Interpretation and use of caloric testing

Noninvasive Targeted Temperature Management of the Inner Ear: Numerical Simulations and Experimental Measurements in a Human Cadaver Model

HYPOTHESIS

Mild therapeutic hypothermia (MTH) could be delivered to the human inner ear using a localized, noninvasive approach to achieve protective temperature reductions without systemic side effects.

BACKGROUND

MTH has demonstrated protective effects in the cochlea following injuries such as device implantation, ototoxicity, and noise overexposure. It targets key cellular mechanisms, including proinflammatory pathways, oxidative stress, pyroptosis, and apoptosis. However, systemic and invasive methods for MTH carry risks and are less practical for broader clinical applications. Developing a localized, noninvasive approach could offer a safer, more accessible solution for hearing preservation after cochlear injury.

METHODS

Cadaveric middle and inner ear structures, maintained near physiological conditions, were used to test a custom-designed cooling gel pack (ReBound) placed externally on the temporal bone. Temperature changes were recorded over 60 or 30 minutes. To complement experimental findings, three-dimensional geometrical models were created from imaging data, and finite element heat transfer analysis simulated temperature changes across inner ear structures.

RESULTS

With external gel pack application, inner ear temperatures dropped by 2.9°C within 30 minutes and 4.6°C within 60 minutes. Cooling persisted for 10 minutes post-device removal. Numerical modeling corroborated these findings, indicating average temperature reductions of 2°C to 4°C. Biological sex differences were observed in cooling efficiency and overall temperature drop.

CONCLUSION

This study demonstrates that localized, noninvasive MTH can effectively reduce inner ear temperatures to therapeutically relevant levels. These findings support a promising, clinically translatable approach for protecting cochlear structure and function after injury, with minimal systemic risks.

Nystagmus and Vertigo During Aural Toilet Using Microsuction

Background/Objectives: Aural toilet using microsuction is a common procedure in ENT clinics, and vertigo is a frequent complaint during this procedure. This study aimed to investigate the characteristics and incidence of microsuction-induced nystagmus and vertigo based on the appearance of the tympanic membrane (TM). Methods: In 85 patients with various TM appearances, microsuction-induced vertigo and nystagmus were assessed. Results: Microsuction elicited nystagmus in 95% (81 of 85) of patients and vertigo in 36% (31 of 85). The nystagmus direction was towards the ipsilateral ear in a bowing position and towards the contralateral ear in a leaning position. The proportion of patients who complained of rotatory vertigo was significantly higher in those with TM perforation, open cavity mastoidectomy, and adhesive otitis media (74%, 26 of 35) compared to those without TM perforation (10%, 5 of 50) (p < 0.001, X2 test). Conclusions: Aural toilet using microsuction commonly induces vertigo due to convection in the lateral semicircular canal endolymph caused by the cooling effect. While microsuction-induced nystagmus was observed in most patients, the incidence of vertigo varied depending on the TM condition. Clinicians should closely monitor patients for vertigo during the procedure, and methods to prevent microsuction-induced vertigo should be explored.

Efficacy of vestibular rehabilitation using unidirectional rotation paradigm in VOR asymmetry: systematic review and meta-analysis

PURPOSE

Unilateral vestibular dysfunction leads to significant asymmetry in the horizontal vestibulo-ocular reflex (VOR) during swift head movements. This reflex can be enhanced through rehabilitation exercises and visual-vestibular adaptation techniques. This systematic review aims to evaluate the current evidence on the effectiveness of unidirectional rotation treatments for improving symptoms and function in patients with vestibular disorders.

METHODS

A systematic review was conducted following the PRISMA 2020 guidelines, using databases such as PubMed, Cochrane Library, EMBASE, and Scopus. Included were experimental studies, randomized controlled trials (RCTs), or pilot RCTs. Meta-analysis was performed based on the findings of these studies.

RESULTS

Among 24 articles identified, three addressed the systematic review's question, two observational studies (one retrospective and one prospective) and a RCT. Studies included data from a total of 200 participants with vestibular disorders (n = 96; 48% males) for the meta-analysis. A meta-analysis, including a subgroup analysis, was conducted to assess the improvement in VOR asymmetry following vestibular rehabilitation. The analysis compared pre- and post-rehabilitation directional preponderance (DP) across three studies. Results showed a significant improvement in VOR asymmetry, with a mean difference of 18.72% in favour of rehabilitation.

CONCLUSION

Our findings substantiate the efficacy of unilateral vestibular stimulation in reducing asymmetry in the VOR among patients with vestibular dysfunction. This modality represents a promising rehabilitation strategy, significantly enhancing vestibular function and patient outcomes.

Association of vertigo with adult obstructive sleep apnea: A systematic review and meta-analysis

BACKGROUND

Several studies have demonstrated a relationship between vertigo and obstructive sleep apnea (OSA) in adults. This review examined the association between vertigo and OSA and investigated the effects of OSA treatment on vestibular function.

METHODS

Searches were conducted in PubMed, MEDLINE, EMBASE, Cochrane, Scopus, and Web of Science databases. Two authors independently searched the databases up to November 2023. Meta-analysis of caloric test, cervical vestibular evoked myogenic potential (cVEMP), and ocular vestibular evoked myogenic potential (oVEMP), between adults with and without OSA was done.

RESULTS

Overall, 28 studies were identified, and most of which focused on vestibular dysfunction in the OSA group. Compared with controls, adults with OSA had an increased risk of abnormal caloric test results (odds ratio [OR] = 4.8), absence of cVEMP (OR = 7.9), absence of oVEMP (OR = 6.2), decreased n1p2 amplitude (standardized mean difference [SMD] = -0.78), decreased p1n1 amplitude (SMD = -0.92), decreased p1n1 interval (SMD = -2.37) in cVEMP testing and prolonged n1 latency (SMD = 0.81) and decreased p1n1 amplitude (SMD = -0.51) in oVEMP testing. Three population-based studies implied a high risk of vertigo in adult OSA, although not statistically significant (OR = 2.53, 95 % confidence interval = 0.97 to 6.61). According to 3 studies, OSA is relatively prevalent among patients with vertigo. Another 3 studies regarding OSA treatment on vestibular functions revealed inconsistent findings.

CONCLUSION

Adults with OSA exhibit abnormalities in caloric, cVEMP, and oVEMP test results, indicating impairments in the semicircular canal, saccule, and utricle.

Dizziness in Fabry Disease

Background/Objectives: Fabry disease is an X-linked lysosomal storage disease. Earlier studies have mentioned dizziness/balance issues and vestibular involvement as a symptom of Fabry disease. Research on the matter remains scarce. This pilot study aims to show the prevalence of dizziness/balance issues and whether it is due to peripheral, central, or other factors. Methods: A Dizziness Handicap Inventory, with added questions, was sent out to 91 Fabry patients to estimate the prevalence of dizziness/balance issues. Additionally, this study reports analyses from eight Fabry patients with self-reported dizziness/balance issues who were offered referrals for in-depth investigations of their condition. All eight underwent a comprehensive oto-neurological examination, Videonystagmography, a Video Head impulse test, vestibular myogenic evoked potential, and audiometry. Results: A total of 55 of the 91 patients with Fabry disease answered the survey. Of these, 78.2% felt symptoms of dizziness/balance issues. The most common form of dizziness/balance issues was short-lasting attacks. All eight ENT-examined patients had normal outer and middle ear conditions. Five of eight Fabry patients had abnormal results in the optokinetic test and audiometry. Conclusions: The survey showed a high prevalence of dizziness/balance issues in Fabry patients. The abnormal optokinetic test suggested a central cause and was the only objective measurement we found that could lead to an explanation for dizziness/balance issues. Polypharmacy was present in all eight examined patients and could also explain the dizziness/balance issues in Fabry patients. There is no other clear pattern regarding the characteristics of dizziness/balance issues in Fabry patients in this exploratory study.

Balance Control Impairments in Usher Syndrome

OBJECTIVES

To explore postural disability in Usher Syndrome (USH) patients using temporal posturographic analysis to better elucidate sensory compensation strategies of deafblind patients for posture control and correlate the Activities-specific Balance Confidence (ABC) scale with posturographic variables.

DESIGN

Thirty-four genetically confirmed USH patients (11 USH1, 21 USH2, 2 USH 4) from the Otolaryngology Outpatient Clinic and 35 controls were prospectively studied using both classical and wavelet temporal analysis of center of pressure (CoP) under different visual conditions on static and dynamic platforms. The functional impact of balance was assessed with the ABC scale. Classical data in the spatial domain, Sensorial Organization Test, and frequency analysis of the CoP were analyzed.

RESULTS

On unstable surfaces, USH1 had greater CoP surface area with eyes open (38.51 ± 68.67) and closed (28.14 ± 31.64) versus controls (3.31 ± 4.60), p < 0.001 and (7.37 ± 7.91), p < 0.001, respectively. On an unstable platform, USH consistently showed increased postural sway, with elevated angular velocity versus controls with eyes open (USH1 [44.94 ± 62.54]; USH2 [55.64 ± 38.61]; controls [13.4 ± 8.57]) ( p = 0.003; p < 0.001) and closed (USH1 [60.36 ± 49.85], USH2 [57.62 ± 42.36]; controls [27.31 ± 19.79]) ( p = 0.002; p = 0.042). USH visual impairment appears to be the primary factor influencing postural deficits, with a statistically significant difference observed in the visual Sensorial Organization Test ratio for USH1 (80.73 ± 40.07, p = 0.04) and a highly significant difference for USH2 (75.48 ± 31.67, p < 0.001) versus controls (100). In contrast, vestibular ( p = 0.08) and somatosensory ( p = 0.537) factors did not reach statistical significance. USH exhibited lower visual dependence than controls (30.31 ± 30.08) (USH1 [6 ± 11.46], p = 0.004; USH2 [8 ± 14.15], p = 0.005). The postural instability index, that corresponds to the ratio of spectral power index and canceling time, differentiated USH from controls on unstable surface with eyes open USH1 (3.33 ± 1.85) p < 0.001; USH2 (3.87 ± 1.05) p < 0.002; controls (1.91 ± 0.85) and closed USH1 (3.91 ± 1.65) p = 0.005; USH2 (3.92 ± 1.05) p = 0.045; controls (2.74 ± 1.27), but not USH1 from USH2. The canceling time in the anteroposterior direction in lower zone distinguished USH subtypes on stable surface with optokinetic USH1 (0.88 ± 1.03), USH2 (0.29 ± 0.23), p = 0.026 and on unstable surface with eyes open USH1 (0.56 ± 1.26), USH2 (0.072 ± 0.09), p = 0.036. ABC scale could distinguish between USH patients and controls, but not between USH subtypes and it correlated with CoP surface area on unstable surface with eyes open only in USH1( ρ = 0.714, p = 0.047).

CONCLUSIONS

USH patients, particularly USH1, exhibited poorer balance control than controls on unstable platform with eyes open and appeared to rely more on proprioceptive information while suppressing visual input. USH2 seems to use different multisensory balance strategies that do not align as well with the ABC scale. The advanced analysis provided insights into sensory compensation strategies in USH subtypes.

Ocular Movement Examination in Peripheral Vestibular Disorders as a Tool to Improve Diagnosis: A Literature Review

Background and Objectives: This study reviews the current literature on ocular movements, specifically focusing on nystagmus associated with peripheral vestibular disorders, to enhance diagnostic accuracy. The evaluation of ocular movements, particularly nystagmus, provides essential insights into the function and dysfunction of the vestibular system, helping clinicians distinguish between peripheral and central causes of vertigo and imbalance. Materials and Methods: A comprehensive search of PubMed was conducted using key terms such as "ocular movements", "nystagmus", "vestibular nystagmus", and "peripheral vestibular disorders". Results: The search yielded 2739 titles, and after a rigorous selection process, 52 articles were reviewed in full. Discussion: The review highlights different classifications and types of nystagmus, including physiological and pathological forms, and their diagnostic relevance in vestibular disorders such as benign paroxysmal positional vertigo (BPPV), vestibular neuritis, and Meniere's disease. Diagnostic techniques like video/electro-oculography are emphasized for their role in assessing vestibular function and identifying abnormalities. The study underscores the importance of detailed ocular examination in the diagnosis of peripheral vestibular disorders and proposes an algorithm to aid this process. Conclusions: While not a systematic review, this study highlights the importance of detailed ocular examination in diagnosing peripheral vestibular disorders and presents an algorithm to facilitate this process. It also emphasizes the need for continued research and advancements in vestibular medicine to further understand ocular movements and their clinical significance, ultimately contributing to improved patient outcomes.

Secondary autoimmune immune ear disease (AIED): a systematic review and meta-analysis on vestibular manifestations of systemic autoimmune and inflammatory disorders

Secondary autoimmune inner ear disease (AIED) is often bilateral and asymmetric in patients presenting with audiovestibular symptoms due to a systemic autoimmune disease. This systematic review and meta-analysis are aimed at identifying and highlighting patterns in prevalence of vestibular dysfunction, symptom presentation, and diagnostic methods in extant literature by combining clinical context from case reports with quantitative analyses from cohort studies. Screening of articles by title, abstract, and full text was completed by four reviewers (K.Z., A.L., S.C., and S.J.). In this study, we grouped secondary AIED and systemic autoimmune diseases by pathophysiologic mechanism: (1) connective tissue disease (CTD), (2) vasculitides (VAS), (3) systemic inflammatory disorders (SID), and (4) other immune-mediated disorders (OIMD). The search for AIED disease identified 120 articles (cohorts and case reports) that met the final inclusion criteria. All 120 were included in the qualitative review, and 54 articles were included for meta-analysis. Of these 54 articles, 22 included a control group (CwC). Ninety individual cases or patient presentations from 66 articles were included for analysis in addition to the 54 cohort articles. Secondary AIED does not have a diagnostic algorithm for managing vestibular symptoms. The management of audiovestibular symptoms requires close collaboration between otolaryngologists and rheumatologists to preserve end-organ function of the ear. To improve our ability to understand the impact on the vestibular system, vestibular clinicians need to develop a standardized reporting method. Clinical presentation should frequently be paired with vestibular testing to contextually investigate symptom severity and provide higher quality care.

Comprehensive Normative Data for Objective Vestibular Tests

INTRODUCTION

 Vestibular dysfunction is a debilitating disorder frequently encountered in neurological and otological settings. The vestibular system is a complex network between peripheral and central mechanisms. This innate complexity of the vestibular system necessitates objective test procedures for evidence-based diagnostic formulations and intervention. Objective tests aid in the evaluation of both peripheral and central vestibular pathologies. Establishing and availability of comprehensive normative data for these objective tests is crucial for clinicians and researchers alike.

MATERIALS AND METHODS

This is a prospective study involving 120 participants (both males and females) aged between 18 and 55 years. All participants were right-handed individuals and had no significant medical history. On pre-set protocols, cVEMP (cervical vestibular evoked myogenic potential), oVEMP (ocular vestibular evoked myogenic potential), vHIT (video head impulse test), and VNG (videonystagmography) were done.

RESULTS

While all participants (n=120) underwent cVEMP, oVEMP, vHIT, saccade, smooth pursuit, and optokinetic tests, only 109 participants consented to the caloric test. Each test's mean, standard deviation, median, quartile, and third quartiles have been recorded. A right-left comparison yielded no significant difference on cVEMP, oVEMP, caloric test, smooth pursuit, and optokinetic test. However, few vHIT and saccade parameters did reveal significant differences.

DISCUSSION

This study presents comprehensive normative data for cVEMP, oVEMP, vHIT, caloric test on VNG, and oculomotor tests (smooth pursuit, saccade, optokinetic) on VNG. The test results were in concordance with previously published data. The significant difference between the right and left sides in vHIT may be because of the monocular goggles used for the testing.

CONCLUSION

This study brings out the normative data for various vestibular tests on individuals aged between 18-55 years. This information could aid both clinicians and researchers working in the field of vestibular science.

Relationship Between Sensory Organization Testing Scores With Lower Extremity Injuries and Prior Concussion in Professional Soccer Players

OBJECTIVE

To evaluate for associations between concussion history or lower extremity (LE) injury and computerized sensory organization testing (SOT) performance in professional soccer players.

DESIGN

Cross-sectional study.

SETTING

Tertiary care center.

PARTICIPANTS

Thirty-three, professional, male soccer players on an American club, between the years 2019 and 2021.

ASSESSMENT OF RISK FACTORS

Player age, history of reported LE injury (gluteal, hamstring, ankle, knee, hip, groin, and sports hernia), history of diagnosed concussion, and the number of prior concussions were documented for each player.

MAIN OUTCOME MEASURES

Baseline SOT of postural sway was conducted in 6 sensory conditions for all players.

RESULTS

Eleven athletes (33%) reported a previous concussion, and 15 (45%) reported a previous LE injury. There were no significant differences in SOT scores between those with and without a previous diagnosis of concussion ( P > 0.05). Those reporting a previous LE injury performed better on condition 3 (eyes open, unstable visual surround) than those who did not ( P = 0.03). Athletes aged 25 years or younger performed worse on condition 3 ( P = 0.01) and had worse, although not statistically significant, median performance on all other balance measures than those older than 25 years. Intraclass correlation coefficient for repeat SOT assessment was 0.58, indicating moderate reliability, without an evident practice effect.

CONCLUSIONS

Professional soccer players with a previous concussion or history of LE injury did not demonstrate long-term deficits in postural control, as assessed by multiyear computerized SOT baseline testing. The SOT was reliable over time with younger athletes exhibiting greater postural sway than older athletes.

Assessing vestibular function using electroencephalogram rhythms evoked during the caloric test

Introduction

The vestibular system is responsible for motion perception and balance preservation in the body. The vestibular function examination is useful for determining the cause of associated symptoms, diagnosis, and therapy of the patients. The associated cerebral cortex processes and integrates information and is the ultimate perceptual site for vestibular-related symptoms. In recent clinical examinations, less consideration has been given to the cortex associated with the vestibular system. As a result, it is crucial to increase focus on the expression of the cortical level while evaluating vestibular function. From the viewpoint of neuroelectrophysiology, electroencephalograms (EEG) can enhance the assessments of vestibular function at the cortex level.

Methods

This study recorded nystagmus and EEG data throughout the caloric test. Four phases were considered according to the vestibular activation status: before activation, activation, fixation suppression, and recovery. In different phases, the distribution and changes of the relative power of the EEG rhythms (delta, theta, alpha, and beta) were analyzed, and the correlation between EEG characteristics and nystagmus was also investigated.

Results

The results showed that, when the vestibule was activated, the alpha power of the occipital region increased, and the beta power of the central and top regions and the occipital region on the left decreased. The changes in the alpha and beta rhythms significantly correlate with nystagmus values in left warm stimulation.

Discussion

Our findings offer a fresh perspective on cortical electrophysiology for the assessment of vestibular function by demonstrating that the relative power change in EEG rhythms can be used to assess vestibular function.

Comparison Between the Video Head Impulse Test and Caloric Irrigation During Acute Vertigo

Caloric irrigation (CI) is the gold standard to investigate peripheral vestibular dysfunction. The video head impulse test (vHIT) is faster and more accessible and may be useful during acute vertigo stroke risk differentiation. Comparative studies between the two methods are needed. The objective of this study was to compare vestibular function data derived from caloric irrigation with that from vHIT. This study included 80 patients with acute onset vertigo who underwent caloric irrigation and vHIT. CI derived sum of slow phase velocities (SPVs) and unilateral weakness (UW) were compared with vHIT vestibulo-ocular reflex (VOR) gain and gain asymmetry (GA) using correlation analyses. Optimal cut offs for vHIT VOR gain and GA were calculated using Youden indexes. There was a strong positive correlation between the asymmetry measures UW and GA whereas the correlation between the sum of SPVs and VOR gain was weaker. The optimal cut offs to diagnose unilateral vestibular weakness were 0.80 for VOR gain and 28% for GA; with specificities for predicting normal caloric irrigation results of 55% and 93%, respectively. In one third of cases the results from caloric irrigation and vHIT dissociated. The results from vHIT correlated with those from CI, still neither test seem to have the accuracy to replace the other. GA appears as an attractive measure in acute vertigo as the high specificity can be used to identify those with a substantial probability of normal vestibular function in need of more comprehensive work-up for central causes. To diagnose vestibular dysfunction, CI remains gold standard.

Smartphone video nystagmography using convolutional neural networks: ConVNG

Background

Eye movement abnormalities are commonplace in neurological disorders. However, unaided eye movement assessments lack granularity. Although videooculography (VOG) improves diagnostic accuracy, resource intensiveness precludes its broad use. To bridge this care gap, we here validate a framework for smartphone video-based nystagmography capitalizing on recent computer vision advances.

Methods

A convolutional neural network was fine-tuned for pupil tracking using > 550 annotated frames: ConVNG. In a cross-sectional approach, slow-phase velocity of optokinetic nystagmus was calculated in 10 subjects using ConVNG and VOG. Equivalence of accuracy and precision was assessed using the “two one-sample t-test” (TOST) and Bayesian interval-null approaches. ConVNG was systematically compared to OpenFace and MediaPipe as computer vision (CV) benchmarks for gaze estimation.

Results

ConVNG tracking accuracy reached 9–15% of an average pupil diameter. In a fully independent clinical video dataset, ConVNG robustly detected pupil keypoints (median prediction confidence 0.85). SPV measurement accuracy was equivalent to VOG (TOST p < 0.017; Bayes factors (BF) > 24). ConVNG, but not MediaPipe, achieved equivalence to VOG in all SPV calculations. Median precision was 0.30°/s for ConVNG, 0.7°/s for MediaPipe and 0.12°/s for VOG. ConVNG precision was significantly higher than MediaPipe in vertical planes, but both algorithms’ precision was inferior to VOG.

Conclusions

ConVNG enables offline smartphone video nystagmography with an accuracy comparable to VOG and significantly higher precision than MediaPipe, a benchmark computer vision application for gaze estimation. This serves as a blueprint for highly accessible tools with potential to accelerate progress toward precise and personalized Medicine.

Comparison between caloric and video-head impulse tests in Ménière's disease and vestibular neuritis

OBJECTIVE

To compare the diagnostic accuracies of air caloric testing with electronystagmography and the vHIT (video-head impulse test).

DESIGN

Prospective, controlled study.

STUDY SAMPLE

MD (Ménière's disease), 26; vestibular neuritis, 27; control, 56.

RESULTS

In MD, CP (canal paresis) was pathological in 88.5%, the GA (gain asymmetry) on vHIT was pathological in 65.3%, and the gain was abnormal in only one patient. The GA and CP, were significantly higher in the MD group than in the control group, indicating hypofunction of the horizontal canals in MD, whereas a hyperfunction may also occur. No correlation was observed between the results of the two tests for evaluating MD, suggesting that pathological outcomes of one test do not guarantee abnormalities on the other test. For vestibular neuritis, significantly higher CP (96.3%), GA (81.5%), and gain (51.9%) values were detected. A correlation was identified between the two tests for vestibular neuritis, indicating a similar diagnostic efficiency. The higher percentage of pathological GA versus pathological gain values indicates that the asymmetry may be more informative.

CONCLUSIONS

The vHIT showed a higher specificity, whereas the caloric test a higher sensitivity. No correlation between the two methods was observed; therefore, the tests appear to provide complementary information.

Can Type of Dizziness Influence the Vestibular Caloric Test Result?

Background:

The broad range of vestibular tests used to diagnose labyrinth diseases allows for a functional assessment of the vestibular system. Among the many tests performed, the caloric test is considered the gold standard by providing an objective measurement of the vestibular function for each labyrinth.

Objective:

to correlate the different types of dizziness with the caloric test result.

Methods:

a descriptive study was performed based on the previous records of vestibular tests performed on patients with body balance disorders evaluated at Audiology Service between 2000 and 2020. The variables evaluated were sex, age, hearing loss, tinnitus, and caloric test result.

Results:

the sample was composed of 892 patients, 654 (73.4%) women, and 238 (26.6%) men. Normal results were obtained for 57.4% (N = 514) of the individuals, while peripheral disease 40.1% (N = 357), and central disease 2.5% (N = 21) accounted for the remaining. Complaint of vertigo was not common in central disorders (P = .02; OR = 0.17) and instability was associated with bilateral vestibular weakness (P = 0.02; OR = 5.92). Vertigo associated with tinnitus and/or hearing loss was more frequent in the caloric test with peripheral abnormality (P = 0.008).

Conclusion:

complaints of vertigo associated with tinnitus and/or hearing loss must be directed for clinical observation of unilateral peripheral lesion and instability to central disease or bilateral peripheral lesion.

Relevance of Artifact Removal and Number of Stimuli for Video Head Impulse Test Examination

OBJECTIVE

To evaluate the effect of artifacts on the impulse and response recordings with the video head impulse test (VHIT) and determine how many stimuli are necessary for obtaining acceptably efficient measurements.

METHODS

One hundred fifty patients were examined using VHIT and their registries searched for artifacts. We compared several variations of the dataset. The first variation used only samples without artifacts, the second used all samples (with and without artifacts), and the rest used only samples with each type of artifact. We calculated the relative efficiency (RE) of evaluating an increasingly large number of samples (3 to 19 per side) when compared with the complete sample (20 impulses per side).

RESULTS

Overshoot was associated with significantly higher speed (p = 0.005), higher duration (p < 0.001) and lower amplitude of the impulses (p = 0.002), and consequent higher saccades' latency (p = 0.035) and lower amplitude (p = 0.025). Loss of track was associated with lower gain (p = 0.035). Blink was associated with a higher number of saccades (p < 0.001), and wrong way was associated with lower saccade latency (p = 0.012). The coefficient of quartile deviation escalated as the number of artifacts of any type rose, indicating an increment of variability. Overshoot increased the probability of the impulse to lay on the outlier range for gain and peak speed. Blink did so for the number of saccades, and wrong way for the saccade amplitude and speed. RE reached a tolerable level of 1.1 at 7 to 10 impulses for all measurements except the PR score.

CONCLUSIONS

Our results suggest the necessity of removing artifacts after collecting VHIT samples to improve the accuracy and precision of results. Ten impulses are sufficient for achieving acceptable RE for all measurements except the PR score.

Vestibular recruitment: new application for an old concept

INTRODUCTION

Vestibular recruitment is a sign of hyperexcitability of central vestibular neurons and may be characteristic of peripheral vestibular damage.

OBJECTIVE

To define the post-caloric recruitment index and its ability to predict the stage of vestibular compensation and peripheral lesion.

METHODS

First of all, we demonstrated that larger values in the cold post-caloric stimulation compared to warm stimulation were equivalent to vestibular recruitment observed during the sinusoidal harmonic acceleration test. In the next step, patients with vestibular complaints and asymptomatic controls were submitted to the caloric test. We calculated post-caloric recruitment index for the control group. Among the study group, we analyzed the relation between post-caloric recruitment and unilateral weakness as well as the types of vestibular diagnoses.

RESULTS

Mean post-caloric recruitment was 17.06% and 33.37% among the control and study group, respectively. The ratio between post-caloric recruitment and unilateral weakness was 1.3 in the study group. Among recruiting subjects, no significant difference of unilateral weakness from the lesioned or healthy side was observed. We found no differences in vestibular diagnoses between recruiting and non-recruiting subjects.

CONCLUSION

Post-caloric recruitment index identified asymmetric vestibular tonus and central compensation. The normal value was established at 17.06%.

Estimated Vestibulogram (EVEST) for Effective Vestibular Assessment

BACKGROUND

The availability and development of methods testing the vestibuloocular reflex (VOR) brought a broader view into the lateral semicircular canal (L-SCC) function. However, the higher number of evaluated parameters makes more difficult the specialist's diagnose-making process.

PURPOSE

To provide medical specialists, a new diagnostic-graphic tool, Estimated Vestibulogram- EVEST, enabling a quick and easy-to-read visualization and comparison of the VOR test results within the L-SCC.

METHODS

The development of EVEST involved 148 participants, including 49 healthy volunteers (28 female and 21 male) and 99 (58 female and 41 male) patients affected by different degrees of peripheral vestibular deficit. The corresponding L-SCC VOR test results, from patients meeting the diagnostic criteria, were used to create the EVEST.

RESULTS

Based on the test results, we depicted and calculated the EVEST vestibular function asymmetry (VFA) in all the groups. To assess a feasibility of EVEST to describe a vestibular function deficit, we calculated sensitivity and specificity of VFA using a receiver operating characteristic curve (ROC) and compared it to single tests. In all the tests, we determined the cutoff value as the point with the highest sensitivity and specificity. For discrimination of any vestibular deficit, the VFA with cutoff 6.5% was more sensitive (91%) and specific (98%) than single tests. Results showed that EVEST is a beneficial graphic tool for quick multifrequency comparison and diagnosis of different types of the peripheral vestibular loss.

CONCLUSIONS

EVEST can help to easily evaluate various types of peripheral vestibular lesion.

Evolution of caloric responses during and between the attacks of Meniere's disease

Caloric tests are useful for disease surveillance of Meniere's disease (MD), although the interpretation of caloric tests remains controversial during the attacks of MD. Therefore, we aimed to characterize the findings of caloric tests during the attacks of MD. We analyzed the results of bithermal caloric tests during and between the attacks in 43 patients with unilateral definite MD. Evaluation was performed during the irritative/recovery phase in 22 and during the paretic phase in 26 patients. During the irritative/recovery phase, less than half of patients (10/22, 45%) showed a caloric asymmetry of more than 25%, lesser responses in the affected ear in six and in the healthy ear in the other four. In contrast, patients usually showed a caloric asymmetry of more than 25% during the paretic phase (19/26, 73%) with a decreased response almost always in the affected ear (18/19, 95%). Between the attacks, caloric asymmetry was found in less than half of the patients (20/43, 47%) with a decreased response almost always in the affected ear (19/20, 95%) when observed. The caloric asymmetry was less during the irritative/recovery phases than between the attacks (p = 0.007). In contrast, the caloric asymmetry was larger during the paretic phase than between the attacks (p = 0.041). The caloric asymmetry decreased during the irritative/recovery phases with an estimated mean difference of 34% (adjusted 95% CI 16-53%, p < 0.001) and 23% (adjusted 95% CI 8-38%, p = 0.002) compared to the paretic and interictal phases. Caloric responses fluctuate during and between the attacks of MD depending on the electrophysiologic status of the vestibular afferents. The results of caloric tests in MD, thus should be interpreted with consideration of each phase when the evaluation was done.

Autonomic laterality in caloric vestibular stimulation

BACKGROUND

Caloric stimulation of the vestibular system is associated with autonomic response. The lateralization in the nervous system activities also involves the autonomic nervous system.

AIM

To compare the effect of the right and left ear caloric test on the cardiac sympathovagal tone in healthy persons.

METHODS

This self-control study was conducted on 12 healthy male volunteers. The minimal ice water caloric test was applied for vestibular stimulation. This was done by irrigating 1 milliliter of 4 ± 2 °C ice water into the external ear canal in 1 s. In each experiment, only one ear was stimulated. For each ear, the pessimum position was considered as sham control and the optimum position was set as caloric vestibular stimulation of horizontal semicircular channel. The order of right or left caloric vestibular stimulation and the sequence of optimum or pessimum head position in each set were random. The recovery time between each calorie test was 5 min. The short-term heart rate variability (HRV) was used for cardiac sympathovagal tone metrics. All variables were compared using the analysis of variance.

RESULTS

After caloric vestibular stimulation, the short-term time-domain and frequency-domain HRV indices as well as, the systolic and the diastolic arterial blood pressure, the respiratory rate and the respiratory amplitude, had no significant changes. These negative results were similar in the right and the left sides. Nystagmus duration of left caloric vestibular stimulations in the optimum and the pessimum positions had significant differences (e.g., 72.14 ± 39.06 vs 45.35 ± 35.65, P < 0.01). Nystagmus duration of right caloric vestibular stimulations in the optimum and the pessimum positions had also significant differences (e.g., 86.42 ± 67.20 vs 50.71 ± 29.73, P < 0.01). The time of the start of the nystagmus following caloric vestibular stimulation had no differences in both sides and both positions.

CONCLUSION

Minimal ice water caloric stimulation of the right and left vestibular system did not affect the cardiac sympathovagal balance according to HRV indices.

Associations of Video Head Impulse Test and Caloric Testing among Patients with Vestibular Schwannoma

OBJECTIVE

To determine relationships between caloric testing (CT) and video head impulse testing (vHIT) among patients with unilateral vestibular schwannoma (VS). To describe the distribution of CT and vHIT measurements and assess associations with tumor size and self-perceived handicapping effects.

STUDY DESIGN

Retrospective review.

SETTING

Tertiary referral hospital.

SUBJECTS AND METHODS

Subjects were adults with presumed unilateral VS between 2014 and 2017. Interventions were CT and vHIT. Primary outcomes were vHIT value (abnormal <0.8) and CT value (abnormal >25%). Secondary outcomes were tumor size and Dizziness Handicap Inventory scores.

RESULTS

Fifty-one individuals had complete data for CT and vHIT. The odds of abnormal gain increases by 2.18 for every 10% increase in unilateral weakness on CT (range, 1.44-3.34; P < .001). A significant negative correlation between CT and gain exists (r_s = -0.64, P < .001). Odds of observing saccades increased by 2.68 for every 10% increase in unilateral weakness (range, 1.48-4.85; P = .001). This association was larger in magnitude for overt than covert saccades (odds ratios, 2.48 and 1.59, respectively). Tumor size was significantly associated with an increase in caloric weakness (β = 0.135, P < .001). With every 10-mm increase of tumor size, odds of abnormal gain on vHIT increased 4.13 (range, 1.46-11.66; P = .007). Mean Dizziness Handicap Inventory score was 19.7 (σ = 22), without association to caloric weakness, gain, or tumor size.

CONCLUSION

CT and vHIT both effectively assess vestibular function for patients with VS and correlate to tumor size. These findings are important as vHIT has a lower overall cost, improved patient tolerance, and demonstrated reliability.

Caloric test and video head impulse test sensitivity as vestibular impairment predictors before cochlear implant surgery

OBJECTIVES

Currently, cochlear implant procedures are becoming increasingly broad and have greatly expanded. Bilateral cochlear implants and cochlear implants are more frequently applied in children. Our hypothesis is that the video head impulse test may be more sensitive than the caloric test in detecting abnormal vestibular function before cochlear implant surgery. The objective of this study was to compare the video head impulse test and caloric test results of patients selected for cochlear implant procedures before surgery.

METHODS

The patients selected for cochlear implant surgery were submitted to a bithermal caloric test and video head impulse test.

RESULTS

By comparing angular slow phase velocity values below 5° in the bithermal caloric test (hypofunction) and video head impulse test with a gain lower than 0.8, we identified 37 (64.9%) patients with vestibular hypofunction or canal paresis and 21 (36.8%) patients with abnormal video head impulse test gain before the cochlear implant procedure. Of the 37 patients with caloric test vestibular hypofunction, 20 (54%) patients exhibited an abnormal gain in the video head impulse test.

CONCLUSION

The caloric test is more sensitive than the video head impulse test (Fisher's exact test, p=0.0002) in detecting the impaired ear before cochlear implant delivery. The proportion of caloric test/video head impulse test positive identification of abnormal vestibular function or caloric test/video head impulse test sensitivity was 1.8:1.

The Reliance on Vestibular Information During Standing Balance Control Decreases With Severity of Vestibular Dysfunction

The vestibular system is involved in gaze stabilization and standing balance control. However, it is unclear whether vestibular dysfunction affects both processes to a similar extent. Therefore, the objective of this study was to determine how the reliance on vestibular information during standing balance control is related to gaze stabilization deficits in patients with vestibular dysfunction. Eleven patients with vestibular dysfunction and twelve healthy subjects were included. Gaze stabilization deficits were established by spontaneous nystagmus examination, caloric test, rotational chair test, and head impulse test. Standing balance control was assessed by measuring the body sway (BS) responses to continuous support surface rotations of 0.5° and 1.0° peak-to-peak while subjects had their eyes closed. A balance control model was fitted on the measured BS responses to estimate balance control parameters, including the vestibular weight, which represents the reliance on vestibular information. Using multivariate analysis of variance, balance parameters were compared between patients with vestibular dysfunction and healthy subjects. Robust regression was used to investigate correlations between gaze stabilization and the vestibular weight. Our results showed that the vestibular weight was smaller in patients with vestibular dysfunction than in healthy subjects (F = 7.67, p = 0.011). The vestibular weight during 0.5° peak-to-peak support surface rotations decreased with increasing spontaneous nystagmus eye velocity (ρ = −0.82, p < 0.001). In addition, the vestibular weight during 0.5° and 1.0° peak-to-peak support surface rotations decreased with increasing ocular response bias during rotational chair testing (ρ = −0.72, p = 0.02 and ρ = −0.67, p = 0.04, respectively). These findings suggest that the reliance on vestibular information during standing balance control decreases with the severity of vestibular dysfunction. We conclude that particular gaze stabilization tests may be used to predict the effect of vestibular dysfunction on standing balance control.

Bilateral Vestibular Weakness

Bilateral vestibular weakness (BVW) is a rare cause of imbalance. Patients with BVW complain of oscillopsia. In approximately half of the patients with BVW, the cause remains undetermined; in the remainder, the most common etiology by far is gentamicin ototoxicity, followed by much rarer entities such as autoimmune inner ear disease, meningitis, bilateral Ménière’s disease, bilateral vestibular neuritis, and bilateral vestibular schwannomas. While a number of bedside tests may raise the suspicion of BVW, the diagnosis should be confirmed by rotatory chair testing. Treatment of BVW is largely supportive. Medications with the unintended effect of vestibular suppression should be avoided.

Focal hyperintensity in the dorsal brain stem of patients with cerebellopontine angle tumor: A high-resolution 3 T MRI study

Focal hyperintensity (FHI) in the dorsal brain stem on T2-weighted images of patients with cerebellopontine angle (CPA) tumor was thought to indicate degeneration of the vestibular nucleus and to be specific to vestibular schwannoma. The purpose of this study was to evaluate FHI by using high-resolution 3 Tesla magnetic resonance imaging (3 T MRI) and the relation to clinical characteristics. We retrospectively reviewed the clinical data and MRI of 45 patients with CPA tumors (34 vestibular schwannomas and 11 other tumors). FHI in the dorsal brain stem was found in 25 (55.6%) patients (20 vestibular schwannomas and 5 other tumors). For the vestibular schwannomas, the factors contributing to positive FHI were age (p = 0.025), max CPA (p =  < 0.001), hearing ability (P = 0.005), and canal paresis (p =  < 0.001) in the univariate analysis. Multivariate regression analysis showed that max CPA (p = 0.029) was a significant factor of positive FHI. In other CPA tumors, these factors were not significant predictors. With the use of 3 T MRI, FHI was observed more frequently than previously reported. Our results suggest that FHI is not a specific indicator of vestibular schwannoma and is related to not only vestibular function but also other factors.

Bilateral vestibulopathy: Diagnostic criteria Consensus document of the Classification Committee of the Bárány Society

This paper describes the diagnostic criteria for bilateral vestibulopathy (BVP) by the Classification Committee of the Bárány Society. The diagnosis of BVP is based on the patient history, bedside examination and laboratory evaluation. Bilateral vestibulopathy is a chronic vestibular syndrome which is characterized by unsteadiness when walking or standing, which worsen in darkness and/or on uneven ground, or during head motion. Additionally, patients may describe head or body movement-induced blurred vision or oscillopsia. There are typically no symptoms while sitting or lying down under static conditions.

The diagnosis of BVP requires bilaterally significantly impaired or absent function of the vestibulo-ocular reflex (VOR). This can be diagnosed for the high frequency range of the angular VOR by the head impulse test (HIT), the video-HIT (vHIT) and the scleral coil technique and for the low frequency range by caloric testing. The moderate range can be examined by the sinusoidal or step profile rotational chair test.

For the diagnosis of BVP, the horizontal angular VOR gain on both sides should be <0.6 (angular velocity 150–300°/s) and/or the sum of the maximal peak velocities of the slow phase caloric-induced nystagmus for stimulation with warm and cold water on each side <6°/s and/or the horizontal angular VOR gain <0.1 upon sinusoidal stimulation on a rotatory chair (0.1 Hz, Vmax = 50°/sec) and/or a phase lead >68 degrees (time constant of <5 seconds). For the diagnosis of probable BVP the above mentioned symptoms and a bilaterally pathological bedside HIT are required.

Complementary tests that may be used but are currently not included in the definition are: a) dynamic visual acuity (a decrease of ≥0.2 logMAR is considered pathological); b) Romberg (indicating a sensory deficit of the vestibular or somatosensory system and therefore not specific); and c) abnormal cervical and ocular vestibular-evoked myogenic potentials for otolith function.

At present the scientific basis for further subdivisions into subtypes of BVP is not sufficient to put forward reliable or clinically meaningful definitions. Depending on the affected anatomical structure and frequency range, different subtypes may be better identified in the future: impaired canal function in the low- or high-frequency VOR range only and/or impaired otolith function only; the latter is evidently very rare.

Bilateral vestibulopathy is a clinical syndrome and, if known, the etiology (e.g., due to ototoxicity, bilateral Menière’s disease, bilateral vestibular schwannoma) should be added to the diagnosis. Synonyms include bilateral vestibular failure, deficiency, areflexia, hypofunction and loss.

Brainstem injury associated with supratentorial lesions is revealed by electronystagmography of the cold caloric reflex test

To explore the brainstem injury associated with supratentorial lesions, we conducted analysis of ICP levels and detected ENG parameters by using the cold caloric reflex test and histopathological examinations of the brainstem. Rat model of intracerebral hemorrhage was well-established in the study of supratentorial lesions of varying severities (n=210). Intracerebral pressure monitoring and electronystagmography of the cold caloric reflex test were simultaneously performed in animals. Apoptotic, immunohistochemical, and histopathological changes in different segments of the brainstem were investigated at various time intervals. Electronystagmography parameters were analyzed by cold caloric reflex test. The result showed that the increase of intracerebral pressure was correlated with lesion severity including elevating levels and rostral-caudal progression of neuronal apoptosis, demyelination, N-methyl-D-aspartate cell receptor down-regulation (r=0.815), and histopathological changes. Mutiple discrimination analysis of electronystagmography parameters presented a diagnostic accuracy rate of 79.5% in localizing brainstem injury. In conclusion, our data demonstrated that electronystagmography monitoring along with the cold caloric reflex test performed a favorable effect on the estimation of brainstem injury in ICH rat model, which provided a potential bedside diagnostic tool to assess and predict the progress of supratentorial lesion patient in future.

Does spectacle use lead to vestibular suppression?

BACKGROUND

Laboratory experiments indicate that changes in retinal image size result in adaptive recalibration or suppression of the vestibulo-ocular reflex. Myopia correction with spectacles or contact lenses also leads to retinal image size changes, and may bring about similar vestibulo-ocular reflex alterations.

METHODS

A hypothesis-generating preliminary investigation was conducted. In this cross-sectional study, findings of electronystagmography including bithermal caloric testing were compared between 17 volunteer myopes using spectacles or contact lenses and 17 volunteer emmetropes (with no refractive error).

RESULTS

Bilateral hypoactive caloric responses were demonstrated in 6 of 11 spectacle users, in 1 of 6 contact lens users and in 1 of 17 emmetropes. Hypoactive caloric responses were significantly more likely in spectacle users than in emmetropes (p < 0.01; relative risk = 9.3).

CONCLUSION

A significant proportion of myopes using spectacles have vestibulo-ocular reflex suppression, as demonstrated by the caloric test. This has implications for the interpretation of electronystagmography and videonystagmography results, and highlights spectacle use as a possible cause of vestibular impairment. Further corroboration of these findings is warranted, with more precise and direct vestibulo-ocular reflex tests such as rotational tests and the head impulse test.

Determining vestibular hypofunction: start with the video-head impulse test

Caloric testing is considered the 'reference standard' in determining vestibular hypofunction. Recently, the video-head impulse test (vHIT) was introduced. In the current study we aimed to assess the diagnostic value of the vHIT as compared to caloric testing in determining vestibular function. In a cross-sectional study between May 2012 and May 2013, we prospectively analysed patients with dizziness who had completed caloric testing and the vHIT. For the left and right vestibular system we calculated the mean vHIT gain. We used a gain cut-off value of 0.8 for the vHIT and presence of correction saccades to define an abnormal vestibular-ocular reflex. An asymmetrical ocular response of 22 % or more (Jongkees formula) or an irrigation response with a velocity below 15°/s was considered abnormal. We calculated sensitivity, specificity, positive and negative predictive values with 95 % confidence intervals for the dichotomous vHIT. Among 324 patients [195 females (60 %), aged 53 ± 17 years], 39 (12 %) had an abnormal vHIT gain and 113 (35 %) had an abnormal caloric test. Sensitivity was 31 % (23-40 %), specificity 98 % (95-99 %), positive predictive value was 88 % (74-95 %), and negative predictive value 73 % (67-77 %). In case of vHIT normality, additional caloric testing remains indicated and the vHIT does not replace the caloric test. However, the high positive predictive value of the vHIT indicates that an abnormal vHIT is strongly related to an abnormal caloric test result; therefore, additional caloric testing is not necessary. We conclude that the vHIT is clinically useful as the first test in determining vestibular hypofunction in dizzy patients.

The Effects of Aging on Clinical Vestibular Evaluations

Balance disorders are common issues for aging populations due to the effects of normal aging on peripheral vestibular structures. These changes affect the results of vestibular function evaluations and make the interpretation of these results more difficult. The objective of this article is to review the current state of knowledge of clinically relevant vestibular measures. We will first focus on otolith function assessment methods cervical-VEMP (cVEMP) and ocular-VEMP (oVEMP), then the caloric and video-head impulse test (vHIT) methods for semicircular canals assessment. cVEMP and oVEMP are useful methods, though research on the effects of age for some parameters are still inconclusive. vHIT results are largely independent of age as compared to caloric stimulation and should therefore be preferred for the evaluation of the semicircular canals function.

Subjective Visual Vertical during Caloric Stimulation in Healthy Subjects: Implications to Research and Neurorehabilitation

Background. The subjective visual vertical (SVV) is a perception often impaired in patients with neurologic disorders and is considered a sensitive tool to detect otolithic dysfunctions. However, it remains unclear whether the semicircular canals (SCCs) are also involved in the visual vertical perception. Objective. The aim of this study was to analyze the influence of horizontal SCCs on SVV by caloric stimulation in healthy subjects. Methods. SVV was performed before and during the ice-cold caloric stimulation (4°C, right ear) in 30 healthy subjects. Results. The mean SVV tilts before and during the caloric stimulation were 0.31° ± 0.39 and −0.28° ± 0.40, respectively. There was no significant difference between the mean SVV tilts before and during stimulation (p = 0.113). Conclusion. These results suggest that horizontal SCCs do not influence SVV. Therefore, investigations and rehabilitation approaches for SVV misperceptions should be focused on otolithic and cognitive strategies.

Vestibular perception and the vestibulo-ocular reflex in young and older adults

OBJECTIVES

Quantification of the perceptual thresholds to vestibular stimuli may offer valuable complementary information to that provided by measures of the vestibulo-ocular reflex (VOR). Perceptual thresholds could be particularly important in evaluating some subjects, such as the elderly, who might have a greater potential of central as well as peripheral vestibular dysfunction. The authors hypothesized that perceptual detection and discrimination thresholds would worsen with aging, and that there would be a poor relation between thresholds and traditional measures of the angular VOR represented by gain and phase on rotational chair testing.

DESIGN

The authors compared the detection and discrimination thresholds of 19 younger and 16 older adults in response to earth-vertical, 0.5 Hz rotations. Perceptual results of the older subjects were then compared with the gain and phase of their VOR in response to earth-vertical rotations over the frequency range from 0.025 to 0.5 Hz.

RESULTS

Detection thresholds were found to be 0.69 ± 0.29 degree/sec (mean ± standard deviation) for the younger participants and 0.81 ± 0.42 degree/sec for older participants. Discrimination thresholds in younger and older adults were 4.83 ± 1.80 degree/sec and 4.33 ± 1.57 degree/sec, respectively. There was no difference in either measure between age groups. Perceptual thresholds were independent of the gain and phase of the VOR.

CONCLUSIONS

These results indicate that there is no inevitable loss of vestibular perception with aging. Elevated thresholds among the elderly are therefore suggestive of pathology rather than normal consequences of aging. Furthermore, perceptual thresholds offer additional insight, beyond that supplied by the VOR alone, into vestibular function.

Modification of the postrotary nystagmus test for evaluating young children

This article explores the use of the postrotary nystagmus (PRN) test for children younger than current norms (children 4.0 yr-8.11 yr). In the first study, 37 children ages 4-9 yr were examined in the standard testing position and in an adult-held adapted position to determine whether holding a child affected the reflex. Because the position did not affect the reflex, in the second study, PRN in 44 children ages 2 mo-47 mo was compared with published normative mean raw scores for 44 children age 5 yr to determine whether norms for older children were applicable to younger children. No statistically significant differences were found between <4-yr-old and 5-yr-old children, suggesting that the PRN test can be used in infants and toddlers with valid comparison to current norms for 4-yr-olds on the Sensory Integration and Praxis Tests (4.0 yr-8.11 yr). Future research exploring the predictive value of this measure is warranted.

Vestibular effects of lidocaine intratympanic injection in rats

When lidocaine is locally delivered into the inner ear, it rapidly paralyzes the peripheral vestibular afferent neurons and induces unilateral vestibular loss. The goals of this study were to explore the possibility of developing intratympanic injection (IT) of lidocaine as a modality for treating acute vertigo. To evaluate the minimum concentration required, latent time, action duration, and possibility of lidocaine IT readministration to the vestibular system, we compared the development of horizontal nystagmus after IT of 2, 4, 6, 8, and 10% lidocaine solutions in rats. To identify the induction of vestibular compensation, c-Fos-like protein expression was observed in the vestibular nucleus. Results of our investigation showed that lidocaine IT concentrations greater than 4% induced vestibular hyporeflexia in the injected ear. In order to induce hyporeflexia 4 and 6% lidocaine solutions could also be repeatedly injected. Regardless of concentration, effects of the lidocaine IT dissipated gradually over time. Our findings could be used to develop novel methods for symptom control in vestibular disorder patients.

Triple test as predictive screen for unilateral weakness on caloric testing in routine practice

OBJECTIVE

To investigate in vertigo patients in routine practice to what extent a rapid and straightforward triple bedside test (spontaneous nystagmus, head-shaking nystagmus, and the head impulse test) can predict a normal result on caloric testing.

STUDY DESIGN

Prospective, single-blind, diagnostic study.

SETTING

Tertiary referral center.

PATIENTS

151 patients (78 male and 73 female subjects; mean age, 52.5 +/- 16.4 yr) presenting with acute or recent symptoms of vertigo.

INTERVENTION

Diagnostic evaluation.

MAIN OUTCOME MEASURE

The negative predictive value (NPV) of the triple test in relation to a normal caloric test response.

RESULTS

In unilateral weakness (UW) on caloric testing (UW, >=25%), the triple test had sensitivity of 63.6%, specificity of 85.4%, a positive predictive value (PPV) of 71.4%, and an NPV of 80.4%. In other words, 80.4% of patients with a negative triple test also had a normal response on caloric testing. In pronounced canal paresis (UW, >=50%), the triple test had sensitivity of 81.8%, specificity of 81.4%, a PPV of 55.1%, and an NPV of 94.1%. Significant differences were found between 2 subgroups assessed by examiners with differing levels of experience (p < 0.05).

CONCLUSION

The triple test represents a good screening tool that quickly and reliably excludes unilateral weakness and in particular pronounced canal paresis on caloric testing.