The Validation of a Simultaneous Ocular and Cervical VEMP Recording Protocol to Unilateral AC Stimuli

Abstract

Introduction A simultaneous recording of cervical and ocular vestibular evoked myogenic potential (sVEMP) to unilateral air-conducted (AC) stimulation reduces the test time and halves the sound load. Materials and Methods The sVEMP has been compared with the conventional sequential unilateral AC cervical and ocular VEMP in a consecutive cohort of 120 subjects attending the vestibular laboratory. The stimulus was a 500-Hz 6-ms tone burst, at 130 dB peSPL for sequential recordings but at 125 dB for the added sVEMP, for cumulative sound load containment. Amplitudes, latencies, and amplitude asymmetry ratios (ARs) were the parameters included in analysis. Results Relevant results were as follows: 1) significantly lower amplitudes in sVEMP versus VEMP (ocular recordings, median = 2.90 [IQR = 0–4.98] vs. 4.15 [1.73–8.98] μV, p < 0.001; cervical, 0.84 [0.30–1.69] vs. 1.36 [0.60–2.30], p < 0.001; electromyography scaled values); 2) 10% lower response rate at cervical recordings and 11% at ocular recordings in sVEMP, particularly in older subjects; 3) significant correlations between cervical amplitudes (r s = 0.88, p < 0.001), ocular amplitudes (r s = 0.71, p < 0.001), peak latencies (r s = 0.36–0.67, p < 0.001), and ARs (ocular, r s = 0.56; cervical, r s = 68, p < 0.001); and 4) good agreement in pathological AR detection (cervical recordings, Cohen’s κ = 0.649, p < 0.001; ocular, κ = 0.589, p < 0.001). Discussion AC sVEMP showed good correlation/agreement with sequential AC VEMP. Test time containment and halved sound load are clinical adds in sVEMP, opening to its use as laboratory standard. However, AC sVEMP presented reduced amplitudes and response rates, secondary to the reduced AC stimulation used in this study to allow checking of the null responses and the pathological ARs at AC sVEMP with conventional AC VEMP.