Analysis of head and eye dynamic may explain saccades in dizzy patients with normal VOR gain

Objective: Compare the vestibulo-ocular reflex (VOR) gain, compensatory saccades and head and eye coordination during head impulses between patients with dizziness but normal VOR gain and healthy controls.

Methods: Video head impulses test (vHIT; ICS impulse, Otometrics, Denmark) was reviewed in 40 participants (20 patients with dizziness; 20 controls). VOR gain, saccades characteristics (frequency of occurrence, amplitude, latency) and time difference between head and eye velocity was compared.

Results: No significant difference between groups was observed for VOR gain. However, saccade frequency was greater and time difference between head and eye was prolonged in patients with dizziness. No significant difference was observed for saccade amplitude, nor for saccade latency between groups.

Conclusions: The present study highlights that saccades observed in patients with normal VOR gain could reflect a clinical marker for dizziness in patients with normal VOR gain. We propose that theses saccades are caused by a prolonged time delay between head and eye velocity leading to a gaze position error.

Significance: The results support previous findings suggesting additional value of saccades and time delay when interpreting vHIT results. This study goes further by proposing time delay as a possible mechanism to explain increased saccade frequency in dizzy patients with normal VOR gain.