Electroacoustic evaluation of the bone conduction transducer B250 for vestibular and hearing diagnostics in comparison with Radioear B71 and B81.

OBJECTIVE: The objective is to evaluate the electroacoustic performance of the B250 transducer and to compare it with the two most widely used audiometric transducers B71 and B81. DESIGN: The electroacoustic performance was evaluated in terms of sensitivity level, distortion, maximum hearing level and electrical impedance. STUDY SAMPLE: Six B250 prototype transducers were evaluated and compared with published data of B71 and B81 together with complementary measurements of maximum hearing level at 125 Hz and phase of electrical impedance. Differences in reference equivalent threshold vibratory force levels were estimated by comparing hearing threshold measurements of 60 healthy ears using B81 and B250. RESULTS: B250 has approximately 27 dB higher sensitivity levels than both B71 and B81 at 250 Hz and can generate higher maximum hearing level at low frequencies: 11.8 to 35.8 dB (125-1000 Hz) higher than B71, and 1.4 to 18.6 dB (125-750 Hz) higher than B81. The maximum average difference in reference threshold force levels was 13.5 ± 8.7 dB higher for B250 at 250 Hz compared to B81. CONCLUSIONS: B250 can produce higher output force with less distortion than B71 and B81, especially at 125 and 250 Hz, which could possibly improve low frequency investigations of the audio-vestibular system.

Vestibular function in children with vestibulocochlear nerve aplasia/hypoplasia.

BACKGROUND: Infants and young children with vestibulocochlear nerve (VCN) hypoplasia/aplasia present with severe hearing loss and are candidates for cochlear implantation (CI). It is unknown whether vestibular function is related to CI outcome and if vestibular tests can guide the operation decision. AIMS/OBJECTIVES: Our aim was to describe the vestibular function in patients with VCN hypoplasia/aplasia before a possible CI. MATERIALS AND METHODS: Forty-two ears in 23 patients were tested between 2019 and 2022 with bone-conducted cervical vestibular evoked myogenic potentials (BCcVEMP), video head impulse test (vHIT) and miniice-water caloric test (mIWC). RESULTS: All ears could be tested with at least one vestibular test and 83% could be tested with more than one method. Twenty-nine ears (61%) showed normal function with at least one method. The presence of a normal response to any test doubled the likelihood of a measured hearing threshold after CI, the best predictors being the BCcVEMP and vHIT (p < 0.05). CONCLUSION: Canal function may represent a predictor of auditive pathway integrity with a possible favourable audiological outcome after CI operation. SIGNIFICANCE: Our results demonstrate high vestibular response rates suggesting a functioning pathway despite the radiological diagnosis.

The Validation of a Simultaneous Ocular and Cervical VEMP Recording Protocol to Unilateral AC Stimuli.

INTRODUCTION: A simultaneous recording of cervical and ocular vestibular evoked myogenic potential (sVEMP) to unilateral air-conducted (AC) stimulation reduces the test time and halves the sound load. MATERIALS AND METHODS: The sVEMP has been compared with the conventional sequential unilateral AC cervical and ocular VEMP in a consecutive cohort of 120 subjects attending the vestibular laboratory. The stimulus was a 500-Hz 6-ms tone burst, at 130 dB peSPL for sequential recordings but at 125 dB for the added sVEMP, for cumulative sound load containment. Amplitudes, latencies, and amplitude asymmetry ratios (ARs) were the parameters included in analysis. RESULTS: Relevant results were as follows: 1) significantly lower amplitudes in sVEMP versus VEMP (ocular recordings, median = 2.90 [IQR = 0-4.98] vs. 4.15 [1.73-8.98] µV, p < 0.001; cervical, 0.84 [0.30-1.69] vs. 1.36 [0.60-2.30], p < 0.001; electromyography scaled values); 2) 10% lower response rate at cervical recordings and 11% at ocular recordings in sVEMP, particularly in older subjects; 3) significant correlations between cervical amplitudes ( rs = 0.88, p < 0.001), ocular amplitudes ( rs = 0.71, p < 0.001), peak latencies ( rs = 0.36-0.67, p < 0.001), and ARs (ocular, rs = 0.56; cervical, rs = 68, p < 0.001); and 4) good agreement in pathological AR detection (cervical recordings, Cohen's κ = 0.649, p < 0.001; ocular, κ = 0.589, p < 0.001). DISCUSSION: AC sVEMP showed good correlation/agreement with sequential AC VEMP. Test time containment and halved sound load are clinical adds in sVEMP, opening to its use as laboratory standard. However, AC sVEMP presented reduced amplitudes and response rates, secondary to the reduced AC stimulation used in this study to allow checking of the null responses and the pathological ARs at AC sVEMP with conventional AC VEMP.

Vestibular Loss in Children Affected by LVAS and IP2 Malformation and Operated with Cochlear Implant.

This is a single center cohort study regarding the prevalence of vestibular loss in hearing impaired children affected by large vestibular aqueduct syndrome (LVAS) with incomplete cochlear partition malformation type II (IP2), fitted with cochlear implant (CI). Twenty-seven children received CI operations at 0.4-13 years on one or both ears and tested for vestibular loss with head impulse test, video head impulse test, mini ice-water test and cervical VEMP. Vestibular loss was found in 19% of operated ears and in 13.9% of non-operated ears. The difference was not statistically significant and was not significantly modified by age at implantation, age at testing, sex, presence of SLC26A4 gene mutation or bilaterality. However, the presence of anatomic anomalies at the level of the vestibulum or semicircular canals was significantly associated with a higher incidence of vestibular loss in CI operated children but not in those non-operated. No other factors, such as the surgical access, the electrode type, the presence of Gusher perioperatively, or post-operative vertigo modified significantly the prevalence of vestibular loss. In conclusion, LVAS/IP2 appears to be the major determinant of vestibular loss in these children, with a less obvious impact of CI, excluding the cases with vestibulum/canal anomalies: this group might have a higher risk for vestibular loss after CI surgery.

Ankle Audiometry: A Clinical Test for the Enhanced Hearing Sensitivity for Body Sounds in Superior Canal Dehiscence Syndrome.

INTRODUCTION: The aim of this study was to develop a clinical test for body sounds' hypersensitivity in superior canal dehiscence syndrome (SCDS). METHOD: Case-control study, 20 patients affected by SCDS and body sounds' hypersensitivity and 20 control matched subjects tested with a new test called ankle audiometry (AA). The AA consisted of a psychoacoustic hearing test in which the stimulus was substituted by a controlled bone vibration at 125, 250, 500, and 750 Hz, delivered at the medial malleolus by a steel spring-attached bone transducer prototype B250. For each subject, it was defined an index side (the other being non-index), the one with major symptoms in cases or best threshold for each tested frequency in controls. In 3 patients, the AA was measured before and after SCDS surgery. RESULTS: The AA thresholds for index side were significantly lower in SCDS patients (115.6 ± 10.5 dB force level [FL]) than in control subjects (126.4 ± 8.56 dB FL). In particular, the largest difference was observed at 250 Hz (-16.5 dB). AA thresholds in patients were significantly lower at index side in comparison with non-index side (124.2 ± 11.4 dB FL). The response obtained with 250 Hz stimuli outperformed the other frequencies, in terms of diagnostic accuracy for SCDS. At specific thresholds' levels (120 dB FL), AA showed relevant sensitivity (90%) and specificity (80%) for SCDS. AA did not significantly correlate to other clinical markers of SCDS such as the bone and air conducted hearing thresholds and the vestibular evoked myogenic potentials. The AA thresholds were significantly modified by surgical intervention, passing from 119.2 ± 9.7 to 130.4 ± 9.4 dB FL in 3 patients, following their relief in body sounds' hypersensitivity. CONCLUSION: AA showed interesting diagnostic features in SCDS with significantly lower hearing thresholds in SCDS patients when compared to healthy matched subjects. Moreover, AA could identify the affected or more affected side in SCDS patients, with a significant threshold elevation after SCDS surgery, corresponding in body sounds' hypersensitivity relief. Clinically, AA may represent a first objective measure of body sounds' hypersensitivity in SCDS and, accordingly, be an accessible screening test for SCDS in not tertiary audiological centers.

Wideband tympanometry in ears with superior canal dehiscence before and after surgical correction.

OBJECTIVES: Wideband tympanometry (WBT) has been shown to be sensitive to mechanical changes in the ear. This study investigated the effect of surgical correction of superior canal dehiscence (SCD) on WBT (i.e. absorbance and middle ear resonance frequency) compared to those on common surgical outcomes such as symptom resolution, vestibular evoked myogenic potentials (VEMP), and hearing thresholds. STUDY SAMPLE AND STUDY DESIGN: Seven patients (eight ears with SCD) who underwent surgical correction of SCD underwent WBT in addition to pure-tone audiometry and VEMP assessment. RESULTS: Postoperatively, all ears showed normalised/decreased absorbance at low frequencies and slightly enhanced absorbance in the middle frequency range (7/8 ears). The middle ear resonance frequency, which was initially lower than normal in most patients, increased in 6/8 operated ears, and decreased in two ears with no/partial symptom relief. In comparison, complete symptom control was observed in 6/8 operated ears, VEMP amplitudes reduced or normalised in all ears, and hearing thresholds remained stable or improved in 6/8 ears and worsened in two ears. CONCLUSIONS: Surgery seems to change the response to WBT in patients with SCD. The results of WBT may represent mechanical changes induced by SCD, and should be considered when evaluating surgical outcomes.

Identical twins affected by congenital cytomegalovirus infections showed different audio-vestibular profiles.

This study explored whether there were long-term hearing and vestibular outcome differences between five pairs of identical twins who had been infected with the congenital cytomegalovirus (CMV) infection before birth. Data were collected from the medical records at the Audiological Clinic, Karolinska University Hospital, Stockholm. The congenital CMV infection resulted in high variations in vestibular and hearing function within, and between, the genetically identical twin pairs. Clinicians need to be aware that treatment and interventions may need to differ substantially when identical twins have hearing issues related to the congenital CMV infection.

The feasibility, validity and reliability of a child friendly vestibular assessment in infants and children candidates to cochlear implant.

OBJECTIVES: The pediatric vestibular assessment has developed significantly in the past two decades, especially in terms of assessment of cochlear implant (CI) candidates. Different methods and test protocols have been applied, however without a general consensus. We present here the feasibility, validity and reliability of a child friendly vestibular testing in use at our department for the assessment of pediatric CI candidates. METHODS: The test battery consisted of head impulse test (HIT), video head impulse test (vHIT), cervical evoked myogenic potentials (cVEMP) and mini ice water caloric test (mIWC), all adapted from previous methods, mentioned in literature. We defined specific criteria for test feasibility, for test validity and test positivity (i.e. indicating vestibular insufficiency). The reliability of the whole protocol was assessed with test agreement analysis. RESULTS: Complete data from 35 children, all CI candidates, age ranging 4-79 months (67% under 2 years) and recruited over two years, were obtained. All but one child could complete at least one test with valid responses bilaterally, with the best compliance for HIT (97,1%) and least for cVEMP (68,6%). Feasibility did not appear to be affected by age or hearing loss etiology. Among the valid responses there was a substantial test agreement between HIT and vHIT, moderate agreement between vHIT/HIT and mIWC and no apparent agreement between the canal tests and cVEMP. Simple clinical guidelines were introduced to solve the tests' disagreement and to improve the protocol reliability: a) a pathological response had to be confirmed in at least two different canal tests and in at least three cVEMP trials; b) a canal/otolith disagreement was interpreted as a partial vestibular loss to be opposed to a complete vestibular insufficiency. CONCLUSIONS: The search for vestibular insufficiency in infants and young children can be attained with an opportunely adapted vestibular assessment, such the test battery proposed here. That assessment resulted easy to conduct and to interpret in a representative sample of CI candidates in preschool age, the most of whom were younger than 2 years. This method appears to particularly suit the demands of a vestibular assessment in young children CI candidates.

The effects of meclizine on motion sickness revisited.

AIMS: Antihistamines make up the first line of treatments against motion-sickness. Still, their efficacy and specific mechanism have come into question. The aim of this study was to investigate the effect of meclizine on motion-sensitivity. METHODS: This study was carried out as a triple-blinded randomized trial involving 12 healthy subjects who were exposed to (i) vestibular (VES), (ii) visual (VIS) and (iii) visual-vestibular (VIS+VES) stimulations in the roll plane. Subjects were divided into 2 groups by stratified randomization, receiving either meclizine or a placebo. Stimulations were carried out before, and after, drug administration, presented at 2 intensity levels of 14 and 28°/s2 . Eye movements were tracked, and torsional slow-phase velocities, amplitudes and nystagmus beats were retrieved. Subjects initially graded for their motion-sickness susceptibility. RESULTS: Susceptibility had no effect on intervention outcome. Despite large variations, repeated ANOVAS showed that meclizine led to a relative increase in torsional velocity compared to placebo during vestibular stimulation for both intensities: 2.36 (7.65) from -0.01 (4.17) during low intensities, and 2.61 (6.67) from -3.49 (4.76) during high. The visual-vestibular stimuli yielded a decrease during low acceleration, -0.40 (3.87) from 3.75 (5.62), but increased during high, 3.88 (6.51) from -3.88 (8.55). CONCLUSIONS: Meclizine had an inhibitory effect on eye movement reflexes for low accelerations during VIS+VES trials. This indicates that meclizine may not primarily work through sensory-specific mechanisms, but rather on a more central level. Practically, meclizine shows promise in targeting motion-sickness evoked by everyday activities, but its use may be counterproductive in high-acceleration environments.

Methodological aspects of testing vestibular evoked myogenic potentials in infants at universal hearing screening program.

Motor development in infants is dependent upon the function of the inner ear balance organ (vestibular organ). Vestibular failure causes motor delays in early infancy and suboptimal motor skills later on. A vestibular test for newborns and infants that is applicable on a large scale, safe and cost effective is in demand in various contexts: in the differential diagnosis of early onset hearing loss to determine forms associated with vestibular failure; in early hearing habilitation with cochlear implant, indicating the vestibular predominant side; and in the habilitation of children affected by motor skill disorders, revealing the contribution of a vestibular failure. This work explored the feasibility of cervical vestibular evoked myogenic potentials (VEMP) in conjunction with newborn universal hearing screening program. VEMP was measured after the hearing tests and was evoked by bone-conducted stimuli. Moreover, stimulus delivery was regulated by neck muscle activity, with infants rested unconstrained in their parents´ arms and with the head supported by the operator´s hand. This VEMP protocol showed a high level of feasibility in terms of test viability and result reproducibility. VEMP integrated into the newborn hearing screening program may represent a practical method for large-scale assessment of balance function in infants.

The cerebellar phenotype of Charcot-Marie-Tooth neuropathy type 4C.

BACKGROUND: Friedreich ataxia (FRDA) is the most common familial ataxia syndrome in Central and Southern Europe but rare in Scandinavia. Biallelic mutations in SH3 domain and tetratricopeptide repeats 2 (SH3TC2) cause Charcot-Marie-Tooth disease type 4C (CMT4C), one of the most common autosomal recessive polyneuropathies associated with early onset, slow disease progression and scoliosis. Beyond nystagmus reported in some patients, neither ataxia nor cerebellar atrophy has been documented as part of the CMT4C phenotype. METHODS: Here we describe a single centre CMT4C cohort. All patients underwent a comprehensive characterization that included physical examination, neurophysiological studies, neuroimaging and genetic testing. In a patient with cerebellar features, an evaluation of the vestibular system was performed. RESULTS: All five patients in this cohort harbored the R954X mutation in SH3TC2 suggesting a founder effect. Two patients had been diagnosed as FRDA. One of them, an 80-year-old woman had onset of unsteadiness during childhood leading to gradual loss of mobility. She also had scoliosis and hearing loss. On examination she had generalized muscle atrophy, leg flaccidity, pes cavus, facial myokymia, limb dysmetria, dysarthria and gaze-evoked nystagmus. She exhibited bilateral vestibular areflexia. Neuroimaging demonstrated atrophy in the frontoparietal regions and cerebellar hemispheres. CONCLUSIONS: CMTC4A may present with a cerebellar phenotype and mimic a flaccid-ataxic form of FRDA. Absence of cardiomyopathy or endocrine abnormalities and lack of pathological dentate iron accumulation in CMT4C distinguish it from FRDA.

Vestibular myogenic potentials evoked by air-conducted stimuli at safe acoustic intensity levels retain optimal diagnostic properties for superior canal dehiscence syndrome.

BACKGROUND: Vestibular-evoked myogenic potential (VEMP) is commonly conducted with air-conducted (AC) stimuli whose intensity may exceed the prudential levels of acoustic exposure in susceptible subjects. OBJECTIVES: To determine the diagnostic accuracy of AC VEMP for superior canal dehiscence syndrome (SCDS) at lowered acoustic stimulation levels. MATERIAL AND METHODS: VEMP was tested in 10 SCDS patients and in 10 age/sex matched control subjects. VEMP were recorded on cervical muscles (cVEMP) and extraocular muscles (oVEMP) in response to short AC tone bursts at 500, 1000 and 2000 Hz delivered at 80 dB nHL (103 dB peSPL). Parameters of interest were the response amplitude and the frequency tuning. RESULTS: VEMP evoked by AC stimuli at safe acoustic stimulation levels did effectively separate SCDS patients from healthy controls. The separation was optimal at all the frequencies tested, however 500 Hz resulted the best VEMP tuning frequency, especially at oVEMP. CONCLUSIONS: Lowering the AC stimulation to the levels compatible with testing of patients susceptible to acoustic exposure didn't affect the VEMP diagnostic properties for SCDS. SIGNIFICANCE: SCDS may be screened by VEMP even among subjects susceptible for acoustic exposure.

Diagnostic Accuracy of Ocular Vestibular Evoked Myogenic Potentials for Superior Canal Dehiscence Syndrome in a Large Cohort of Dizzy Patients.

OBJECTIVES: To determine the diagnostic accuracy of ocular vestibular evoked myogenic potentials (oVEMPs) for superior canal dehiscence syndrome (SCDS) in a large cohort of unselected dizzy patients. Most SCDS patients are dizzy (90%); however, only 30% demonstrate archetypical SCDS clinical proxies (Tullio or Hennebert findings). Several case-control studies have addressed specific SCDS markers using VEMP testing, but the diagnostic value of VEMP for SCDS has not been demonstrated in a target population of dizzy patients. The aim of this study was to confirm the diagnostic properties of oVEMP for SCDS in an unselected cohort of dizzy patients. DESIGN: This diagnostic accuracy study was performed in a tertiary referral center and included a consecutive sample of dizzy patients referred for vestibular function testing. One hundred fifty subjects were collected prospectively; five were excluded due to middle ear disorders, 10 had the target condition (SCDS group), and 135 had an alternative condition (non-SCDS group), based on diagnostic criteria for SCDS used in our department as reference standard. The non-SCDS group was subdivided into diagnostic categories including an "undefined dizziness" group. The index test applied to the total sample (missing data: 1%) consisted of oVEMP recording using three different stimulation modalities, that is, air-conducted (AC) sound stimulation and midsagittal bone-conducted (BC) vibration at both forehead (Fz) and vertex (Cz). Data analysis was conducted on four oVEMP parameters: amplitude, latency, amplitude asymmetry ratio, and interaural latency difference. Between-group analysis was conducted with nonparametric tests. The oVEMP diagnostic accuracy for SCDS was determined with uni/multiparametric receiver operating characteristic analysis. Best cutoff points were computed for those parameters or parameter combinations that showed an accuracy level appropriate for clinical use (area under the curve [AUC] > 0.8). RESULTS: Different oVEMP parameters, in particular, the amplitude to AC stimulation (SCDS: 53, inter quartile range [IQR]: 27.6-68.3 µV; non-SCDS: 4.4, IQR: 2.0-8.1 µV; p < 0.001), were able to separate SCDS from non-SCDS conditions with statistical significance. AC oVEMP amplitude had the highest diagnostic accuracy (area under the curve = 0.96) for SCDS, with optimal sensitivity (100%) and high specificity (89%) at a specific cutoff point (16.7 µV); as an SCDS index, it could distinguish these patients not only from those with other vestibular diagnoses but also from patients with undefined dizziness (sensitivity 100%; specificity 81%). CONCLUSIONS: oVEMP was able to identify all subjects affected by SCDS, according to our diagnostic criteria, in a large cohort of unselected dizzy patients. The AC oVEMP amplitude parameter showed optimal sensitivity and high specificity for SCDS and may represent an ideal screening test for SCDS among dizzy patients. This is noteworthy when considering that not all SCDS patients express the clinical key features of vestibular hypersensitivity to sound or pressure change, even though most complain of dizziness.

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.

Enhanced Auditory Sensitivity to Body Vibrations in Superior Canal Dehiscence Syndrome.

A key feature of superior canal dehiscence (SCD) syndrome is supranormal hearing of body sounds. The aim of the present study was to quantify this phenomenon and to ascertain whether auditory sensitivity to body vibrations can distinguish SCD patients. Hearing thresholds in response to vibration at the vertex, at the spinous process of the 7th cervical vertebra, and at the medial malleolus were tested in 10 SCD patients and 10 controls. Both patients and controls had insert earphones in both ears. The insert in the test ear was blocked while masking was presented to the other ear. Vibration in the frequency range of 125-1,000 Hz was presented to each of the 3 stimulation sites. The SCD patients were found to have significantly lower hearing thresholds compared with controls. The two study groups reacted differently with respect to frequency. The SCD patients showed an enhanced sensitivity for the lower stimulus frequencies. The difference was, however, rather independent of stimulus presentation site. The findings suggest that hearing thresholds in response to low-frequency body vibration at sites distant from the ears can distinguish SCD patients. The present findings may also support the idea that auditory sensation to body vibrations is a response related to soft tissue conduction.

Impaired balance and neurodevelopmental disabilities among children with congenital cytomegalovirus infection.

AIM: Although cytomegalovirus (CMV) is the most common congenital infection, existing research has not provided us with a full picture of how this can affect children in the future. The aim of this case-control study was to evaluate disabilities in a well-defined group of children with congenital cytomegalovirus (CMV) infection, who had been fitted with cochlear implants because of severe hearing impairment. METHODS: A multidisciplinary team assessed 26 children with congenital CMV infection for balance difficulties, neurodevelopmental disabilities and language and visual impairment. We also included a control group of 13 children with severe hearing impairment due to connexin 26 mutations. RESULTS: The majority of the children with congenital CMV infection (88%) displayed balance disturbances, including walking at a later age, but there were no cases in the control group. The CMV group also displayed frequent neurodevelopmental disabilities and feeding difficulties. CONCLUSION: Congenital CMV infection affects the general development of the brain and gives rise to a complex pattern of difficulties. Identifying comorbid conditions is very important, as children with associated difficulties and disabilities need more support than children with just hearing impairment. Congenital CMV infection needs to be considered in children with hearing impairment and/or balance disturbance and/or neurodevelopmental disabilities.

Superior vestibular dysfunction in severe decompression sickness suggests an embolic mechanism.

BACKGROUND: Both nitrogen bubble embolism and the difficulty of inner ear tissues to wash out nitrogen have been discussed as possible reasons for the selective vulnerability of the inner ear to decompression illness. This case report suggests that nitrogen bubble embolism plays a crucial role in the pathogenesis of inner ear lesions in decompression accidents. CASE REPORT: The current patient, a 48-yr-old male dive master, suffered a severe decompression illness with vertigo as the only residual symptom. At the 1-mo follow-up, neuro-otological evaluation revealed a selective lesion of the superior vestibular division of the left labyrinth with normal functioning inferior vestibular division. At vestibular testing, there was no caloric response from the affected left ear, and the head impulse tests for the lateral and anterior semicircular canal were also impaired. Tests of vestibular evoked myogenic potentials (VEMP) showed divergent results. Ocular VEMP in response to left ear stimulation were absent, whereas the cervical VEMP were completely symmetrical and normal. Thus, the lesion profile implies a partial vestibular loss selectively affecting the superior vestibular division of the inner ear. DISCUSSION: The most likely explanation for such a selective injury seems to be bubble microembolism coupled with both the specific anatomy of this terminally supplied subunit, and with the slow nitrogen wash-out of the vestibular organ.

Effectiveness of different click stimuli in diagnosing superior canal dehiscence using cervical vestibular evoked myogenic potentials.

CONCLUSION: Testing cervical vestibular evoked myogenic potential (cVEMP) in response to 90 dB nHL clicks can, in contrast to high-intensity 500 Hz tone bursts, be used as a screening test for superior canal dehiscence (SCD) syndrome. OBJECTIVES: cVEMP testing has its key clinical significance for evaluating saccular and inferior vestibular nerve function, but also for assessment of vestibular hypersensitivity to sounds in patients with SCD syndrome. The routine stimulus used in cVEMP testing is high-intensity 500 Hz tone bursts. The aim of the present study was to compare the high-intensity tone burst stimulation with less intense click stimulations for the diagnosis of SCD syndrome. METHODS: cVEMP amplitudes in response to 500 Hz tone bursts and clicks were studied in 38 patients with SCD syndrome unilaterally. RESULTS: cVEMP testing using high-intensity 500 Hz tone bursts did not consistently distinguish SCD patients. This nonfunctioning of high-intensity 500 Hz stimulation is most likely due to saturation. With 90 and 80 dB nHL clicks there is low risk for saturation and both these click stimulations were effective. Testing with both 80 and 90 dB nHL clicks did not have any significant advantage over just using 90 nHL dB clicks.

Vestibular evoked myogenic potentials in response to lateral skull taps are dependent on two different mechanisms.

OBJECTIVE: To explore the mechanisms for skull tap induced vestibular evoked myogenic potentials (VEMP). METHODS: The muscular responses were recorded over both sternocleidomastoid (SCM) muscles using skin electrodes. A skull tapper which provided a constant stimulus intensity was used to test cervical vestibular evoked myogenic potentials (VEMP) in response to lateral skull taps in healthy subjects (n=10) and in patients with severe unilateral loss of vestibular function (n=10). RESULTS: Skull taps applied approximately 2 cm above the outer ear canal caused highly reproducible VEMP. There were differences in VEMP in both normals and patients depending on side of tapping. In normals, there was a positive-negative ("normal") VEMP on the side contra-lateral to the skull tapping, but no significant VEMP ipsi-laterally. In patients, skull taps above the lesioned ear caused a contra-lateral positive-negative VEMP (as it did in the normals), in addition there was an ipsi-lateral negative-positive ("inverted") VEMP. When skull taps were presented above the healthy ear there was only a small contra-lateral positive-negative VEMP but, similar to the normals, no VEMP ipsi-laterally. CONCLUSIONS: The present data, in conjunction with earlier findings, support a theory that skull-tap VEMP responses are mediated by two different mechanisms. It is suggested that skull tapping causes both a purely ipsi-lateral stimulus side independent SCM response and a bilateral and of opposite polarity SCM response that is stimulus side dependent. Possibly, the skull tap induced VEMP responses are the sum of a stimulation of two species of vestibular receptors, one excited by vibration (which is rather stimulus site independent) and one excited by translation (which is more stimulus site dependent). SIGNIFICANCE: Skull-tap VEMP probably have two different mechanisms. Separation of the two components might reveal the status of different labyrinthine functions.