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. 2012 Mar 23:3:39.
doi: 10.3389/fneur.2012.00039. eCollection 2012.

A Device for the Functional Evaluation of the VOR in Clinical Settings

Stefano Ramat  1 , Silvia Colnaghi, Andreas Boehler, Serena Astore, Paola Falco, Marco Mandalà, Daniele Nuti, Paolo Colagiorgio, Maurizio Versino
Affiliations

A Device for the Functional Evaluation of the VOR in Clinical Settings

Stefano Ramat et al. Front Neurol. .

Abstract

We developed the head impulse testing device (HITD) based on an inertial sensing system allowing to investigate the functional performance of the rotational vestibulo-ocular reflex (VOR) by testing its gaze stabilization ability, independently from the subject's visual acuity, in response to head impulses at different head angular accelerations ranging from 2000 to 7000 deg/s(2). HITD was initially tested on 22 normal subjects, and a method to compare the results from a single subject (patient) with those from controls was set up. As a pilot study, we tested the HITD in 39 dizzy patients suffering, non-acutely, from different kinds of vestibular disorders. The results obtained with the HITD were comparable with those from the clinical head impulse test (HIT), but an higher number of abnormalities was detectable by HITD in the central vestibular disorders group. The HITD appears to be a promising tool for detecting abnormal VOR performance while providing information on the functional performance of the rotational VOR, and can provide a valuable assistance to the clinical evaluation of patients with vestibular disorders.

Keywords: VOR testing; dynamic visual acuity; head impulse test; rVOR; semicircular canals.

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Figures

Figure 1
Figure 1
Representative example of visual stimulus timing with respect to head angular velocity during a test performed with the HITD. Black traces: head angular velocities recorded during individual head impulses on one subject. Gray traces: visual stimulus appearance timing recorded by the photodiode applied to the testing screen. Low value indicates no stimulus; high value indicates the stimulus is displayed on screen.
Figure 2
Figure 2
Box plot representation of the distribution of correct answers ratios per acceleration bin, in control subjects. Each acceleration bin is labeled using the lower acceleration threshold, e.g., the 2000 deg/s2 bin includes accelerations in (2000, 2999). In each box plot the thick horizontal line indicates the median of the sample, and the thin line at the lower extremity of the box the 25th percentile. Whiskers extend to the extreme data points considered in the distribution, while crosses indicate individual outlier data points.
Figure 3
Figure 3
Box plot representation of the distribution of correct answers ratios per acceleration bin, in patients. Data is represented as in Figure 2, with the addition that the thin line at the upper extremity of the box represents the 75th percentile.
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