Veterans with dizziness recruit compensatory saccades in each semicircular canal plane although VOR gain is normal.

Abstract

Exposure to brain injury via blast or blunt mechanisms disrupts multiple sensorimotor systems simultaneously. Large numbers of US Gulf War era and Operation Iraqi/Enduring Freedom veterans with traumatic brain injury (TBI) are suffering the symptom of dizziness - presumed due to "Multi-Sensory Impairment", a clinical pattern of damage to the auditory, visual and vestibular sensorimotor systems. To describe the oculomotor response to rapid head rotation in a population of veterans with dizziness. We also describe the reliability of using the video head impulse test (vHIT) in a veteran population. We used the vHIT to evaluate the vestibular-ocular reflex (VOR) gain and presence of compensatory saccades (CS) in each semicircular canal of 81 veterans (31% TBI) with dizziness. Data was collected using the ICS Otometric™ vHIT. Data was processed using both the Otometric™ software and custom software written in MATLAB™. This data was evaluated through Kruskal-Wallis rank-sum test and analysis of regression. Veterans with dizziness recruit CS in all semicircular canal planes even though their VOR gain is normal. The vHIT is a reliable clinical test to quantify the metrics of the VOR and CS in veterans. Veterans with dizziness symptoms use compensatory saccades in all planes of semicircular canal rotation, despite having normal peripheral VOR gain during rapid head rotation. The video head impulse test is a stable measure of vestibular slow phase and metrics of compensatory saccades in veterans with dizziness.