'Standard’ versus ‘nose reference’ electrode placement for measuring oVEMPs with air-conducted sound : test–retest reliability and preliminary patient results

Abstract

OBJECTIVES : This study compared two electrode placements (‘standard’ versus ‘nose reference’ placement) for measuring oVEMPs, elicited by air-conducted 500 Hz tone bursts. The test–retest reliability of both positions was evaluated and additionally both electrode placements were applied on a group of vestibular patients. METHODS : Eighteen healthy volunteers (range of 20–25 years) participated in the first part and were retested after one week for evaluation of the test–retest reliability. Eleven patients (range of 41–74 years) with a variety of vestibular pathologies were tested once. RESULTS : In the normal group, the nose reference electrode placement resulted in significantly larger peakto-peak amplitudes (p < 0.001), shorter n10 (p = 0.001) and p15 (p < 0.001) latencies and smaller 95% prediction intervals for the Inter-Ocular Ratio (IOR) ([68, 68] for the standard position versus [32, 32] for the nose reference position). Furthermore, an excellent amplitude and IOR test–retest reliability was observed with the nose reference configuration, as shown by the intraclass correlation coefficient (ICC), the coefficient of variation of the method error (CVME) and the minimal detectable differences (MDD). In the patient group, the same significant amplitude difference was found. Moreover, three patients presented with absent oVEMPs when recorded with the standard placement, whereas the nose reference placement could evoke a detectable oVEMP response. CONCLUSIONS : This study demonstrated that a nose reference electrode position results in larger oVEMP amplitudes and achieves a better reliability for the most important clinical parameters (amplitude and IOR). Our patient data substantiate the possible clinical benefit of this position, but further systematic patient verification is required.