Sensitivity and Specificity of Clinical and Laboratory Otolith Function Tests

Objective: To evaluate clinic based and laboratory tests of otolith function for their sensitivity and specificity in demarcating unilateral compensated complete vestibular deficit from normal. Study Design: Prospective cross-sectional study. Setting: Tertiary care hospital vestibular physiology laboratory. Subjects: Control group - 30 healthy adults, 20-45 years age; Case group-15 subjects post vestibular shwannoma excision or post-labyrinthectomy with compensated unilateral complete audio-vestibular loss. Intervention: Otolith function evaluation by precise clinical testing (head tilt test - HTT; subjective visual vertical - SVV) and laboratory testing (headroll-eye counterroll - HR-ECR; vesibular evoked myogenic potentials - cVEMP). Main Outcome Measure: Sensitivity and specificity of clinical and laboratory tests in differentiating case and control subjects. Results: Measurable test results were universally obtained with clinical otolith tests (SVV; HTT) but not with laboratory tests. The HR-ECR test did not indicate any definitive wave forms in 10% controls and 26% cases. cVEMP responses were absent in 10% controls. HTT test with normative cutoff at 2 degrees deviations from vertical noted as 93.33% sensitive and 100% specific. SVV test with normative cutoff at 1.3 degrees noted as 100% sensitive and 100% specific. Laboratory tests demonstrated poorer specificities owing primarily to significant unresponsiveness in normal controls. Conclusions: Clinical otolith function tests, if conducted with precision, demonstrate greater ability than laboratory testing in discriminating normal controls from cases with unilateral complete compensated vestibular dysfunction.