Ocular Vestibular-Evoked Myogenic Potential Amplitudes Elicited at 4 kHz Optimize Detection of Superior Semicircular Canal Dehiscence

[Update on diagnostic procedures in third window syndromes. German version]

BACKGROUND

The diagnosis of third window syndromes often poses a challenge in clinical practice.

OBJECTIVE

This paper provides an up-to-date overview of diagnostic procedures in third window syndromes, with special emphasis on superior canal dehiscence syndrome (SCDS), large vestibular aqueduct syndrome (LVAS), and X-chromosomal malformation of the cochlea.

MATERIALS AND METHODS

A literature search was performed in PubMed up to December 2023. Furthermore, a selection of the authors' own cases is presented.

RESULTS

Audiovestibular tests for the diagnosis of third window syndromes are most often reported for patients with SCDS in the literature. In this context, cut-off values with different sensitivities and specificities have been defined for different outcome parameters of vestibular evoked myogenic potentials. Current developments include the application of electrocochleography, broadband tympanometry, video head impulse testing, and vibration-induced nystagmus. Genetic analyses are increasingly applied in LVAS.

CONCLUSION

The diagnosis of third window syndromes is always based on the synthesis of patients' symptoms, clinical signs, audiovestibular test results, and imaging.

Effect of Electrode Montage on Frequency Tuning Properties of Air-Conducted Ocular Vestibular-Evoked Myogenic Potential

OBJECTIVES

The use of a 500 Hz tone burst over other frequencies was adopted for the clinical recording of ocular vestibular-evoked myogenic potential (oVEMP) on the basis that this stimulus frequency produces larger response amplitudes (frequency tuning) than the other frequencies. However, the possibility of reflex contamination due to a spatially displaced reference electrode from the muscle of the response origin raises questions about using an infraorbital (IO) montage. Nonetheless, the belly-tendon (BT) montage, which places both the recording electrodes over the inferior oblique muscle, increases the chances of obtaining a response with greater contribution from the inferior oblique muscle. However, whether this response continues to show the frequency tuning to 500 Hz is not known. Therefore, the present study aimed to examine the frequency tuning of oVEMP using various electrode montages.

DESIGN

Thirty-eight young adults underwent simultaneous oVEMP recording from IO, BT, chin-referenced, and sternum-referenced electrode montages in response to 250, 500, 750, 1000, 1500, 2000, 3000, and 4000 Hz tone bursts.

RESULTS

The frequency tuning most often coincided with a 750-Hz tone burst irrespective of the montage, with the BT montage exhibiting significantly higher response rates and larger peak to peak amplitudes than other montages ( p < 0.008). Further, there was a "substantial" agreement on frequency tuning between BT and IO montages.

CONCLUSIONS

With better response rates and response amplitudes yet similar frequency tuning to the IO montage, the BT montage can be a better option for the clinical recording of oVEMP across frequencies.

The Third Mobile Window Syndrome: A Clinical Spectrum of Different Anatomical Locations-Characterization, Therapeutic Response, and Implications in the Development of Endolymphatic Hydrops

Background/Objectives: Multiple dehiscences of the otic capsule can exhibit behavior similar to Ménière's disease, not only from a clinical perspective but also in the results of audiovestibular tests. The main objective of this study is to characterize third mobile window etiologies from an audiovestibular perspective, while also evaluating the therapeutic response to four different treatment protocols. Furthermore, we aim to explore a potential association with the development of radiologically defined endolymphatic hydrops (EH). Methods: This is a retrospective cohort study conducted from 2017 to 2024 at a tertiary-level otology and otoneurology unit. All patients underwent pure tone audiometry, vHIT, cVEMP, and oVEMP. Some of these patients, selected under rigorous inclusion criteria based on clinical and audiometric findings, were subjected to a 4-h delayed intravenous gadolinium-enhanced 3D-FLAIR MRI. Results: We obtained a sample of 86 patients, with a mean age of 52.2 ± 7.64 years: 62.76% were female (n = 54) and 37.21% were male (n = 32); 88.37% (n = 76) were diagnosed with superior semicircular canal dehiscence syndrome (SSCDS), while 11.62% (n = 10) had other forms of otic capsule dehiscence. The most common symptom observed was unsteadiness (44%). While surgery is the only curative treatment, other medical treatments, such as acetazolamide, also helped reduce symptoms such as autophony, falls, instability, and vertigo attacks, with a relative risk reduction (RRR) exceeding 75% (95% CI, p < 0.05). The results of the MRI in EH sequences indicate that 7.89% of the patients diagnosed with SSCDS also developed radiological EH, compared to 40.00% of the patients with other otic capsule dehiscences, a difference that was statistically significant (p = 0.0029. Conclusions: Otic capsule dehiscences are relatively unknown conditions that require clinical diagnosis. Although VEMP testing is useful, imaging studies are necessary to localize and characterize the defect, most commonly found in the superior semicircular canal. We should consider these dehiscences in cases where there is a suspicion of EH development. Further research, including in vivo neuroimaging studies using hydrops sequences, is required to better understand their relationship to potential Ménière's disease.

Development and Standardization of Modified Simultaneous Multifrequency Stimulus for Recording Ocular Vestibular-Evoked Myogenic Potential and Its Interaction with the Alternate Electrode Montages

BACKGROUND

 Simultaneous multifrequency (SiMFy) is a time-saving and reliable stimulus to determine the frequency tuning of ocular vestibular-evoked myogenic potential (oVEMP); however, the absence of 4000 Hz in SiMFy potentially makes it a less potent tool for the diagnosis of superior semicircular canal dehiscence, a pathology with an ever-increasing prevalence. Further, SiMFy was validated using only the infraorbital (IO) electrode montage. However, the recordings obtained using the IO montage might be susceptible to reference contamination introduced by a small separation between the recording electrodes and also susceptible to reflex impurity due to the spatially displaced reference electrode from the inferior oblique muscle, rendering it vulnerable to picking up responses from other muscles. Nonetheless, little is known about the similarities/differences between the SiMFy-induced oVEMPs using alternate montages (belly-tendon [BT], chin-reference [CR], and sternum-reference [SR]) and the nonsimultaneous multifrequency oVEMPs (NSM-oVEMPs) using the IO montage.

PURPOSE OF THE STUDY

 To develop a modified SiMFy stimulus and investigate its effects on frequency tuning of oVEMP using various electrode montages.

RESEARCH DESIGN

 Within-subject experimental design.

STUDY SAMPLE

 Thirty-three healthy adults aged 20 to 30 years.

DATA COLLECTION AND ANALYSIS

 Tone bursts of octave and mid-octave frequencies from 250 to 4000 Hz were generated and concatenated to create the modified SiMFy stimulus. All participants underwent NSM oVEMPs and modified SiMFy oVEMPs using BT, CR, SR, and IO montages simultaneously. The response rate, peak-to-peak amplitude, and frequency tuning were compared between NSM-oVEMP and modified SiMFy oVEMP and also between the electrode montages.

RESULTS

 BT montage recorded the largest amplitude among the montages in NSM stimulation and modified SiMFy stimulation. Although the response rates were comparable, the modified SiMFy produced significantly lower oVEMP amplitudes than the NSM stimulation within each electrode montage (p < 0.05). A moderate-to-strong agreement on frequency tuning existed between the NSM stimuli and modified SiMFy stimulus for all the montages, except for the SR montage.

CONCLUSIONS

 Although the modified SiMFy produces smaller amplitude oVEMPs than the NSM stimulation for the respective montages, its use in combination with the BT montage yields higher response rates and larger peak-to-peak amplitudes than the NSM recording using IO montage.

Effects of aging on ocular vestibular-evoked myogenic potential using ER-3A insert earphone and B81 bone vibrator

Purpose

Aging is a process associated with degeneration and dysfunction of peripheral vestibular system or apparatus. This study aimed to investigate the influence of aging on ocular vestibular-evoked myogenic potential (oVEMP) response rates and recording parameters using the B81 bone vibrator and compare them with air conduction stimuli (ACS) oVEMP response characteristics.

Methods

In 60 healthy participants aged 10–71 years (mean age 39.9; 29 male participants), the oVEMP response was elicited using a B81 bone vibrator and an ER-3A insert earphone. The effects of age and stimulus on oVEMP response rates and recording parameters were evaluated.

Results

Response rates and amplitudes declined with aging using either ACS or bone-conducted vibration (BCV) stimulation, particularly in individuals over 60 years of age, whereas thresholds increased and N1 latencies were prolonged. BCV showed fewer risks of absent oVEMP response than ACS (p = 0.002). BCV acquired higher amplitudes (p &lt; 0.001), lower thresholds, and shorter N1 and P1 latencies (all p &lt; 0.001) than ACS.

Conclusions

The absence of an oVEMP response may be attributed to aging rather than a concurrent vestibular disorder. B81-BCV likely produces higher mechanical drives to the vestibular hair cells at safer and non-traumatic levels compared with ACS and therefore may be more likely to evoke a response in the elderly cohort, whose vestibular function and mechanical sensitivity have declined. Thus, B81-BCV stimulation is more effective and safer to elicit oVEMPs, and it should be recommended when ACS fails in the clinic, particularly in the elderly population.

A Single Fast Test for Semicircular Canal Dehiscence—oVEMP n10 to 4000 Hz—Depends on Stimulus Rise Time

As previously reported, a single test measuring oVEMP n10 to 4000 Hz stimuli (bone-conducted vibration (BCV) or air-conducted sound (ACS)) provides a definitive diagnosis of semicircular canal dehiscence (SCD) in 22 CT-verified patients, with a sensitivity of 1.0 and specificity of 1.0. This single short screening test has great advantages of speed, minimizing testing time, and the exposure of patients to stimulation. However, a few studies of the 4000 Hz test for SCD have reported sensitivity and specificity values which are slightly less than reported previously. We hypothesized that the rise time of the stimulus is important for detecting the oVEMP n10 to 4000 Hz, similarly to what we had shown for 500 and 750 Hz BCV. We measured oVEMP n10 in 15 patients with CT-verified SCD in response to 4000 Hz ACS or BCV stimuli with rise times of 0, 1, and 2 ms. As a result, increasing the rise time of the stimulus reduced the oVEMP n10 amplitude. This outcome is expected from the physiological evidence of guinea pig primary vestibular afferents, which are activated by sound or vibration. Therefore, for clinical VEMP testing, short rise times are optimal (preferably 0 ms).

Simultaneous Multifrequency (SiMFy) Stimulus: A Novel and Reliable Stimulus for Frequency Tuning of Ocular Vestibular-Evoked Myogenic Potentials

BACKGROUND

Frequency tuning of ocular vestibular evoked myogenic potential (oVEMP) refers to the frequency of tone burst that produces the largest amplitude oVEMP. There is an ever-growing pool of published studies that found the frequency tuning of oVEMP distinctly different in Ménière's disease than the age-matched controls and benign paroxysmal positional vertigo. However, recording oVEMP in response to many frequencies makes an already lengthy vestibular test battery even more cumbersome and time-consuming.

PURPOSE

The aim of this study was to develop a novel time-saving stimulus that produces reliable results.

RESEARCH DESIGN

Prospective study.

STUDY SAMPLE

The study included 25 young, healthy adults.

DATA COLLECTION

The tone-bursts of 2000, 1500, 1000, 750, 500, and 250 Hz were generated and sequenced in this order to prepare a stimulus for simultaneous multifrequency (SiMFy) oVEMP. The response parameters of SiMFy and conventional oVEMP methods were compared.

RESULTS

No significant difference in peak-to-peak amplitude and frequency tuning existed between conventional and SiMFy oVEMP (p > 0.05). SiMFy had better test-retest reliability and was less time-consuming than the conventional oVEMP.

CONCLUSIONS

SiMFy is a time-saving and reliable stimulus for obtaining frequency tuning of oVEMP with no compromise on the outcomes. It can be immediately applied in most commercially available evoked potential systems with a facility for loading an external stimulus.

Simultaneous Multifrequency (SiMFy) Stimulus: A Novel and Reliable Stimulus for Frequency Tuning of Ocular Vestibular-Evoked Myogenic Potentials

Background Frequency tuning of ocular vestibular evoked myogenic potential (oVEMP) refers to the frequency of tone burst that produces the largest amplitude oVEMP. There is an ever-growing pool of published studies that found the frequency tuning of oVEMP distinctly different in Ménière's disease than the age-matched controls and benign paroxysmal positional vertigo. However, recording oVEMP in response to many frequencies makes an already lengthy vestibular test battery even more cumbersome and time-consuming.

Purpose The aim of this study was to develop a novel time-saving stimulus that produces reliable results.

Research Design Prospective study.

Study Sample The study included 25 young, healthy adults.

Data Collection The tone-bursts of 2000, 1500, 1000, 750, 500, and 250 Hz were generated and sequenced in this order to prepare a stimulus for simultaneous multifrequency (SiMFy) oVEMP. The response parameters of SiMFy and conventional oVEMP methods were compared.

Results No significant difference in peak-to-peak amplitude and frequency tuning existed between conventional and SiMFy oVEMP (p > 0.05). SiMFy had better test–retest reliability and was less time-consuming than the conventional oVEMP.

Conclusions SiMFy is a time-saving and reliable stimulus for obtaining frequency tuning of oVEMP with no compromise on the outcomes. It can be immediately applied in most commercially available evoked potential systems with a facility for loading an external stimulus.

Usefulness of Cervical Vestibular-Evoked Myogenic Potentials for Diagnosing Patients With Superior Canal Dehiscence Syndrome: A Meta-Analysis

OBJECTIVES

To compare the diagnostic accuracy of cervical vestibular-evoked myogenic potential (cVEMP) for detecting superior canal dehiscence (SCD) syndrome to that of computed tomography (CT) and surgical findings.

DATABASES REVIEWED

PubMed, SCOPUS, Embase, Web of Science, and the Cochrane database.

METHODS

Databases were searched up to July 2021. True positives, true negatives, false positives, and false negatives were extracted. Methodological quality was assessed using the Quality Assessment of Diagnostic Accuracy Studies 2 tool.

RESULTS

Our search yielded nine studies with 721 patients. Including all cVEMP thresholds, the diagnostic odds ratio (DOR) was 32.8483 (95% confidence interval [CI]: 19.6577, 54.8900; I2 = 49.9%). The area under the summary receiver operating characteristic curve (AUC) was 0.879. Sensitivity and specificity were 0.8278 (95% CI: 0.7517, 0.8842; I2 = 76.4%) and 0.8824 (95% CI: 0.7859, 0.9387; I2 = 92.8%), respectively. However, there was a high degree of heterogeneity (I2 ≥ 70%) due to the different VEMP threshold values used among the studies. In subgroup analysis, higher cVEMP threshold values showed higher sensitivity (threshold ≤ 85: 0.9568; threshold ≤ 65: 0.7691) but lower specificity (threshold ≤ 85: 0.5879; threshold ≤ 65: 0.8913). The threshold ≤75 subgroup showed moderate sensitivity of 0.7455, high specificity of 0.9526, and the highest DOR of 38.9062. The AUC of this subgroup was 0.894.

CONCLUSIONS

cVEMP is a reliable adjunctive tool for the clinical diagnosis of SCD. Taking the balance between sensitivity and specificity into consideration, a cVEMP threshold value of 75 showed good diagnostic accuracy.

Rare Disorders of the Vestibular Labyrinth: of Zebras, Chameleons and Wolves in Sheep's Clothing

The differential diagnosis of vertigo syndromes is a challenging issue, as many - and in particular - rare disorders of the vestibular labyrinth can hide behind the very common symptoms of "vertigo" and "dizziness". The following article presents an overview of those rare disorders of the balance organ that are of special interest for the otorhinolaryngologist dealing with vertigo disorders. For a better orientation, these disorders are categorized as acute (AVS), episodic (EVS) and chronic vestibular syndromes (CVS) according to their clinical presentation. The main focus lies on EVS sorted by their duration and the presence/absence of triggering factors (seconds, no triggers: vestibular paroxysmia, Tumarkin attacks; seconds, sound and pressure induced: "third window" syndromes; seconds to minutes, positional: rare variants and differential diagnoses of benign paroxysmal positional vertigo; hours to days, spontaneous: intralabyrinthine schwannomas, endolymphatic sac tumors, autoimmune disorders of the inner ear). Furthermore, rare causes of AVS (inferior vestibular neuritis, otolith organ specific dysfunction, vascular labyrinthine disorders, acute bilateral vestibulopathy) and CVS (chronic bilateral vestibulopathy) are covered. In each case, special emphasis is laid on the decisive diagnostic test for the identification of the rare disease and "red flags" for potentially dangerous disorders (e. g. labyrinthine infarction/hemorrhage). Thus, this chapter may serve as a clinical companion for the otorhinolaryngologist aiding in the efficient diagnosis and treatment of rare disorders of the vestibular labyrinth.