Can the Video Head Impulse Test Define Severity of Bilateral Vestibular Hypofunction?

OBJECTIVE:The objective of the study was to compare rotary chair and video head impulse test (vHIT) findings in patients with bilateral vestibular hypofunction (BVH) to determine whether vHIT can: 1) define severity of BVH and 2) accurately predict rotary chair findings in patients with BVH. STUDY DESIGN:Retrospective chart review. SETTING:Research hospital. PATIENTS:Twenty subjects with bilateral vestibular hypofunction as assessed by rotary chair. INTERVENTION:Rotary chair and vHIT. MAIN OUTCOME MEASURES:The main outcome measures were rotary chair phase, gain, and symmetry and vHIT vestibulo-ocular reflex (VOR) gain. Rotary chair and vHIT results were assessed and subjects were stratified into groups according to the severity of their vestibular hypofunction. For rotary chair, subjects were classified as mild, moderate, or severe BVH. For vHIT, subjects were classified as normal, unilateral, or bilateral. RESULTS:Average lateral canal vHIT VOR gain: 1) significantly increased as severity of BVH decreased, and 2) demonstrated a significant and positive, linear relationship with rotary chair gains. vHIT was in disagreement with rotary chair in the classification of five subjects, which could be due to right-left asymmetry of BVH. CONCLUSION:vHIT can serve as an initial tool for identifying patients with BVH. Lower vHIT gains are consistent with having severe BVH. There was disagreement between vHIT and rotary chair, though not for any patients with severe BVH. Compared with rotary chair, the clinical gold standard for identifying BVH, vHIT possesses 100% sensitivity for excluding severe BVH when average vHIT gains are greater than 0.46.