Evidence-based diagnostic use of VEMPs : From neurophysiological principles to clinical application

Abstract

Background: Vestibular evoked myogenic potentials (VEMPs) are increasingly being used for testing otolith organ function.

Objective: This article provides an overview of the anatomical, biomechanical and neurophysiological principles underlying the evidence-based clinical application of ocular and cervical VEMPs (oVEMPs and cVEMPs).

Material and methods: Systematic literature search in PubMed until April 2019.

Results: Sound and vibration at a frequency of 500 Hz represent selective vestibular stimuli for the otolith organs. The predominant specificity of oVEMPs for contralateral utricular function and of cVEMPs for ipsilateral saccular function is defined by the different central projections of utricular and saccular afferents. VEMPs are particularly useful in the diagnosis of superior canal dehiscence and otolith organ specific vestibular dysfunction and as an alternative diagnostic approach in situations when video oculography is not possible or useful.

Conclusion: The use of VEMPs is a simple, safe, reliable and selective test of dynamic function of otolith organs.

Keywords: Bone conduction; Otolithic membrane; Vestibular evoked myogenic potentials; Vestibular neuritis; Vibration.

Fig. 1

Reflex pathways and VEMPs recorded in a–c a healthy subject and d–f a patient with right-sided unilateral vestibular loss (uVL). III oculomotor nucleus; XI spinal accessory nucleus; black hexagon inhibitory interneurons in the vestibular nuclei projecting to the motoneurons of the ipsilateral sternocleidomastoid muscle (SCM). a–c In a healthy subject, symmetric oVEMP n10 responses are recorded from the inferior oblique muscle beneath the left and right eyes. Likewise, symmetric cVEMP p13n23 responses are present in the left and right SCM. d–f In a patient with right-sided uVL (X), however, contralateral (= left) oVEMPs (crossed reflex pathway) and ipsilateral (= right) cVEMPs (uncrossed reflex pathway) are absent. VEMPs vestibular evoked myogenic potentials, c cervical, o ocular, inf inferior. (Slightly modified and reprinted from [17] with permission from © John Wiley & Sons)

Fig. 2

Schematic diagrams of a the otolith organs, b,c their vestibular hair cells and d their afferent innervation. a Spatial orientation of the utricular and saccular maculae in the labyrinth. Dashed lines: lines of polarity reversal/striola. Arrows: polarization vectors of the vestibular hair cells. For details see [69]. b Amphora-shaped type I vestibular hair cell (with calyx synapse) and cylindrical type II vestibular hair cell (with bouton synapse) and the overlying otoconia at rest: no deflection of hair cell stereocilia. c Vestibular hair cells and otoconia during constant or low-frequency linear acceleration: relative motion of the otoconial membrane relative to the neuroepithelial layer and deflection of hair cell stereocilia opposite to the direction of linear acceleration. (Slightly modified and reprinted from [21] with permission from © I.S. Curthoys et al., CC BY 4.0 [https://creativecommons.org/licenses/by/4.0/]). d Afferent innervation of the vestibular organ. Yellow: superior vestibular nerve; blue: inferior vestibular nerve; SG Scarpa’s ganglion; ant./hor./post. SCC anterior (= superior)/horizontal/posterior semicircular canal. (Reprinted from [17] with permission from © John Wiley & Sons)

Fig. 3

Dual mode of action of the otolith organs as a accelerometers for constant and low-frequency linear accelerations (= sustained channel of otolithic function) and b seismometers for high-frequency changes in acceleration (= transient channel). (Reprinted from [21] with permission from © I.S. Curthoys et al., CC BY 4.0, https://creativecommons.org/licenses/by/4.0)

Fig. 4

Response of an utricular afferent neuron with irregular resting discharge to 500 Hz bone-conducted vibration (BCV) and air-conducted sound (ACS) in the guinea pig: both BCV and ACS cause a stimulus-locked increase in spike discharge rate in the irregular utricular afferent neuron. (Modified from [13])

Fig. 5

Placement of surface electrodes for the recording of a ocular and b cervical vestibular evoked myogenic potentials. X: Fz (midline of the forehead at the hairline)

Fig. 6

Effect of a superior canal dehiscence (SCD) on ocular vestibular evoked myogenic potentials (oVEMPs). a Enhanced contralateral oVEMP n10 amplitude (arrowhead) during application of 500 Hz bone-conducted vibration (BCV) at Fz (midline of the forehead at the hairline). (Reprinted from [54] with permission from © Wolters Kluwer Health, Inc.). b Presence of a contralateral oVEMP n10 response to 4000 Hz BCV and air-conducted sound (ACS) in a case of SCD. (Slightly modified and reprinted from [55] with permission from © SAGE Publications)