Acute VOR gain differences for outward vs. inward head impulses

Schubert, Michael C.; Mantokoudis, Georgios; Xie, Li; Agrawal, Yuri

doi:10.3233/ves-140523

Cited by 11 publications

(8 citation statements)

References 15 publications

(18 reference statements)

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“…During this period, the activity of the nervous system is considerably attenuated and thus unable to appropriately express immediate functional deficits [8]. Compared to typical patients with a vestibular syndrome that are seen by a clinician days and weeks after the incident, a planned tumor surgery of the VIIIth nerve [9] or a comparable experimental manipulation, e.g. in rabbits [10] or mice [11] are currently the closest conditions that allow an evaluation of the acute stage after a vestibular lesion.…”

Section: Introductionmentioning

confidence: 99%

Acute consequences of a unilateral VIIIth nerve transection on vestibulo-ocular and optokinetic reflexes in Xenopus laevis tadpoles

et al. 2020

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Loss of peripheral vestibular function provokes severe impairments of gaze and posture stabilization in humans and animals. However, relatively little is known about the extent of the instantaneous deficits. This is mostly due to the fact that in humans a spontaneous loss often goes unnoticed initially and targeted lesions in animals are performed under deep anesthesia, which prevents immediate evaluation of behavioral deficits. Here, we use isolated preparations of Xenopus laevis tadpoles with functionally intact vestibulo-ocular (VOR) and optokinetic reflexes (OKR) to evaluate the acute consequences of unilateral VIIIth nerve sections. Such in vitro preparations allow lesions to be performed in the absence of anesthetics with the advantage to instantly evaluate behavioral deficits. Eye movements, evoked by horizontal sinusoidal head/table rotation in darkness and in light, became reduced by 30% immediately after the lesion and were diminished by 50% at 1.5 h postlesion. In contrast, the sinusoidal horizontal OKR, evoked by large-field visual scene motion, remained unaltered instantaneously but was reduced by more than 50% from 1.5 h postlesion onwards. The further impairment of the VOR beyond the instantaneous effect, along with the delayed decrease of OKR performance, suggests that the immediate impact of the sensory loss is superseded by secondary consequences. These potentially involve homeostatic neuronal plasticity among shared VOR-OKR neuronal elements that are triggered by the ongoing asymmetric activity. Provided that this assumption is correct, a rehabilitative reduction of the vestibular asymmetry might restrict the extent of the secondary detrimental effect evoked by the principal peripheral impairment.

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Section: Introductionmentioning

confidence: 99%

Acute consequences of a unilateral VIIIth nerve transection on vestibulo-ocular and optokinetic reflexes in Xenopus laevis tadpoles

et al. 2020

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“…Active and passive HITs render different VOR gain results due to planned, predicted head movements (18). For passive vHITs, however, the examiner has to avoid any predictive cues such as anticipation of the planned head direction since prediction during passive vHIT has an impact on the gain of VOR (19,20). Some students forgot to follow the instructions of the video regarding the randomness of cadence and HIT direction.…”

Section: Discussionmentioning

confidence: 99%

Quantifying a Learning Curve for Video Head Impulse Test: Pitfalls and Pearls

et al. 2021

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Objective: The video head impulse test (vHIT) is nowadays a fast and objective method to measure vestibular function. However, its usability is controversial and often considered as a test performed by experts only. We sought to study the learning curve of novices and to document all possible mistakes and pitfalls in the process of learning.Methods: In a prospective cohort observational study, we included 10 novices. We tested their ability to perform correctly horizontal head impulses recorded with vHIT. We assessed vHITs in 10 sessions with 20 impulses per session giving a video instruction after the first session (S1) and individual feedback from an expert for session 2 (S2) up to session 10 (S10). We compared VOR gain, the HIT acceptance rate by the device algorithm, mean head velocity, acceleration, excursion, and overshoot between sessions.Results: A satisfying number of accepted HITs (80%) was reached after an experience of 160 vHITs. Mean head velocity between sessions was always in accepted limits. Head acceleration was too low at the beginning (S1) but improved significantly after the video instruction (p = 0.001). Mean head excursion and overshoot showed a significant improvement after 200 head impulses (p < 0.001 each).Conclusions: We showed that novices can learn to perform head impulses invHIT very fast provided that they receive instructions and feedback from an experienced examiner. Video instructions alone were not sufficient. The most common pitfall was a low head acceleration.

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“…The normal response to a rapid, passive eye movement as a subject fixates on a central target is an equal and opposite eye movement of the same magnitude (Gain: ratio of head velocity/eye velocity is 1.0). The head thrusts may be performed with the head moving towards or away from centre position, the VOR gain does not change 37. In the event of a peripheral vestibular lesion involving the primary VOR pathway, the acceleration signal to move the eyes is impaired, resulting in gain loss (less than 1.0), consequently the eyes cannot stay on target and once the head stops a refixation saccade is thus required.…”

Section: Historical Backgroundmentioning

confidence: 99%

Use of HINTS in the acute vestibular syndrome. An Overview

Kattah

2018

Stroke Vasc Neurol

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Following the initial description of HINTS to diagnose acute vestibular syndrome (AVS) in 2009, there has been significant interest in the systematic evaluation of HINTs to diagnose stroke and other less common central causes of AVS. This trend increased with availability of the video head impulse test (video-HIT). This article reviews the original papers and discusses the main publications from 2009 to 2017. Many authors use video-HIT in the diagnosis of patients with AVS; this paper focuses on the major publications on the topic featuring nystagmus, manual and video-HIT, and skew deviation. Twenty-five papers provide a summary of the last 8 years’ application of HINTS, the video-HIT added quantitative information to the early clinical observations. Further research will undoubtedly provide specific combination of abnormalities with high degree of lesion localisation and aetiology. In a short time following the original description, neurotologist and neurologists in the evaluation of AVS use the HINTS triad. The introduction of the video-HIT added greater understanding of the complex interaction between the primary vestibular afferents, brainstem and cerebellum. In addition, it permits evaluation of the angular vestibulo-ocular reflex in the plane of all six semicircular canals, with accurate peripheral versus central lesion localisation often corroborated by brain imaging.

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Acute VOR gain differences for outward vs. inward head impulses

Cited by 11 publications

References 15 publications

Acute consequences of a unilateral VIIIth nerve transection on vestibulo-ocular and optokinetic reflexes in Xenopus laevis tadpoles

Acute consequences of a unilateral VIIIth nerve transection on vestibulo-ocular and optokinetic reflexes in Xenopus laevis tadpoles

Quantifying a Learning Curve for Video Head Impulse Test: Pitfalls and Pearls

Use of HINTS in the acute vestibular syndrome. An Overview

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