Vestibulo-ocular responses during static head roll and three-dimensional head impulses after vestibular neuritis

This study aimed to investigate whether unilateral vestibular neuritis (VN) causes the same deficits of ocular counter-roll during static head roll (O CRS) and dynamic vestibule-ocular reflex gains during head impulses (VORHI) 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 upri ght (binocular cyclorotation) and dual search coil recordings in a three-fi eld magnetic frame. With one dual search coil on the right eye and the othe r on the forehead. the Following stimuli were given: i) Halmagyi-Curthoys h ead impulses about the vertical, horizontal and torsional axes. ii) Static roll positions of the head up to 20 degrees right- and left-ear-down by mov ement of the neck. The comparison group consisted of 19 healthy subjects. C ompared with the VD-patients, as reported in the literature, acute VN-patie nts showed the same pattern of OCRS gain reduction and binocular cyclorotat ion (CRb). The main feature that distinguished chronic VN-patients from chr onic VD-patients was the normalization of the torsional VORHI gain to the a ffected side, whereas the VORHI gains in the horizontal and vertical direct ions 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 CR, reward the affected side. and iii) a normal torsion al VORHI gain reward the affected side. Since the ipsilesional torsional VO RHI 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 fu nction on the side of thr lesion after the neuritis.