The Different Stages of Vestibular Neuritis from the Point of View of the Video Head Impulse Test

Abstract

Vestibular neuritis (VN) is one of the most common causes of acute vestibular syndrome (AVS). Quantifying the vestibulo-ocular reflex (VOR) gain by the video Head Impulse Test (vHIT) could provide useful information to diagnose VN. This study aims to retrospectively evaluate the VOR gain values during the acute and subacute stages of the VN and to correlate these values with the patients' dizziness-related handicap. Medical record of 28 patients with VN were reviewed. Patients were assigned to two groups according to the time since the acute vestibular syndrome (AVS). One group with patients assessed within seventy-two hours since the AVS (AVSg) and one group with patients evaluated from four days to six weeks since the AVS (PAVSg). VOR gain was evaluated in all selected patients and correlated to Dizziness Handicap Inventory (DHI). Significant differences were found in the between-subjects analysis in DHI score (p = 0.000) and in the ipsilesional hVOR gain values (p = 0.001). The correlation analysis showed significant results (p = 0.017) between DHI score (40 ± 16.08) and ipsilesional VOR gain (0.54 ± 0.09) in the PAVSg. Patients evaluated within 72 h since the AVS showed anticompensatory saccades (AcS) turning the head toward the contralesional side. Patients with unilateral Superior VN (SVN) could have dissimilar hVOR gain values and DHI score according to the damage of the VIII pair of cranial nerves. AcS in the contralesional side is a sign of acute phase in patients with unilateral SVN.

Keywords: Saccade; Vestibular Neuritis; Vestibulo-Ocular Reflex; anticompensatory saccades; video Head Impulse Test.

Figure 1

Graphical representation of the correlation between DHI scores and ipsilesional hVOR gain in the two groups. Data from 1 to 15 referred to the AVSg, data from 16 to 28 referred to the PAVSg. DHI = Dizziness Handicap Inventory; hVOR = horizontal vestibulo-ocular reflex; patient IDs are indicated on the x-axis; AVSg = Acute vestibular syndrome group; PAVSg = Post-acute vestibular syndrome group.

Figure 2

Objective measures of horizontal semicircular canal function at 2 testing occasions for one patient from AVS group with acute unilateral (right) vestibular neuritis: occasion 1 (A,B) and at succeeding time thereafter (C,D). Each panel shows a superimposed time series of head velocity (blue for the left impulses and black for the right impulses) and the corresponding eye velocity (orange) for the tests of horizontal canal dynamic function using vHIT. The signs of head velocity for leftward impulses and of eye velocity for rightward impulses have been inverted to allow for easier comparison. Normal horizontal VOR gains are about 0.7–1.0 [4]. For rotations to the affected side, eye velocity is substantially less than the corresponding head velocity during the head turn so the VOR is significantly less, VOR gain is 0.28, then for head turns to the healthy side, VOR gain is 0.7. There is a shower of compensatory (Covert + Overt) saccades during and at the end of the head turn (black arrow). While when the head is turned to the left contralesional side, anti compensatory saccades (AcS) eye movements in the direction of the head movement can be observed (grey arrow) at the time of the attack. On succeeding testing occasion, two months later, for head turns to the affected side the slow phase eye velocity improves and the corrective saccades are still the same, VOR gain is 0.38, for head turns to the healthy side the slow phase velocity is quite the same while anti-compensatory saccades disappear.