous recording of ocular and cervical VEMPs can be achieved without a loss in diagnostic sensitivity and specificity. METHODS: Simultaneous recording of ocular and cervical VEMPs on each side during monaural stimulation, bilateral simultaneous recording of ocular VEMPs and cervical VEMPs during binaural stimulation, and conventional sequential recording of ocular and cervical VEMPs on each side using air-conducted sound (500 Hz, 5-millisecond tone burst) were compared in 40 healthy participants (HPs) and 20 patients with acute vestibular neuritis. RESULTS: Either simultaneous recording during monaural and binaural stimulation effectively reduced the recording time by ≈55% of that for conventional sequential recordings in both the HP and patient groups. The simultaneous recording with monaural stimulation resulted in latencies and thresholds of both VEMPs and the amplitude of cervical VEMPs similar to those found during the conventional recordings but larger ocular VEMP amplitudes (156%) in both groups. In contrast, compared to the conventional recording, simultaneous recording of each VEMP during binaural stimulation showed reduced amplitudes (31%) and increased thresholds for cervical VEMPs in both groups. CONCLUSIONS: The results of simultaneous recording of cervical and ocular VEMPs during monaural stimulation were comparable to those obtained from the conventional recording while reducing the time to record both VEMPs on each side. CLINICALTRIALSGOV IDENTIFIER: NCT03049683.

Effect of practicing yoga on cervical vestibular evoked myogenic potential.

The present study attempted to determine the effect of practicing yoga on functioning of sacculo-collic pathway using cervical vestibular evoked myogenic potential (cVEMP). cVEMP was recorded from 40 participants (20 who practice yoga regularly and 20 who do not practice yoga regularly). The differences in amplitude of P1, N1, P1-N1 complex, asymmetry ratio and latencies of P1 and N1 of cVEMP were compared between both the groups. The results of the study showed that there was a significant increase (p < 0.05) in the amplitude of P1, N1 and P1-N1 complex and a significant reduction in latency (p < 0.05) for experimental group. The asymmetry ratio in individuals who practice yoga was significantly lower (Mean = 6.73) compared to the control group (Mean = 19.13). Multivariate regression analyses suggested that the number of years of yoga practice significantly predicted the amplitude of P1-N1 complex (ß = 0.70, p < 0.01) and amplitude ratio (ß = 0.72, p < 0.01). Thus, practicing yoga improves postural control and strengthens the muscles and vestibular system leading to enhanced cVEMP responses. The plastic changes in the vestibular system and increased muscular strength because of constant practicing of yoga could have led to changes in cVEMP responses. However, further studies on a larger group of individuals are essential for better clinical applicability of the results.

Contrasting results of tests of peripheral vestibular function in patients with bilateral large vestibular aqueduct syndrome.

OBJECTIVE: To analyze and summarize the effect of bilateral large vestibular aqueducts in peripheral vestibular organ function. METHODS: Eighteen patients with bilateral large vestibular aqueduct syndrome (LVAS; Study Group) and 18 healthy volunteers (Control Group) were investigated using audiometry, caloric test, sensory organization test (SOT), and vestibular-evoked myogenic potential (VEMP) tests. RESULTS: All 18 patients (36 ears) exhibited sensorineural hearing loss. For cervical VEMP (cVEMP), the Study Group showed lower thresholds (Study Group vs. CONTROL GROUP: 71.4vs. 75.3dBnHL; p=0.006), N1 latencies (24.1vs. 25.2ms; p=0.026) and shorter P1 (15.3vs. 16.6ms; p=0.003), and higher amplitudes (400.7vs. 247.2µV; p<0.001) than the Control Group. For ocular VEMP (oVEMP), the Study Group had lower thresholds (79.3vs. 81.8dBnHL; p=0.046) and higher amplitudes (40.6vs. 14.4µV; p<0.001) than the Control Group. Fourteen of 16 patients (87.5%) who completed caloric tests had abnormal results, and 10 of 18 patients (55.6%) exhibited abnormal results in SOTs. CONCLUSIONS: The hyperfunction of vestibular test in otolithic organs and the hypofunction of vestibular test in semicircular canals, as well as the dysfunction in the balance test were demonstrated in patients with LVAS. SIGNIFICANCE: Our findings can help clinicians gain a better understanding of the characteristics of vestibular organ function in patients with LVAS, which can facilitate optimal targeted treatment.

Standing Up for Scope.

The Texas Medical Association triumphed when a Travis County district court sided with medicine in a lawsuit against the Texas Board of Chiropractic Examiners over its granting chiropractors the authority to perform certain diagnostic tests.

Effect of personal music system use on sacculocollic reflex assessed by cervical vestibular-evoked myogenic potential: A preliminary investigation.

Listening to music through a portable personal music system (PMS) is a growing trend, especially among the youth. The preferred listening level in such kinds of PMS has been reported to cross the safe levels and its impact on the auditory system was demonstrated in several previous investigations. Owing to the commonality in several aspects between the auditory and the vestibular systems, it appears likely that the deleterious effects of PMS use could also be impinging on the vestibular system, which has never been investigated. The present study therefore, aimed at evaluating the effects of PMS use on the sacculocollic reflex assessed by the cervical vestibular-evoked myogenic potential (cVEMP) technique. Thirty-two regular PMS users and 32 nonregular PMS users underwent cVEMP testing using alternating polarity 500 Hz tone bursts. The results revealed no significant group difference in latencies and interaural asymmetry ratio. However, the cVEMP was significantly reduced in the group of individuals in whom the diffused field equivalent sound pressure levels (SPLs) were above the damage risk criteria (DRC) compared to those with diffused field equivalent SPLs below it (P< 0.01). Therefore, the use of PMS at high levels of volume controls could be deleterious to the vestibular well-being of an individual.

Ocular vestibular evoked myogenic potentials to vertex low frequency vibration as a diagnostic test for superior canal dehiscence.

OBJECTIVE: To explore ocular vestibular evoked myogenic potentials (oVEMP) to low-frequency vertex vibration (125 Hz) as a diagnostic test for superior canal dehiscence (SCD) syndrome. METHODS: The oVEMP using 125 Hz single cycle bone-conducted vertex vibration were tested in 15 patients with unilateral superior canal dehiscence (SCD) syndrome, 15 healthy controls and in 20 patients with unilateral vestibular loss due to vestibular neuritis. Amplitude, amplitude asymmetry ratio, latency and interaural latency difference were parameters of interest. RESULTS: The oVEMP amplitude was significantly larger in SCD patients when affected sides (53 µVolts) were compared to non-affected (17.2 µVolts) or compared to healthy controls (13.6 µVolts). Amplitude larger than 33.8 µVolts separates effectively the SCD ears from the healthy ones with sensitivity of 87% and specificity of 93%. The other three parameters showed an overlap between affected SCD ears and non-affected as well as between SCD ears and those in the two control groups. CONCLUSIONS: oVEMP amplitude distinguishes SCD ears from healthy ones using low-frequency vibration stimuli at vertex. SIGNIFICANCE: Amplitude analysis of oVEMP evoked by low-frequency vertex bone vibration stimulation is an additional indicator of SCD syndrome and might serve for diagnosing SCD patients with coexistent conductive middle ear problems.

Electrophysiologic vestibular evaluation in type 2 diabetic and prediabetic patients: Air conduction ocular and cervical vestibular evoked myogenic potentials.

OBJECTIVE: Chronically increased blood glucose levels may affect the vestibular system by damaging cells and neural structures in diabetes mellitus (DM). We aimed to search the effects of neurovascular degeneration on the vestibular system in type 2 DM and prediabetic patients by using air-conducted ocular (oVEMP) and cervical (cVEMP) vestibular evoked myogenic potentials. DESIGN: Prospective study. STUDY SAMPLE: Thirty diabetic, 30 prediabetic patients, and 31 age- and sex-matched controls having no peripheral or central vestibular disease, were enrolled. All participants were evaluated by audiovestibular tests, oVEMP, and cVEMP. RESULTS: In the diabetic group, mean values of both oVEMP and cVEMP p1, n1 latencies were significantly longer compared to the prediabetic group and the control group, whereas latencies were similar in prediabetic and the control groups. Bilateral neural dysfunction was recognized in both tests and lateralization was not seen in VEMP asymmetric ratios. In the diabetic group, prevalence of pathological p1 and n1 latencies in oVEMP were 30.4% and 37.5%, whereas they were 53.7%, 59.3% in cVEMP, respectively. p1 latencies of cVEMP and oVEMP were positively correlated with HbA1c and fasting plasma glucose level in the diabetic group. CONCLUSION: Subclinical vestibular neuropathy can be a newly defined diabetes-related complication.

The effect of increased intracranial pressure on vestibular evoked myogenic potentials in superior canal dehiscence syndrome.

OBJECTIVE: To determine if vestibular evoked myogenic potential (VEMP) responses change during inversion in patients with superior canal dehiscence syndrome (SCDS) compared to controls. METHODS: Sixteen subjects with SCDS (mean: 43, range 30-57 years) and 15 age-matched, healthy subjects (mean: 41, range 22-57 years) completed cervical VEMP (cVEMP) in response to air conduction click stimuli and ocular VEMP (oVEMP) in response to air conduction 500 Hz tone burst stimuli and midline tap stimulation. All VEMP testing was completed in semi-recumbent and inverted conditions. RESULTS: SCDS ears demonstrated significantly larger oVEMP peak-to-peak amplitudes in comparison to normal ears in semi-recumbency. While corrected cVEMP peak-to-peak amplitudes were larger in SCDS ears; this did not reach significance in our sample. Overall, there was not a differential change in o- or cVEMP amplitude with inversion between SCDS and normal subjects. CONCLUSIONS: Postural-induced changes in o- and cVEMP responses were measured in the steady state regardless of whether the labyrinth was intact or dehiscent. SIGNIFICANCE: VEMP responses are blunted during inversion. Although steady-state measurements of VEMPs during inversion do not increase diagnostic accuracy for SCDS, the findings suggest that inversion may provide more general insights into the equilibration of pressures between intracranial and intralabyrinthine fluids.

Neural basis of new clinical vestibular tests: otolithic neural responses to sound and vibration.

Extracellular single neuron recording and labelling studies of primary vestibular afferents in Scarpa's ganglion have shown that guinea-pig otolithic afferents with irregular resting discharge are preferentially activated by 500 Hz bone-conducted vibration (BCV) and many also by 500 Hz air-conducted sound (ACS) at low threshold and high sensitivity. Very few afferent neurons from any semicircular canal are activated by these stimuli and then only at high intensity. Tracing the origin of the activated neurons shows that these sensitive otolithic afferents originate mainly from a specialized region, the striola, of both the utricular and saccular maculae. This same 500 Hz BCV elicits vestibular-dependent eye movements in alert guinea-pigs and in healthy humans. These stimuli evoke myogenic potentials, vestibular-evoked myogenic potentials (VEMPs), which are used to test the function of the utricular and saccular maculae in human patients. Although utricular and saccular afferents can both be activated by BCV and ACS, the differential projection of utricular and saccular afferents to different muscle groups allows for differentiation of the function of these two sensory regions. The basic neural data support the conclusion that in human patients in response to brief 500 Hz BCV delivered to Fz (the midline of the forehead at the hairline), the cervical VEMP indicates predominantly saccular function and the ocular VEMP indicates predominantly utricular function. The neural, anatomical and behavioural evidence underpins clinical tests of otolith function in humans using sound and vibration.

Differing response properties of cervical and ocular vestibular evoked myogenic potentials evoked by air-conducted stimulation.

OBJECTIVE: To determine the amplitude changes of vestibular evoked myogenic potentials (VEMPs) recorded simultaneously from the neck (cVEMPs) and eyes (oVEMPs) in response to 500 Hz, 2 ms air-conducted sound pips over a 30 dB range. METHODS: Fifteen healthy volunteers (mean age 29, range 18-57 years old) and one patient with unilateral superior canal dehiscence (SCD) were studied. The stimulus was reduced in increments to 105 dB pSPL for the normals (81 dB pSPL for the SCD patient). A statistical criterion was used to detect responses. RESULTS: Ipsilateral (i-p13/n23) and contralateral (c-n12/p24/n30) peaks for the cVEMP montage and contralateral (c-n10/p16/n21) and ipsilateral (i-n13) peaks for the oVEMP montage were present for the baseline intensity. For the lowest intensity, 6/15 subjects had responses for the i-p13 cVEMP potential and 4/15 had c-n10 oVEMP responses. The SCD patient showed larger responses for nearly all intensities. The cVEMP potentials were generally well fitted by a power law relationship, but the oVEMP c-n10, p16 and n21 potentials showed a significant increase in gradient for the higher intensities. CONCLUSION: Most oVEMP and cVEMP responses follow a power law relationship but crossed oVEMP responses showed a change in gradient above a threshold. SIGNIFICANCE: The pattern of response to AC stimulation may be a property of the pathways underlying the potentials.

Relationship between postural stability and spatial hearing.

BACKGROUND: Maintaining balance is known to be a multisensory process that uses information from different sensory organs. Although it has been known for a long time that spatial hearing cues provide humans with moderately accurate abilities to localize sound sources, how the auditory system interacts with balance mediated by the vestibular system remains largely a mystery. PURPOSE: The primary goal of the current study was to determine whether auditory spatial cues obtained from a fixed sound source can help human participants balance themselves as compared to conditions in which participants use vision. RESEARCH DESIGN: The experiment uses modified versions of conventional clinical tests: the Tandem Romberg test and the Fukuda Stepping test. In the Tandem Romberg test, participants stand with their feet in a heel-to-toe position, and try to maintain balance for 40 sec. In the Fukuda Stepping test, a participant is asked to close his or her eyes and to march in place for 100 steps. The sway and angular deviation of each participant was measured with and without vision and spatial auditory cues. An auditory spatial reference was provided by presenting a broadband noise source from a loudspeaker directly in front of the participant located 1-2 m away. STUDY SAMPLE: A total of 19 participants (11 women and 8 men; mean age = 27 yr; age range = 18∼52 yr), voluntarily participated in the experiment. All participants had normal vision, hearing, and vestibular function. INTERVENTION: The primary intervention was the use of a broadband noise source to provide an auditory spatial referent for balance measurements in the Tandem Romberg test and Fukuda Stepping test. Conditions were also tested in which the participants had their eyes opened or closed. DATA COLLECTION AND ANALYSIS: A head tracker recorded the position of the participant's head for the Tandem Romberg test. The angular deviation of the feet after 100 steps was measured in the Fukuda Stepping test. An average distance or angle moved by the head or feet was calculated relative to the head or feet resting position for each test. The average head sway or angular deviation was measured in an eyes-open condition (no sound), eyes-closed condition (no sound), and an eyes-closed condition with sound. Repeated-measures analysis of variance was used for both tests. RESULTS: The results showed a significant benefit in postural stability in both experiments when spatial auditory cues were present (p < .01). For the Tandem Romberg test, the benefit from spatial auditory cues alone is a 9% reduction in mean sway, as compared to 44% from visual cues alone. For the Fukuda Stepping test, the benefit from spatial auditory cues alone is a 76% reduction in mean body sway, as compared to 98% from visual cues alone. CONCLUSIONS: The current study demonstrated a connection between spatial hearing and balance. The experiments showed that a single fixed sound source can provide sufficient spatial cues for the central nervous system to better control postural stability. The compensation effect that the vestibular system receives from the auditory cues, however, is weaker than that received from visual cues.

The impact of stimulation rates in vestibular evoked myogenic potential testing.

UNLABELLED: Vestibular evoked myogenic potentials (VEMP) have been used in complementary otoneurological assessment, but the use of VEMP in clinical settings is limited. VEMPs can be used to assess vestibular function, particularly of the saccule, the inferior vestibular nerve, and/or the vestibular nucleus. OBJECTIVE: To verify the highest possible - and reliable - stimulation rate to obtain VEMPs. METHOD: The VEMPs of 18 subjects were acquired using stimulation rates ranging between 5.1 and 40.8 stimuli per second. STUDY DESIGN: cross-sectional contemporary cohort study. RESULTS: Latencies were kept unaltered and amplitudes were progressively reduced as stimulation rates were increased. However, ANOVA and the Kruskal-Wallis test failed to find statistically significant differences between the tested parameters. The study further indicated that when stimulation rates of 5.1 and 10.2 stimuli per second were compared, no statistically significant differences were observed in latency. CONCLUSION: The highest reliable stimulation rate observed in the group of young adults with normal hearing included in this study was 10.2 stimuli per second.

Interferencia da taxa de estimulo na avaliacao do potencial evocado miogenico vestibular / The impact of stimulation rates in vestibular evoked myogenic potential testing

Os potenciais miogênicos evocados vestibulares (VEMP) vêm sendo empregados como exame complementar para estudos otoneurológicos, ainda pouco explorados clinicamente. Esse potencial avalia a função vestibular, especificamente do sáculo, nervo vestibular inferior e/ou núcleo vestibular. OBJETIVO: Verificar a maior taxa de estímulos possível (e confiável) na obtenção do VEMP. MÉTODO: Foi registrado o potencial em 18 sujeitos, variando-se a taxa de estímulos entre 5,1 e 40,8 estímulos/s. Forma de estudo: Estudo de coorte contemporânea com corte transversal. RESULTADOS: As latências se mantiveram constantes e as amplitudes foram progressivamente reduzidas com o aumento da taxa de estimulação. Contudo, não houve diferença estatisticamente significativa entre os parâmetros simultaneamente, quando aplicados os testes ANOVA e Kruskal-Wallis. Os dados obtidos nesta pesquisa demonstraram que, quando comparadas as taxas de estimulação de 5,1 e 10,2 estímulos/s, houve ausência de diferença estatisticamente significativas para o parâmetro latência. CONCLUSÃO: Conclui-se que a maior taxa de estimulação confiável é a de 10,2 estímulos/s, para a amostra estudada de adultos jovens ouvintes normais. .

Vestibular evoked myogenic potentials (VEMP) have been used in complementary otoneurological assessment, but the use of VEMP in clinical settings is limited. VEMPs can be used to assess vestibular function, particularly of the saccule, the inferior vestibular nerve, and/or the vestibular nucleus. OBJECTIVE: To verify the highest possible - and reliable - stimulation rate to obtain VEMPs. METHOD: The VEMPs of 18 subjects were acquired using stimulation rates ranging between 5.1 and 40.8 stimuli per second. Study design: cross-sectional contemporary cohort study. RESULTS: Latencies were kept unaltered and amplitudes were progressively reduced as stimulation rates were increased. However, ANOVA and the Kruskal-Wallis test failed to find statistically significant differences between the tested parameters. The study further indicated that when stimulation rates of 5.1 and 10.2 stimuli per second were compared, no statistically significant differences were observed in latency. CONCLUSION: The highest reliable stimulation rate observed in the group of young adults with normal hearing included in this study was 10.2 stimuli per second. .

Evidence for the utricular origin of the vestibular short-latency-evoked potential (VsEP) to bone-conducted vibration in guinea pig.

Previous studies have shown that the vestibular short-latency-evoked potential (VsEP) in response to the brief head acceleration stimulus is a compound action potential of neurons innervating the otolith organs. However, due to the lack of direct evidence, it is currently unclear whether the VsEP is primarily generated by the activity of utricular or saccular afferent neurons, or some mixture of the two. Here, we investigated the origin of the VsEP evoked by brief bone-conducted vibration pulses in guinea pigs, using selective destruction of the cochlea, semicircular canals (SCCs), saccule, or utricle, along with neural blockade with tetrodotoxin (TTX) application, and mechanical displacements of the surgically exposed utricular macula. To access each end organ, either a dorsal or a ventral surgical approach was used. TTX application abolished the VsEP, supporting the neurogenic origin of the response. Selective cochlear, SCCs, or saccular destruction had no significant effect on VsEP amplitude, whereas utricular destruction abolished the VsEP completely. Displacement of the utricular membrane changed the VsEP amplitude in a non-monotonic fashion. These results suggest that the VsEP evoked by BCV in guinea pigs represents almost entirely a utricular response. Furthermore, it suggests that displacements of the utricular macula may alter its response to bone-conduction stimuli.

Compensatory role of saccule in deaf children and adults: novel hypotheses.

The aim of the present study is to measure sound sensitivity of the saccule for low frequencies in a population of both young and adult prelingual deaf patients using cervical Vestibular Evoked Myogenic Potentials (cVEMPs) and to correlate the findings obtained with the phonological features. The sensitivity of the saccule to sound stimuli is well known in previous studies. The functional role of the human saccule in responding to sound stimuli is still unclear. The study was conducted on a control population of young and adults with normal hearing. The outcomes showed that the amplitude of myogenic vestibular evoked potentials resulted the most significant parameter, indicating the degree of saccular response. We found in the group of deaf adults that the saccule retained an unaltered responsiveness to sound stimuli, without suffering the age-related functional decrease as demonstrated in normal hearing patients. We assumed that the high saccular response in deaf patients is determined by a constant somatosensory stimulation (rehabilitation) of the saccule, represented by the phonetic training. We correlated the phonetic features typical of the deaf with the sensitivity of the saccule to low frequencies. Such sensitivity makes this organ the ending point of the phonetic information (perception) but also the starting point of its regulation (production). Our experience demonstrates the phonetic role of saccule in the regulation of the human voice and provides the basis for further development of this topic. Thus we strongly believe that in the deaf the saccule plays a compensatory role. The high response of the saccule allows phonemic self-regulation, compensating the low/absent tone-verbal feedback. The saccule would come rightfully to be the accessory inner ear in deaf patients. We recommend the cVEMPs in the audio-phonological assessment before starting the speech therapy or during treatment to assess the degree of responsiveness of the saccule. The resulting data would give an extremely useful information that could be ignored by the pure tone audiometry. The presence of the cVEMPs in the deaf patient may improve the expectation of the performance of speech therapy.

Novel method for vestibular evoked myogenic potentials: technique and reproducibility.

OBJECTIVE: A novel method was employed to control the sternocleidomastoid muscle contraction level during vestibular evoked myogenic potential (VEMP) measurement. STUDY DESIGN: A prospective study to measure the normal VEMP response. SETTINGS: A pressure feedback device composed of a firm rubber bulb and a pressure gauge was employed to monitor the muscular contraction level during measurement. METHODS: Nineteen normal-hearing subjects (12 males; mean age 34.0 ± 7.7 years) were tested. Subjects were instructed to position the chin on the rubber bulb and use the neck flexors to maintain a pressure of 120 mm Hg during the measurement. MAIN OUTCOME MEASURES: The P13 latencies, N23 latencies, and P13-N23 amplitudes were recorded. In nine subjects, the reproducibility of the technique was tested weekly for 3 consecutive weeks. RESULTS: The average (± SD) latency of P13 was 13.97 ± 1.33 ms, and the latency of N23 was 24.03 ± 1.79 ms. The average amplitude was 66.89 ± 44.1 µV. There was no significant difference between right and left ears in P13 latencies, N23 latencies, and P13-N23 amplitudes. In nine subjects, the average measured interclass correlation coefficient was 0.97 in amplitude, 0.8 in P13 latency, and 0.93 in N23 latency in three consecutive weekly measurements. CONCLUSIONS: The chin-rest pressure feedback method is easy to perform during VEMP testing. Subjects can maintain a constant level of sternocleidomastoid contraction and neck flexion to facilitate this response with a high degree of test-retest reliability. This technique provides a means to compare VEMPs across different clinical scenarios over time.