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Impact of artifacts on VOR gain measures by video-oculography in the acute vestibular syndrome.

ABSTRACT: The video head impulse test (HIT) measures vestibular function (vestibulo-ocular reflex [VOR] gain - ratio of eye to head movement), and, in principle, could be used to make a distinction between central and peripheral causes of vertigo. However, VOG recordings contain artifacts, so using unfiltered device data might bias the final diagnosis, limiting application in frontline healthcare settings such as the emergency department (ED). We sought to assess whether unfiltered data (containing artifacts) from a video-oculography (VOG) device have an impact on VOR gain measures in acute vestibular syndrome (AVS).This cross-sectional study compared VOG HIT results 'unfiltered' (standard device output) versus 'filtered' (artifacts manually removed) and relative to a gold standard final diagnosis (neuroimaging plus clinical follow-up) in 23 ED patients with acute dizziness, nystagmus, gait disturbance and head motion intolerance.Mean VOR gain assessment alone (unfiltered device data) discriminated posterior inferior cerebellar artery (PICA) strokes from vestibular neuritis with 91% accuracy in AVS. Optimal stroke discrimination cut points were bilateral VOR gain?>0.7099 (unfiltered data) versus?>0.7041 (filtered data). For PICA stroke sensitivity and specificity, there was no clinically-relevant difference between unfiltered and filtered data-sensitivity for PICA stroke was 100% for both data sets and specificity was almost identical (87.5% unfiltered versus 91.7% filtered). More impulses increased gain precision.The bedside HIT remains the single best method for discriminating between vestibular neuritis and PICA stroke in patients presenting AVS. Quantitative VOG HIT testing in the ED is associated with frequent artifacts that reduce precision but not accuracy. At least 10-20 properly-performed HIT trials per tested ear are recommended for a precise VOR gain estimate.

SUBMITTER: Mantokoudis G

PROVIDER: S-EPMC6054448 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature

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Impact of artifacts on VOR gain measures by video-oculography in the acute vestibular syndrome.

Mantokoudis Georgios G Saber Tehrani Ali S AS Wozniak Amy A Eibenberger Karin K Kattah Jorge C JC Guede Cynthia I CI Zee David S DS Newman-Toker David E DE

Journal of vestibular research : equilibrium & orientation 20161101 4

<h4>Objective</h4>The video head impulse test (HIT) measures vestibular function (vestibulo-ocular reflex [VOR] gain - ratio of eye to head movement), and, in principle, could be used to make a distinction between central and peripheral causes of vertigo. However, VOG recordings contain artifacts, so using unfiltered device data might bias the final diagnosis, limiting application in frontline healthcare settings such as the emergency department (ED). We sought to assess whether unfiltered data ...[more]

PMID: 27814312

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Project description:Gaze stability exercises are a critical component of vestibular rehabilitation for individuals with vestibular hypofunction and many studies reveal the rehabilitation improves functional performance. However, few studies have examined the vestibular physiologic mechanisms (semicircular canal; otolith) responsible for such recovery after patients with vestibular hypofunction complete gaze and gait stability exercises. The purpose of this study was to compare behavioral outcome measures (i.e., visual acuity during head rotation) with physiological measures (i.e., gain of the vestibulo-ocular reflex) of gaze stability following a progressive vestibular rehabilitation program in patients following unilateral vestibular deafferentation surgery (UVD). We recruited n = 43 patients (n = 18 female, mean 52 ± 13 years, range 23-80 years) after unilateral deafferentation from vestibular schwannoma; n = 38 (25 female, mean 46.9 ± 15.9 years, range 22-77 years) age-matched healthy controls for dynamic visual acuity testing, and another n = 28 (14 female, age 45 ± 17, range 20-77 years) healthy controls for video head impulse testing. Data presented is from n = 19 patients (14 female, mean 48.9 ± 14.7 years) with UVD who completed a baseline assessment ~6 weeks after surgery, 5 weeks of vestibular physical therapy and a final measurement. As a group, subjective and fall risk measures improved with a meaningful clinical relevance. Dynamic visual acuity (DVA) during active head rotation improved [mean ipsilesional 38.57% ± 26.32 (n = 15/19)]; mean contralesional 39.96% ± 22.62 (n = 12/19), though not uniformly. However, as a group passive yaw VOR gain (mean ipsilesional pre 0.44 ± 0.18 vs. post 0.44 ± 0.15; mean contralesional pre 0.81 ± 0.19 vs. post 0.85 ± 0.09) did not show any change (p ≥ 0.4) after rehabilitation. The velocity of the overt compensatory saccades during ipsilesional head impulses were reduced after rehabilitation; no other metric of oculomotor function changed (p ≥ 0.4). Preserved utricular function was correlated with improved yaw DVA and preserved saccular function was correlated with improved pitch DVA. Our results suggest that 5 weeks of vestibular rehabilitation using gaze and gait stability exercises improves both subjective and behavioral performance despite absent change in VOR gain in a majority of patients, and that residual otolith function appears correlated with such change.

Project description:Background/hypothesisThe video Head Impulse Test (vHIT) is now widely used to test the function of each of the six semicircular canals individually by measuring the eye rotation response to an abrupt head rotation in the plane of the canal. The main measure of canal adequacy is the ratio of the eye movement response to the head movement stimulus, i.e., the gain of the vestibulo-ocular reflex (VOR). However, there is a need for normative data about how VOR gain is affected by age and also by head velocity, to allow the response of any particular patient to be compared to the responses of healthy subjects in their age range. In this study, we determined for all six semicircular canals, normative values of VOR gain, for each canal across a range of head velocities, for healthy subjects in each decade of life.Study designThe VOR gain was measured for all canals across a range of head velocities for at least 10 healthy subjects in decade age bands: 10-19, 20-29, 30-39, 40-49, 50-59, 60-69, 70-79, 80-89.MethodsThe compensatory eye movement response to a small, unpredictable, abrupt head rotation (head impulse) was measured by the ICS impulse prototype system. The same operator delivered every impulse to every subject.ResultsVestibulo-ocular reflex gain decreased at high head velocities, but was largely unaffected by age into the 80- to 89-year age group. There were some small but systematic differences between the two directions of head rotation, which appear to be largely due to the fact that in this study only the right eye was measured. The results are considered in relation to recent evidence about the effect of age on VOR performance.ConclusionThese normative values allow the results of any particular patient to be compared to the values of healthy people in their age range and so allow, for example, detection of whether a patient has a bilateral vestibular loss. VOR gain, as measured directly by the eye movement response to head rotation, seems largely unaffected by aging.

Project description:Background and purposeStrokes can be distinguished from benign peripheral causes of acute vestibular syndrome using bedside oculomotor tests (head impulse test, nystagmus, test-of-skew). Using head impulse test, nystagmus, test-of-skew is more sensitive and less costly than early magnetic resonance imaging for stroke diagnosis in acute vestibular syndrome but requires expertise not routinely available in emergency departments. We sought to begin standardizing the head impulse test, nystagmus, test-of-skew diagnostic approach for eventual emergency department use through the novel application of a portable video-oculography device measuring vestibular physiology in real time. This approach is conceptually similar to ECG to diagnose acute cardiac ischemia.MethodsProof-of-concept study (August 2011 to June 2012). We recruited adult emergency department patients with acute vestibular syndrome defined as new, persistent vertigo/dizziness, nystagmus, and (1) nausea/vomiting, (2) head motion intolerance, or (3) new gait unsteadiness. We recorded eye movements, including quantitative horizontal head impulse testing of vestibulo-ocular-reflex function. Two masked vestibular experts rated vestibular findings, which were compared with final radiographic gold-standard diagnoses. Masked neuroimaging raters determined stroke or no stroke using magnetic resonance imaging of the brain with diffusion-weighted imaging obtained 48 hours to 7 days after symptom onset.ResultsWe enrolled 12 consecutive patients who underwent confirmatory magnetic resonance imaging. Mean age was 61 years (range 30-73), and 10 were men. Expert-rated video-oculography-based head impulse test, nystagmus, test-of-skew examination was 100% accurate (6 strokes, 6 peripheral vestibular).ConclusionsDevice-based physiological diagnosis of vertebrobasilar stroke in acute vestibular syndrome should soon be possible. If confirmed in a larger sample, this bedside eye ECG approach could eventually help fulfill a critical need for timely, accurate, efficient diagnosis in emergency department patients with vertigo or dizziness who are at high risk for stroke.

Project description:BackgroundWe define acute vestibular syndrome (AVS) as a sudden onset vertigo, nausea, vomiting, and head motion intolerance, more frequently associated with an acute peripheral and unilateral vestibulopathy. About 10-20% of all cases with central vestibulopathy are secondary to stroke. We report three patients evaluated over the past decade with an acute AVS along with subtle downbeat nystagmus (DBN), followed by dysarthria and progressive truncal and limb ataxia, as well as increasing DBN intensity.MethodsAll patients underwent neurologic examination, video-oculography, MRI, serum cancer markers, spinal fluid examination, paraneoplastic panel testing, and oncologic workup. With a consolidated diagnosis of cancer/paraneoplastic syndrome, we treated with plasma exchange (PLEX), high-dose steroids, surgery, and oncologic investigation. We additionally provided oncotherapy in one out of three patients.ResultsAll three patients had an acute AVS, downbeat nystagmus DBN, and inability to perform tandem gait. Two of three patients had a normal head impulse test (HIT). As acute vertigo, nausea, and vomiting subsided, a progressive cerebellar syndrome ensued characterized by persistent DBN, impaired horizontal and vertical pursuit, impaired VOR suppression, truncal and limb ataxia, and dysarthria. All patients had normal MRI brain studies excluding stroke. CSF studies demonstrated lymphocytic pleocytosis and elevated protein. One patient had confirmed ovarian cancer with high CA-125 serum levels; another had undifferentiated cancer of unknown primary with high CA-125 and one patient with esophageal cancer. All had a positive PCA-1 antibody titer, also known as anti-Yo antibody. In one patient with expeditious immunosuppression, the ataxia progression slowed for 18 months, whereas the other two patients with delayed initiation of treatment had more rapidly progressive ataxia.DiscussionParaneoplastic encephalitis related to PCA-1 antibody (Anti-Yo) targets Purkinje cells and cells in the granular layer of the cerebellar cortex. Clinically, our patients had a central AVS characterized by DBN and followed with progressive ataxia and unremarkable neuroimaging studies. Rapid initiation of treatment may offer a greater chance to prevent further neurologic decline. Any patient with an AVS as well as DBN and normal MRI should have an expeditious workup to rule out metabolic, toxic, and infectious causes just prior to considering prompt treatment with high-dose steroids and plasma exchange (PLEX) to mitigate the risk of rapidly progressive and irreversible neurologic decline.

Dataset Information

Impact of artifacts on VOR gain measures by video-oculography in the acute vestibular syndrome.

Publications

Impact of artifacts on VOR gain measures by video-oculography in the acute vestibular syndrome.

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