The functional head impulse test: preliminary data

Customized Vestibular Rehabilitation for Vestibular Schwannoma Excision via Translabyrinthine Approach: A Single-Center Experience

Objectives: To evaluate the effectiveness of intensive customized vestibular rehabilitation after vestibular schwannoma (VS) excision. Methods: 52 patients who underwent VS removal via a translabyrinthine approach from 2020 to 2022 were involved in this study. Bedside examination, video head impulse test (vHIT), functional head impulse test (fHIT), and the dizziness handicap inventory (DHI) were performed before and after the rehabilitation, which consisted of 10 sessions of specifically designed vestibular, visual, and physical integrated training. Results: After rehabilitation, the vHIT showed overall unchanged values on the affected and healthy side. In contrast, the scores of fHIT, which explores the higher connection of the vestibular system with visual and cerebellar pathways, improved on both the pathological and healthy sides after training (p-value 0.004 and 0.000, respectively). The effectiveness of the rehabilitation was reinforced by the DHI scores, which were considerably lower after training. Conclusions: To our knowledge, this is the first study to explore fHIT outcomes after removal of VS, estimating the impact of rehabilitation on the overall compensation process. The outcomes support the role of extensive postsurgical rehabilitation in the compensatory process, even just a few days after surgery.

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.

A comparison of functional vestibulo-ocular reflex and proprioception in athletes of combat sports and ball sports

Background

The contribution and role of sensory systems in providing postural control may vary depending on the condition or activity. Vestibulo-ocular reflex (VOR) and proprioception might be affected by the type of sport.

Objective

This study aimed to compare athletes engaged in combat sports and ball sports in terms of functional VOR and proprioception.

Design

This study is a cross-sectional, comperative research.

Method

Twenty-four athletes engaged in combat sports and 20 in ball sports were included in the study. Functional examination of VOR in athletes was performed with a novel Functional Head Impulse Test (fHIT). Proprioception analysis was evaluated using Laser Pointer Assisted Angle Reproduction Test (LPA-ART) in 90° shoulder flexion and abduction.

Results

fHIT lateral and posterior % Correct Answer (CA) values and anterior SCC 6000°/s² values of athletes engaged in ball sports were found to be statistically significantly higher than athletes in combat sports (p < 0.05). Except for anterior SCC 4000°/s² value, scores of the ball players in all accelerations and directions were higher than combat sports athletes, although it was not statistically significant. The 90° shoulder flexion and abduction angle deviation values obtained from the LI-ATT were statistically lower in those who played ball sports (p < 0.05).

Conclusions

Participation in sports branches played with the ball is expected to provide gains for athletes who want to reach high-level performance in proprioceptive and vestibular functioning and those with vestibular/proprioceptive pathology. Maintaining clear vision in dynamic sports branches can be improved by training VOR function.

Advances in dynamic visual acuity test research

The dynamic visual acuity test (DVAT) is a functional evaluation tool for the impairment and compensation of the vestibular system, which could reflect the Vestibulo-ocular reflex (VOR) function. We present an overview of DVAT research, displaying recent advances in test methods, application, and influencing factors; and discussing the clinical value of DVAT to provide a reference for clinical application. There are two primary types of DVAT: dynamic-object DVAT and static-object DVAT. For the latter, in addition to the traditional bedside DVAT, there are numerous other approaches, including Computerized DVAT (cDVAT), DVAT on a treadmill, DVAT on a rotary, head thrust DVA (htDVA) and functional head impulse testing (fHIT), gaze shift dynamic visual acuity with walking (gsDVA), translational dynamic visual acuity test (tDVAT), pediatric DVAT. The results of DAVT are affected by subject [occupation, static visual acuity (SVA), age, eyeglass lenses], testing methods, caffeine, and alcohol. DVAT has numerous clinical applications, such as screening for vestibular impairment, assessing vestibular rehabilitation, predicting fall risk, and evaluating ophthalmology-related disorders, vestibular disorders, and central system disorders.

Vestibular test results in patients with vestibular migraine and Meniere's Disease

BACKGROUND

Vestibular migraine (VM) and Meniere's Disease (MD) are episodic vestibular disorders, sometimes difficult to differentiate from each other on clinical grounds.

OBJECTIVE

To evaluate vestibular test results of the two groups that may help in the differential diagnosis.

METHODS

Twenty-two patients with VM, 21 patients with definite MD and 21 healthy volunteers (HC) were studied. Pure tone hearing thresholds (PTHT), cervical vestibular evoked myogenic potentials (cVEMPs), video head impulse test (vHIT) and functional head impulse test (fHIT) were performed.

RESULTS

PTHT of the MD-affected ears were significantly higher than VM and HC groups (p < .001 for both) when cVEMP amplitudes were lower (p = .005 for HC), (p = .006 for VM). Lateral canal vHIT gain of the MD-affected ears were lower than VM patients (p = .003) and the HC (p < .001). The percentage of correctly identified optotypes (CA%) on fHIT was low for both patient groups when compared with the HC (p < .001).

CONCLUSION

In addition to hearing loss, low cVEMP amplitudes on the affected side with decreased gain on vHIT indicate disturbed saccular and lateral semicircular canal functions in MD patients differentiating them from VM. A functional deficit in gaze stabilization detected by fHIT is the only abnormality found in patients with VM.

Evaluation of effects of optokinetic and rotational stimuli with functional head impulse test (fHIT) in individuals with motion sickness

OBJECTIVES

To evaluate effects of optokinetic and rotational stimulus in individuals with and without motion sickness (MS) using fHIT.

METHODS

The study included subjects aged 18-40; 35 subjects with MS for MS group and 35 subjects without vertigo for control group. Percentage of the correct answer (% CA) with and without optokinetic stimulus (o-fHIT) in the frontal plane in the fHIT test was compared in both groups. In addition, both group subjects were seated on an ordinary rotating office chair. % CA was compared between groups by applying rotational fHIT (r-fHIT) test after the subjects were rotated randomly to the right and left and also simultaneously moved their heads in the vertical plane.

RESULTS

There was no significant difference in % CA in fHIT o-fHIT and r-fHIT in the control group. Both groups showed a significant difference in % CA for fHIT, o-fHIT, and r-fHIT for all SCCs (p < 0.05).

CONCLUSIONS

Since individuals with MS are affected by optokinetic and rotational stimuli, fHIT performed after these stimuli can be used as an objective confirming test for diagnosing MS.

Risk of falls, vestibular multimodal processing, and multisensory integration decline in the elderly-Predictive role of the functional head impulse test

Age-related degeneration of the vestibular system, also known as presbyastasis, leads to unstable gait and higher risk of falls. These conditions affect lifestyle and may have non-negligible social repercussions due to fear-related states of anxiety and depression. In order to develop a model for predicting risk of falls, we assessed vestibulo-ocular function by video and functional Head Impulse Tests (vHIT and fHIT) and their possible correlations with Tinetti Balance Test score. Thirty-one patients over 65 years of age admitted with trauma due to falls were recruited. Vestibular evaluation (complete otoneurological assessment, vHIT, fHIT), cognitive tests (Mini Mental State Examination), anxiety and depression evaluation and Tinetti Balance Test were performed. The possibility of a correlation between the head impulse tests (vHIT, fHIT) and the Tinetti Balance Test was investigated by logistic regression analysis (Nagelkerke r ² and Wald test). A linear correlation was found between the Tinetti Balance Test score and fHIT, whereas no correlation was found for vHIT. Functional HIT is an effective test for predicting the risk of falls in elderly patients.

Vestibulo-ocular reflex evaluation of the children with acquired esotropia

OBJECTIVES

This study aims to evaluate the effects of acquired esotropia on vestibulo-ocular reflex (VOR) gain in children using video (vHIT) and functional head impulse (fHIT) tests.

METHODS

A total of 62 children aged 6-18 years, with acquired esotropia and normal vision, were evaluated in the study. The patients were divided into two sub-groups: accommodative and non-accommodative. VOR gains were analyzed by performing lateral canal vHIT and fHIT with monocular and binocular recordings by a single examiner.

RESULTS

Seventeen (10 male, 7 female) children with accommodative esotropia, 24 (14 male, 10 female) children with non-accommodative esotropia, and 21 (8 male and 12 female) healthy controls were included in this study. The vHIT findings did not differ between the groups (p˃.05). In the non-accommodative esotropia group, the location of the camera in both binocular and monocular vHIT recordings made a significant difference in the left VOR gain (p = .025, z = -2.243, p = .032, and z = -2.143, respectively), but no difference was observed in the right VOR gain. In the accommodative esotropia group, while the camera was on the left there was a significant difference in the right VOR gain between binocular and monocular recordings (p = .016, z = -2.413) but no difference was observed in the left VOR gain. No overt or covert saccade was detected in any group.

CONCLUSIONS

The statistical differences found in vHIT and fHIT in acquired esotropia patients are thought to be sporadic and based on the results of this study no correction or change in recording technique is required for vHIT or fHIT in children with acquired esotropia.

DISCOHAT: An Acronym to Describe the Spectrum of Symptoms Related to Bilateral Vestibulopathy

Objective: To assess the prevalence of each symptom listed in the acronym DISCOHAT (worsening of symptoms in Darkness and/or uneven ground, Imbalance, Supermarket effect, Cognitive complaints, Oscillopsia, Head movements worsen symptoms, Autonomic complaints, and Tiredness) in patients with bilateral vestibulopathy (BVP), compared to patients with unilateral vestibulopathy (UVP). Methods: A descriptive case-control study was performed on BVP and UVP patients who were evaluated for their vestibular symptoms by two of the authors (RvdB, MCG) at a tertiary referral center, between 2017 and 2020. During history taking, the presence of each DISCOHAT symptom was checked and included in the electronic health record. Presence of a symptom was categorized into: "present," "not present," and "missing." Results: Sixty-six BVP patients and 144 UVP patients were included in this study. Prevalence of single DISCOHAT symptoms varied from 52 to 92% in BVP patients and 18-75% in UVP patients. Patients with BVP reported "worsening of symptoms in darkness," "imbalance," "oscillopsia," and "worsening of symptoms with fast head movements" significantly more than UVP patients (p ≤ 0.004). Conclusion: The DISCOHAT acronym is able to capture a wide spectrum of symptoms related to vestibulopathy, while it is easy and quickly to use in clinic. Application of this acronym might facilitate a more thorough and uniform assessment of bilateral vestibulopathy, within and between vestibular clinics worldwide.

The Role of the Functional Head Impulse Test with and without Optokinetic Stimuli in Vestibular Migraine and Acute Unilateral Vestibulopathy: Discovering a Dynamic Visual Dependence

(1) Background: Visually induced vertigo (i.e., vertigo provoked by moving visual scenes) can be considered a noticeable feature of vestibular migraines (VM) and can be present in patients suffering from acute unilateral vestibulopathy (AUV). Hypersensitivity to moving or conflicting visual stimulation is named visual dependence. (2) Methods: Visuo-vestibular interactions were analyzed via the functional Head Impulse Test (fHIT) with and without optokinetic stimulation (o-fHIT) in 25 patients with VM, in 20 subjects affected by AUV, and in 20 healthy subjects. We calculated the percentage of correct answers (%CA) without and with the addition of the optokinetic background (OB). (3) In VM groups, the %CA on the fHIT was 92.07% without OB and 73.66% with OB. A significant difference was found between %CA on the deficit side and that on the normal side in AUV, both without OB and with OB. (4) Conclusions: The fHIT results in terms of %CA with and without OB could be useful to identify the presence of a dynamic visual dependence, especially in patients suffering from VM. The difference in %CA with and without OB could provide instrumental support to help correctly identify subjects suffering from VM. We propose the use of the fHIT in clinical practice whenever there is a need to highlight a condition of dynamic visual dependence.

The relationship between functional head impulse test and age in healthy individuals

BACKGROUND

fHIT is an easily applicable test battery that indirectly evaluates the vestibulo-ocular reflex (VOR) from a functional perspective.

AIMS/OBJECTIVES

The aim of this study was to Individuals determine the correlation between age and the percentage of correct answers (% CA) obtained in the functional head impulse test (fHIT) in healthy individuals.

MATERIAL AND METHODS

A total of 105 volunteers, 50 males and 55 females, between the ages of 18 and 70 years, participated in the study. A Beon Solution fHIT system (Zero Branco (TV), Italy) was used in the study.

RESULTS

In our study, a decrease in the mean % CA was observed in all semicircular canals (SCCs) with increasing age. Between age and mean % CA, a significant negative moderate (-0.311) correlation was observed in lateral SCCs, and a significant negative low (-0.257) correlation was observed in posterior SCCs (p <  0.05). In anterior SCCs, there was no statistically significant relationship between age and mean % CA (p >  0.05).

CONCLUSIONS

The present study performed in a healthy population will be helpful in terms of making comparisons in studies to be conducted in various vestibular diseases. It will also be a guide for identifying pathological consequences in vestibular diseases.

The clinical significance of fHIT in migraine patient without vertigo symptom

OBJECTIVE

The aim of this study was to assess the functional head impulse test on migraine patients without vertigo. fHIT is a new vestibular test which evaluates the ability to see and read clearly during head movement as a functional measurement of the vestibulo-ocular reflex.

MATERIALS AND METHODS

The study included 20 patients suffering from migraine without vertigo between the ages of 20 and 30-years-old who were diagnosed by a neurologist and 20 individuals with non-migraine headaches (control group), with similar demographic characteristics. The functional head impulse test was applied to both groups, and the migraine disability assessment test was applied to migraine patients.

RESULTS

There was no statistically significant difference in the general fHIT results between the migraine group and the control group (p > 0.05). However, a statistically significant decrease was obtained in migraine patients in the left lateral (p = 0.018) and right posterior (p = 0.029) semicircular canals at 4000 Hz and the right anterior semicircular canal at 6000 Hz (p = 0.019). When compared by the degree of migraine disability assessment test, no significant difference in the fHIT results were observed (p > 0.05).

CONCLUSION

The semicircular canals may be affected at high head acceleration (4000-6000 Hz) in migraine patients without a history of vertigo. It should be considered that fHIT results between 4000 and 6000 Hz in migraine patients without vertigo can be pathologic.

Diagnosing vestibular hypofunction: an update

Unilateral or bilateral vestibular hypofunction presents most commonly with symptoms of dizziness or postural imbalance and affects a large population. However, it is often missed because no quantitative testing of vestibular function is performed, or misdiagnosed due to a lack of standardization of vestibular testing. Therefore, this article reviews the current status of the most frequently used vestibular tests for canal and otolith function. This information can also be used to reach a consensus about the systematic diagnosis of vestibular hypofunction.

Evaluation of high frequency horizontal VOR parameters in patients with chronic bilateral and unilateral peripheral vestibulopathy: a preliminary study

BACKGROUND

Caloric test is one of the tests which evaluates the low frequency component of vestibular system for both diagnosis of the BPV and UPV.

AIMS

The main objectives are to determine and increase the diagnostic value of BPV and UPV by evaluating the high frequency horizontal VOR parameters with HIMP, SHIMP and fHIT, to compare test results with healthy controls, and to evaluate correlation of these tests with vertigo dizziness imbalance (VDI) questionnaire results in these patients.

MATERIAL AND METHODS

Six patients with BPV, ten patients with UPV and fifteen healthy controls were recruited. High frequency hVOR were evaluated with HIMP, SHIMP and fHIT. Vestibular symptoms and quality of life were assessed with VDI Questionnaire.

RESULTS

Lower percentage of correct answers, and lower VOR gains were obtained in affected sides for BPV and UPV. HIMP elicited compensatory saccades in patients, whereas SHIMP elicited large anticompensatory saccades in controls and unaffected side of UPV, but no saccades in BPV. No correlation was found between VDI outcomes and all tests.

CONCLUSIONS

The results show that all tests are complementary each other and able to identify the affected labyrinth and to show residual vestibular function. These tests are thought to be important in the vestibular rehabilitation process.

Vestibular Functioning in Children with Neurodevelopmental Disorders Using the Functional Head Impulse Test

Several studies in children with neurodevelopmental disorders (NDDs) including autism spectrum disorders (ASDs), reading impairment, or attention deficit/hyperactive disorder (ADHD) pointed toward a potential dysfunction of the vestibular system, specifically in its complex relationship with the cerebellum. The aim of the present study was to test the functional vestibulo-ocular reflex (VOR) responses in children with NDDs to measure functional performance of the vestibular system. The VOR is specifically involved in this stabilization of the image on the retina during rapid movements of the head. To perform this study, four groups of children with ASD, ADHD, reading impairment, and with neurotypical development (TD) were enrolled (n = 80). We performed the functional head impulse test (fHIT), which measured the percentage of correct responses by asking the child to identify an optotype briefly presented during passive head impulse in each direction of each semicircular canal plane. We observed significantly lower correct answers in children with NDDs compared with those with TD (p < 0.0001). Surprisingly, there was no significant difference between the three groups of children with NDDs. Our study fostered preliminary evidence suggesting altered efficiency of vestibular system in children with NDDs. VOR abnormalities estimated using the fHIT could be used as a proxy of NDD impairments in children, and represent a potential biomarker.

Alcohol binge-drinking damage on the vestibulo-oculomotor reflex

PURPOSE

Binge drinking is associated with several adverse effects in multiple organs. This study aimed at evaluating the effects of a binge-like-drinking on the vestibulo-oculomotor reflex (VOR) using the video Head Impulse Test (vHIT) and the functional Head Impulse Test (fHIT).

METHODS

Eleven healthy men (age range 32-35 years) with moderate drinking habits and no history of vestibular dysfunction were enrolled. A preliminary assessment of breath alcohol concentration (BrAC) to check for zero alcohol value and a pre-intake evaluation of VOR using the vHIT and the fHIT were carried on. Then, the subjects were asked to take drinks with different alcohol content (8-40% ethanol by volume) according to their choice, consuming at least 5 standard drinks. Volunteers stopped drinking after 3 h. After a further 30 min, post-intake BrAC measurements and VOR analysis were repeated.

RESULTS

After alcohol intake, vHIT recorded an overall significant reduction of VOR gain (0.82 ± 0.07 on both sides) although the outcomes were below the normal range only in the four subjects with the highest blood alcohol levels. The post-intake fHIT outcomes were substandard in 9 participants, with a significant deterioration in performance (% of exact answers = 84.54 ± 11.05% on the left, 83.18 ± 14.53 on the right).

CONCLUSIONS

Binge drinking severely affects VOR; fHIT seems more sensitive than vHIT in the assessment of VOR function for complex vestibular lesions, such as those determined by ethanol, suggesting that fHIT could support vHIT in vestibular dysfunction assessment.

The integration of multisensory motion stimuli is impaired in vestibular migraine patients

BACKGROUND

Vestibular migraine (VM) is a relatively recently acknowledged vestibular syndrome with a very relevant prevalence of about 10% among patients complaining of vertigo. The diagnostic criteria for VM have been recently published by the Bárány Society, and they are now included in the latest version of the International Classification of Headache Disorders, yet there is no instrumental test that supports the diagnosis of VM.

OBJECTIVE

In the hypothesis that the integration of different vestibular stimuli is functionally impaired in VM, we tested whether the combination of abrupt vestibular stimuli and full-field, moving visual stimuli would challenge vestibular migraine patients more than controls and other non-vestibular migraineurs.

METHODS

In three clinical centers, we compared the performance in the functional head impulse test (fHIT) without and with an optokinetic stimulus rotating in the frontal plane in a group of 44 controls (Ctrl), a group of 42 patients with migraine (not vestibular migraine, MnoV), a group of 39 patients with vestibular migraine (VM) and a group of 15 patients with vestibular neuritis (VN).

RESULTS

The optokinetic stimulation reduced the percentage of correct answers (%CA) in all groups, and in about 33% of the patients with migraine, in as many as 87% of VM patients and 60% of VN patients, this reduction was larger than expected from controls' data.

CONCLUSIONS

The comparison of the fHIT results without and with optokinetic stimulation unveils a functional vestibular impairment in VM that is not as large as the one detectable in VN, and that, in contrast with all the other patient groups, mainly impairs the capability to integrate different vestibular stimuli.

Functional Head Impulse Test With and Without Optokinetic Stimulation in Subjects With Persistent Postural Perceptual Dizziness (PPPD): Preliminary Report

OBJECTIVE

Persistent postural perceptual dizziness (PPPD) is a clinical condition characterized by unsteadiness present on most days for a period of at least 3 months. The aim of our work was to assess vestibular function, the role of anxiety, and possible interactions between visual and vestibular systems in patients with PPPD.

STUDY DESIGN

Cross-sectional prospective study.

SETTING

Tertiary referral center.

PATIENTS

Twenty-five PPPD patients.

INTERVENTIONS

Clinical history was collected before examination; vestibular function was assessed through bedside examination, video and functional head impulse test (video-HIT, f-HIT). The latter test was based on having the patient identify an optotype displayed on a computer screen during passive head rotations. The test was repeated while optokinetic stimulation (OKS) was given on the screen. Results were compared with those of 25 controls. State and trait anxiety levels were measured with the State-Trait Anxiety Inventory (STAI) questionnaire. Anxiety before and after vestibular examination was assessed using a VAS scale.

MAIN OUTCOME MEASURE

Results of video and functional HIT with and without OKS.

RESULTS

Video-HIT and f-HIT showed normal values in all subjects. f-HIT with OKS provoked more reading errors in patients than in controls. The interaction of group per time detected different decreasing trends between the two groups (p = 0.0002).Patients presented a reduction in anxiety levels after examination. Nine patients fulfilled diagnostic criteria for vestibular migraine, eight of whom presented nystagmus either to positional tests or vibration test. Only anxiety levels before testing were predictive of worsening of f-HIT with optokinetic stimulation (p = 0.0007).

CONCLUSIONS

Our data support the hypothesis that increased anxiety may play a role in visuo-vestibular interactions; moreover, they are not inconsistent with the hypothesis that OKS might provoke a "threatening effect," leading to gaze bias during examination.

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.

The functional head impulse test: Comparing gain and percentage of correct answers

OBJECTIVES

The video head impulse test (vHIT) provides as output a gain value that summarizes the behavior of the vestibulo-ocular reflex as the ratio of a measure of eye movement to the corresponding measure of head movement and is not directly informative of the functional effectiveness of the motor response. The functional HIT (fHIT) is based on the ability to recognize the orientation of a Landolt C optotype that briefly appears on a computer screen during passive head impulses imposed by the examiner over a range of head accelerations; accordingly fHIT is a functional measurement of the vestibular-ocular reflex since it measures the capability to keep clear vision and to read during head movement.

METHODS

We compared the results of the fHIT with those of the vHIT and the results of the Dizziness Handicap Inventory (DHI) questionnaire in a group of 27 vestibular neuritis patients recorded acutely and at 3-months follow-up.

RESULTS

Both the vHIT and fHIT exams correctly classified all patients as abnormal on the affected side when tested in the acute phase. After a 3-month follow-up, both were able to show that compensation phenomena had occurred. Otherwise the data from the two techniques were not correlated. More specifically, the fHIT detected more abnormalities than the vHIT, for head rotation toward the healthy side, both in the acute phase and after 3 months, and for head rotation toward the affected side after 3 months. The asymmetry indices, that compare the performance of the healthy to the affected side, also were larger for the fHIT than for the vHIT both at onset and after 3 months. There was no significant correlation between the different vHIT and fHIT parameters and indices, or with the DHI values after 3 months.

CONCLUSIONS

The fHIT data are able to detect a difference between the healthy and the affected side in the acute phase, and they show an improvement after 3 months. fHIT detects more abnormalities than vHIT, but both these techniques lack a correlation with the DHI score.

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.

The Functional Head Impulse Test to Assess Oscillopsia in Bilateral Vestibulopathy

Introduction: Bilateral vestibulopathy (BV) is a chronic condition in which vestibular function is severely impaired or absent on both ears. Oscillopsia is one of the main symptoms of BV. Oscillopsia can be quantified objectively by functional vestibular tests, and subjectively by questionnaires. Recently, a new technique for testing functionally effective gaze stabilization was developed: the functional Head Impulse Test (fHIT). This study compared the fHIT with the Dynamic Visual Acuity assessed on a treadmill (DVA_treadmill) and Oscillopsia Severity Questionnaire (OSQ) in the context of objectifying the experience of oscillopsia in patients with BV.

Methods: Inclusion criteria comprised: (1) summated slow phase velocity of nystagmus of <20°/s during bithermal caloric tests, (2) torsion swing tests gain of <30% and/or phase <168°, and (3) complaints of oscillopsia and/or imbalance. During the fHIT (Beon Solutions srl, Italy) patients were seated in front of a computer screen. During a passive horizontal head impulse a Landolt C optotype was shortly displayed. Patients reported the seen optotype by pressing the corresponding button on a keyboard. The percentage correct answers was registered for leftwards and rightwards head impulses separately. During DVA_treadmill patients were positioned on a treadmill in front of a computer screen that showed Sloan optotypes. Patients were tested in static condition and in dynamic conditions (while walking on the treadmill at 2, 4, and 6 km/h). The decline in LogMAR between static and dynamic conditions was registered for each speed. Every patient completed the Oscillopsia Severity Questionnaire (OSQ).

Results: In total 23 patients were included. This study showed a moderate correlation between OSQ outcomes and the fHIT [rightwards head rotations (r_s = −0.559; p = 0.006) leftwards head rotations (r_s = −0.396; p = 0.061)]. No correlation was found between OSQ outcomes and DVA_treadmill, or between DVA_treadmill and fHIT. All patients completed the fHIT, 52% of the patients completed the DVA_treadmill on all speeds.

Conclusion: The fHIT seems to be a feasible test to quantify oscillopsia in BV since, unlike DVA_treadmill, it correlates with the experienced oscillopsia measured by the OSQ, and more BV patients are able to complete the fHIT than DVA_treadmill.

Vestibulo-Ocular Responses and Dynamic Visual Acuity During Horizontal Rotation and Translation

Dynamic visual acuity (DVA) provides an overall functional measure of visual stabilization performance that depends on the vestibulo-ocular reflex (VOR), but also on other processes, including catch-up saccades and likely visual motion processing. Capturing the efficiency of gaze stabilization against head movement as a whole, it is potentially valuable in the clinical context where assessment of overall patient performance provides an important indication of factors impacting patient participation and quality of life. DVA during head rotation (rDVA) has been assessed previously, but to our knowledge, DVA during horizontal translation (tDVA) has not been measured. tDVA can provide a valuable measure of how otolith, rather than canal, function impacts visual acuity. In addition, comparison of DVA during rotation and translation can shed light on whether common factors are limiting DVA performance in both cases. We therefore measured and compared DVA during both passive head rotations (head impulse test) and translations in the same set of healthy subjects (n = 7). In addition to DVA, we computed average VOR gain and retinal slip within and across subjects. We observed that during translation, VOR gain was reduced (VOR during rotation, mean ± SD: position gain = 1.05 ± 0.04, velocity gain = 0.97 ± 0.07; VOR during translation, mean ± SD: position gain = 0.21 ± 0.08, velocity gain = 0.51 ± 0.16), retinal slip was increased, and tDVA was worse than during rotation (average rDVA = 0.32 ± 0.15 logMAR; average tDVA = 0.56 ± 0.09 logMAR, p = 0.02). This suggests that reduced VOR gain leads to worse tDVA, as expected. We conclude with speculation about non-oculomotor factors that could vary across individuals and affect performance similarly during both rotation and translation.

Functional and Objective Audiovestibular Evaluation of Children With Apparent Semicircular Canal Dehiscence-A Case Series in a Pediatric Vestibular Center

Semicircular canal dehiscence is a bony abnormality in the otic capsule especially involving the superior semicircular canal. Since its identification in 1998, there is significant research regarding the pathology in the adult population. This condition generates a third window effect that is well–described in the literature. However, the entity is rare in the pediatric population with limited research. Difficulties encountered in children are obtaining a direct history that is essential for the diagnosis followed by neurovestibular tests that may be difficult to perform. This study presents observations regarding different clinical and diagnostic aspects of semicircular canal dehiscences in children as a retrospective audit in a tertiary pediatric vestibular center. Of 580 children assessed in a 30 months period undergoing comprehensive functional and objective audiovestibular assessment, 13 children (2.2%) were detected to possess radiological semicircular canal dehiscences (high resolution computed tomography scans at 0.625 mm slices reformatted in the axial, coronal and sagittal planes). The right superior semicircular canal was most commonly affected (66.6%). There were 4 bilateral semicircular canal dehiscences. Clinical suspicion of the condition was raised with reliable surrogate history from carers or from older children (100%), a mixed or conductive hearing loss (80% of hearing losses) in the presence of normal impedance audiometry (92.3%), normal transient otoacoustic emissions (84.6%) on the side of the dehiscence and the presence of replicable pathological saccades in the video head impulse test (76.9%). Disequilibrium symptoms and typical third window symptoms were absent or difficult to elicit in children (46.15 and 30.76% respectively). Only 3 (0.5%) fulfilled the adult criteria of a superior semicircular canal dehiscence syndrome. The abnormal video head impulse test characterized by pathological saccades may affect other non-dehisced ipsilateral canals. Semicircular canal dehiscences are rare in children but may be considered as an etiology for hearing losses and imbalance. Children with semicircular canal dehiscence may present differently from the classical superior semicircular canal dehiscence syndrome found in adults.

Functional Head Impulse Testing Might Be Useful for Assessing Vestibular Compensation After Unilateral Vestibular Loss

Background: Loss of the vestibulo-ocular reflex (VOR) affects visual acuity during head movements. Previous studies have shown that compensatory eye-saccades improve visual acuity and that the timing of the saccade is important. Most of the tests involved in testing VOR are made with passive head movement, that do not necessarily reflect the activities of daily living and thus not being proportionate to symptoms and distresses of the patients. Objective: To examine differences between active (self-generated) or passive (imposed by the examiner) head rotations while trying to maintain visual focus on a target. Method: Nine subjects with unilateral total vestibular loss were recruited (4 men and 5 women, mean age 47) and tested with video Head Impulse Test (vHIT) and Head Impulse Testing Device-Functional Test (HITD-FT) during passive and active movements while looking at a target. VOR gain, latencies of covert saccades, frequency of covert saccades and visual acuity were measured and analyzed. Results: Active head-impulses toward the lesioned side resulted in better visual acuity (p = 0.002) compared to conventional passive head-impulses and generated eye-saccades with significantly shorter latencies (p = 0.004). Active movements to the lesioned side generated dynamic visual acuities that were as good as when testing the intact side. Conclusion: Actively generated head impulses resulted in normal dynamic visual acuity, even when performed toward the side of total vestibular loss. This might be attributed to the appearance of short-latency covert saccades. The results show a strong relationship between self-generated movements, latencies of covert saccades and outcome in HITD-FT, i.e., a better dynamic visual function with less retinal slip which is the main function of the VOR. The method of active HITD-FT might be valuable in assessing vestibular compensation and monitoring ongoing vestibular rehabilitation.