Feasibility of ocular vestibular-evoked myogenic potentials (oVEMPs) recorded with eyes closed

Abstract

Objective This study compared the characteristic parameters of ocular vestibular-evoked myogenic potential (oVEMP) test between eyes gazing up and eyes closed to evaluate the feasibility of oVEMP test with eyes closed. Methods Twenty-three healthy adults underwent oVEMP testing with upward gaze and with eyes closed in a randomized order. For each condition, the thickness of the inferior oblique and inferior rectus muscles, and the distance from the electrode on the skin to each muscle were measured via ultrasonography. Two patients with pathological ears were also included in this study for comparison. Results Twenty of the 23 subjects showed clear oVEMPs regardless of whether eyes were gazing up or eyes were closed. Mean latencies of nI and pI, and nI–pI interval with eyes closed were significantly prolonged when compared with those measured with eyes up. The mean nI–pI amplitude with eyes closed was significantly smaller than that with eyes up. However, no significant difference existed in the mean asymmetry ratio of amplitude between the two conditions. With eyes closed, the mean distances from the skin to the inferior oblique and inferior rectus muscles are 0.17 ± 0.03 and 0.40 ± 0.09 cm, respectively. In contrast with eyes gazing up, the mean distance from the skin to the inferior rectus muscle reduces significantly to 0.23 ± 0.09 cm, whereas the inferior oblique muscle slips out of ultrasonographic view. Conclusions Ocular VEMP can also be recorded with eyes closed in those who cannot perform upward gaze. However, the characteristic parameters of oVEMP are different between the eyes up and eyes closed conditions, probably because various extraocular muscles are involved in the generation of oVEMPs. Significance In those who cannot gaze upward such as small children, oVEMPs can be recorded by eyes closed.