Vestibulo-ocular Reflex Asymmetry Research Articles

Binocular video head impulse test: Normative data study.

The video head impulse test (vHIT) evaluates the vestibulo-ocular reflex (VOR). It's usually recorded from only one eye. Newer vHIT devices allow a binocular quantification of the VOR. To investigate the advantages of simultaneously recorded binocular vHIT (bvHIT) to detect the differences between the VOR gains of the adducting and the abducting eye, to define the most precise VOR measure, and to assess gaze dys/conjugacy. We aimed to establish normative values for bvHIT adducting/abducting eye VOR gains and to introduce the VOR dysconjugacy ratio (vorDR) between adducting and abducting eyes for bvHIT. We enrolled 44 healthy adult participants in a cross-sectional, prospective study using a repeated-measures design to assess test-retest reliability. A binocular EyeSeeCam Sci 2 device was used to simultaneously record bvHIT from both eyes during impulsive head stimulation in the horizontal plane. Pooled bvHIT retest gains of the adducting eye significantly exceeded those of the abducting eye (mean (SD): 1.08 (SD = 0.06), 0.95 (SD = 0.06), respectively). Both adduction and abduction gains showed similar variability, suggesting comparable precision and therefore equal suitability for VOR asymmetry assessment. The pooled vorDR here introduced to bvHIT was 1.13 (SD = 0.05). The test-retest repeatability coefficient was 0.06. Our study provides normative values reflecting the conjugacy of eye movement responses to horizontal bvHIT in healthy participants. The results were similar to a previous study using the gold-standard scleral search coil, which also reported greater VOR gains in the adducting than in the abducting eye. In analogy to the analysis of saccade conjugacy, we propose the use of a novel bvHIT dysconjugacy ratio to assess dys/conjugacy of VOR-induced eye movements. In addition, to accurately assess VOR asymmetry, and to avoid directional gain preponderance between adduction and abduction VOR-induced eye movements leading to monocular vHIT bias, we recommend using a binocular ductional VOR asymmetry index that compares the VOR gains of only the abduction or only the adduction movements of both eyes.

Effects of Menstrual Cycles on VOR Gain Functions

Abstract Purpose The aim of the present study was to assess the vestibuloocular reflex (VOR) gain function and VOR gain asymmetry during the various phases of the menstrual cycle in young healthy female participants. The study also aimed to characterize the presence or absence of corrective saccades during the various phases of the menstrual cycle. Method Twenty-nine young healthy females participated in the study. The video head impulse test (vHIT) was performed in lateral, left anterior right posterior, and right anterior left posterior plane during the various phases of the menstrual cycle to see the changes in VOR gain function and VOR gain asymmetry ratio changes. Results A repeated measure analysis of variance test did not show any significant main effect for the VOR gain function and VOR gain asymmetry ratio in various phases of the menstrual cycle in all the participants. The result suggested no changes in VOR gain function and VOR asymmetry ratio in healthy females during the menstrual cycle. Also, there was an absence of saccades in the entire participants group during the various phases of the menstrual cycle. Conclusions As the VOR gain function does not change during the various phases of the menstrual cycle in young healthy females, there is no need to consider the various phases of the menstrual cycle while testing any female participant during the vHIT test.

Normative values for semicircular canal function with the video head impulse test (vHIT) in healthy adolescents

Background The vHIT device, which has a mechanism based on measuring the VOR gain, helps us to quickly evaluate six semicircular canals. Aims/Objectives The aim of this study was to establish normative values for semicircular canal function with the video head impulse test (vHIT) battery in normal adolescents. Material and methods 100 (50 females, 50 males) individuals aged 11–18 years, with a mean age of 14.99 years, were included in the study. Results As a result of the vHIT evaluations performed with vHIT Otometrics ICS Impulse A/S Taastrup, Denmark, the mean lateral canal vestibulo-ocular reflex (VOR) gain value was 0.96, the mean anterior canal VOR gain value was 0.89, and the mean posterior canal VOR gain value was 0.87, all of which were within the normal value range. Conclusion and significance While the VOR gain values and asymmetry values are within the normal value range and are similar to the literature, no statistically significant correlation was observed between these values and age. As a result, the vHIT battery is an easy, fast, and practical test method that can be used in adolescents.

Vestibular and audiological findings in the Alport syndrome.

Alport syndrome (AS) is caused by mutations in collagen IV, which is widespread in the basement membranes of many organs, including the kidneys, eyes, and ears. Whereas the effects of collagen IV changes in the cochlea are well known, no changes have been described in the posterior labyrinth. The aim of this study was to investigate both the auditory and the vestibular function of a group of individuals with AS. Seventeen patients, aged 9-52, underwent audiological tests including pure-tone and speech audiometry, immittance test and otoacoustic emissions and vestibular tests including video head impulse test, rotatory test, and vestibular evoked myogenic potentials. Hearing loss affected 25% of the males and 27.3% of the females with X-linked AS. It was sensorineural with a cochlear localization and a variable severity. 50% of the males and 45.4% of the females had a hearing impairment in the high-frequency range. Otoacoustic emissions were absent in about one-third of the individuals. A peripheral vestibular dysfunction was present in 75% of the males and 45.4% of the females, with no complaints of vertigo or dizziness. The vestibular impairment was compensated and the vestibulo-ocular reflex asymmetry was more evident in rotatory tests carried out at lower than higher speeds; a vestibular hypofunction was present in all hearing impaired ears although it was also found in subjects with normal hearing. A posterior labyrinth injury should be hypothesized in AS even when the patient does not manifest hearing disorders or evident signs of renal failure.

Oculomotor functions in focal dystonias: A systematic review.

Focal Dystonia (FD) is a chronic neurological disorder, which causes twisting and repetitive movements and abnormal postures induced by involuntary sustained contractions of agonist and antagonist muscles.Based on the hypothesis that several dystonia-related brain regions, including cerebellum, are implicated in oculomotor disturbances (OCD), a number of studies investigated oculomotor function in patients with dystonia. However, conceptual clarity with respect to the used assessment tools and interpretation of the findings is lacking in the literature. This is the first article to systematically review studies that assessed oculomotor function in patients with FD.In total, 329 publications, published until September 1, 2019, were identified through MEDLINE search. Twenty out of 329 studies, involving 232 subjects in total, met the inclusion criteria. Most of the studies reported oculomotor disturbances in patients with FD. Abnormalities included asymmetry in vestibulo-ocular reflex (VOR), disturbances in saccadic functions, and prolonged latencies of eye motion. Discrepancies in the results could be explained, at least partially, by the long period of time over which the reviewed studies were published, the different methods used for testing the eye movements, and the limited number of patients assessed since the majority of data derived from case reports or small-scale studies. Further prospective studies with larger subject numbers are needed, using advanced tools for the assessment of oculomotor function in focal dystonia.

Rebalancing the Vestibular System by Unidirectional Rotations in Patients With Chronic Vestibular Dysfunction.

Introduction: Vestibular dysfunction is a common disorder that results in debilitating symptoms. Even after full compensation, the vestibulo-ocular reflex (VOR) could be further improved by using rehabilitation exercises and visual-vestibular adaptation. We hypothesized that in patients with asymmetric vestibular function, the system could be rebalanced by unidirectional rotations toward the weaker side (i.e., a pure vestibular stimulation).Methods: Sixteen subjects (5 female and 11 male, 43.2 ± 17.0 years old) with chronic vestibular dysfunction that was non-responsive to other types of medical treatment were recruited for the study (ClinicalTrials.gov Identifier: NCT01080430). Subjects had VOR asymmetry quantified by an abnormal directional preponderance (DP) with rotation test and no previous history of central vestibular problems or fluctuating peripheral vestibular disorders. They participated either in the short-term study (one session) or the long-term study (7 visits over 5 weeks). Rehabilitation consisted of five trapezoid unidirectional rotations (peak velocity of 320°/s) toward the weaker side. Care was taken to slowly stop the rotation in order to avoid stimulation in the opposite direction during deceleration. To study the short-term effect, VOR responses were measured before and 10, 40, and 70 min after a single unidirectional rotational rehabilitation session. For long-term effects, the VOR gain was measured before and 70min after rehabilitation in each session.Results: We observed a significant decrease in VOR asymmetry even 10 min after one rehabilitation session (short-term study). With consecutive rehabilitation sessions in the long-term study, DP further decreased to reach normal values during the first 2 sessions and only one subjects required further rehabilitation after week 4. This change in DP was due to an increase in responses during rotations toward the weaker side and a decrease in VOR responses during rotations in the other direction.Conclusion: Our results show that unidirectional rotation can reduce the VOR imbalance and asymmetry in patients with previously compensated vestibular dysfunction and could be used as an effective supervised method for vestibular rehabilitation even in patients with longstanding vestibular dysfunction.

Comparison of the Bedside Head-Impulse Test with the Video Head-Impulse Test in a Clinical Practice Setting: A Prospective Study of 500 Outpatients.

The primary aim was to determine the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the bedside head-impulse test (bHIT) using the video HIT (vHIT) as the gold standard for quantifying the function of the vestibulo-ocular reflex (VOR). Secondary aims were to determine the bHIT inter-rater reliability and sensitivity in detecting unilateral and bilateral vestibulopathy. In this prospective study, 500 consecutive outpatients presenting to a tertiary neuro-otology clinic with vertigo or dizziness of various vestibular etiologies who did not have any of the pre-defined exclusion criteria were recruited. Bedside HITs were done by three experienced neuro-otology clinicians masked to the diagnosis, and the results were compared with the vHIT. The patients were likewise blinded to the bHIT and vHIT findings. Patients with VOR deficits were identified on the vHIT by referencing to the pre-selected "pathological" gain of <0.7. The data were then analyzed using standard statistical methods. For the primary outcome (vHIT "pathological" VOR gain <0.7), the three-rater mean bHIT sensitivity = 66.0%, PPV = 44.3%, specificity = 86.2%, and NPV = 93.9%. Shifting the "pathological" threshold from 0.6 to 0.9 caused the bHIT sensitivity to decrease while the PPV increased. Specificity and NPV tended to remain stable. Inter-rater agreement was moderate (Krippendorff's alpha = 0.54). For unilateral vestibulopathy, overall bHIT sensitivity = 69.6%, reaching 86.67% for severely reduced unilateral gain. For VOR asymmetry <40% and >40%, the bHIT sensitivity = 51.7 and 83%, respectively. For bilateral vestibulopathy, overall bHIT sensitivity = 66.3%, reaching 86.84% for severely reduced bidirectional gains. For the primary outcome, the bHIT had moderate sensitivity and low PPV. While the study did not elucidate the best choice for vHIT reference, it demonstrated how the bHIT test properties varied with vHIT thresholds: selecting a lower threshold improved the sensitivity but diminished the PPV, while a higher threshold had the opposite effect. The VOR was most likely normal if the bHIT was negative due to its high NPV. The bHIT was moderately sensitive for detecting unilateral and bilateral vestibulopathy overall, but better for certain subgroups.

The vestibular implant: frequency-dependency of the electrically evoked vestibulo-ocular reflex in humans.

The vestibulo-ocular reflex (VOR) shows frequency-dependent behavior. This study investigated whether the characteristics of the electrically evoked VOR (eVOR) elicited by a vestibular implant, showed the same frequency-dependency. Twelve vestibular electrodes implanted in seven patients with bilateral vestibular hypofunction (BVH) were tested. Stimuli consisted of amplitude-modulated electrical stimulation with a sinusoidal profile at frequencies of 0.5, 1, and 2 Hz. The main characteristics of the eVOR were evaluated and compared to the “natural” VOR characteristics measured in a group of age-matched healthy volunteers who were subjected to horizontal whole body rotations with equivalent sinusoidal velocity profiles at the same frequencies. A strong and significant effect of frequency was observed in the total peak eye velocity of the eVOR. This effect was similar to that observed in the “natural” VOR. Other characteristics of the (e)VOR (angle, habituation-index, and asymmetry) showed no significant frequency-dependent effect. In conclusion, this study demonstrates that, at least at the specific (limited) frequency range tested, responses elicited by a vestibular implant closely mimic the frequency-dependency of the “normal” vestibular system.

Cochlear Implantation Rarely Alters Horizontal Vestibulo-ocular Reflex in Motorized Head Impulse Test

Determine the change in vestibular function in patients receiving a unilateral cochlear implant, and to compare these results with other signs and symptoms. Prospective cohort study. Academic tertiary referral center. Forty-four adults (mean age, 55 yr; range, 30-76 yr) receiving their first cochlear implant. Cochlear implantation. Horizontal high-frequency vestibulo-ocular reflex (VOR) was measured using the motorized head impulse rotator preoperatively and twice (on average two and 19 months) postoperatively. VOR gain and asymmetry were calculated (mean ± standard deviation). Symptoms were assessed with a structured questionnaire. Gain on the operated side was 0.77 ± 0.26 preoperatively, 0.75 ± 0.30 in the early and 0.73 ± 0.33 in the late postoperative control, and did not change significantly. Mean asymmetry remained within 9% to 10% in all test occasions. Dizziness symptom score or dizziness-related quality of life score did not change significantly. General quality-of-life score improved significantly from that of preoperative 3.5 ± 1.2 to that of 2.6 ± 1.1 postoperatively (p = 0.01). Subjective hearing scores improved significantly from 4.9 ± 0.3 to 2.4 ± 1.0, respectively (p = 0.0000). Gain was decreased significantly in 4 patients (10%) in the early and in 2 patients (7%) in the late postoperative control. Late high-frequency loss of vestibular function or vestibular symptoms is rare but possible after cochlear implantation surgery. This should be taken into account in patient counseling especially when considering bilateral cochlear implant surgery.

Recovery of the horizontal vestibulo-ocular reflex in motorized head impulse test is common after vestibular loss

Conclusion: Decreased horizontal vestibulo-ocular reflex (VOR) gain measured with the motorized head impulse rotator usually recovers at least partially within a few months after sudden unilateral vestibular loss. In addition to traditional evaluation of nystagmus, head impulse test responses provide valuable information on the severity and recovery of vestibular loss. Objectives: To quantify recovery of vestibular function with the motorized head impulse test in patients with acute unilateral peripheral vestibular loss, and to compare these results with other signs and symptoms. Methods: We recorded prospectively the horizontal VOR with the motorized head impulse rotator in 30 patients with sudden unilateral vestibular deficit on average 3 days after the onset (early). Twenty patients were measured sequentially on average 3 months later (late). We calculated VOR gain and asymmetry (mean ± standard deviation). Results: The early ipsilesional gain of 0.49 ± 0.21 improved highly significantly to the late gain of 0.79 ± 0.23 (p = 0.0000). The respective asymmetry improved highly significantly from 32 ± 18% to 12 ± 14% (p = 0.0002). Gain or asymmetry recovered at least partially in 80% of the patients. The late high symptom score correlated with low gain (p = 0.043) and high asymmetry (p = 0.018).

CLICK-EVOKED VESTIBULO-OCULAR REFLEX DISTINGUISHES POSTERIOR FROM SUPERIOR CANAL DEHISCENCE

A 26-year old man had oscillopsia in response to loud sounds following head trauma in a skiing accident. His vision would blur when he heard loud music or when listening to the telephone with his right ear. His examination was unremarkable without sound- or pressure-induced eye movements. His symptoms suggested a pathologic third window into the inner ear labyrinth, most commonly due to a superior canal dehiscence.1 However, posterior canal dehiscence (PCD) due to jugular bulb abnormalities2,3 or cholesteatoma erosion4 has been described. We used binocular, 3-dimensional click-evoked vestibulo-ocular reflex (VOR),1 ocular vestibular evoked myogenic potentials (oVEMP),5 and CT imaging1,2,6 to identify the cause of his symptoms. Stimulation of the unaffected left ear with 5-click trains at 110 dB NHL yielded normal miniscule eye rotations,1 but stimulation of the symptomatic right ear yielded enlarged, downward, contraversive-torsional (counterclockwise, i.e., eye's upper pole rotated away from the right ear) and rightward eye rotations (figure 1A). Eye velocity magnitudes from left ear stimulation were ≤1.0 °/s; for right ear stimulation, they were 37.3 °/s for the ipsilateral eye and 49.3 °/s for the contralateral eye, with a left-right VOR asymmetry of 1:37 (ipsilateral eye) and 1:49 (contralateral eye). Figure 1 Click-evoked vestibulo-ocular reflex in a posterior canal dehiscence confirmed by CT imaging (A) Binocular, 3-dimensional 5-click evoked vestibulo-ocular reflex (VOR) from a right posterior canal dehiscence patient. Left ear 5-click evoked VOR at 110 dB normal hearing level (NHL) with miniscule eye rotations (x, y, z < ± 0.006)° and (x, y, z ≤ 1) °/s was normal.1 Right ear 5-click VOR shows enlarged downward, contraversive-torsional counterclockwise and small rightward eye rotations in positions and velocities from ipsilateral eye: (x = …

Computer-aided vestibular autorotational testing of the vestibulo-ocular reflex in senile vestibular dysfunction

Background and objective Studies have already investigated vestibulo-ocular reflex (VOR) responses in elderly subjects, mostly at low frequencies (<1 Hz) during passive head turns, or continuous active head turns in a rotational chair. However, natural head movements usually occur at frequencies above 1 Hz and at varying rates, rather than at continuously increasing rates as tested in most studies to date. The aim of this study was to compare VOR responses within or between normal and bilateral peripheral vestibular hypofunction (BPVH) elderly subjects with a computer base program incorporating random active high-frequency head movements. Subjects Seventeen senior patients with bilateral peripheral vestibular hypofunction and 13 age-matched paid healthy subjects participated in this study. Design All the subjects performed 8 s of active, side-to-side head motions at 1 Hz, 2 Hz and 3 Hz in response to four experimental conditions: (A) a stationary visual target; (B) a stationary visual target and a moving target with a horizontal trajectory; (C) a stationary visual target and a moving target with a spiral trajectory; and (D) a stationary visual target with combined horizontal- and vertical-spiral moving targets. Results Repeated-measures ANOVA showed that across the different frequencies of headshaking, a significant increase took place in the phase lag of the BPVH subjects ( p < 0.001) compared with the normal controls. Post hoc analysis showed significant within-group differences in BPVH subjects (1 Hz vs 2 Hz, 2 Hz vs 3 Hz) and normal controls (1 Hz vs 2 Hz, 1 Hz vs 3 Hz). A significant VOR gain took place among the BPVH subjects at 3 Hz VAT ( p < 0.001) as compared with 1 Hz VAT and no significant differences in VOR gain could be detected among the controls at either of these frequencies. Repeated-measures ANOVA revealed that under our test conditions, significant main effect was noted for VOR asymmetry ( F = 4.45, p < 0.05). Post hoc analysis showed significant within-group differences in the BPVH subjects (test A vs test B, test A vs test C, and test A vs test D). Conclusions Our results showed that the VAT paradigm can be improved by using concurrent horizontal and vertical moving targets. The VOR phase may be useful for differentiating VAT responses between BPVH and healthy elderly subjects. Moreover, the results of this study demonstrate that gains in VOR at different frequencies of headshaking and asymmetry during different test conditions can be useful parameters for within-group assessment.

Effects of eccentric rotation on the human pitch vestibulo-ocular reflex

Conclusion. The pitch plane vestibulo-ocular reflex (VOR) gain and symmetry at low frequencies (≤0.3 Hz) are enhanced by otoliths and/or somatosensory sensory cues during combined angular and linear stimuli. We conclude that neural processing of these linear motion cues is used to improve the VOR when stimulus frequencies are below the optimal range for the canals. Objective. The purpose of this study was to examine the effects of eccentric rotation on the passive pitch VOR responses in humans. Subjects and methods. Eleven subjects were placed on their left sides (90° roll position) and rotated in the pitch plane about an earth-vertical axis at 0.13, 0.3, and 0.56 Hz. The inter-aural axis was either aligned with the axis of rotation (no modulation of linear acceleration) or offset from it by 50 cm (centripetal linear acceleration directed feet-ward). The modulation of pitch VOR responses was measured in the dark with a binocular videography system. Results. The pitch VOR gain was significantly increased and the VOR asymmetry was significantly reduced at the lowest stimulus frequencies during eccentric rotation. There was no effect of eccentric rotation on the pitch gain or asymmetry at the highest frequency tested.

Motorized head impulse rotator in patients with vestibular schwannoma

Conclusion. Motorized head impulse rotator is an effective technique to assess peripheral vestibular function. Approximately a quarter of patients with vestibular schwannoma (VS) had preserved preoperative responses. Vestibular disability could not be predicted based on vestibulo-ocular reflex (VOR) performance during motion stimuli, or in the caloric test. Objectives. To explore motorized head impulse rotator for evaluation of angular horizontal VOR in patients with VS, and to compare these responses to those of the caloric test and the symptoms. Patients and methods. We prospectively recorded head and eye position during unpredictable motorized head impulses in 38 patients with VS. We calculated gain and asymmetry of VOR (mean±95% CI), and the results were compared to those of the caloric test and a questionnaire regarding dizziness, hearing and quality of life. Results. The VOR during motorized impulses was abnormal in 71% of patients. Asymmetry in gain correlated significantly (p<0.001) with unilateral weakness in the caloric test. Preoperative gain was significantly lowered to 0.83±0.08 on the ipsilateral side compared to 0.98±0.06 on the contralateral side. Postoperative gain on the operated side of 0.53±0.05 was significantly different from preoperative gain (p<0.001). Findings in vestibular tests did not correlate with subjective sensation of dizziness.

Effects of Vestibulo-ocular Reflex Exercises on Vestibular Compensation after Vestibular Schwannoma Surgery

To assess vestibular function in a large group of vestibular schwannoma patients so that we could determine whether simple vestibular exercises speed vestibular dysfunction recovery after tumor removal surgery. A prospective investigation of the vestibular dysfunction experienced by patients in the first 12 weeks after surgery. Vestibular investigation unit at a tertiary referral institution. Sixty-five patients with identified vestibular schwannoma referred for preoperative vestibular investigations. Thirty-two men and 33 women, with a mean age 51 years (range, 24-77 yr). There were 27 control patients, 30 exercise patients, and 8 patients that had balance physiotherapy. Exercise patients began simple vestibulo-ocular reflex gaze stabilization exercises 3 days after surgery. Postoperative vestibular function testing was performed at 2 to 3, 6 to 7, and 10 to 12 weeks after surgery. Objective measurements of vestibular compensation status were as follows: spontaneous nystagmus and sinusoidal harmonic acceleration asymmetry and gain values. Dizziness Handicap Inventory questionnaires were used to assess subjective perceptions. The main findings were reduced dispersion in vestibulo-ocular reflex asymmetry at 2 to 3 weeks, reduced mean in asymmetry at 6 to 7 weeks, less dizziness/imbalance according to the Dizziness Handicap Inventory questionnaire, and that preoperative caloric tests did not predict postoperative severity of vestibular systems. This large study provided unique evidence that a program of simple vestibular exercises and education can speed the rate of compensation after vestibular schwannoma surgery.

Evidence for interacting cortical control of vestibular function and spatial representation in man

The objective of this research was to determine the possible relation between deficits in spatial representation capability and vestibular function following cortical lesions. We thus investigated vestibulo-ocular behaviour in a group of 14 patients with unilateral cortical damage involving the occipito-temporo-parietal junction. Patients were divided in three sub-groups: (1) Group R+: five patients with right sided cortical lesions associated with a left hemi-neglect, (2) Group R−: four patients with right sided cortical lesions with no hemi-neglect and (3) Group L: five patients with left-sided cortical lesions. The patient groups were compared to a group of eight healthy age-matched subjects. The vestibulo-ocular reflex (VOR) was tested in complete darkness by rotating the subject around the vertical axis by sinusoidal rotation at different frequencies, and by steps of acceleration or deceleration. The nystagmus slow phase velocity was measured and plotted as a function of the head velocity and the VOR parameters including gain, bias, time constant and phase were calculated. The cortical lesions induced a significant VOR asymmetry in terms of: a directional preponderance of the VOR gain to the contralesion side, only during sinusoidal rotation, and, in contrast, a VOR bias and a directional preponderance of the VOR time constant and of the nystagmus frequency to the side of the cortical lesion. These latter VOR deficits were the most significant in the R+ group, i.e. in right cortical lesions with hemi-neglect syndrome. These results demonstrate in man, the existence of a cortical influence on vestibular function related to the mechanisms of spatial representation.

Dynamic asymmetry of the vestibulo-ocular reflex in unilateral peripheral vestibular and cochleovestibular loss.

Rotatory tests in the horizontal plane have shown various degrees of vestibulo-ocular reflex (VOR) asymmetry in patients after surgical deafferentation of one labyrinth. The purpose of this work was to characterize dynamic horizontal VOR responses among patients presenting with a unilateral peripheral labyrinthine deficit of nonsurgical origin and to compare results in isolated vestibular loss versus cochleovestibular loss. This study included 40 patients who presented with an acute, spontaneous unilateral peripheral labyrinthine lesion. Twenty-two patients had vestibular loss alone (without associated hearing impairment) and 18 presented with a cochleovestibular deficit (sudden hearing loss with vertigo). The majority of these patients were part of a long-term protocol to evaluate vestibular compensation. All patients underwent both the clockwise test and the counterclockwise rotatory test in the horizontal plane, using brief impulses of moderate intensity. Results were analyzed by a simplified model of vestibular function, allowing a parametric estimation of the response. A weak and transitory horizontal VOR asymmetry was observed in the 22 patients with vestibular loss. However, the 18 patients with cochleovestibular loss demonstrated a more severe and persistent asymmetry. This study revealed a difference in the dynamic characteristics of the horizontal VOR between patients with vestibular loss and those with cochleovestibular loss. Our results support the presence of an extensive labyrinthine lesion in cochleovestibular deficit that involves the otolith organs. The implications of this involvement on the central mechanisms of otolith-canal interaction are discussed.

Vestibulo-ocular dysfunction induced by cortical damage in man:: a case report

We studied the rare case of a patient presenting with vestibulo-ocular dysfunction and clinical vestibular symptoms after right temporo-parietal cortex infarction. The vestibulo-ocular reflex (VOR) was elicited in the dark, by sinusoidal (0.02; 0.05 and 0.1 Hz) and by step velocity rotation (100°/s 2) in clockwise and counterclockwise directions. Horizontal and vertical eye movements were recorded by DC electro-oculography (EOG). When compared to a control group of 8 healthy subjects, this patient presented VOR asymmetry with (1) a significant VOR velocity bias toward the lesioned side revealed as a vestibulo-ocular offset that occurred only under dynamic conditions (2) a significant reduction of the VOR time constant when rotation was directed to the lesioned side. VOR gain was normal. We suggest that the parieto-temporal cortex is implicated in the regulation of vestibulo-ocular symmetry in man. This cortical processing of vestibular integration might involve a multidimensional velocity storage integrator that subserves the maintenance of spatial coordinates along the spatial vertical axis.

Comparison of Manual Whole-Body and Passive and Active Head-On-Body Rotational Testing with Conventional Rotary Chair Testing

New methods of rotational testing of the vestibulo-ocular reflex (VOR) using manually generated or patient-generated sinusoidal head movements have recently been advocated for clinical use in circumstances where conventional rotary chair testing methods are not feasible. However, studies seeking to provide evidence for the validity of these methods by comparing their results with an accepted "gold-standard" have been conspicuously absent in the literature. In this study, we compared results for VOR gain, phase, and asymmetry obtained using whole-body and head-on-body rotational stimuli with those obtained by conventional rotary chair testing in 35 subjects with either unilateral or bilateral vestibular deficits over the range of frequencies from 0.025 Hz to 1 Hz. Our results provide evidence for the validity of manual whole-body and active and passive head-on-body rotational testing methods by demonstrating excellent agreement between each of these and conventional rotational chair testing for VOR gain, phase, and asymmetry within the frequency range studied. Small differences at specific-paradigm datapoints are likely secondary to subtle limitations of our experimental design. With further refinement, we expect the new methods will be useful adjuncts for evaluating patients with vestibular complaints in selected clinical situations.

Assessment of auditory and vestibular functions after vestibular neurectomy for Menière's disease.

Fourteen patients (12 Meniere's disease, one delayed endolymphatic hydrops and one labyrinthitis) suffering from intractable vertigo were treated with retrosigmoid vestibular neurectomy (RSVN) in our institute. Dizziness was controlled completely in all patients. Hearing was preserved in 91.7% of the cases with pure tone threshold deteriorating by more than 10 dB in one case, remained unchanged in 10 cases and improved in one case during long term observation. Substantial decrease of tinnitus was observed in 78.6%. Vestibular compensation was chronologically analyzed with a stabilometer, ENG and vestibular rotation test (0.01-0.64 Hz). Vestibular compensation under static conditions was accomplished within 2 weeks, except for spontaneous nystagmus measured in the dark. Asymmetry of vestibulo-ocular reflex was noted 2 weeks after the operation but had disappeared after 4 weeks. However, for over 2 years the VOR time constant remained lower (4.3-5.2 s) than the pre-operative value (8.2 s). Electro-cochleogram (ECoG) was recorded before and after RSVN. The -SP/AP ratio tended to increase after RSVN in the operated ear, though there was no change in the contralateral ear. The efferent olivo-cochlear bundle was thought to play a potential role in this increase of the -SP/AP ratio.