Clinical application of the head impulse test of semicircular canal function

Modernising vestibular assessment

BACKGROUND

There is a high prevalence of dizziness, vertigo and balance symptoms in the general population. Symptoms can be generated by many inner-ear vestibular disorders and there are several diagnostic tests available that can help identify the site of the vestibular lesion. There is little consensus on what diagnostic tests are appropriate, with diagnostics either not completed or minimally performed, leading to missed diagnosis, unsatisfactory results for patients and costs to healthcare systems.

METHODS

This study explored the literature for different neuro-vestibular diagnostic tests not currently considered in the traditional standard vestibular test battery, and examined how they fit effectively into a patient care pathway to help quickly and succinctly identify vestibular function.

RESULTS

A vestibular patient care pathway is presented for acute and subacute presentation of vestibular disorders.

CONCLUSION

An accurate diagnosis following a rigorous anamnesis and vestibular testing is paramount for successful management and favourable outcomes.

A comparison of the video head impulse test and the functional head impulse test in chronic unilateral vestibular loss

OBJECTIVE

To examine the correlation of video head impulse test, functional head impulse test and Dizziness Handicap Inventory results in patients with chronic unilateral vestibular loss, and to compare the results with healthy controls.

METHODS

Forty-eight patients diagnosed with chronic unilateral vestibular loss and 35 healthy individuals, aged 18-65 years, were included. The video head impulse test, functional head impulse test and Dizziness Handicap Inventory were administered.

RESULTS

A significant positive correlation was found between functional head impulse test and video head impulse test results for the study group in all semicircular canals (p < 0.05). There was no significant correlation between Dizziness Handicap Inventory, functional head impulse test and video head impulse test results (p > 0.05). The functional head impulse test and video head impulse test results of the control group were significantly higher than those of the study group in all semicircular canals planes (p < 0.05).

CONCLUSION

In chronic unilateral vestibular loss patients, with high head accelerations, the functional head impulse test indicates deterioration in vestibulo-ocular reflex functionality. It would be beneficial to include the video head impulse test and functional head impulse test in clinical practice as complementary tests in vestibulo-ocular reflex evaluation.

Normative Ranges for, and Interrater Reliability of, Rotational Vestibular and Balance Tests in U.S. Military Service Members and Veterans

PURPOSE

The objectives of this study were to (a) describe normative ranges-expressed as reference intervals (RIs)-for vestibular and balance function tests in a cohort of Service Members and Veterans (SMVs) and (b) to describe the interrater reliability of these tests.

METHOD

As part of the Defense and Veterans Brain Injury Center (DVBIC)/Traumatic Brain Injury Center of Excellence 15-year Longitudinal Traumatic Brain Injury (TBI) Study, participants completed the following: vestibulo-ocular reflex suppression, visual-vestibular enhancement, subjective visual vertical, subjective visual horizontal, sinusoidal harmonic acceleration, the computerized rotational head impulse test (crHIT), and the sensory organization test. RIs were calculated using nonparametric methods and interrater reliability was assessed using intraclass correlation coefficients between three audiologists who independently reviewed and cleaned the data.

RESULTS

Reference populations for each outcome measure comprised 40 to 72 individuals, 19 to 61 years of age, who served either as noninjured controls (NIC) or injured controls (IC) in the 15-year study; none had a history of TBI or blast exposure. A subset of 15 SMVs from the NIC, IC, and TBI groups were included in the interrater reliability calculations. RIs are reported for 27 outcome measures from the seven rotational vestibular and balance tests. Interrater reliability was considered excellent for all tests except the crHIT, which was found to have good interrater reliability.

CONCLUSION

This study provides clinicians and scientists with important information regarding normative ranges and interrater reliability for rotational vestibular and balance tests in SMVs.

X-Linked Gusher Disease DFNX2 in Children, a Rare Inner Ear Dysplasia with Mixed Hearing and Vestibular Loss

Conductive hearing losses are typically present in disorders of the external/middle ear. However, there is a rare group of inner ear conditions called third windows that can also generate a conductive hearing loss. This is due to an abnormal connection between the middle and the inner ear or between the inner ear and the cranial cavity. X-linked gusher disorder is an extremely rare congenital inner ear dysplastic syndrome with an abnormal connection due to a characteristic incomplete cochlear partition type III and an incomplete internal auditory meatus fundus. The disorder is inherited in an X-linked fashion due to the mutation of the POU3F4 gene. We present two siblings diagnosed with the condition and their long-term follow-ups. They both presented audiovestibular symptoms and showed progressive mixed losses and bilateral vestibular weakness. They were treated with cochlear implant, digital amplification and with vestibular rehabilitation. Significant others around them were involved in their journey with the medical team, and in both, a very favourable outcome was achieved. This is the first time that we have reported evolving audiovestibular function with vestibular quantification in X-linked gusher disorder and emphasize on the multidisciplinary holistic approach to manage these children effectively.

A review of the geometrical basis and the principles underlying the use and interpretation of the video head impulse test (vHIT) in clinical vestibular testing

This paper is concerned mainly with the assumptions underpinning the actual testing procedure, measurement, and interpretation of the video head impulse test-vHIT. Other papers have reported in detail the artifacts which can interfere with obtaining accurate eye movement results, but here we focus not on artifacts, but on the basic questions about the assumptions and geometrical considerations by which vHIT works. These matters are crucial in understanding and appropriately interpreting the results obtained, especially as vHIT is now being applied to central disorders. The interpretation of the eye velocity responses relies on thorough knowledge of the factors which can affect the response-for example the orientation of the goggles on the head, the head pitch, and the contribution of vertical canals to the horizontal canal response. We highlight some of these issues and point to future developments and improvements. The paper assumes knowledge of how vHIT testing is conducted.

Evaluating the Vestibulo-Ocular Reflex Following Traumatic Brain Injury: A Scoping Review

Purpose:To identify the tests and tools used to evaluate vestibulo-ocular reflex (VOR) function after traumatic brain injury (TBI) in all age groups and across TBI severity.Methods: An electronic search was conducted to include relevant peer-reviewed literature published up to November 2019. Studies included those done with humans, of all ages, and had assessments of oculomotor and/or vestibulo-ocular function in TBI.Results: Of the articles selected (N = 48), 50% were published in 2018/2019. A majority targeted mild TBI, with equal focus on non-computerized versus computerized measures of VOR. Computerized assessment tools used were videonystagmography, dynamic visual acuity/gaze stability, rotary chair, and caloric irrigation. Non-computerized tests included the head thrust, dynamic visual acuity, gaze stability, head shaking nystagmus, rotary chair tests and the vestibular/oculomotor screening tool. High variability in administration protocols were identified. Namely: testing environment, distances/positioning/equipment used, active/passive state, procedures, rotation frequencies, and variables observed.Conclusions: There is a rapid growth of literature incorporating VOR tests in mild TBI but moderate and severe TBI continues to be under-represented. Determining how to pair a clinical test with a computerized tool and developing standardized protocols when administering tests will help in developing an optimal battery assessing the VOR in TBI.

Efficient Use of Vestibular Testing

While the majority of vestibular disorders may be diagnosed solely on clinical grounds, a variety of clinical scenarios exist in which objective functional assessment of the vestibular system provides data that facilitate diagnosis and treatment decisions. There exists a veritable armamentarium of sophisticated vestibular test modalities, including videonystagmography, rotary chair testing, video head impulse testing, and vestibular-evoked myogenic potentials. This article aims to help clinicians apply an accessible decision-making rubric to identify the clinical scenarios that may and may not benefit from data derived from specific vestibular function tests.

Vestibular Function Measured Using the Video Head Impulse Test in Congenital Nystagmus and Vertigo: A Case Report

In patients with congenital nystagmus (CN), the study of vestibular function is complicated by many factors related to the measurement of the vestibulo-ocular reflex (VOR) by means of caloric testing and the video head impulse test (vHIT), and to date no such studies have successfully employed the vHIT to evaluate vestibular function in these patients. We present a case with CN and vertigo in which peripheral vestibular function was evaluated using the vHIT system, including head impulse testing and the suppression head impulse protocol. We show that it is possible (a) to identify lateral VOR changes such as abnormalities resembling those produced by bilateral vestibular lesions, though not necessarily related to the same mechanism; (b) to identify peripheral VOR lesions of the vertical semicircular canals (SCC); and (c) to document compensation and recovery subsequent to these peripheral lesions during follow-up of patients with CN. vHIT is a useful tool that should be used to study vestibular function in patients with CN and vertigo, which could constitute a new clinical application of this technique.

Directional effects of whole-body spinning and visual flow in virtual reality on vagal neuromodulation

BACKGROUND

Neural circuits allow whole-body yaw rotation to modulate vagal parasympathetic activity, which alters beat-to-beat variation in heart rate. The overall output of spinning direction, as well as vestibular-visual interactions on vagal activity still needs to be investigated.

OBJECTIVE

This study investigated direction-dependent effects of visual and natural vestibular stimulation on two autonomic responses: heart rate variability (HRV) and pupil diameter.

METHODS

Healthy human male subjects (n = 27) underwent constant whole-body yaw rotation with eyes open and closed in the clockwise (CW) and anticlockwise (ACW) directions, at 90°/s for two minutes. Subjects also viewed the same spinning environments on video in a VR headset.

RESULTS

CW spinning significantly decreased parasympathetic vagal activity in all conditions (CW open p = 0.0048, CW closed p = 0.0151, CW VR p = 0.0019,), but not ACW spinning (ACW open p = 0.2068, ACW closed p = 0.7755, ACW VR p = 0.1775,) as indicated by an HRV metric, the root mean square of successive RR interval differences (RMSSD). There were no direction-dependent effects of constant spinning on sympathetic activity inferred through the HRV metrics, stress index (SI), sympathetic nervous system index (SNS index) and pupil diameter. Neuroplasticity in the CW eyes closed and CW VR conditions post stimulation was observed.

CONCLUSIONS

Only one direction of yaw spinning, and visual flow caused vagal nerve neuromodulation and neuroplasticity, resulting in an inhibition of parasympathetic activity on the heart, to the same extent in either vestibular or visual stimulation. These results indicate that visual flow in VR can be used as a non-electrical method for vagus nerve inhibition without the need for body motion in the treatment of disorders with vagal overactivity. The findings are also important for VR and spinning chair based autonomic nervous system modulation protocols, and the effects of motion integrated VR.

Is regression gain or instantaneous gain the most reliable and reproducible gain value when performing video head impulse testing of the lateral semicircular canals?

BACKGROUND

Several different video Head Impulse Test (vHIT) systems exist. The function of each individual semicircular canal (SCC) may be determined by performing this test. All vHIT systems provide information about the function of the vestibular ocular reflex by means of two modalities: SACCADES and GAIN. However, different gain calculation methods exist.

OBJECTIVE

Primary endpoint:•Is instantaneous gain or regression gain the most reproducible and reliable gain value when performing vHIT with testing of the lateral SCCs?Secondary endpoints:•Comparison of each of the instantaneous gain values at 40, 60, and 80ms with the regression gain.•Examination of any intra- and inter examiner variability.•Mean instantaneous gain values, and at different velocities, compared with regression gain values of the lateral SCCs.

METHODS

60 subjects between 18-65 years were included. All patients filled out the Dizziness Handicap Inventory (DHI) questionnaire and underwent four separate vHIT tests, two by an experienced neurotologist and two by an inexperienced examiner.

RESULTS/CONCLUSIONS

240 datasets were obtained, displaying both regression and instantaneous gain values. Regression gain was more reproducible than instantaneous gain. The experienced examiner provided the most reproducible results.When comparing instantaneous gain, we found the gain at 40 ms to be the least reproducible. There was no significant difference between 60 ms and 80 ms.For both examiners no significant intra examiner variability was found.

Audiovestibular Quantification in Rare Third Window Disorders in Children

Third window disorders are structural abnormalities in the bony otic capsule that establish a connection between the middle/inner ear or the inner ear/cranial cavity. Investigated extensively in adults, they have hardly been studied in children. This study is a retrospective study of children (aged 5-17 years) diagnosed with rare third window disorders (third window disorders reported rarely or not reported in children) in a tertiary pediatric vestibular unit in the United Kingdom. It aimed to investigate audiovestibular function in these children. Final diagnosis was achieved by high resolution CT scan of the temporal bones. Of 920 children attending for audiovestibular assessment over a 42 month period, rare third windows were observed in 8 (<1%). These included posterior semicircular canal dehiscence (n = 3, 0.3%), posterior semicircular canal thinning (n = 2, 0.2%), X linked gusher (n = 2, 0.2%), and a combination of dilated internal auditory meatus/irregular cochlear partition/deficient facial nerve canal (n = 1, 0.1%). The majority of them (87.5%) demonstrated a mixed/conductive hearing loss with an air-bone gap in the presence of normal tympanometry (100%). Transient otoacoustic emissions were absent with a simultaneous cochlear pathology in 50% of the cohort. Features of disequilibrium were observed in 75% and about a third showed deranged vestibular function tests. Video head impulse test abnormalities were detected in 50% localizing to the side of the lesion. Cervical vestibular evoked myogenic potential test abnormalities were observed in all children in the cohort undergoing the test where low thresholds and high amplitudes classically found in third window disorders localized to the side of the defects in 28.5%. In the series, 71.4% also demonstrated absent responses/amplitude asymmetry, some of which did not localize to the ipsilesional side. Two children presented with typical third window symptoms. This study observes 2 new rare pediatric third window phenotypes and the presence of a cochlear hearing loss in these disorders. It emphasizes that these disorders should be considered as an etiology of hearing loss/disequilibrium in children. It also suggests that pediatric third window disorders may not present with classical third window features and are variable in their presentations/audiovestibular functions.

Postural instability in children with severe inner ear malformations: Characteristics of vestibular and balance function

OBJECTIVE

To investigate the postural instability and vestibular functions in children with severe inner ear malformations (IEMs).

DESIGN

A prospective case-control study.

STUDY SAMPLE

The study group consisted of 10 children using unilateral auditory brainstem implant (ABI) with labyrinthine aplasia or rudimentary otocyst. The age-matched control groups consisted of 10 unilateral cochlear implant (CI) users with normal inner ear structures and 10 healthy peers. All tests were performed to implant users when the implants were off.

RESULTS

All median VOR gains in the ABI group (median anterior, lateral, and posterior canal 0.15, 0.05, and 0.05, respectively, for the non-implanted sides) were significantly lower than those of the control groups (median VOR gains ≥ 0.90 in both control groups). There were no oVEMP and cVEMP responses in the study group. The mean BOT-2 balance scores of the ABI (3.70 ± 1.34) group was dramatically lower than those of the CI (9.40 ± 2.88) and healthy control (16.20 ± 4.16, p < 0.001).

CONCLUSIONS

The postural instability in children with severe IEMs was higher than those in CI users with normal inner ear structures and healthy peers. The level of deficiency in the labyrinthine was more important for postural stability in children.

A Practical Approach to Vertigo: A Synthesis of the Emerging Evidence

Vestibular presentations represent a large financial and symptomatic burden of disease^1,2 , while remaining one of the most elusive presentations to accurately and confidently diagnose. A primary cause for this is that the same symptom can be the end-product of numerous aetiologies, and uncertainties can lead to unnecessary investigations and associated increased cost and delays in diagnosis. An effective method to narrow the diagnosis is firstly to determine, from a limited list, which type of vestibular syndrome the patient possesses, and then apply a focussed history and examination to define the most likely aetiology within that syndrome. This review provides a diagnostic approach to the vertiginous patient, outlining the underlying pathophysiology that accounts for the clinical symptoms and signs. With this approach, physicians should be able to diagnose the majority of common vestibular presentations and know when to refer the urgent, complex, or rare cases to sub-specialist neuro-otologists for prompt and appropriate management. This article is protected by copyright. All rights reserved.

Vestibulo-ocular reflex involvement in childhood-onset multiple sclerosis

BACKGROUND

Multiple Sclerosis (MS), an autoimmune demyelinating disease of the central nervous system, is an important cause of disability in young adults. The purpose of this cross-sectional study was to evaluate the vestibular system with video Head Impulse Test (vHIT) and determine the impairment of the Vestibulo-ocular Reflex (VOR) in childhood-onset MS.

METHODS

The study group, 20 persons with MS (pwMS) with onset before 18 years of age (6 M, 14 F; mean age 19.06 ± 1.66) and the control group, 20 healthy, age- and sex-matched individuals were retrieved from vHIT recordings. The mean age of MS onset in the study group was 14.60 ± 1.53 years. The VOR pathway was evaluated using vHIT.

RESULTS

The median VOR gains of right anterior (1.00), left lateral (0.96) and left posterior (0.91) semicircular canals were significantly lower in the pwMS group than those of the healthy control group (1.05, 1.00, 0.98 respectively, p < 0.05). Four of pwMS (20%) had abnormal VOR gains. The pwMS with dizziness had significantly lower VOR gains (median 0.91) compared with pwMS without dizziness (median 1.01, p < 0.05).

CONCLUSION

This study demonstrates vestibulo-ocular system can be affected in patients with childhood-onset MS and suggests using vHIT especially in the follow-up of pwMS with dizziness.

An exploration of vestibular function pre and post unilateral cochlear implantation

Objectives: To examine the effects of unilateral cochlear implantation on the balance system for adult patients with bilateral severe to profound sensory neural hearing loss. Methods: 7 CI candidates. The function of the sacculus, utricle, and three semi-circular canals (SCCs) was assessed separately using air conduction cervical vestibular evoked myogenic potentials (VEMP), vibration ocular VEMP and the video head impulse test (vHIT) respectively on each side, pre- and post-operatively. Results: The Otoliths appear more affected by implantation than SCCs. In 3 of 7 cases VEMP was affected by implantation. In 2 cases this was associated with short-term dizziness. Discussion: Differential assessment of vestibular end organ function may elucidate how cochlear implantation affects the vestibular system. As many CI candidates have some vestibular function, pre-implant vestibular assessment may help to inform which side of implantation may best preserve that function if other audiology and surgical considerations are equal. Post-implant assessment with VEMP may help to predict short-term dizziness. More work with a larger sample will be needed to make the case for routine clinical assessment. Conclusions: There is potential benefit of conducting multimodal vestibularassessment pre and post cochlear implantation. The otoliths appear more affected by implantation than the SCC.

Veterans with dizziness recruit compensatory saccades in each semicircular canal plane although VOR gain is normal

BACKGROUND

Exposure to brain injury via blast or blunt mechanisms disrupts multiple sensorimotor systems simultaneously. Large numbers of US Gulf War era and Operation Iraqi/Enduring Freedom veterans with traumatic brain injury (TBI) are suffering the symptom of dizziness - presumed due to "Multi-Sensory Impairment", a clinical pattern of damage to the auditory, visual and vestibular sensorimotor systems.

OBJECTIVE

To describe the oculomotor response to rapid head rotation in a population of veterans with dizziness. We also describe the reliability of using the video head impulse test (vHIT) in a veteran population.

METHODS

We used the vHIT to evaluate the vestibular-ocular reflex (VOR) gain and presence of compensatory saccades (CS) in each semicircular canal of 81 veterans (31% TBI) with dizziness. Data was collected using the ICS Otometric™ vHIT. Data was processed using both the Otometric™ software and custom software written in MATLAB™. This data was evaluated through Kruskal-Wallis rank-sum test and analysis of regression.

RESULTS

Veterans with dizziness recruit CS in all semicircular canal planes even though their VOR gain is normal. The vHIT is a reliable clinical test to quantify the metrics of the VOR and CS in veterans.

CONCLUSION

Veterans with dizziness symptoms use compensatory saccades in all planes of semicircular canal rotation, despite having normal peripheral VOR gain during rapid head rotation. The video head impulse test is a stable measure of vestibular slow phase and metrics of compensatory saccades in veterans with dizziness.

Residual vestibular function after vestibular schwannoma surgery

OBJECTIVES

This study aimed to assess vestibular function in 39 patients who underwent neurectomy for vestibular schwannoma.

METHOD

Semicircular canal reactivity was measured by video head-impulse test using high-frequency passive head acceleration. Response gain was calculated as a ratio between the areas under the eye-velocity curve and the head-velocity curve.

STATISTICAL ANALYSIS

Student t-test was used for to compare quantitative variables. ANOVA was used to test inter-group differences in categoric variables.

RESULTS

In all cases, surgery-side gain on head impulse test was low, with increased gain asymmetry. A subgroup of 7 patients (18%) showed relatively high gain in vestibulo-ocular reflex on the surgery side. Caloric reaction was absent in all cases. These findings indicate that residual vestibular function can be conserved following vestibular schwannoma extirpation.

CONCLUSION

Cases with moderate vestibulo-ocular reflex gain were a subgroup with partial conservation of vestibular nerve fibers. Whether this is a predictor of better functional prognosis remains to be elucidated. Higher gain correlated with less extensive surgery and sparing of the inferior vestibular nerve. Low gain correlated with complete vestibular neurectomy. This information may guide rehabilitation strategy following surgery.

Restoring the High-Frequency Dynamic Visual Acuity with a Vestibular Implant Prototype in Humans

INTRODUCTION

The vestibular implant could become a clinically useful device in the near future. This study investigated the feasibility of restoring the high-frequency dynamic visual acuity (DVA) with a vestibular implant, using the functional Head Impulse Test (fHIT).

METHODS

A 72-year-old female, with bilateral vestibulopathy and fitted with a modified cochlear implant incorporating three vestibular electrodes (MED-EL, Innsbruck, Austria), was available for this study. Electrical stimulation was delivered with the electrode close to the lateral ampullary nerve in the left ear. The high-frequency DVA in the horizontal plane was tested with the fHIT. After training, the patient underwent six trials of fHIT, each with a different setting of the vestibular implant: (1) System OFF before stimulation; (2) System ON, baseline stimulation; (3) System ON, reversed stimulation; (4) System ON, positive stimulation; (5) System OFF, without delay after stimulation offset; and (6) System OFF, 25 min delay after stimulation offset. The percentage of correct fHIT scores for right and left head impulses were compared between trials.

RESULTS

Vestibular implant stimulation improved the high-frequency DVA compared to no stimulation. This improvement was significant for "System ON, baseline stimulation" (p = 0.02) and "System ON, positive stimulation" (p < 0.001). fHIT scores changed from 19 to 44% (no stimulation) to maximum 75-94% (System ON, positive stimulation).

CONCLUSION

The vestibular implant seems capable of improving the high-frequency DVA. This functional benefit of the vestibular implant illustrates again the feasibility of this device for clinical use in the near future.

Functional Head Impulse Test in Professional Athletes: Sport-Specific Normative Values and Implication for Sport-Related Concussion

Dizziness, slow visual tracking, or blurred vision following active head (or body) movements are among the most common symptoms reported following sport-related concussion, often related to concurrent dysfunctions of the vestibular system. In some cases, symptoms persist even if bedside and auxiliary standard vestibular tests are unremarkable. New functional tests have been developed in recent years to objectify neurological alterations that are not captured by standard tests. The functional head impulse test (fHIT) requires the patient to recognize an optotype that is briefly flashed during head rotations with various angular accelerations (2,001–6,000 deg/s²) and assesses the proportion if correct answers (pca). 268 active professional athletes (23.70 ± 5.32y) from six different sports were tested using fHIT. Pca were analyzed both pooling head acceleration in the range of 2,001–6,000 deg/s² and computing a single pca value for each 1,000 deg/s² bin in the range 2,001–8,000 deg/s². No significant difference (p = 0.159) was found between responses to head impulses in the plane of horizontal (pca: 0.977) and vertical semicircular canals (pca: 0.97). The sport practiced had a major effect on the outcome of the fHIT. Handball players achieved a better performance (p < 0.001) than the whole athlete group, irrespective of the direction of head impulses. The pca achieved by athletes practicing snowboard, bob and skeleton were instead significantly below those of the whole athlete group (p < 0.001) but only when vertical head impulses were tested. Overall, pca declined with increasing head acceleration. The decline was particularly evident in the range not included in the standard fHIT exam, i.e., 6,001–8,000 deg/s² for horizontal and 5,001–8,000 deg/s² for vertical head impulses. When vertical head impulses were tested, athletes practicing snowboard, bob and skeleton (non-ball sports) showed, beside the lower overall pca, also a steeper decline as a function of vertical head acceleration. The findings suggest that: (1) functional VOR testing can help understanding sport-specific VOR requirements; (2) the fHIT is able to detect and objectify subtle, sport-specific changes of functional VOR performance; (3) if sport-specific normative values are used, the fHIT test procedure needs to be optimized, starting from the highest acceleration to minimize the number of head impulses.