Vestibulo-Ocular Responses During Static Head Roll and Three-Dimensional Head Impulses After Vestibular Neuritis

Abstract

This study aimed to investigate whether unilateral vestibular neuritis (VN) causes the same deficits of ocular counter-roll during static head roll (OCR_S) and dynamic vestibulo-ocular reflex gains during head impulses (VOR_HI) as unilateral vestibular deafferentation (VD). Ten patients with acute and 14 patients with chronic vestibular paralysis after VN were examined. The testing battery included fundus photography of both eyes with the head upright (binocular cyclorotation) and dual search coil recordings in a three-field magnetic frame. With one dual search coil on the right eye and the other on the forehead, the following stimuli were given: i) Halmagyi-Curthoys head impulses about the vertical, horizontal and torsional axes. ii) Static roll positions of the head up to 20° right- and left-ear-down by movement of the neck. The comparison group consisted of 19 healthy subjects. Compared with the VD-patients, as reported in the literature, acute VN-patients showed the same pattern of OCR_S gain reduction and binocular cyclorotation (CR_b). The main feature that distinguished chronic VN-patients from chronic VD-patients was the normalization of the torsional VOR_HI gain to the affected side, whereas the VOR_HI gains in the horizontal and vertical directions did not show recovery (as in the patients with chronic VD). Chronic VN-patients differed from acute VN-patients by: i) symmetrical OCRS gains, ii) a less pronounced CRb toward the affected side, and iii) a normal torsional VOR_HI gain toward the affected side. Since the ipsilesional torsional VOR_HI gain did not recover in VD-patients, the normalization of this gain in our VN-patients can only be explained by a (partial) recovery of otolith function on the side of the lesion after the neuritis.