Neuro-otology- some recent clinical advances

Cervical vestibular evoked myogenic potentials in healthy children: Normative values for bone and air conduction

Objectives

To characterize cervical vestibular evoked myogenic potentials (c-VEMPs) in bone conduction (BC) and air conduction (AC) in healthy children, to compare the responses to adults and to provide normative values according to age and sex.

Design

Observational study in a large cohort of healthy children (n = 118) and adults (n = 41). The c-VEMPs were normalized with the individual EMG traces, the amplitude ratios were modeled with the Royston-Wright method.

Results

In children, the amplitude ratios of AC and BC c-VEMP were correlated (r = 0.6, p < 0.001) and their medians were not significantly different (p = 0.05). The amplitude ratio was higher in men than in women for AC (p = 0.04) and BC (p = 0.03). Children had significantly higher amplitude ratios than adults for AC (p = 0.01) and BC (p < 0.001). Normative values for children are shown. Amplitude ratio is age-dependent for AC more than for BC. Confidence limits of interaural amplitude ratio asymmetries were less than 32%. Thresholds were not different between AC and BC (88 ± 5 and 86 ± 6 dB nHL, p = 0.99). Mean latencies for AC and BC were for P-wave 13.0 and 13.2 msec and for N-wave 19.3 and 19.4 msec.

Conclusion

The present study provides age- and sex-specific normative data for c-VEMP for children (6 months to 15 years of age) for AC and BC stimulation. Up to the age of 15 years, c-VEMP responses can be obtained equally well with both stimulation modes. Thus, BC represents a valid alternative for vestibular otolith testing, especially in case of air conduction disorders.

Do otosclerosis and stapedotomy affect semicircular canal functions? Preliminary results of video head impulse test

BACKGROUND

Otosclerosis and stapedotomy have some effects on the vestibular system, but there are very limited data on their effects on semicircular canals (SCCs).

OBJECTIVE

The aim of the study is to investigate if otosclerosis and stapedotomy have an effect on SCCs and video head impulse test (vHIT).

MATERIAL AND METHODS

This retrospective study included 11 otosclerosis patients who had undergone stapedotomy and 30 healthy participants. Twenty-two ears of 11 patients with otosclerosis were divided into two groups based on whether the ear had been operated (12 ears) or not (10 ears). All participants underwent vHIT. We compared gains of all SCCs, presence of saccades among the operated ears, unoperated ears and control ears.

RESULTS

Significant difference (p<.05) was noted in comparisons of gain of lateral SCCs among all groups. Control group had the highest gain, followed by unoperated and operated groups, respectively. Comparison of incidence of covert saccade showed significant difference (p<.05) for lateral and posterior SCCs.

CONCLUSIONS AND SIGNIFICANCE

Otosclerosis and otosclerosis surgery may have some effects on SCC functions and thereby vHIT. Lateral SCC is the most affected SCC in terms of gain. These findings appear to add important contributions to our knowledge.

Comparison of test results from two separate video head impulse test systems in a cohort of patients diagnosed with a unilateral vestibular schwannoma

PURPOSE

Video head impulse testing (vHIT) is a relatively new technology enabling evaluation of vestibular function. The aim of this study was to compare the test results from two separate vHIT systems in a group of patients diagnosed with a unilateral vestibular schwannoma (VS) with regards to sensitivity, specificity and inter-examiner differences.

METHODS

Forty-two patients were examined with two separate vHIT systems: EyeSeeCam^® (system A) and ICS Impulse^® (system B), by one of two examiners. All six semicircular canals (SCCs) were tested under standardized conditions, and strict criteria were set up for post-test interpretation.

RESULTS

With the majority of test parameters, the two test systems were in agreement. Vestibular deficits were found in 40.5% (system A) to 45% (system B) of patients with a VS on the tested side; corresponding to a positive predictive value (PPV) of 86.4% (system B) to 94.4% (system A). The specificity was 97.6% for system A and 92.9% for system B. An overall agreement between the two vHIT systems measured as kappa was computed to be 0.61. There were no significant inter-examiner differences. When testing the vertical SCCs, a tendency of too high mean gain values was seen with system A but not with system B.

CONCLUSION

In patients with unilateral VS, vHIT is a test with moderate sensitivity and high specificity in regard to identification of a vestibular deficit. There were no significant differences in test results between the two vHIT systems.

Clinical Validity of Quantified Visually Enhanced Vestibulo-ocular Reflex Test to Detect Horizontal Semicircular Canal Hypofunction

OBJECTIVE

To investigate the clinical validity of the mathematical measured VVOR test results to detect horizontal semicircular canal hypofunction.

STUDY DESIGN

Prospective, nonrandomized, observational study.

SETTING

Tertiary referral center, hospital.

PATIENTS

Consecutive patients on first time visit to otoneurology unit.

INTERVENTION(S)

Diagnostic.

MAIN OUTCOME MEASURE(S)

Values of statistical indicators of clinical validity for VVOR test to detect horizontal canal hypofunction were used considering vHIT horizontal aVOR gain values as gold standard.

RESULTS

Area under curve of ROC curve for quantified VVOR testing was 0.92. Head movement frequency on VVOR test and contralateral VVOR gain were identified as significant influence factors of (unilateral) VVOR gain (p < 0.0001) on statistical linear model.

CONCLUSIONS

According to the obtained results, the quantified VVOR test has excellent clinical validity for detecting angular horizontal VOR hypofunction.

Mathematical Methods for Measuring the Visually Enhanced Vestibulo-Ocular Reflex and Preliminary Results from Healthy Subjects and Patient Groups

Background

Visually enhanced vestibulo–ocular reflex (VVOR) is a well-known bedside clinical test to evaluate visuo–vestibular interaction, with clinical applications in patients with neurological and vestibular dysfunctions. Owing to recently developed diagnostic technologies, the possibility to perform an easy and objective measurement of the VVOR has increased, but there is a lack of computational methods designed to obtain an objective VVOR measurement.

Objectives

To develop a method for the assessment of the VVOR to obtain a gain value that compares head and eye velocities and to test this method in patients and healthy subjects.

Methods

Two computational methods were developed to measure the VVOR test responses: the first method was based on the area under curve of head and eye velocity plots and the second method was based on the slope of the linear regression obtained for head and eye velocity data. VVOR gain and vestibulo–ocular reflex (VOR) gain were analyzed with the data obtained from 35 subjects divided into four groups: healthy (N = 10), unilateral vestibular with vestibular neurectomy (N = 8), bilateral vestibulopathy (N = 12), and cerebellar ataxia, neuropathy, and vestibular areflexia syndrome (CANVAS) (N = 5).

Results

Intra-class correlation index for the two developed VVOR analysis methods was 0.99. Statistical differences were obtained by analysis of variance statistical method, comparing the healthy group (VVOR mean gain of 1 ± 0) with all other groups. The CANVAS group exhibited (VVOR mean gain of 0.4 ± 0.1) differences when compared to all other groups. VVOR mean gain for the vestibular bilateral group was 0.8 ± 0.1. VVOR mean gain in the unilateral group was 0.6 ± 0.1, with a Pearson’s correlation of 0.52 obtained when VVOR gain was compared to the VOR gain of the operated side.

Conclusion

Two computational methods to measure the gain of VVOR were successfully developed. The VVOR gain values appear to objectively characterize the VVOR alteration observed in CANVAS patients, and also distinguish between healthy subjects and patients with some vestibular disorders.