Saccadic Velocity in the New Suppression Head Impulse Test: A New Indicator of Horizontal Vestibular Canal Paresis and of Vestibular Compensation.

Julien Sadoun,Ian S Curthoys,Olivier Sterkers,Georges Lamas,Catherine De Waele,Christophe Magnani,Pierre-Paul Vidal,Qiwen Shen

doi:10.3389/fneur.2016.00160

Abstract

To determine whether saccadic velocity in the suppression head impulse paradigm (SHIMP) test is a reliable indicator of vestibular loss at the acute and at the chronic stage in patients suffering from different vestibular pathologies. Thirty-five normal subjects and 57 patients suffering from different vestibular pathologies associated with unilateral vestibular loss (UVL) or bilateral vestibular loss (BVL) were tested in the SHIMPs paradigm. SHIMPs were performed by turning the head 10 times at high velocities to the left or right side, respectively. The patients were instructed to fixate on a red spot generated by a head-fixed laser projected on the wall. In this SHIMPs paradigm, healthy subjects made a large anti-compensatory saccade at the end of the head turn (a SHIMP saccade). The peak saccadic velocity, the percentage of the trials completed with saccades in 10 trials, and the latency of the saccades were quantified in each group. A video-head impulse test (v-HIT) was systematically performed in all of our subjects as well as a caloric test. The dizziness handicap inventory questionnaire was also given to chronic UVL and BVL patients. At the acute stage after a complete UVL, patients had zero or a few anti-compensatory saccades for low velocity head turns toward the lesioned side. These saccades had lower velocity than the anti-compensatory saccades recorded during head rotation toward the intact side and/or compared with the saccades measured in control subjects. At the chronic stage, some of the patients recovered the ability to perform SHIMP saccades at each head turn toward the lesioned side, but very often these saccades were of significantly lower velocity. In BVL patients, no anti-compensatory saccades, or only significantly smaller ones, could be detected for head turns to both sides. SHIMP is a specific and sensitive test to detect a complete horizontal canal loss at the acute stage. In addition, it reflects the ability of patients with moderate horizontal vestibulo-ocular reflex gain decrease to generate anti-compensatory saccades in the chronic stage. In association with v-HIT, it allows determination of the residual vestibular function and to detect anti-compensatory saccades.

Highlights

Video-head impulse test (v-HIT) was recently developed to measure the gain of the vestibulo–ocular reflex (VOR) in the horizontal and the vertical plane for testing the horizontal, anterior, and posterior canals [1,2,3,4,5,6]
When the head impulse was delivered to the right side (Figure 2B), the eyes moved toward the left because of the slow phase of horizontal VOR (HVOR), and the subjects had to make a reflexive saccade to the right to regain fixation of the target (Video S2 in Supplementary Material)
Our study showed that suppression Head Impulse Paradigm (SHIMP) provided important information on vestibular function

Summary

Introduction

Video-head impulse test (v-HIT) was recently developed to measure the gain of the vestibulo–ocular reflex (VOR) in the horizontal and the vertical plane for testing the horizontal, anterior, and posterior canals [1,2,3,4,5,6]. This test is called the head impulse test (HIMP). The HVOR is deficient and, the slow phase it generates drives the eyes through a smaller distance than the target so that the size of the corrective SHIMP saccades is smaller [7]. The eye movement recording in SHIMPs during head impulses evaluates the VOR gain as it does in the standard HIMPs paradigm

Methods

Results

Discussion

Conclusion