Reducción de la ganancia del canal semicircular posterior en el test del impulso cefálico con la edad. Estudio observacional

Correlation between nystagmus intensity and vestibular-ocular reflex gain in benign paroxysmal positional vertigo: A prospective, clinical study

BACKGROUND

Video head impulse test (vHIT) and videonystagmography (VNG) provide significant benefits in evaluating benign paroxysmal positional vertigo (BPPV) and determining the semicircular canal localization of the otoconia.

OBJECTIVE

This study aimed to investigate the relationship between vestibular-ocular reflex (VOR) gains measured via vHIT and the slow-phase velocity (SPV) of nystagmus in patients with the posterior semicircular canal (PSCC)-BPPV.

METHODS

Sixty-two patients were included in this study and divided into the study (n = 32, patients with isolated PSCC-BPPV) and control (n = 30, age- and sex-matched healthy individuals) groups. While VOR gains were measured with vHIT in both groups and compared between groups, the SPV values of nystagmus observed during the Dix-Hallpike maneuver in the study group were recorded using VNG and compared with the VOR gains of the study group.

RESULTS

There were significant differences in posterior canal VOR gains between the study and control groups (p < 0.001 and p < 0.01, respectively). Although the affected PSCC had decreased VOR gains versus the control group, it was still within the normal range. However, there was no significant relationship between the VOR gains of the affected PSCC and the SPV of the nystagmus.

CONCLUSIONS

vHIT can help detect semicircular canal dysfunction in patients with PSCC-BPPV. The SPV values of nystagmus on VNG during the Dix-Hallpike maneuver do not correlate with the level of VOR gain.

Discordant vestibulo-ocular reflex function according to the frequency and mode of stimulation

This study aimed to determine the incidence, pattern, and etiology of dissociated vestibulo-ocular reflex (VOR) function according to the stimulus frequency in dizzy patients. We retrospectively evaluated the results of bithermal caloric tests and video-head impulse tests (vHITs) in 1022 patients with dizziness or vertigo between July 2016 and April 2021. Patients were classified into concordant group (normal or abnormal results on both tests) and discordant group (dissociated results between two tests). Of 1022 patients, discordant group had 159 (16%), comprising abnormal horizontal vHITs with normal caloric responses (n = 36, 23%) and abnormal caloric tests with normal horizontal vHITs (n = 123, 77%). The former group showed similar frequency of peripheral (44%) and central (42%) causes, and more common involvement of bilateral horizontal semicircular canals in central than peripheral causes (86.7 vs 37.5%, p = 0.005). The most common peripheral causes were Meniere's disease and chronic vestibular neuritis, while central causes were variable, but mainly affecting the cerebellum. In the latter group, peripheral causes were common (67%), with the main etiologies being Meniere's disease and vestibular neuritis, whereas central causes were found in only 5%. The degree of canal paresis did not differ significantly between patients with central and peripheral causes. Discordant VOR function according to the stimulus frequency was not uncommon in dizzy patients. Specific patterns of VOR dissociation according to the disease etiologies may offer insight into underlying pathophysiology.

Which Inner Ear Disorders Lie Behind a Selective Posterior Semicircular Canal Hypofunction on Video Head Impulse Test?

OBJECTIVE

To assess all different patterns of associated abnormalities on audiometry, bithermal caloric test (BCT) and cervical/ocular vestibular-evoked myogenic potentials (VEMPs) to air/bone-conduction in patients with selective posterior semicircular canal (PSC) hypofunction and to correlate them with underlying disorders.

STUDY DESIGN

Retrospective review.

SETTING

Tertiary referral center.

PATIENTS

51 patients (23 men, 28 women, mean age 57.5 yr) with isolated PSC deficit (one bilateral).

INTERVENTIONS

Correlation with instrumental data and underlying diagnoses.

MAIN OUTCOME MEASURES

Video-oculographic findings, objective measurements on audiometry, BCT, VEMPs and video-head impulse test (vHIT).

RESULTS

Ongoing or previous acute vestibular loss (AVL) was diagnosed in 13 patients (25.5%, 3 inferior vestibular neuritis, 10 AVL with sudden sensorineural hearing loss [SSNHL]), Meniere's disease (MD) in 12 (23.5%), cerebellopontine angle (CPA) lesion in 9 (17.6%), various causes in 7 (13.7%), benign paroxysmal positional vertigo (BPPV) involving the non-ampullary arm of PSC in 5 cases (9.8%) whereas unknown pathology in 5 (9.8%). Involvement of at least one additional receptor besides PSC was seen in 89.8% of cases. Cochlear involvement was diagnosed in 74.5% with pure-tone average significantly greater in patients with AVL+SSNHL (p < 0.05). Overall involvement of labyrinthine receptors or afferents was highest in patients with AVL+SSNHL (p < 0.01), MD and CPA lesions (p < 0.05).

CONCLUSIONS

Isolated loss of PSC function on vHIT is mostly accompanied by additional labyrinthine deficits that could only be identified through an accurate instrumental evaluation. Assessment of all receptors and afferents should be always pursued to identify the lesion site and better understand the underlying pathophysiological mechanisms.

The Video Head Impulse Test in the acute stage of posterior canal benign paroxysmal positional vertigo

OBJECTIVE

Study the high-frequency vestibulo-oculomotor reflex in posterior canal benign paroxysmal positional vertigo (BPPV) through Video Head Impulse Test (vHIT).

METHODS

150 patients suffering for the first time from posterior canal BPPV were studied. Posterior canal vestibulo ocular reflex (VOR) gain was analysed through stimulations in right anterior-left posterior and left anterior-right posterior planes before treatment, immediately after resolution of the acute stage and one month later. Results were compared with a group of 100 healthy individuals.

RESULTS

No significant difference between the study the control groups was observed, except for normalised asymmetry ratio of the posterior canal which was significantly higher in the study group. VOR gains of both affected posterior canals and contralateral healthy posterior canals were not significantly correlated with the VOR gain of ipsilateral and contralateral anterior canals.

CONCLUSIONS

vHIT does not seem to represent an essential tool to study typical posterior canal BPPV in patients affected by this disease for the first time. Different results might be expected in relapsing forms, non-responsive forms, long lasting forms, or atypical variants in which major damage could be provoked by the persistence of otoconia in the canal or by its complete or partial jam.

Feasibility of Using the Video-Head Impulse Test to Detect the Involved Canal in Benign Paroxysmal Positional Vertigo Presenting With Positional Downbeat Nystagmus

Positional downbeat nystagmus (pDBN) represents a relatively frequent finding. Its possible peripheral origin has been widely ascertained. Nevertheless, distinguishing features of peripheral positional nystagmus, including latency, paroxysm and torsional components, may be missing, resulting in challenging differential diagnosis with central pDBN. Moreover, in case of benign paroxysmal positional vertigo (BPPV), detection of the affected canal may be challenging as involvement of the non-ampullary arm of posterior semicircular canal (PSC) results in the same oculomotor responses generated by contralateral anterior canal (ASC)-canalolithiasis. Recent acquisitions suggest that patients with persistent pDBN due to vertical canal-BPPV may exhibit impaired vestibulo-ocular reflex (VOR) for the involved canal on video-head impulse test (vHIT). Since canal hypofunction normalizes following proper canalith repositioning procedures (CRP), an incomplete canalith jam acting as a "low-pass filter" for the affected ampullary receptor has been hypothesized. This study aims to determine the sensitivity of vHIT in detecting canal involvement in patients presenting with pDBN due to vertical canal-BPPV. We retrospectively reviewed the clinical records of 59 consecutive subjects presenting with peripheral pDBN. All patients were tested with video-Frenzel examination and vHIT at presentation and after resolution of symptoms or transformation in typical BPPV-variant. BPPV involving non-ampullary tract of PSC was diagnosed in 78%, ASC-BPPV in 11.9% whereas in 6 cases the involved canal remained unidentified. Presenting VOR-gain values for the affected canal were greatly impaired in cases with persistent pDBN compared to subjects with paroxysmal/transitory nystagmus (p < 0.001). Each patient received CRP for BPPV involving the hypoactive canal or, in case of normal VOR-gain, the assumed affected canal. Each subject exhibiting VOR-gain reduction for the involved canal developed normalization of vHIT data after proper repositioning (p < 0.001), proving a close relationship with otoliths altering high-frequency cupular responses. According to our results, overall vHIT sensitivity in detecting the affected SC was 72.9%, increasing up to 88.6% when considering only cases with persistent pDBN where an incomplete canal plug is more likely to occur. vHIT should be routinely used in patients with pDBN as it may enable to localize otoconia within the labyrinth, providing further insights to the pathophysiology of peripheral pDBN.

Bilateral posterior semicircular canal dysfunction: a new finding with video head impulse test

Development of the video head impulse test (vHIT) assessing all three semicircular canals in both labyrinths has uncovered the existence of new vestibular failure patterns and made bilateral posterior canal dysfunction detection possible. We conducted a retrospective analysis of 41 patients with bilateral posterior semicircular canal failure and compared results to 37 controls, with normal posterior semicircular canal function. Mean calculated gain showed significant difference between patients and controls in right [0.54 (SD 0.016)] and left [0.57 (SD 0.014)] posterior semicircular canals. There was a peak in prevalence between 71 and 80 years. Presentation was chronic in 78% of patients, and gait instability was the most common complaint. Sixty eight percent of cases were classified as idiopathic. Significant difference between groups was seen regarding the presence of Meniere's disease, presbycusis, and positional down-beat nystagmus (posDBN). This new vHIT pattern is most often seen in elderly patients, mainly of idiopathic etiology and presents together with sensorineural hearing loss and posDBN. Our findings suggest idiopathic cases may well contribute to the so-called "presbyastasis".

Importance of Vestibulo-ocular Reflex Gain and Refixation Saccade Analysis in Individuals with Auditory Neuropathy Spectrum Disorder

Introduction  Auditory neuropathy spectrum disorder (ANSD) features the presence of otoacoustic emissions, poor speech identification score and absent auditory brainstem response. Objective  The present study was designed to evaluate the functioning of all six semicircular canals in individuals with ANSD and to compare it with those of normal-hearing individuals. Methods  A total of 50 individuals participated in the present study, in which Group I comprised 25 normal-hearing individuals, and Group II comprised 25 individuals with ANSD. All of the participants underwent case history, pure tone audiometry, immittance, otoacoustic emissions, auditory evoked response and video head impulse test (vHIT). Results  The independent sample t-test revealed significantly lower vestibulo-ocular reflex gain values in individuals with ANSD. A presence of 100% corrective refixation saccades was observed in the same group. The Pearson correlation test revealed no significant correlation between vestibulo-ocular reflex (VOR) gain with duration of hearing loss and pure tone thresholds for any of the three orthogonal planes. The chi-squared test revealed no association between the VOR gain values and the presence or absence of saccades in any of the semicircular canals ( p  > 0.05). Conclusion  Huge percentages of individuals with ANSD have been found to have associated vestibular dysfunction as well. Therefore, the vHIT can be used as one of the important tests of the vestibular test battery to evaluate all six semicircular canals in individuals with ANSD.

Balance in Virtual Reality: Effect of Age and Bilateral Vestibular Loss

Background

Quantitative balance measurement is used in clinical practice to prevent falls. The conditions of the test were limited to eyes open, eyes closed, and sway-referenced vision. We developed a new visual perturbation to challenge balance using virtual reality (VR), measuring postural stability by a Wii Balance Board (WBB).

Methods

In this study, we recorded balance performance of 116 healthy subjects and of 10 bilateral vestibular loss patients using VR to assess the effect of age and the effect of total loss of vestibular function. We used several conditions: eyes open (normal visual inputs), eyes closed (no visual inputs), stable visual world (vision referenced), and perturbed visual world (visual perturbation) at different amplitudes of perturbation. Balance under these visual conditions was assessed on the WBB (stable support surface) and on the WBB plus foam rubber (unstable support surface).

Results

In healthy subjects, we found that the percentage of falls increased with age and with the amplitude of perturbation for both conditions: WBB or WBB + foam. Moreover, we can define a threshold for falls in each age group as the amplitude of perturbation which induced falls. For bilateral vestibular loss patients, on the WBB + foam, all of them failed with eyes closed and with perturbed visual world even at the minimal amplitude of perturbation. Finally, we observed that stable visual world induced fewer falls than eyes closed whatever the subject’s group (healthy or bilateral vestibular loss) and whatever the age decade.

Conclusion

VR allowed us to develop a useful new tool with a wide range of visual perturbations. Rather than only two levels of visual condition (eyes open and eyes closed), the VR stimulus can be continuously adjusted to produce a visual perturbation powerful enough to induce falls even in young healthy subjects and which has allowed us to determine a threshold for falls.

Assessment of VOR gain function and its test-retest reliability in normal hearing individuals

Video head impulse test (vHIT) aids to assess all three pairs of semi-circular canals (SCCs) separately and can be utilized to find out the exact site of lesion in any three SCCs by measuring vestibulo ocular reflex (VOR) gain. VOR gain value of vHIT has been used to diagnose different vestibular pathologies. Hence, it is important to establish the test-retest reliability of the VOR gain parameters before it could be administered to the patients. Therefore, the aim of the present study was to obtain VOR gain data, correlate all planes in both sides of head (right and left) and assess the test-retest reliability of VOR gain measure using vHIT in 25 normal young adult participants. Video head impulse test tests were carried out with prototype ICS impulse video goggles with a camera speed of 250 frames/s, recording motion of the right eye in all three planes (lateral, right anterior left posterior, left anterior right posterior) for all the participants. vHIT testing was repeated for all the participants after 15 days. Statistical analysis revealed that mean VOR gain for right horizontal canal was higher than the left horizontal canal; right anterior canal was higher than left anterior canal and left anterior was higher than right posterior canal. Horizontal canals have more gain compared to anterior and posterior canals. There was no significant difference between the VOR gain of session 1 and session 2 for each SCC.