Video head-impulse test (vHIT) in dizzy children with normal caloric responses
Introduction
Caloric irrigation is the most widely used tool in routine vestibular testing to identify the presence and side of a peripheral vestibular hypofunction. It is performed using water or air as the stimulus to create a temperature gradient in the temporal bone. Caloric ear irrigation produces a unilateral low-frequency stimulation of the peripheral vestibular organ. The caloric test has greater capacity to independently test each labyrinth, although it uses a non-physiological stimuli equivalent to a <0.002-Hz sinusoidal stimulation [1].
The major limitation of caloric irrigation is that it provides only a non-physiological stimulation of the peripheral vestibular organ. In contrast, the assessment of the high-frequency vestibulo-ocular reflex (VOR) by passive head impulses allows a more physiological testing of the vestibular system [2].
New video-based equipment that enables registration of the eye response to sudden head impulses mimicking the performance of the scleral search coil (SSC) in a magnetic field installation has recently become available for clinical use [3], [4]. With the introduction of video Head Impulse Testing (vHIT), clinicians have a “child friendly,” relatively easy-to-use, and simple tool to evaluate each of the 6 semicircular canals. Hamilton et al. [5] mentioned that vHIT has the advantages over the rotary chair and caloric tests in evaluating children since it does not require fear-inducing darkness or provocation of dizziness. Moreover, using three-dimensional search coils and applying head impulses in different directions, the function of individual semicircular canals can be quantified precisely. This system is good not only for initial evaluation of the patient but also for follow-up, as has been demonstrated in patients with Meniere disease (MD) with rapid fluctuations in vestibular function [6].
In terms of frequency analysis, the information provided by both systems is relevant. At high frequencies of stimulation, such as those provided in the vHIT, the VOR is the main physiological function that helps to stabilize gaze in the initial post-stimulus period of time (<100 ms). However, we also have to deal with low velocities and low frequencies of stimulation, for which velocity storage, smooth pursuit, and optokinetic nystagmus provide important help to the VOR and with which the caloric test is very informative [7].
The purpose of this work was to evaluate the results of vHIT in children and adolescents seen because of vertigo (regardless of etiology) with normal caloric test results. As both tests provide data about the functioning of the semicircular canals, we were interested in assessing patients with normal caloric testing and checking whether vHIT will add in their diagnosis.
Section snippets
Patients
In this study, we have included patients seen because of dizziness with different types of vestibular disease as we are not looking for the etiology of dizziness. In the assessment, several other tests were performed to provide a specific diagnosis, although we will review children with caloric test and the vHIT. Our initial population was 63 patients, but we excluded 14 because of technical problems in the caloric test: thermal artifact (n = 5), poor quality of the traces because of excessive
Statistical anaylsis
All data were stored and analyzed in a Statistical Package for the Social Sciences (SPSS) file version 19.0 (Inc.; Chicago, IL, USA). All tests were two-tailed, and p-values <0.05 were considered significant. The caloric test was classified as normal or abnormal; in the former case, both canal paresis and directional preponderance should have been under the normal limits. The vHIT was also classified as normal or abnormal.
Means of the gain of the VOR were compared with the Wilcoxon test.
Results
In the present study, age ranged between 13 and 19 years old with a mean age 16 years old. Fig. 1 shows the results for both tests (caloric and vHIT testes). Both tests were normal in 8 patients (16%) whereas 41 patients were abnormal in vHIT test only (84%) (see Fig. 2).
The average gain and SD in normal patients in each canal Table 1
The average gain and SD in abnormal patients in each canal Table 2.
Single canal affection is seen in 29 patients whereas 12 patients have combined canal affection.
Discussion
The vHIT is a mobile, non-invasive, quantitative test for the vestibulo-ocular reflex (VOR). Compared to the clinical head impulse test (HIT) it provides a higher sensitivity and specificity. The vHIT can help differentiate central from peripheral vertigo in patients with acute vestibular syndrome. In acute vestibular syndrome, vHIT in combination with examinations of both skew deviation and nystagmus that changes direction on eccentric gaze distinguished a peripheral vestibular deficit (e.g.
Conclusion
The caloric and vHIT is very important testing in diagnosis of dizzy patients. The information from both methods is redundant in some cases but complementary in most, and the existence of discrepancies is very low. vHIT is complementary to caloric testing especially with normal findings in caloric testing and can be applied easily in children.
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Clinical evaluation of the vestibular impairment using video head impulse test In children with acute otitis media
2021, International Journal of Pediatric OtorhinolaryngologyCitation Excerpt :These studies indicated that the vHIT might detect a low proportion of patients who had a vestibular deficit in caloric test whereas an abnormal vHIT was strongly related to an abnormal caloric test result especially below a gain of 0.6 [2]. Additionally, vHIT can detect isolated canal deficits that cannot be detected with caloric testing [16]. It should be reminded that the temporal frequency and the way of stimulation are different in both tests; vHIT provides a physiologic endolymphatic flow whereas the caloric test induces the endolymphatic flow in a non-physiologic way [17].
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2020, International Journal of Pediatric OtorhinolaryngologyCitation Excerpt :Interest in the clinical usefulness of vHIT has been increasing, and many studies have been conducted in adults. Several studies have been published on the results of the vHIT in pediatric patients [9,10]. There are not many studies in children.
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2020, International Journal of Pediatric OtorhinolaryngologyCitation Excerpt :Recent studies support that the vHIT test is a sensitive and efficient vestibular test in the pediatric population as well [16,22]. It is well tolerated by children aged 3–16 years [16] and introduced as a child friendly, relatively easy-to-use, and simple tool to evaluate each of the 6 SSCs [14]. The efficacy of VOR in vHIT test is defined by either the gain of the eye movement to the corresponding head movement, called vHIT gain or by the presence of corrective catch up saccades [23].
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