Search

Bone-conducted vibration of the forehead, in the midline at the hairline (Fz) causes linear acceleration stimulation of both mastoids and results in an ocular vestibular-evoked myogenic potential (oVEMP), recorded by surface electromyogram (EMG) electrodes just beneath the eyes. The early n10 component of the oVEMP is symmetrical in healthy subjects, absent in patients with bilateral vestibular loss, and in patients after unilateral vestibular loss (uVL) n10 is small or absent on the side contralateral to the uVL, but of normal amplitude on the side contralateral to the healthy ear. The n10 component probably reflects mainly otolithic function, since in the guinea pig, primary otolith irregular neurons are selectively activated by bone-conducted vibration (BCV) at low intensities (0.1 g), whereas semicircular canal primary afferents are not activated even at high intensities (10 g). [ABSTRACT FROM AUTHOR]

Abstract: Objective: To provide the empirical basis for using ocular vestibular evoked myogenic potentials (oVEMPS) in response to Fz bone conducted vibration (BCV) stimulation to indicate vestibular function in human subjects. To show the generality of the response by testing a large number of unselected healthy subjects across a wide age range and the repeatability of the response within subjects. To provide evidence that the response depends on otolithic function. Methods: The early negative component (n10) of the oVEMP to brief BCV of the forehead, in the midline at the hairline (Fz) is recorded by surface EMG electrodes just beneath the eyes. We used a Bruel and Kjaer 4810 Mini-Shaker or a light tap with a tendon hammer to provide adequate BCV stimuli to test a large number (67) of unselected healthy people to quantify the individual differences in n10 magnitude, latency and symmetry to Fz BCV. A Radioear B-71 bone oscillator at Fz is not adequate to elicit a reliable n10 response. Results: The n10 oVEMP response showed substantial differences in amplitude between subjects, but is repeatable within subjects. n10 is of equal magnitude in both eyes with an average asymmetry around 11%. The average n10 amplitude for Mini Tone Burst BCV is 8.47μV±4.02 (sd), the average latency is 10.35ms±0.63 (sd). The amplitude of n10 decreases and its latency increases with age. Conclusions: oVEMPs are a new reliable, repeatable test to indicate vestibular and probably otolithic function. Significance: This study shows the optimum conditions for recording oVEMPs and provides baseline values for individual differences and asymmetry. oVEMPs can be measured in senior subjects without difficulty. [Copyright &y& Elsevier]