Left Anterior-right Posterior Research Articles

Vestibular-evoked myogenic potentials and video head impulse test in cochlear otosclerosis

BackgroundOtosclerosis is one of the most common causes of hearing loss in adults with clinical onset between 20 and 40 years of age. Vestibular symptoms may be the most agonizing and primary symptom in cases with otosclerosis, so the assessment of patients is important. The vestibular-evoked myogenic potentials test (VEMP) is used to assess the saccular and the utricular functions using cervical and ocular vestibular-evoked myogenic potentials (cVEMP and oVEMP), respectively. The video head impulse test (vHIT) which measure vestibulo-ocular reflex (VOR) to rapid impulsive head acceleration in the plane of each semicircular canal (SCC) has allowed quantitative monitoring of each canal function.MethodsTwenty subjects with bilateral otosclerosis were studied, ranging in age from 30 to 55 years, divided into two groups. One group consisted of 10 adult patients with bilateral conductive otosclerosis. The second group consisted of 10 adult patients with bilateral mixed otosclerosis. All the patients underwent cVEMP and oVEMP, using a BC 500Hz tone burst stimulus and vHIT in three planes, left anterior right posterior (LARP), right anterior left posterior (RALP), and lateral SCCs.ResultsThe findings indicate statistically significant differences in the peak-to-peak amplitudes of cVEMP and oVEMP in the two studied groups, and the mixed cases had lower amplitudes than conductive cases and a significant increase in p13 latencies. Also, there is a statistically significant difference in the lateral SCC gain between the two groups, as mixed cases had lower gain than conductive cases, but not for anterior or posterior SCCs, with no gain less than 0.8 in all three canals.ConclusionThe findings suggested that the saccule is more liable to be affected by cochlear otosclerosis followed by the utricle. The three SCCs are mostly spared.

Is it possible to diagnose Posterior Semicircular Canal BPPV from the sitting position? The role of the Head Pitch Test and the upright tests along the RALP and LARP planes

PurposeThe diagnosis of benign paroxysmal positional vertigo (BPPV) involving the posterior semicircular canal (PSC) is traditionally entrusted to positioning tests where patients are rapidly brought in the supine position. This prospective study aims to define the role of a diagnostic protocol for PSC-BPPV including only upright tests. Materials and methods109 patients with PSC-BPPV were enrolled. The Head Pitch Test (HPT) was carried out first. If uneventful, the patient's head was turned 45° to each side and bent back-and-forth along the plane aligning either with the right anterior-left posterior (RALP) or left anterior-right posterior (LARP) canals, thus performing the upright RALP / upright LARP (uRALP/uLARP) test. Nystagmus observed was used to predict the diagnosis, which was therefore confirmed by Dix-Hallpike tests. ResultsPSC-BPPV could be correctly diagnosed in 75.2% of cases with the sole HPT and in 87.2% of cases by adding the uRALP/uLARP test (Upright Protocol). The time elapsed from symptoms onset was closely related to the protocol sensitivity, as it reached 100% (64/64) in acute patients while decreased to 68.9% (31/45) in cases evaluated after 7 days (p < 0.001). ConclusionsUpright maneuvers could correctly diagnose PSC-BPPV in most cases. uRALP/uLARP test demonstrated to improve the sensitivity of the HPT, mainly in recent-onset BPPV.

Assessment of the effects of menopause on semicircular canal using the video head impulse test

This cross-sectional study included early menopausal and late menopausal women aged between 40 and 60 years to evaluate the effects of menopause on semicircular canal function. A video head impulse test (vHIT) was performed for all subjects. Vestibulo-ocular reflex (VOR) mean gains of each semicircular canal and gain asymmetry were compared between groups. Of the 87 subjects, 37(42.5%) were reproductive age 28(32.5%) were early menopausal and 22(25.3%) were late menopausal patients. VOR gain of semicircular canals or gain asymmetry values did not differ between groups. In postmenopausal women, presence of vasomotor symptoms was associated with higher gain asymmetry of the left anterior-right posterior (LARP) plane (p = .01), and presence of balance problems was associated with lower right anterior (RA) VOR gain (p = .01). In conclusion semicircular canal function in postmenopausal women was similar to that in women of reproductive age. IMPACT STATEMENT What is already known on this subject? During menopause, women face potential risks such as dizziness, balance problems, falls and fractures. Postmenopausal patients were tested with dynamic posturography to measure balance before and after oestrogen treatment, and it was shown that balance problems significantly improved with oestrogen treatment. Healthy vestibular system is one of the components for sustaining normal balance. What do the results of this study add? In postmenopausal women the function of the semicircular canals is normal and the balance deficit in postmenopausal women may not be caused by the vestibular system. In this study changes within normal limits were observed in vestibular system of postmenopausal women. What are the implications of these findings for clinical practice and/or further research? Reported balance deficits might have been due to central origin. Further research to differentiate origin of balance deficits are needed. Specific research on symptomatic postmenopausal patients would reveal more information.

Normal Vestibulo Ocular Reflex (VOR) gain Measured Using the Video Head Impulse Test (vHIT) in Healthy Young Adults

Introduction: Many new objective tests to assess the function of specific structures of the vestibular organ are currently adopted in vestibular clinics. One of the objective assessments include the video head impulse test (vHIT) where gain &amp; velocity responses of eye relative to the head movements are recorded using an infrared camera. Methods: Thirty normal hearing subjects age between 18 to 25 years old participated in this study. At least ten Lateral, Left Anterior Right Posterior (LARP), and Right Anterior Left Posterior (RALP) responses were recorded for each participant by making small and rapid unpredictable head movements. Results: The average velocity gain for Lateral responses at 40 ms, 60 ms and 80 ms were 1.05 ± 0.003, 1.03 ± 0.002 and 1.01 ± 0.003 respectively. The LARP average velocity regression were 1.01 ± 0.24 for Left Anterior and 1.05 ± 0.25 for Right Posterior, with an average gain asymmetry of 5.13%. The RALP average velocity regression were 1.08 ± 0.31 for Right Anterior and 1.12 ± 0.30 for Left Posterior, with an average gain asymmetry of 5.87%. One sample T-test were conducted to compare Lateral responses to a previous study by Mossman et al. (2015) where significant differences in velocity gain at 60 ms and 80 ms between studies were found where, t (59) = 5.56, p &lt;0.01 and t (59) = 2.86, p &gt;&lt; 0.01 respectively. Conclusion: This indicates the importance of establishing on-site norms for every clinical settings as techniques used and equipment differences could affect the results.

Evaluation of the vestibular system with video head impulse test in pregnant women with hyperemesis gravidarum.

We aimed to evaluate the semicircular canal functions of the vestibular system in pregnant women with hyperemesis gravidarum. This is a prospective case-control study. Among pregnant women in their first trimester (<14. gestational weeks) who presented to our outpatient clinic, 36 patients diagnosed with hyperemesis gravidarum defined as persistent nausea and vomiting requiring intravenous hydration or loss of at least 5% of prepregnancy weight and 34 healthy pregnant without nausea and vomiting were included. Otorhinolaryngologic examination and video head impulse test (vHIT) was performed to all patients. Vestibular-ocular reflex (VOR) gain and gain asymmetry were assessed between groups. The VOR gains in each semicircular canal did not differ between hyperemesis and control groups. Using a VOR gain cut-off value of 0.8, the groups were compared in terms of the frequency of low values. In the hyperemesis group, abnormally low gain values of left anterior canal were more frequently observed than in the control group (32 [88.9%], 22 [64.7%], respectively, P = 0.01). In left anterior-right posterior (LARP) plane VOR gain asymmetry was higher in hyperemesis group (13.5 [1.0-71.0], 6.0 [0.0-35.0], P = 0.001). No significant gain asymmetry was detected between the groups in the other planes. Semicircular canal functions were not abnormal globally in women with hyperemesis gravidarum. However, higher LARP plane asymmetry and low LA gain in women with hyperemesis suggests need for further research to clarify functional role of vestibular system on hyperemesis gravidarum.

Normal Saccadic Responses Using Video Head Impulse Test In Healthy Young Adults

Introduction: Vertigo and dizziness are common symptoms reported in audiology and ENT clinics. One of the objective assessments includes the video head impulse test (vHIT) where gain &amp; amp; velocity responses of eye movements relative to the head movements are recorded using an infrared camera. Materials and Methods: Thirty normal hearing subjects age between 18 to 25 years old participated in this study. Exclusion factors include those with the history of head or neck injury and vertigo. At least ten lateral, left anterior right posterior (LARP), and right anterior left posterior (RALP) responses were recorded for each participant by making small unpredictable head movements. Results: The average velocity gain for lateral responses at 40 ms, 60 ms and 80 ms were 1.05 ± 0.003, 1.03 ± 0.002 and 1.01 ± 0.003 respectively. The LARP and RALP average velocity regression were 1.01 ± 0.24 for left anterior and 1.05 ± 0.25 for right posterior, 1.08±0.31 for right anterior and 1.12 ± 0.30 for left posterior. One sample T-test was conducted to compare lateral responses to a previous study by Mossman et al. 2015. There were significant differences in velocity gain at 60 ms and 80 ms where, t (59) = 5.56, p &lt; 0.01 and t (59) = 2.86, p &lt; 0.01, respectively. Conclusion: This indicates the importance of establishing norms for clinics as various factors could affect the results such as techniques used and equipment differences. A follow-up study on subjects with vestibular disorders is required to validate this data as a normative reference.

Range of Peak Head Velocity in Video Head Impulse Testing for Pediatric Patients.

To examine peak head velocity in video head impulse testing of pediatric patients and its effect on vestibulo-ocular reflex (VOR) gain. Retrospective case review. Tertiary referral center. Pediatric patients ages 3 to 18 years old who underwent video head impulse testing during clinical evaluation of dizziness and/or imbalance. Conducted video head impulse test (vHIT) in horizontal, left anterior-right posterior (LARP), and right anterior-left posterior (RALP) planes. Peak head velocity and mean VOR gain for individual semicircular canals in different age groups. For the horizontal plane, vHIT peak head velocity greater than 150 degrees/s was achieved in 43 to 63% of 219 patients. In contrast, vHIT peak head velocity greater than 150 degrees/s was achieved in only 3 to 14% for the LARP and RALP planes. Analyses of differences in mean VOR gains among three ranges of peak head velocity (100-125 degrees/s, 126-150 degrees/s, and >150 degrees/s) by paired-t tests were not significant (p > 0.05) within individual patients. Mean VOR gains of three vertical canals in younger patients were significantly lower with higher peak head velocities compared with older children (p < 0.05). Peak head velocities of greater than 150 degrees/s may not be feasible in a large proportion of children and adolescents, especially in LARP and RALP planes. However, such high velocities may not be necessary in the pediatric population since VOR gain values obtained at lower peak head velocities of 100 to 150 degrees/s were found to be comparable to those observed at higher velocities.

O97 Video head impulse test in evaluation of brainstem dysfunction in multiple sclerosis

Objectives The aim of this study was to investigate the role of the video head impulse test (vHIT) in the detection of brainstem lesions in patients with multiple sclerosis (MS). Methods One hundred thirty participants were enrolled: 66 healthy subjects (HC) (132 ears, 38 females, mean age 45.8 ± 13.7) and 64 MS patients (128 ears, 45 females, mean age 36.8 ± 9.1). The impulses of the head were delivered in 3 planes: lateral, right anterior-left posterior (RALP) and left anterior-right posterior (LARP) with a minimum of 5 head impulses in each plane and direction. vHIT pathology was defined if lateral gain or posterior/anterior slope was lower than 0.7. Results In HC there was no pathology on lateral and posterior canals, while 16 (12.5%) and 6 (4.7%) out of 128 ears had pathological results on lateral and posterior canals, respectively, in the MS group ( p p = 0.008, respectively). Posterior canal pathology was associated with higher EDSS ( p = 0.007). Mean gain of the lateral (0.900 ± 0.206 vs. 0.964 ± 0.167, p = 0.007, respectively) and slope of anterior canals (1.223 ± 0.248 vs. 1.338 ± 0.348, p = 0.005, respectively) was significantly reduced in MS group compared to HC. MS patients with clinically evident brainstem dysfunction had significantly higher percentage of pathologies of posterior canals p = 0.017. MS patients with brainstem lesions (specifically midbrain and pontine lesions) had significantly higher percentage of pathologies of posterior canals p = 0.039 ( p = 0,028 and p = 0.007, respectively). Discussion Current research has already shown the capability of vHIT to differentiate peripheral causes of vertigo from their central counterparts. However, several publications have shown that central causes of vertigo, especially brainstem stroke can influence vHIT results. Conclusion Our results indicate that vHIT can detect brainstem dysfunction in patients with MS. Significance vHIT can be impaired when central part of the vestibular system is damaged.

Horizontal Eye Position Affects Measured Vertical VOR Gain on the Video Head Impulse Test.

Background/hypothesis: With the video head impulse test (vHIT), the vertical VOR gain is defined as (vertical eye velocity/vertical head velocity), but compensatory eye movements to vertical canal stimulation usually have a torsional component. To minimize the contribution of torsion to the eye movement measurement, the horizontal gaze direction should be directed 40° from straight ahead so it is in the plane of the stimulated canal plane pair. Hypothesis: as gaze is systematically moved horizontally away from canal plane alignment, the measured vertical VOR gain should decrease.Study design: Ten healthy subjects, with vHIT measuring vertical eye movement to head impulses in the plane of the left anterior-right posterior (LARP) canal plane, with gaze at one of five horizontal gaze positions [40°(aligned with the LARP plane), 20°, 0°, −20°, −40°].Methods: Every head impulse was in the LARP plane. The compensatory eye movement was measured by the vHIT prototype system. The one operator delivered every impulse.Results: The canal stimulus remained identical across trials, but the measured vertical VOR gain decreased as horizontal gaze angle was shifted away from alignment with the LARP canal plane.Conclusion: In measuring vertical VOR gain with vHIT the horizontal gaze angle should be aligned with the canal plane under test.

The Video Head Impulse Test (vHIT) Detects Vertical Semicircular Canal Dysfunction

BackgroundThe video head impulse test (vHIT) is a useful clinical tool to detect semicircular canal dysfunction. However vHIT has hitherto been limited to measurement of horizontal canals, while scleral search coils have been the only accepted method to measure head impulses in vertical canals. The goal of this study was to determine whether vHIT can detect vertical semicircular canal dysfunction as identified by scleral search coil recordings.MethodsSmall unpredictable head rotations were delivered by hand diagonally in the plane of the vertical semicircular canals while gaze was directed along the same plane. The planes were oriented along the left-anterior-right-posterior (LARP) canals and right-anterior-left-posterior (RALP) canals. Eye movements were recorded simultaneously in 2D with vHIT (250 Hz) and in 3D with search coils (1000 Hz). Twelve patients with unilateral, bilateral and individual semicircular canal dysfunction were tested and compared to seven normal subjects.ResultsSimultaneous video and search coil recordings were closely comparable. Mean VOR gain difference measured with vHIT and search coils was 0.05 (SD = 0.14) for the LARP plane and −0.04 (SD = 0.14) for the RALP plane. The coefficient of determination R2 was 0.98 for the LARP plane and 0.98 for the RALP plane and the results of the two methods were not significantly different. vHIT and search coil measures displayed comparable patterns of covert and overt catch-up saccades.ConclusionsvHIT detects dysfunction of individual vertical semicircular canals in vestibular patients as accurately as scleral search coils. Unlike search coils, vHIT is non-invasive, easy to use and hence practical in clinics.

The Role of Gravity in Adaptation of the Vertical Angular Vestibulo‐Ocular Reflex

The gain of the vertical angular vestibulo-ocular reflex (aVOR) was adapted in side-down and prone positions in two monkeys and tested in four planes: left-/right-side down; forward/backward; and two intermediate planes that lie approximately in the planes of the vertical semicircular canal pairs, left anterior/right posterior (LA/RP) and right anterior/left posterior (RA/LP). Gain changes, expressed as a percent of preadapted values, were plotted as a function of head orientation in the planes of tilt, and fitted with sinusoids to obtain the gravity-dependent (amplitude) and gravity-independent (bias) components of adaptation. Gravity-dependent gain changes were always maximal when tested in a plane that included the head orientation in which the aVOR gain had been adapted. Changes were minimal when the head was tilted in a plane orthogonal to the plane of adaptation, and were smaller but still significant when tested in the two intermediate planes. Gravity-independent VOR gain changes were uniform over all planes of head tilt. Thus, the gravity-dependent and gravity-independent components could be separated experimentally. The aVOR gain changes from the head tilts in different directions were utilized to reconstruct the gain changes in three dimensions. They formed a continuous surface, which peaked in and around the position of adaptation. These studies support the postulate that gain adaptation has both gravity-independent and gravity-dependent components, and further show that these gain changes have a three-dimensional structure. These results are similar to those in humans, indicating that the gravity-dependent adaptation of the aVOR is likely to be a common phenomenon across species.

The three-dimensional vestibulo-ocular reflex evoked by high-acceleration rotations in the squirrel monkey.

The aim of this study was to determine if the angular vestibulo-ocular reflex (VOR) in response to pitch, roll, left anterior-right posterior (LARP), and right anterior-left posterior (RALP) head rotations exhibited the same linear and nonlinear characteristics as those found in the horizontal VOR. Three-dimensional eye movements were recorded with the scleral search coil technique. The VOR in response to rotations in five planes (horizontal, vertical, torsional, LARP, and RALP) was studied in three squirrel monkeys. The latency of the VOR evoked by steps of acceleration in darkness (3,000 degrees /s(2) reaching a velocity of 150 degrees /s) was 5.8+/-1.7 ms and was the same in response to head rotations in all five planes of rotation. The gain of the reflex during the acceleration was 36.7+/-15.4% greater than that measured at the plateau of head velocity. Polynomial fits to the trajectory of the response show that eye velocity is proportional to the cube of head velocity in all five planes of rotation. For sinusoidal rotations of 0.5-15 Hz with a peak velocity of 20 degrees /s, the VOR gain did not change with frequency (0.74+/-0.06, 0.74+/-0.07, 0.37+/-0.05, 0.69+/-0.06, and 0.64+/-0.06, for yaw, pitch, roll, LARP, and RALP respectively). The VOR gain increased with head velocity for sinusoidal rotations at frequencies > or =4 Hz. For rotational frequencies > or =4 Hz, we show that the vertical, torsional, LARP, and RALP VORs have the same linear and nonlinear characteristics as the horizontal VOR. In addition, we show that the gain, phase and axis of eye rotation during LARP and RALP head rotations can be predicted once the pitch and roll responses are characterized.

Neural basis for eye velocity generation in the vestibular nuclei of alert monkeys during off-vertical axis rotation.

Activity of "vestibular only" (VO) and "vestibular plus saccade" (VPS) units was recorded in the rostral part of the medial vestibular nucleus and caudal part of the superior vestibular nucleus of alert rhesus monkeys. By estimating the "null axes" of recorded units (n = 79), the optimal plane of activation was approximately the mean plane of reciprocal semicircular canals, i.e., lateral canals, left anterior-right posterior (LARP) canals or right anterior-left posterior (RALP) canals. All units were excited by rotation in a direction that excited a corresponding ipsilateral semicircular canal. Thus, they all displayed a "type I" response. With the animal upright, there were rapid changes in firing rates of both VO and VPS units in response to steps of angular velocity about a vertical axis. The units were bidirectionally activated during vestibular nystagmus (VN), horizontal optokinetic nystagmus (OKN), optokinetic after-nystagmus (OKAN) and off-vertical axis rotation (OVAR). The rising and falling time constants of the responses to rotation indicated that they were closely linked to velocity storage. There were differences between VPS and VO neurons in that activity of VO units followed the expected time course in response to a stimulus even during periods of drowsiness, when eye velocity was reduced. Firing rates of VPS units, on the other hand, were significantly reduced in the drowsy state. Lateral canal-related units had average firing rates that were linearly related to the bias or steady state level of horizontal eye velocity during OVAR over a range of +/- 60 deg/s. These units could be further divided into two classes according to whether they were modulated during OVAR. Non-modulated units (n = 5) were VO types and all modulated units (n = 5) were VPS types. There was no significant difference between the bias level sensitivities relative to eye velocity of the units with and without modulation (P > 0.05). The modulated units had no sustained change in firing rate in response to static head tilts and their phases relative to head position varied from unit to unit. The phase did not appear to be linked to the modulation of horizontal eye velocity during OVAR. The sensitivities of unit activity to eye velocity were similar during all stimulus modalities despite the different gains of eye velocity vs stimulus velocity during VN, OKN and OVAR. Therefore, VO and VPS units are likely to carry an eye velocity signal related to velocity storage.(ABSTRACT TRUNCATED AT 400 WORDS)