Vestibular recovery and central compensation after acute unilateral vestibulopathy - changes in saccadic response...

Acute unilateral vestibulopathy (AUVP), or vestibular neuritis, disrupts the vestibulo-ocular reflex (VOR), leading to impaired gaze stability during head movements. Vestibular function typically recovers to some extent. However, if recovery is incomplete, corrective eye saccades must compensate for the deficient VOR function. The aim was to analyze the progression of VOR gain recovery and development of different corrective eye saccade patterns after AUVP.

A prospective longitudinal study was performed, including 43 patients with AUVP, that were examined using the video head impulse test (vHIT) during the first week after symptom onset and after 1 month, 3 months, and 12 months. Data collected included ipsilesional and contralesional gain recovery and the presence of covert and overt saccades.

Both ipsilesional (p < 0.001) and contralesional (p ≤ _0.038) VOR gain improved significantly over 12 months, with the most pronounced recovery occurring within the first 3 months (p < 0.001). The presence of covert (p = 0.005) and overt (p < 0.001) saccades decreased over time. The lower the VOR gain, the more covert saccades were present. With intermediate VOR gain there were more overt saccades, and with a gain close to normal no corrective saccades were present. Correlation analysis revealed strong relationships between lower gains on the lesion side with lower gains on the healthy side.

VOR recovery manifests with variable patterns. The degree of VOR gain deficit appears to drive the specific type of compensatory saccade patterns employed. Unilateral vestibular impairment may result in bilateral overt saccades, whereas bilateral covert saccades are rarely observed. The presence of covert saccades is a strong indicator of significant underlying VOR hypofunction.