Gaze stabilization test: A new clinical test of unilateral vestibular dysfunction

OBJECTIVE: Evaluate the sensitivity, specificity, and reliability of the Gaze Stabilization Test (GST) for detection of unilateral vestibular dysfunction. STUDY DESIGN: Prospective controlled clinical trial. SETTING: Tertiary academic referral laboratory. PATIENTS: Fourteen patients (mean age, 63.8 yr; range, 43-77 yr) with history of vertigo and greater than 50% bithermal caloric asymmetry; 14 control subjects (mean age, 45.8 yr; range, 23-78 yr). INTERVENTION(S): Diagnostic test protocol with computerized system of target presentation and head velocity monitoring. MAIN OUTCOME MEASURE(S): Comparison of peak head velocity with ipsilesional and contralesional head movement-allowing gaze stability by randomly presenting transient (75 ms) targets of three optotypes above static acuity in patients and healthy subjects during self-generated headshake movements. RESULTS: GST demonstrated 93% specificity, 64% sensitivity, and a reliability index of 0.91 for the detection of unilateral dysfunction with ipsilesional movement. Peak head velocity in healthy subjects averaged 147 degrees per second, whereas ipsilesional velocities dropped significantly to an average of 84 degrees per second. Surprisingly, peak velocities were also significantly reduced to an average of 112 degrees per second with contralesional movements. CONCLUSION: GST is a reliable specific test of gaze stability which has diagnostic and rehabilitative applications in patients with vestibular dysfunction. Reduced contralesional velocities may help explain oscillopsia in patients with unilateral dysfunction.