Functional Head Impulse Testing Might Be Useful for Assessing Vestibular Compensation After Unilateral Vestibular Loss

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Abstract

Background: Loss of the vestibulo-ocular reflex (VOR) affects visual acuity during head movements. Previous studies have shown that compensatory eye-saccades improve visual acuity and that the timing of the saccade is important. Most of the tests involved in testing VOR are made with passive head movement, that do not necessarily reflect the activities of daily living and thus not being proportionate to symptoms and distresses of the patients.

Objective: To examine differences between active (self-generated) or passive (imposed by the examiner) head rotations while trying to maintain visual focus on a target.

Method: Nine subjects with unilateral total vestibular loss were recruited (4 men and 5 women, mean age 47) and tested with video Head Impulse Test (vHIT) and Head Impulse Testing Device-Functional Test (HITD-FT) during passive and active movements while looking at a target. VOR gain, latencies of covert saccades, frequency of covert saccades and visual acuity were measured and analyzed.

Results: Active head-impulses toward the lesioned side resulted in better visual acuity ( p = 0.002) compared to conventional passive head-impulses and generated eye-saccades with significantly shorter latencies ( p = 0.004). Active movements to the lesioned side generated dynamic visual acuities that were as good as when testing the intact side.

Conclusion: Actively generated head impulses resulted in normal dynamic visual acuity, even when performed toward the side of total vestibular loss. This might be attributed to the appearance of short-latency covert saccades. The results show a strong relationship between self-generated movements, latencies of covert saccades and outcome in HITD-FT, i.e., a better dynamic visual function with less retinal slip which is the main function of the VOR. The method of active HITD-FT might be valuable in assessing vestibular compensation and monitoring ongoing vestibular rehabilitation.

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Most cited references 23

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A clinical sign of canal paresis.

G M Halmagyi, I S Curthoys (1988)

Unilateral loss of horizontal semicircular canal function, termed canal paresis, is an important finding in dizzy patients. To our knowledge, apart from head-shaking nystagmus, no clinical sign of canal paresis has yet been described and the term derives from the characteristic finding on caloric tests: little or no nystagmus evoked by either hot or cold irrigation of the affected ear. We describe a simple and reliable clinical sign of total unilateral loss of horizontal semicircular canal function: one large or several small oppositely directed, compensatory, refixation saccades elicited by rapid horizontal head rotation toward the lesioned side. Using magnetic search coils to measure head and eye movement, we have validated this sign in 12 patients who had undergone unilateral vestibular neurectomy.

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The video head impulse test: diagnostic accuracy in peripheral vestibulopathy.

H G Macdougall, K. P. Weber, L A McGarvie … (2009)

The head impulse test (HIT) is a useful bedside test to identify peripheral vestibular deficits. However, such a deficit of the vestibulo-ocular reflex (VOR) may not be diagnosed because corrective saccades cannot always be detected by simple observation. The scleral search coil technique is the gold standard for HIT measurements, but it is not practical for routine testing or for acute patients, because they are required to wear an uncomfortable contact lens. To develop an easy-to-use video HIT system (vHIT) as a clinical tool for identifying peripheral vestibular deficits. To validate the diagnostic accuracy of vHIT by simultaneous measures with video and search coil recordings across healthy subjects and patients with a wide range of previously identified peripheral vestibular deficits. Horizontal HIT was recorded simultaneously with vHIT (250 Hz) and search coils (1,000 Hz) in 8 normal subjects, 6 patients with vestibular neuritis, 1 patient after unilateral intratympanic gentamicin, and 1 patient with bilateral gentamicin vestibulotoxicity. Simultaneous video and search coil recordings of eye movements were closely comparable (average concordance correlation coefficient r(c) = 0.930). Mean VOR gains measured with search coils and video were not significantly different in normal (p = 0.107) and patients (p = 0.073). With these groups, the sensitivity and specificity of both the reference and index test were 1.0 (95% confidence interval 0.69-1.0). vHIT measures detected both overt and covert saccades as accurately as coils. The video head impulse test is equivalent to search coils in identifying peripheral vestibular deficits but easier to use in clinics, even in patients with acute vestibular neuritis.

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Head impulse test in unilateral vestibular loss: vestibulo-ocular reflex and catch-up saccades.

K. P. Weber, S Aw, M. Todd … (2008)

Quantitative head impulse test (HIT) measures the gain of the angular vestibulo-ocular reflex (VOR) during head rotation as the ratio of eye to head acceleration. Bedside HIT identifies subsequent catch-up saccades after the head rotation as indirect signs of VOR deficit. To determine the VOR deficit and catch-up saccade characteristics in unilateral vestibular disease in response to HIT of varying accelerations. Eye and head rotations were measured with search coils during manually applied horizontal HITs of varying accelerations in patients after vestibular neuritis (VN, n = 13) and unilateral vestibular deafferentation (UVD, n = 15) compared to normal subjects (n = 12). Normal VOR gain was close to unity and symmetric over the entire head-acceleration range. Patients with VN and UVD showed VOR gain asymmetry, with larger ipsilesional than contralesional deficits. As accelerations increased from 750 to 6,000 degrees /sec(2), ipsilesional gains decreased from 0.59 to 0.29 in VN and from 0.47 to 0.13 in UVD producing increasing asymmetry. Initial catch-up saccades can occur during or after head rotation. Covert saccades during head rotation are most likely imperceptible, while overt saccades after head rotation are detectable by clinicians. With increasing acceleration, the amplitude of overt saccades in patients became larger; however, initial covert saccades also became increasingly common, occurring in up to about 70% of trials. Head impulse test (HIT) with high acceleration reveals vestibulo-ocular reflex deficits better and elicits larger overt catch-up saccades in unilateral vestibular patients. Covert saccades during head rotation, however, occur more frequently with higher acceleration and may be missed by clinicians. To avoid false-negative results, bedside HIT should be repeated to improve chances of detection.

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Author and article information

Contributors

Julia Sjögren: URI : http://loop.frontiersin.org/people/612188/overview

Per-Anders Fransson: URI : http://loop.frontiersin.org/people/622299/overview

Mikael Karlberg: URI : http://loop.frontiersin.org/people/622173/overview

Måns Magnusson: URI : http://loop.frontiersin.org/people/17896/overview

Fredrik Tjernström: URI : http://loop.frontiersin.org/people/614769/overview

Journal

Journal ID (nlm-ta): Front Neurol

Journal ID (iso-abbrev): Front Neurol

Journal ID (publisher-id): Front. Neurol.

Title: Frontiers in Neurology

Publisher: Frontiers Media S.A.

ISSN (Electronic): 1664-2295

Publication date (Electronic): 19 November 2018

Publication date Collection: 2018

Volume: 9

Electronic Location Identifier: 979

Affiliations

Department of Clinical Sciences Lund, Faculty of Medicine, Skåne University Hospital, Lund University , Lund, Sweden

Author notes

Edited by: Stefano Ramat, University of Pavia, Italy

Reviewed by: Michael Fetter, Stiftung Rehabilitation Heidelberg, Germany; Americo Migliaccio, Neuroscience Research Australia (NeuRA), Australia

*Correspondence: Julia Sjögren julia.sjogren@ 123456med.lu.se

This article was submitted to Neuro-Otology, a section of the journal Frontiers in Neurology

Article

DOI: 10.3389/fneur.2018.00979

PMC ID: 6252383

PubMed ID: 30510538

SO-VID: 695b644d-361e-401f-9d26-082b9e843049

License:

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

History

Date received : 14 September 2018

Date accepted : 30 October 2018

Page count

Figures: 3, Tables: 4, Equations: 0, References: 25, Pages: 7, Words: 4637

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Functional Head Impulse Testing Might Be Useful for Assessing Vestibular Compensation After Unilateral Vestibular Loss

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Karger: Neurology and Neuroscience

Most cited references 23

A clinical sign of canal paresis.

The video head impulse test: diagnostic accuracy in peripheral vestibulopathy.

Head impulse test in unilateral vestibular loss: vestibulo-ocular reflex and catch-up saccades.

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