Low-frequency loud acoustic stimulation and goal-directed arm movements

OBJECTIVE: To analyse the effects of low-frequency loud acoustic stimulation on goal-directed movements involving the arm. Low-frequency sound stimulation impairs eye stability, evokes a subjective tilt of the visual surround in subjects presenting Tullio's phenomenon and induces, in normal subjects, short-latency evoked potentials in the neck and limb muscles. MATERIAL AND METHODS: Healthy subjects performed goal-directed movements in the horizontal plane with the right (dominant) arm to a fixed 3 degree-wide target positioned at an angle of 30 degrees, with the instruction to perform fast and accurate movements to the target and to hold the final position. This fast-pointing task was performed in association with sound-induced vestibular-otolithic stimulation (110 dB SPL, 500 Hz) in the absence of visual guidance (i.e. pointing at a memorized target in the absence of target or pointer cues). Pointing errors were analysed by computing the constant errors made by the subjects (mean error). Pointing errors were also correlated with movement kinematics (movement duration, peak velocity, time to peak velocity) and with the reaction time of movement. RESULTS: The low-frequency loud acoustic stimulation modified the final position of the arm-pointing task at the memorized target in the absence of vision. CONCLUSION: Goal-directed movements are achieved by means of sensory interactions between visual, somatosensory and vestibular information and the vestibular-otolithic signals contribute to the accuracy of voluntary arm movements.     

The impact of stimulation rates in vestibular evoked myogenic potential testing

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.ObjectiveTo verify the highest possible - and reliable - stimulation rate to obtain VEMPs.MethodThe 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.ResultsLatencies 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.ConclusionThe highest reliable stimulation rate observed in the group of young adults with normal hearing included in this study was 10.2 stimuli per second.     

Loudness balance between electric and acoustic stimulation

Binaural loudness balance between electric and acoustic stimulation is obtained in auditory brainstem implant listeners who had substantial acoustic hearing in one ear. The data are well described by a linear relationship between acoustic decibels and electric microamps. Based upon this linear relationship, we propose an exponential model of loudness growth in electric stimulation. The exponential model predicts that the loudness growth function can be determined solely by the threshold and the uncomfortable loudness level in electric stimulation. This prediction is consistent with previous psychophysical data on loudness functions. Implications of this finding for speech processor designs are discussed.     

Habituation to galvanic vestibular stimulation for analysis of susceptibility to carsickness

Objective In a previous study we developed a standardized procedure for a reproducible quantification of galvanic-induced body sway (GBS). In line with other reports, GBS shows short-term (fast) habituation upon stimulus repetition. The aim of this study was to evaluate whether the degree of short-term habituation to galvanic vestibular stimulation (GVS) is correlated with susceptibility to carsickness.

Material and Methods A total of 24 female subjects underwent computer-controlled GVS as part of a prospective experimental study conducted in a tertiary referral center. A binaural 1–cosinusoidal stimulus of 0.5 Hz and 1 mA was repeated five times. Binaural stimulation was chosen to obtain maximum responses, making possible habituation to repetitive GVS obvious. The groups consisted of 12 subjects suffering from carsickness and 12 healthy subjects.

Results Analysis of the repeated measurements test showed that the GBS–gain curve for the carsickness group was always superimposed on that for the healthy subjects. However, the (absolute) first to fifth GBS gains showed no significant differences (p=0.134?0.995). When comparing short-term habituation in subjects suffering from carsickness versus healthy subjects, the results showed no differences in the mean values of the first (30.534% vs 27.024%), final (42.637% vs 38.544%) and average (35.544% vs 33.644%) habituations (p=0.875, 0.991 and 0.951, respectively).

Conclusion We did not observe any significant differences in sensitivity or habituation of the GBS in carsick subjects compared to healthy subjects. This implies that carsick subjects show a similar ability to discard an irrelevant, non-motion sickness-inducing galvanic stimulus as healthy subjects.     

Unbiased stereologic type I and type II hair cell counts in human utricular macula

OBJECTIVE: The objective of the study was to obtain unbiased estimates of the total number of type I and type II hair cells in human utricular macula from individuals with documented normal vestibular function. STUDY DESIGN: Application of unbiased stereology using microdissected human temporal bone specimens was conducted in an observational study. METHODS: Postmortem temporal bones were obtained from 10 normal patients (age range, 42-96 y; mean age, 82 y). The utricular maculae were microdissected, embedded in plastic, and cut into serial 2-microm sections. Unbiased estimates of the total number of type I and type II hair cells were obtained using the physical fractionator technique of stereology. RESULTS: The average total number of hair cells was 27,508 (CV = 11%) consisting of 17,326 (coefficient of variation [CV] = 11%) type I hair cells and 10,182 (CV = 13%) type II hair cells. The ratio of type I to type II hair cells was 1.70:1. In the age range of the study, there was no statistically significant correlation between hair cell counts and age. CONCLUSIONS: Morphometric studies of the human utricular sensory epithelium can be accomplished using unbiased stereology on microdissected specimens. There was no effect of age on total hair cell counts or on the ratio of type I to type II hair cells in the age range of the study. Further studies on younger subjects are needed to establish the effect of age. The results from the present study are closely aligned with prior studies that estimated total hair cell counts using surface mount preparations. The current data represent the first total type I and type II hair cell counts in human utricular neuroepithelium.     

Sensitivity evaluation in air and water caloric stimulation of the vestibular organs using videonystagmography

Introduction

The aim of the study was to compare air and water caloric stimulation of the vestibular organs using videonystagmography (VNG).

Material and methods

The study covered 18 women aged 21–63 and 11 men aged 21–74 years hospitalized at the ENT, without complaints for vertigo and/or balance disorders. The alternate binaural bithermal caloric test with cool 30 °C and warm 44 °C air or water irrigations (after 2 h interval for the recordings) with the use of VNG was done.

Results

All parameters of air and water vestibular caloric stimulations, assessed in the VNG, differed significantly but were within the normal range. The research showed a statistically significant difference between canal paresis but only for the left ear at 30 °C and 44 °C. Absolute directional preponderance, relative directional preponderance, vestibular excitability, slow component velocity, frequency were different statistically for both ears at both temperatures.

Conclusions

Our study showed that both air and water caloric stimulations were able to distinguish physiological and impaired vestibular function. The obtained results showed statistically higher response for water than air stimulation.     

年龄因素对直流电刺激诱发的前庭诱发肌源性电位的影响

目的 评估年龄因素对直流电刺激(GVS)诱发的颈肌前庭诱发肌源性电位(cVEMP)和眼肌前庭诱发肌源性电位(oVEMP)的影响。 方法 选择健康志愿者61名(122耳)作为研究对象,22~81岁,平均(45.0±13.8)岁。按年龄分为20~40岁组(26例,52耳)、41~60岁组(24例,48耳)以及>60岁组(11例,22耳),分别记录GVS-cVEMP和GVS-oVEMP。计算GVS-c/oVEMP在不同年龄段的引出率、阈值、潜伏期、振幅、振幅不对称比(interaural amplitude asymmetryratio,IAR),采用SPSS18.0软件进行统计学分析。 结果 GVS-cVEMP在20~40岁、41~60岁、>60岁年龄段的引出率分别为96.15%、89.58%和95.45%,组间比较差异无统计学意义(P>0.05)。GVS-oVEMP在20~40岁、41~60岁、>60岁年龄段的引出率分别为98.07%、91.67%和72.13%,随着年龄增长逐渐降低(P<0.05)。从参数分析来看,cVEMP的引出率、阈值、p1潜伏期、n1潜伏期、振幅和振幅不对称比在不同年龄组间差异无统计学意义(P>0.05);随着年龄增大,oVEMP的引出率下降、阈值增高、振幅减小(P<0.05),其他参数年龄组间差异无统计学意义(P>0.05)。 结论 随着年龄的增长,周围前庭系统的功能降低,有可能会对直流电刺激诱发的VEMP产生影响。     

Efferent Actions in the Chinchilla Vestibular Labyrinth

Efferent fibers were electrically stimulated in the brain stem, while afferent activity was recorded from the superior vestibular nerve in barbiturate-anesthetized chinchillas. We concentrated on canal afferents, but otolith afferents were also studied. Among canal fibers, calyx afferents were recognized by their irregular discharge and low rotational gains. In separate experiments, stimulating electrodes were placed in the efferent cell groups ipsilateral or contralateral to the recording electrode or in the midline. While single shocks were ineffective, repetitive shock trains invariably led to increases in afferent discharge rate. Such excitatory responses consisted of fast and slow components. Fast components were large only at high shock frequencies (200–333/s), built up with exponential time constants <0.1 s, and showed response declines or adaptation during shock trains >1 s in duration. Slow responses were obtained even at shock rates of 50/s, built up and decayed with time constants of 15–30 s, and could show little adaptation. The more regular the discharge, the larger was the efferent response of an afferent fiber. Response magnitude was proportional to cv*^b, a normalized coefficient of interspike-interval variation (cv*) raised to the power b = 0.7. The value of the exponent b did not depend on unit type (calyx vs. bouton plus dimorphic, canal vs. otolith) or on stimulation site (ipsilateral, contralateral, or midline). Responses were slightly smaller with contralateral or midline stimulation than with ipsilateral stimulation, and they were smaller for otolith, as compared to canal, fibers. An anatomical study had suggested that responses to contralateral afferent stimulation should be small or nonexistent in irregular canal fibers. The suggestion was not confirmed in this study. Contralateral responses, including the large responses typically seen in irregular fibers, were abolished by shallow midline incisions that should have severed crossing efferent axons.     

Effect of stimulation repetition rate on galvanic-evoked vestibulo-collic reflexes

Conclusion Taking examination time and patient compliance into consideration, we propose that 5 Hz is the optimal stimulation rate of galvanic vestibular-evoked myogenic potentials for clinical use.

Objectives To evaluate the influence of stimulation repetition rate on galvanic-evoked vestibulo-collic reflexes and to propose the optimal stimulation rate for clinical use.

Material and methods Both ears of 30 healthy adults were tested at 5 different galvanic stimulation rates (1, 3, 5, 7 and 9 Hz) in a random order.

Results Responses were evident in all 60 ears only at 5 Hz; some ears showed no response at the other frequencies. The relative amplitudes in individual ears were higher at 1, 3 and 5 Hz than at 7 and 9 Hz. Comparison of the latencies of p13g and n23g showed no significant difference among the five stimulation rates.     

Promontory electrical stimulation to elicit vestibular evoked myogenic potentials (VEMPs)

Conclusion: Vestibular evoked myogenic potentials (VEMPs) provoked electrically at the promontory provide a feasible method to record vestibular responses in awake patients. Objectives: Electrically evoked VEMP testing has been performed by galvanic stimulation at the mastoid so far. The present study examined an electrical stimulation mode close to the otolith organs at the promontory. Methods: Fourteen cochlear implant candidates who were planned for clinical routine promontory stimulation testing (PST) to assess auditory nerve function underwent promontory VEMP testing. After testing the cochlear nerve function during PST promontory cervical VEMPs (p-c-VEMPs) and promontory ocular VEMPs (p-o-VEMPs) were recorded during subsequent transtympanic electrical stimulation at the promontory. Results: Promontory VEMP testing was well tolerated by the patients. Mean latencies for p-c-VEMPs were 10.30 ± 2.23 ms (p1) and 17.86 ± 3.83 ms (n1). Mean latencies for p-o-VEMPs were 7.64 ± 1.24 ms (n1) and 11.2 ± 1.81 ms (p1). The stimulation threshold level was measured at 0.15 ± 0.07 mA for p-c-VEMPs and at 0.19 ± 0.11 mA for p-o-VEMPs. The discomfort level was found to be at 0.78 ± 0.29 mA for p-c-VEMPs and at 0.69 ± 0.25 mA for p-oVEMPs. Mean p1-n1 amplitude in p-c-VEMPs was 124.78 ± 56.55 µV and p-o-VEMPs showed a mean n1-p1 amplitude of 30.94 ± 18.98 µV.     

Idiosyncratic compensation of the subjective visual horizontal and vertical in 60 patients after unilateral vestibular deafferentation

Objective To investigate long-term compensation mechanisms of utricular function after translabyrinthine surgery for vestibular schwannoma. Correlations between the subjective visual horizontal (SVH) and subjective visual vertical (SVV) and other parameters of vestibular compensation were studied. The correlation between the SVH and SVV was also investigated to see whether these measurements are compatible for patients.

Material and Methods Sixty consecutive patients were investigated 3 months before and 6 months after surgery by means of electronystagmography and SVH and SVV tests. Tumor size was measured using MRI.

Results The SVH and SVV increased significantly towards the ipsilesional side postoperatively. Preoperative tilt correlated with age. Postoperative tilt correlated weakly with preoperative caloric sensitivity and inversely with tumor size. The correlation between the SVH and SVV was high both before and after surgery (r_s>0.74; p<0.001).

Conclusions The long-term compensation of static tilt perception was dependent on age and not on dynamic canal functions. We propose an idiosyncrasy in the SVH and SVV compensation after unilateral vestibular deafferentation, incongruous with the general course of vestibular compensation. The results suggest a probable dependence on non-vestibular information, i.e. proprioception, in facilitating compensation of static vestibular deficits. The similarity between the SVH and SVV measurements confirms that either test can be used clinically for patients with vestibular lesions.     

Optimizing maps for electric acoustic stimulation users

Objectives: To optimize patient’s maps in Electric Acoustic Stimulation (EAS) users based on the degree of post-operative aided hearing thresholds.

Methods: Twenty-one adult EAS patients participated in this study. Patients were subdivided into three groups, based on their unaided hearing threshold: (1) electric complementary (EC, n?=?6) patients with ≤30?dB HL at 125–500?Hz with severe to profound hearing loss at higher frequencies who only use electric stimulation, (2) EAS (n?=?8) patients with 30–70?dB HL from 125 to 250?Hz and profound hearing loss in high frequencies who use combined EAS, and (3) Marginal-EAS (M-EAS, n?=?7) patients with 70–95?dB HL at frequencies ≤250?Hz who use combined EAS. Sentence perception in noise, melodic contour identification, and subjective preference were measured using Full Overlap, Narrow Overlap, Gap, and Meet maps.

Result: Of the 21 patients that participated, 12 subjects were classified as complete hearing preservation and 9 subjects were classified as partial hearing preservation. The highest performing maps in sentence-in-noise perception and melodic contour identification were Gap, Meet, and Full Overlap for the EC, EAS, and the M-EAS groups, respectively. These results are consistently across different test materials and align with subject preference as well.

Conclusion: These results suggest that clinical fitting in EAS listening should be individually tailored. EAS performance can be enhanced by optimizing maps between acoustic and electric stimulation based on the degree of aided hearing thresholds.     

Combining acoustic and electric stimulation in the service of speech recognition

Abstract

The majority of recently implanted, cochlear implant patients can potentially benefit from a hearing aid in the ear contralateral to the implant. When patients combine electric and acoustic stimulation, word recognition in quiet and sentence recognition in noise increase significantly. Several studies suggest that the acoustic information that leads to the increased level of performance resides mostly in the frequency region of the voice fundamental, e.g. 125 Hz for a male voice. Recent studies suggest that this information aids speech recognition in noise by improving the recognition of lexical boundaries or word onsets. In some noise environments, patients with bilateral implants can achieve similar levels of performance as patients who combine electric and acoustic stimulation. Patients who have undergone hearing preservation surgery, and who have electric stimulation from a cochlear implant and who have low-frequency hearing in both the implanted and not-implanted ears, achieve the best performance in a high noise environment.

Sumario

La mayoría de los usuarios recientes de implante coclear, pueden potencialmente beneficiarse de un auxiliar auditivo en el oído contralateral al implantado. Cuando los pacientes combinan la estimulación eléctrica y acústica, el reconocimiento de palabras en silencio y el reconocimiento de oraciones aumenta significativamente. Algunos estudios sugieren que la información acústica que permite el mayor nivel de rendimiento, reside sobre todo en la región frecuencial de la fundamental de la voz, p.ej., 125 Hz en la voz masculina. Estudios recientes sugieren que esta información ayuda para reconocer el lenguaje en ruido, mejorando el reconocimiento de las transiciones lexicales que ocurren en el inicio de las palabras. En algunos ambientes, los pacientes con implante bilateral pueden alcanzar niveles similares de rendimiento a los de quienes combinan la estimulación eléctrica con la acústica. Los pacientes que han sido sujetos de cirugía para preservar la audición, y que tienen estimulación eléctrica de un implante coclear y audición en las frecuencias graves tanto en el oído implantado como en el no implantado, alcanzan los mejores rendimientos en ambientes con ruido intenso.     

Hearing preservation in cochlear implantation for electric acoustic stimulation

Objective To evaluate the possibility of preservation of low-frequency hearing in atraumatic cochlear implant electrode insertion procedures for combined, ipsilateral electric and acoustic stimulation.

Material and Methods A total of 21 patients were implanted with a MED EL C40+ cochlear implant using an atraumatic electrode insertion technique to preserve residual low-frequency hearing. Pure-tone audiometric thresholds were measured pre- and postoperatively to evaluate the degree of preserved hearing. Speech discrimination tests in quiet and with background noise were performed in a patient with successful hearing preservation.

Results Using the atraumatic electrode insertion procedure with an insertion depth of 360° (18–24 mm), hearing preservation could be achieved in 18/21 patients (85.7%). Three patients (14.3%) lost their residual low-frequency hearing after the implantation. Residual hearing was preserved completely in 13 patients (61.9%) and partial hearing preservation was possible in 5 (23.8%). Preliminary speech discrimination tests showed a dramatic benefit for the combined electric and acoustic stimulation mode compared to cochlear implantation alone.

Conclusion Preservation of low-frequency hearing in cochlear implantation is possible in patients implanted because of profound high-frequency deafness. With the development of new, more atraumatic electrode designs, preservation of residual hearing should be further improved.     

Comparison of auditory single fiber responses during acoustic and electric stimulation of the intact cat cochlea

Summary Electric stimulation of the cat round window showed that thresholds of auditory afferents differ and are independent of characteristic frequency (CF). Vestibular fibers are also activated.Supported by the DFG (SFB 45)Presented at the 18th Workshop on Inner Ear Biology in Montpellier/La Grande Motte, September 14–16, 1981     

Utricular paresis and semicircular canal hyperactivity: a distinct otolith syndrome

Conclusions: Although combined utricular and canal paresis has been described previously, this is the first report of canal hyperactivity associated with utricular hypofunction. Unsteadiness and swaying were the most common symptoms, and patients with shorter duration of symptoms also had positional vertigo. We propose that this syndrome is a variant of utricular dysfunction and should be considered in the differential diagnosis of peripheral vestibular disorders. Objective: To describe a syndrome of instability associated with utricular dysfunction and hyperactive caloric responses. Methods: The study comprised 11 consecutive patients exhibiting abnormalities of the eccentric subjective visual vertical test (e-SVV) and high responses during the caloric test of the videonystagmography (VNG). We carried out a review of symptoms, physical examination, and vestibular tests. Results: There was no gender predilection or obvious etiology. The patients’ main complaint included instability with linear symptoms (i.e., tilting, rocking, and swaying), with positional vertigo as a secondary symptom. Oculomotor testing, visual fixation index, and brain MRI were normal, excluding a central nervous system disorder. VNG was essentially normal except for hyperactive responses during the caloric testing in all patients. Abnormal e-SVV was found in 10 patients unilaterally and bilaterally in 1 patient. Abnormal oVEMP was found in seven of seven patients, further supporting a utricular site of lesion.     

Development and evaluation of an improved cochlear implant electrode design for electric acoustic stimulation

OBJECTIVE: The objective of this study was to assess the intracochlear position and the extent of trauma to cochlear structures using a new prototype electrode carrier (Flex EAS). Special emphasis was placed on the practicality for combined electric and acoustic stimulation of the auditory system. STUDY DESIGN: Human temporal bones were evaluated histologically after insertion of the electrodes, and insertion forces were measured in an acrylic model of the scala tympani. METHODS: 1) Insertion forces with the regular C40+ array and the new electrode prototype were measured in an acrylic model of the scala tympani. 2) Ten human temporal bones were implanted using the same surgical procedure as in vivo. All bones underwent fixation methylmethacrylate embedding to allow cutting of the undecalcified bone with the electrode in situ. In addition, radiography of the implanted devices was performed and correlated to histologic results. Electrode positions and trauma to cochlear structures were then evaluated histologically. RESULTS: All insertions of the new electrode array were performed in the scala tympani of the cochlea. All insertions were atraumatic and covered one cochlear turn. The only effect on cochlear structures that could be observed was a slight lifting of the basilar membrane in the middle turn limited to the tip of the electrode. In three bones, basal trauma, which resulted from the cochleostomy itself, could be observed as well. All neural structures remained intact. CONCLUSIONS: The new electrode prototype provides very good mechanical properties for safe and atraumatic implantation. All criteria for the use in hearing-preservation cochlear implantation for electric and acoustic stimulation were fulfilled. Surgical measures to prevent basal trauma appear to be very important.     

选择注意与对侧声刺激对畸变产物耳声发射潜伏期的影响

目的 :观察选择注意和对侧声刺激对畸变产物耳声发射 (DPOAE)潜伏期的影响。方法 :对正常人15例 (30耳 ) ,进行视选择注意任务及对侧声刺激 ,以及两者同时出现时 DPOAE潜伏期测试。结果 :3种测试条件下 DPOAE潜伏期皆无变化。结论 :选择注意和对侧声刺激对 DPOAE潜伏期是否存在影响 ,尚需进一步研究。     

Eye movements evoked by the selective stimulation of the utricular nerve in cats

Objective: Eye movements evoked by otolith organ are not well-investigated compare with canal related eye movements due to the technical difficulties. We try to solve this problem by means of our methods. Methods: Eye movements evoked by selective utricular (UT) nerve stimulation were investigated using both electrooculography (EOG) and video recording in decerebrated cats in the presence or absence of anesthesia. Electrical stimulation was applied to the UT nerve through implanted acupuncture needles. Results: In the absence of anesthesia and with stimulus intensities less than 2.6±0.7×N₁T, we found ipsilaterally directed horizontal eye movements in both eyes in one cat, abduction in the ipsilateral eye in two cats, and adduction in the contralateral eye in another cat. Other types of eye movements (e.g., supraduction or diagonal eye movements) were observed in both eyes of cats in the absence of anesthesia at a stimulus intensity of 12.2±7.6×N₁T, an intensity in which current spread to the adjacent nerve could not be ruled out. In the presence of anesthesia, UT nerve stimulation alone failed to evoke horizontal eye movements, but with an intensity 13.8±6.4×N₁T, supraduction or diagonal eye movements were evoked. UT nerve stimulation at 2–3×N₁T facilitated horizontal eye movements induced by ipsilateral abducens (AB) nucleus stimulation or contralateral horizontal canal nerve stimulation. Conclusion: This is the first report to our knowledge in which UT nerve-evoked horizontal eye movements are documented. These results confirm the known monosynaptic and disynaptic anatomical connections from utricular primary afferents to the ipsilateral AB nucleus neurons.     

重复经颅磁刺激治疗慢性前庭综合征疗效评价

目的 探讨重复经颅磁刺激(rTMS)治疗慢性前庭综合征(CVS)的疗效.方法 慢性前庭综合征(CVS)患者60例,随机数字法分为对照组和治疗组各30例,两组均进行垂直方向和水平方向的平稳跟踪眼动练习,治疗组另加以rTMS治疗4周.以治疗前后两组患者的头晕评价量表(DHI)评分、冷热试验单/双侧半规管反应减退(UW)值为...