Horizontal Head Impulse Test Research Articles

Video head impulse testing in patients with isolated (hemi)nodular infarction.

Isolated (hemi)nodular strokes as underlying cause of acute dizziness are rare, thus there are still gaps of knowledge in the clinical presentation of affected patients. Clinical and experimental evidence has suggested that lesions involving the nodulus lead to various vestibulo-ocular deficits including prolonged velocity-storage, periodic-alternating nystagmus, positional nystagmus, abolished suppression of post-rotatory nystagmus by head-tilt and impaired verticality perception. At the bedside, the angular vestibulo-ocular reflex (aVOR), as assessed by the horizontal head-impulse test (HIT), has been reported to be normal, however quantitative assessments of all six semicircular canals are lacking. The primary aim of this case series was to characterize the spectrum of clinical presentations in isolated (hemi)nodular strokes. Furthermore, based on preliminary observations, we hypothesized that the aVOR is within normal limits in isolated nodular strokes. We retrospectively included patients with isolated (hemi)nodular stroke on diffusion-weighted MR-imaging from a prospective stroke-registry. All patients received a standardized bedside neuro-otological assessment and quantitative, video-based HIT (vHIT) of all six semicircular canals. Overall ratings of vHIT (normal vs. abnormal function) were performed independently by two reviewers and disagreements were resolved. Between January 2015 and December 2021 six patients with isolated nodular (n = 1) or heminodular (n = 5) ischemic stroke were included. Clinical presentation met diagnostic criteria for acute vestibular syndrome (AVS) in 5/6 patients and for episodic vestibular syndrome (EVS) in 1/6 patients. Ocular motor abnormalities observed included the presence of spontaneous horizontal nystagmus (n = 2), positional nystagmus (5/6), head-shaking nystagmus (3/6), skew deviation (n = 1), and moderate or severe truncal ataxia (5/6). Bedside HIT was normal in all patients and no gaze-evoked or periodic alternating nystagmus was observed. aVOR-gains were within normal range in all patients and overall aVOR-function as assessed by vHIT was rated as normal in all six patients. Using quantitative, video-based testing of the horizontal and vertical aVOR, preserved integrity of the aVOR in (hemi)nodular strokes was confirmed, extending preliminary findings at the bedside. Furthermore, widespread deficits of both ocular stability, postural control and volitional eye movements were observed in our study cohort, being consistent with findings reported in previous studies.

Comparison of EOG and VOG obtained eye movements during horizontal head impulse testing.

IntroductionVideo head impulse testing is frequently used to evaluate the vestibular function. During this test, eye movement responses are recorded with video-oculography (VOG). However, the use of VOG can sometimes be challenging, especially due to pupil detection problems (e.g., blinking, droopy eyelids, etc.). Therefore, this study investigated whether electro-oculography (EOG), a technique that does not depend on pupil tracking but on the orientation of the corneoretinal potential, might be an alternative to VOG for quantifying eye movement responses during head impulse testing.Subjects and methodsHead impulse testing was performed in 19 healthy subjects without a prior history of vestibular symptoms. Horizontal eye movements were recorded simultaneously with EOG (using an EOG system) and VOG (using a VHIT system: ICS Impulse). The eye movement responses to each side of both techniques were compared using a concordance correlation coefficient (rc), t-testing, and Bayes Factor (BF) paired t-testing.ResultsEOG and VOG obtained eye movement traces that correlated well with each other during head impulse testing (average rc = 0.89). Average VOR gains obtained with EOG and VOG were not significantly different from each other for all subjects during left head impulses. However, VOG gains differed between both techniques regarding right head impulses. VOG showed significant VOR gain asymmetry (5% to the right), whereas EOG showed no significant asymmetry (1% to the right).ConclusionThis study demonstrated the use of EOG to record eye movements during head impulse testing for the first time. EOG and VOG obtained eye movement traces that correlated well with each other during horizontal head impulse testing. In addition, EOG showed smaller VOR gain asymmetry in healthy individuals, in contrast to VOG. These findings indicate that EOG might potentially be applicable as an alternative to VOG for collecting eye movement responses during head impulse testing.Trial registration number10192021-38 dated 19.10.21.

Head impulse testing in bilateral vestibulopathy in patients with genetically defined CANVAS.

BackgroundTo investigate the association between disease duration and the severity of bilateral vestibulopathy in individuals with complete or incomplete CANVAS (Cerebellar Ataxia with Neuropathy and Vestibular Areflexia Syndrome) and biallelic RFC1 repeat expansions.MethodsRetrospective analysis of clinical data and the vestibulo‐ocular reflex quantified by the video head impulse test in 20 patients with confirmed biallelic RFC1 repeat expansions.ResultsVestibulo‐ocular reflex gain at first admittance 6.9 ± 5.0 years after disease onset was 0.16 [0.15–0.31] (median [interquartile range]). Cross‐sectional analysis revealed that gain reduction was associated with disease duration. Follow‐up measurements were available for ten individuals: eight of them exhibited a progressive decrease of the vestibulo‐ocular reflex gain over time. At the first visit, six of all patients (30%) did not show clinical signs of cerebellar ataxia.ConclusionsOur data suggest a pathological horizontal head impulse test, which can easily be obtained in many outpatient clinics, as a sign of bilateral vestibulopathy in genetically confirmed CANVAS that can precede clinically accessible cerebellar ataxia at least in a subset of patients. The presumably continuous decline over time possibly reflects the neurodegenerative character of the disease. Thus, genetic testing for RFC1 mutations in (isolated) bilateral vestibulopathy might allow disease detection before the onset of cerebellar signs. Further studies including a wider spectrum of vestibular function tests are warranted in a prospective design.

Agreement Between Caloric and Horizontal Video Head Impulse Testing in School-Aged Children Presenting With Dizziness.

The purpose of this investigation was to determine the relationship between the horizontal semicircular canal video head impulse test (hvHIT) and the caloric test in a sample of school-age children evaluated due to complaints of dizziness or imbalance. In adults, these two tests provide different but complementary information regarding vestibular function and/or pathology. However, the most common causes of vestibular loss in children are different than those in adults, and it is not clear how these two tests of horizontal semicircular canal function are related in a pediatric population. This is a retrospective study of electronic records of pediatric patients (< 18 years old) who were referred for vestibular function testing and completed both hvHIT and caloric testing. Agreement between both test results was evaluated by examining measures of sensitivity, specificity, and calculating Cohen's kappa. Results from 117 patients (mean age = 13.7 years, age range: 8-17 years, 37 males) were analyzed. Most patients (97/115 [84.3%]) demonstrated both normal hvHIT and caloric test results. Compared to caloric testing, the hvHIT had poor sensitivity (38.9%) and excellent specificity (98.0%). Cohen's kappa analysis revealed moderate agreement between the methods (coefficient = 0.49 [0.24, 0.73]). Where disagreement between the two tests occurred, the final diagnosis was not contingent on either test result. There is a moderate agreement between the hvHIT and the caloric test in pediatric patients presenting to a tertiary care medical center for a vestibular evaluation. Most patients in this cohort presented with normal findings. The specificity of hvHIT was excellent, although the sensitivity was low. This may be related to the low prevalence of peripheral vestibular system disease in this study cohort, and these results do not generalize to centers that serve populations of children where vestibular disorders are more prevalent (e.g., children with sensorineural hearing loss).

Assessing the Clinical Value of Objective and Patient-Reported Audiovestibular Outcome Measures in the Risk Estimation of Systemic Cobalt Toxicity for Patients With a Metal-on-Metal Hip Implant.

Based on limited evidence from case reports and small cohort studies of metal-on-metal (MoM) hip implant patients with presumed systemic cobalt (Co) toxicity, and a few animal studies on Co-induced damage to the otovestibular system, it was hypothesised that Co exhibits an ototoxic potential alongside other systemic manifestations. Preliminary investigations from our research group in MoM patients confirmed this assumption for the auditory system, whereas no signs of Co-induced vestibular impairment were detected, and a clear dose-response relationship between the auditory function and the blood Co levels was lacking. Therefore, the current study aimed to extend and validate these findings in a larger sample of MoM patients and control subjects, to explore the potential clinical value of audiovestibular outcome measures in the risk estimation of systemic Co toxicity in this patient population. Fifty patients (32 to 68 years) with a primary unilateral/bilateral MoM hip implant were matched for age, gender, and noise exposure to 50 nonimplanted control subjects. Both groups underwent the same protocol, consisting of an objective auditory [i.e., conventional and high-frequency audiometry, transient-evoked and distortion (TEOAEs and DPOAEs), auditory brainstem responses] and vestibular (i.e., cervical and ocular vestibular evoked myogenic potentials, horizontal and vertical video head impulse tests) test battery, a questionnaire inquiring auditory, balance, and general neurological symptoms, and a blood sample collection to determine the plasma Co concentration. The auditory test battery presented consistently higher audiometric thresholds in the MoM patient group, with group differences ranging from 2.1 to 5.7 dB in the lower frequencies (0.25 to 6.0 kHz) and from 4.6 to 9.3 dB in the high frequencies (8.0 to 14.0 kHz). Group differences at high frequencies were statistically significant ( p ≤ 0.001). Additionally, significantly lower TEOAE ( p = 0.009) and DPOAE ( p < 0.001) amplitudes were observed in the MoM patients when the better ear was included in the analysis, and more absent TEOAE and DPOAE responses were found between 1.0 and 4.0 kHz (0.008 ≤ p ≤ 0.039). Within the vestibular test battery, the MoM patients showed longer N1 and P1 ocular vestibular evoked myogenic potentials latencies for the left ear, and lower video head impulse test gains for the left anterior and right posterior semicircular canals (0.005 ≤ p ≤0.035). The patient-reported (questionnaire) outcome delivered no significant group differences ( p > 0.01). Six patients had elevated Co levels according to our local institutional threshold (>4 or 5 µg/l for unilateral or bilateral MoM hip implants, resp.), but their audiovestibular outcome measures did not differ significantly from those of the other patients. Corresponding to our preliminary investigations, the results indicate possibly Co-induced (predominantly high-frequency) auditory impairment, probably triggered by toxic damage to the cochlear structures. However, the low mean difference values, the lack of group differences for the patient-reported outcome measures, and the lack of any relationship with the blood Co levels strongly reduce the clinical relevance of these findings. Therefore, the risk of Co-induced ototoxic impairment is considered to be clinically negligible for the majority of MoM hip implant patients, and the use of auditory tests in the risk estimation of systemic Co toxicity should be decided on a case-by-case basis.

A new ocular motor sign in acute vestibular syndrome: Is HINTS plus enough?

A 66-year-old hypertensive and diabetic male presented with acute vestibular syndrome for three days. HINTS plus examination was performed. The horizontal head impulse test was positive on the left side. Video oculography showed centripetal nystagmus on gaze testing in the dark and test of skew was negative. There was no new hearing loss on the finger rub test. On neurological examination, he had severe postural instability and saccadic smooth pursuit. Radio-imaging studies were conducted to rule out the possibility of stroke. CT brain showed infarction in the territory of the medial branch of the right posterior inferior cerebellar artery. MRI brain confirmed the diagnosis. Thus, posterior circulation stroke can present with acute vestibular syndrome mimicking acute unilateral vestibulopathy. However, the presence of associated neurological symptoms like gait ataxia, centripetal nystagmus and vascular risk factors pointed towards a central cause. Clinical evaluation suggesting a peripheral lesion should never be taken in isolation and needs to be correlated with other associated signs. We describe centripetal nystagmus without fixation as a new oculomotor sign in acute vestibular syndrome.

Isolated cerebellar nodulus infarction: Two case reports and literature review

BackgroundIsolated cerebellar nodulus infarction (ICNI) is rare and has great clinical similarity with acute peripheral vestibulopathy (APV), from which it is difficult to distinguish. We report two cases of ICNI followed by a literature review to identify the discriminant clinical elements that differentiate ICNI from APV. MethodsWe describe in detail our 2 cases. Besides, a literature search in Medline via PubMed and Scopus was performed up to May 17, 2020. Clinical characteristics, mainly of well-described cases, were extracted and analyzed. ResultsOur search yielded 43 total publications, among which 13 were selected, including 23 patients. Spontaneous or positional rotatory vertigo with unidirectional spontaneous horizontal nystagmus, associated with the postural imbalance and unilateral lateropulsion or fall on Romberg’s test, was the most common clinical picture. According to our literature review, the discriminant clinical elements which differentiate ICNI from APV were direction-changing gaze-evoked nystagmus, bilateral lateropulsion or fall on Romberg’s test, and normal horizontal head impulse test. Our two patients reported a positional fleeting abnormal visual perception of spatial orientation of objects. We proposed this symptom as a discriminant clinical element. ConclusionThe ICNI constitutes a difficult differential diagnosis of APV. Through our two patients reported here, we proposed a supplementary discriminant symptom helpful for the clinical diagnosis.

How Good Are We in Evaluating a Bedside Head Impulse Test?

Clinicians performing a horizontal head impulse test (HIT) are looking for a corrective saccade. The detection of such saccades is a challenge. The aim of this study is to assess an expert's likelihood of detecting corrective saccades in subjects with vestibular hypofunction. In a prospective cohort observational study at a tertiary referral hospital, we assessed 365 horizontal HITs performed clinically by an expert neurootologist from a convenience sample of seven patients with unilateral or bilateral deficient vestibulo-ocular reflex (VOR). All HITs were recorded simultaneously by video-oculography, as a gold standard. We evaluated saccades latency and amplitude, head velocity, and gain. Saccade amplitude was statistically the most significant parameter for saccade detection (p < 0.001).The probability of saccade detection was eight times higher for HIT toward the pathological side (p = 0.029). In addition, an increase in saccade amplitude resulted in an increased probability of detection (odds ratio [OR] 1.77 [1.31 to 2.40] per degree, p < 0.001). The sensitivity to detect a saccade amplitude of 1 degree was 92.9% and specificity 79%. Saccade latency and VOR gain did not significantly influence the probability of the physician identifying a saccade (OR 1.02 [0.94 to 1.11] per 10-msec latency and OR 0.84 [0.60 to 1.17] per 0.1 VOR gain increase). The saccade amplitude is the most important factor for accurate saccade detection in clinically performed head impulse tests. Contrary to current knowledge, saccade latency and VOR gain play a minor role in saccade detection.

VOR gain calculation methods in video head impulse recordings.

BACKGROUND:International consensus on best practices for calculating and reporting vestibular function is lacking. Quantitative vestibulo-ocular reflex (VOR) gain using a video head impulse test (HIT) device can be calculated by various methods.OBJECTIVE:To compare different gain calculation methods and to analyze interactions between artifacts and calculation methods.METHODS:We analyzed 1300 horizontal HIT traces from 26 patients with acute vestibular syndrome and calculated the ratio between eye and head velocity at specific time points (40 ms, 60 ms) after HIT onset (‘velocity gain’), ratio of velocity slopes (‘regression gain’), and ratio of area under the curves after de-saccading (‘position gain’).RESULTS:There was no mean difference between gain at 60 ms and position gain, both showing a significant correlation (r2 = 0.77, p < 0.001) for artifact-free recordings. All artifacts reduced high, normal-range gains modestly (range –0.06 to –0.11). The impact on abnormal, low gains was variable (depending on the artifact type) compared to artifact-free recordings.CONCLUSIONS:There is no clear superiority of a single gain calculation method for video HIT testing. Artifacts cause small but significant reductions of measured VOR gains in HITs with higher, normal-range gains, regardless of calculation method. Artifacts in abnormal HITs with low gain increased measurement noise. A larger number of HITs should be performed to confirm abnormal results, regardless of calculation method.

Changes in Vestibular Function in Patients With Head-and-Neck Cancer Undergoing Chemoradiation.

While the cochleotoxicity of cisplatin has been well investigated, less is known about the effects of platinum-based chemotherapy on the vestibular system. In particular, there is a lack of prospective studies using modern laboratory vestibular testing that examine the effects of cisplatin on the semicircular canals and on the otolith organs. The aim of the present study was, therefore, to investigate the vestibulotoxic effect of cisplatin in patients with head and neck tumors who are undergoing chemoradiation. Forty-five patients undergoing cisplatin-based chemoradiation for head and neck cancer received a vestibular assessment consisting of anamnesis, a horizontal video head impulse test (vHIT), ocular and cervical vestibular evoked myogenic potential testing, as well as pure tone audiometry. This assessment was performed before therapy, 6 weeks after therapy, and 3 months after therapy. Video head impulse test showed a significantly reduced median gain 6 weeks after chemoradiation. In addition, significantly more refixational saccades could be detected after therapy. Vestibular evoked myogenic potential testing results also revealed significant changes, whereas pure tone audiometry did not. None of the patients mentioned "dizziness" during the follow-up examinations. We demonstrated a vestibulotoxic effect of cisplatin-based chemoradiation in patients with head and neck cancer. Future studies are needed to better understand cisplatin-induced vestibulotoxicity and to identify possible vestibuloprotective substances. Still, before and after chemoradiation, patients should undergo not only auditory testing but also vestibular testing in order to detect potential vestibular loss as soon as possible and to quickly initiate vestibular physiotherapy.

Dissociated Results between Caloric and Video Head Impulse Tests in Dizziness: Prevalence, Pattern, Lesion Location, and Etiology.

Background and PurposeThis study was designed to determine the prevalence, pattern, lesion location, and etiology of dissociation in the results of the bithermal caloric test and the horizontal video head impulse test (vHIT) in dizzy patients with various etiologies and disease durations.MethodsWe analyzed the results of bithermal caloric tests and vHITs performed over 26 months in 893 consecutive patients who underwent both tests within a 10-day period.ResultsDissociation in the results of the two tests was found in 162 (18.1%) patients. Among them, 123 (75.9%) had abnormal caloric tests (unilateral paresis in 118 and bilateral paresis in 5) but normal vHITs. Peripheral lesions were identified in 105 (85.4%) of these patients, with the main underlying diseases being Meniere's disease (62/105, 59%) and vestibular neuritis/labyrinthitis (29/105, 27.6%). In contrast, central pathologies of diverse etiologies were found only in 18 (14.6%) patients. Abnormal vHIT (bilaterally positive in 18, unilaterally positive in 19, and hyperactive in 2) and normal caloric responses were found in 39 patients, with an equal prevalence of central (n=19) and peripheral (n=20) lesions. The peripheral lesions included vestibular neuritis/labyrinthitis in seven patients and Meniere's disease in another seven. The central lesions had diverse etiologies.ConclusionsDissociation in the results between caloric tests and horizontal vHITs is not uncommon. The present patients with abnormal caloric tests and normal vHITs mostly had peripheral lesions, while central lesions were likely to underlie those with abnormal vHITs and normal caloric tests.

Dissociation of caloric and head impulse tests: a marker of Meniere's disease.

A retrospective analysis of the horizontal video head impulse test (vHIT) results and caloric testing results was undertaken on 644 patients who attended a neuro-otology outpatient facility. Presenting symptoms included spontaneous vertigo, positional vertigo, imbalance or chronic subjective dizziness. For 570 patients, the results of vHIT and caloric testing were concordant. Both tests were normal in 500 subjects with an average vHIT gain = 0.92 ± 0.09 (L); 0.98 ± 0.10 (R) and canal paresis (CP) = 7.88 ± 6.12; (range 0-28%). 54 had concordant asymmetries, average ipsilesional vHIT gain = 0.56 ± 0.15, average contralesional vHIT gain = 0.88 ± 0.12. CP = 68.02 ± 24.38 (range 31-100%). 16 subjects had bilateral vestibular hypofunction with average vHIT gains of 0.42 ± 0.20 (L); 0.41 ± 0.19 (R), peak slow phase velocity (SPV) on warm caloric testing = 2.68 ± 2.08, range 0-6°/s (L) and 3.75 ± 3.43 range, 0-10°/s (R). 36 patients showed a dissociation of results between the two tests. In these subjects, the vHIT gain was normal (0.93 ± 0.06 left and 0.98 ± 0.07 right) and the caloric test showed a CP > 30% (48 ± 13.8%). Their final diagnoses included clinically definite Meniere's disease (MD) (n = 27), vestibular schwannoma (VS) (n = 2) vestibular migraine (VM) (n = 1), vestibular neuritis (VN) (n = 5) and unknown (n = 1). No patient with abnormal HSCC gain on vHIT had a normal caloric result. The caloric test complements the vHIT in the assessment of vestibular disorders and is most useful in suspected endolymphatic hydrops. Asymmetric caloric function in the presence of normal horizontal head impulse tests is most commonly associated with Meniere's disease and may function as a diagnostic marker.

Recent advances in head impulse test findings in central vestibular disorders.

The head impulse test (HIT) is used to evaluate the vestibulo-ocular reflex (VOR) during a high-velocity head rotation. Corrective catch-up saccades that occur during or after the HITs usually indicate peripheral vestibular hypofunction, whereas in acute vestibular syndrome, normal clinical (bedside) HITs should prompt a search for a central lesion. However, recent quantitative studies that evaluated HITs using magnetic search coils or video-based techniques have demonstrated that specific patterns of HIT abnormalities are associated with central vestibular disorders. While normal clinical HITs are typical of central lesions, discrepancies have been observed between clinical and quantitative HITs. The horizontal head impulse VOR gains can be significantly reduced unilaterally or bilaterally (positive HITs) in lesions involving the vestibular nucleus, nucleus prepositus hypoglossi, or flocculus. In diffuse cerebellar lesions, the VOR gain during horizontal head impulses may increase (hyperactive) with corrective saccades directed the opposite way. The presence of cross-coupled vertical corrective saccades during horizontal HITs is also suggestive of diffuse cerebellar lesions. Lesions involving the vestibular nucleus, medial longitudinal fasciculus, and cerebellum may show decreased or increased gains of the VOR during vertical HITs. Defining the differences in patterns observed during abnormal HITs may help practitioners localize the responsible lesions in both central and peripheral vestibulopathy.

Are Covert Saccade Functionally Relevant in Vestibular Hypofunction?

The vestibulo-ocular reflex maintains gaze stabilization during angular or linear head accelerations, allowing adequate dynamic visual acuity. In case of bilateral vestibular hypofunction, patients use saccades to compensate for the reduced vestibulo-ocular reflex function, with covert saccades occurring even during the head displacement. In this study, we questioned whether covert saccades help maintain dynamic visual acuity, and evaluated which characteristic of these saccades are the most relevant to improve visual function. We prospectively included 18 patients with chronic bilateral vestibular hypofunction. Subjects underwent evaluation of dynamic visual acuity in the horizontal plane as well as video recording of their head and eye positions during horizontal head impulse tests in both directions (36 ears tested). Frequency, latency, consistency of covert saccade initiation, and gain of covert saccades as well as residual vestibulo-ocular reflex gain were calculated. We found no correlation between residual vestibulo-ocular reflex gain and dynamic visual acuity. Dynamic visual acuity performance was however positively correlated with the frequency and gain of covert saccades and negatively correlated with covert saccade latency. There was no correlation between consistency of covert saccade initiation and dynamic visual acuity. Even though gaze stabilization in space during covert saccades might be of very short duration, these refixation saccades seem to improve vision in patients with bilateral vestibular hypofunction during angular head impulses. These findings emphasize the need for specific rehabilitation technics that favor the triggering of covert saccades. The physiological origin of covert saccades is discussed.

Clinical practice of horizontal video head impulse test in healthy children

Clinical practice of horizontal video head impulse test in healthy children

Saccadic entropy of head impulses in acute unilateral vestibular loss.

To evaluate the complexity of vestibular-ocular reflex (VOR) in patients with acute unilateral vestibular loss (AUVL) via entropy analysis of head impulses. Horizontal head impulse test (HIT) with high-velocity alternating directions was used to evaluate 12 participants with AUVL and 16 healthy volunteers. Wireless electro-oculography and electronic gyrometry were used to acquire eye positional signals and head velocity signals. The eye velocity signals were then obtained through differentiation, band-pass filtering. The approximate entropy of eye velocity to head velocity (RApEn) was used to evaluate chaos property. VOR gain, gain asymmetry ratio, and RApEn asymmetry ratio were also used to compare the groups. For the lesion-side HIT of the patient group, the mean VOR gain was significantly lower and the mean RApEn was significantly greater compared with both nonlesion-side HIT and healthy controls (p < 0.01, one-way analysis of variance). Both the RApEn asymmetry ratio and gain asymmetry ratio of the AUVL group were significantly greater compared with those of the control group (p < 0.05, independent sample t test). Entropy and gain analysis of HIT using wireless electro-oculography system could be used to detect the VOR dysfunctions of AUVL and may become effective methods for evaluating vestibular disorders.

Test-retest and Interrater Reliability of the Video Head Impulse Test in the Pediatric Population.

Determine reliability of horizontal and vertical video head impulse test (vHIT) and effect of maturation on angular vestibular ocular reflex (AVOR) gain estimations and peak head velocities of individual canals in typically developing children and adolescents. Reliability study. University research laboratory : Two normal adults mean age 51.5 ± 0.5 years and 28 typically developing children and adolescents mean age 10 ± 3.5 years (range, 4.33-17.25 years). Mean AVOR gain estimate and peak head impulse velocity for individual canals. In adult sample, mean AVOR gain estimates were 1.00 to 1.04 for lateral and 1.07 to 1.13 for vertical canals. In pediatric sample, mean AVOR gain estimates were 1.00 to 1.04 for lateral and 1.03 to 1.08 vertical canals. Mean AVOR gain intrarater reliability scores (intraclass correlation coefficient [ICC] ≥ 0.821 ≤ 0.945) and interrater reliability scores (ICC ≥ 0.800 ≤ 0.971) had good consistency. For each canal, across each age group, the range of percentage of trials with peak head velocities greater than 100 degrees/s was 32 to 49% right lateral, 31 to 49% left lateral, 0 to 11% right anterior, 3 to 4% left anterior, 1 to 7% right posterior, and 2 to 8% left posterior. Children aged less than 12 years, required 10 to 49% more trials compared with adults to obtain five valid, filtered trials. Adolescents required a similar number of trials compared with adults. In pediatric population, vHIT is a reliable clinical test to quantify individual canal function using high velocity head impulses. With children, it was difficult to acquire head impulse velocities of greater than 100 degrees/s especially in the plane of the vertical canals. These higher head velocities are required to reveal asymmetry in compensatory eye movements.

A new saccadic indicator of peripheral vestibular function based on the video head impulse test.

While compensatory saccades indicate vestibular loss in the conventional head impulse test paradigm (HIMP), in which the participant fixates an earth-fixed target, we investigated a complementary suppression head impulse paradigm (SHIMP), in which the participant is fixating a head-fixed target to elicit anticompensatory saccades as a sign of vestibular function. HIMP and SHIMP eye movement responses were measured with the horizontal video head impulse test in patients with unilateral vestibular loss, patients with bilateral vestibular loss, and in healthy controls. Vestibulo-ocular reflex gains showed close correlation (R(2) = 0.97) with slightly lower SHIMP than HIMP gains (mean gain difference 0.06 ± 0.05 SD, p < 0.001). However, the 2 paradigms produced complementary catch-up saccade patterns: HIMP elicited compensatory saccades in patients but rarely in controls, whereas SHIMP elicited large anticompensatory saccades in controls, but smaller or no saccades in bilateral vestibular loss. Unilateral vestibular loss produced covert saccades in HIMP, but later and smaller saccades in SHIMP toward the affected side. Cumulative HIMP and SHIMP saccade amplitude differentiated patients from controls with high sensitivity and specificity. While compensatory saccades indicate vestibular loss in conventional HIMP, anticompensatory saccades in SHIMP using a head-fixed target indicate vestibular function. SHIMP saccades usually appear later than HIMP saccades, therefore being more salient to the naked eye and facilitating vestibulo-ocular reflex gain measurements. The new paradigm is intuitive and easy to explain to patients, and the SHIMP results complement those from the standard video head impulse test. This case-control study provides Class III evidence that SHIMP accurately identifies patients with unilateral or bilateral vestibulopathies.

Stability of the aVOR to Repeat Head Impulse Testing.

The angular vestibulo-ocular reflex (aVOR) is known to be influenced by factors such as arousal and cognition during traditional vestibular function testing. However, the inherent variability of the aVOR to head impulse testing has not been explicitly examined. The purpose of this study was to determine the variability of the aVOR to active and passive head impulses using the gold standard scleral search coil method to record head and eye rotation. Descriptive. Tertiary referral center. Twenty six healthy control subjects agreed to active and passive horizontal head impulse testing on at least two separate sessions from two unique institutions. An additional 27 individuals with cochlear implantation (CI) underwent passive horizontal and vertical semicircular canal plane head impulse testing. Test sessions were separated from 3 to 210 days in the normal subjects and from 49 to 537 days in the subjects with CI. Reliability of the angular VOR gain (eye velocity/head velocity) over time. In the healthy control subjects, there was no difference in aVOR gain between right and left ears, between session one and session two, or between active (self-generated, 0.99 ± 0.08) or passive (imposed, 1.0 ± 0.08) head impulses. In the patients, we also found the aVOR gain very stable over time. However, the aVOR gains of the patients were different across the semicircular canal planes tested (p < 0.001) with the four vertical semicircular canals having lower aVOR gains than the two horizontal canals. Our data suggest the aVOR gain is quite stable when tested across unique days in healthy controls and patients with auditory-only inner ear pathology.

VOR gain by head impulse video-oculography differentiates acute vestibular neuritis from stroke.

Vestibular neuritis is often mimicked by stroke (pseudoneuritis). Vestibular eye movements help discriminate the two conditions. We report vestibulo-ocular reflex (VOR) gain measures in neuritis and stroke presenting acute vestibular syndrome (AVS). Prospective cross-sectional study of AVS (acute continuous vertigo/dizziness lasting >24 h) at two academic centers. We measured horizontal head impulse test (HIT) VOR gains in 26 AVS patients using a video HIT device (ICS Impulse). All patients were assessed within 1 week of symptom onset. Diagnoses were confirmed by clinical examinations, brain magnetic resonance imaging with diffusion-weighted images, and follow-up. Brainstem and cerebellar strokes were classified by vascular territory-posterior inferior cerebellar artery (PICA) or anterior inferior cerebellar artery (AICA). Diagnoses were vestibular neuritis (n = 16) and posterior fossa stroke (PICA, n = 7; AICA, n = 3). Mean HIT VOR gains (ipsilesional [standard error of the mean], contralesional [standard error of the mean]) were as follows: vestibular neuritis (0.52 [0.04], 0.87 [0.04]); PICA stroke (0.94 [0.04], 0.93 [0.04]); AICA stroke (0.84 [0.10], 0.74 [0.10]). VOR gains were asymmetric in neuritis (unilateral vestibulopathy) and symmetric in PICA stroke (bilaterally normal VOR), whereas gains in AICA stroke were heterogeneous (asymmetric, bilaterally low, or normal). In vestibular neuritis, borderline gains ranged from 0.62 to 0.73. Twenty patients (12 neuritis, six PICA strokes, two AICA strokes) had at least five interpretable HIT trials (for both ears), allowing an appropriate classification based on mean VOR gains per ear. Classifying AVS patients with bilateral VOR mean gains of 0.70 or more as suspected strokes yielded a total diagnostic accuracy of 90%, with stroke sensitivity of 88% and specificity of 92%. Video HIT VOR gains differ between peripheral and central causes of AVS. PICA strokes were readily separated from neuritis using gain measures, but AICA strokes were at risk of being misclassified based on VOR gain alone.