Secondary Logo

Journal Logo

New perspectives on vestibular evoked myogenic potentials

Rosengren, Sally M.a; Kingma, Hermanb

doi: 10.1097/WCO.0b013e32835c5ef3
NEURO-OPHTHALMOLOGY AND NEURO-OTOLOGY: Edited by François-Xavier Borruat and Michael Strupp
Free

Purpose of review Although the vestibular evoked myogenic potential (VEMP) measured from the cervical muscles (cVEMP, cervical VEMP) is well described and has documented clinical utility, its analogue recorded from the extraocular muscles (oVEMP, ocular VEMP) has been described only recently and is currently emerging as an additional test of otolith function. This review will, therefore, summarize recent developments in VEMP research with a focus on the oVEMP.

Recent findings Recent studies suggest that the oVEMP is produced by otolith afferents in the superior vestibular nerve division, whereas the cVEMP evoked by sound is thought to be an inferior vestibular nerve reflex. Correspondingly, the oVEMP correlates better with caloric and subjective visual vertical tests than sound-cVEMPs. cVEMPs are more complicated than often thought, as shown by the presence of crossed responses and conflicting results of recent vibration studies. Altered inner ear mechanics produced by the vestibular diseases superior semicircular canal dehiscence and Ménière's disease lead to changes in the preferred frequency of the oVEMP and cVEMP.

Summary The oVEMP provides complementary diagnostic information to the cVEMP and is likely to be a useful addition to the diagnostic test battery in neuro-otology.

aNeurology Department, Royal Prince Alfred Hospital, Camperdown, Australia

bDepartment of Otorhinolaryngology, Maastricht University Hospital, Maastricht, The Netherlands

Correspondence to Dr Sally Rosengren, Neurology Department, Royal Prince Alfred Hospital, Missenden Rd, Camperdown, NSW 2050, Australia. Tel: +61 295157565; e-mail: sally@srosengren.org

Back to Top | Article Outline

INTRODUCTION

Since its first description in 1992 [1], the vestibular evoked myogenic potential (VEMP) has become a well established vestibular function test. It is a muscle reflex evoked by stimulation of the vestibular organs (typically with loud sound) and recorded from electrodes placed over the sternocleidomastoid (SCM) muscles. It is thought to be primarily a measure of saccular function. The VEMP recorded under these conditions is now often referred to as a cervical VEMP (cVEMP) to distinguish it from the more recently described ocular VEMP (oVEMP). Similar to the cVEMP, which is a manifestation of the vestibulo-collic reflex, the oVEMP is a myogenic reflex of the extraocular muscles that is a form of vestibulo-ocular reflex.

Back to Top | Article Outline

THE PHYSIOLOGICAL BASIS OF VESTIBULAR EVOKED MYOGENIC POTENTIALS

The sound-evoked cVEMP is primarily an ipsilateral reflex consisting of a biphasic positive–negative surface potential with peak latencies at about 13 and 23 ms (Fig. 1) [2,3]. Single motor unit recordings have shown that the basis of this reflex is a short-latency inhibition of the SCM muscle [4]. This evidence supports recent papers describing models of the cVEMP. In terms of signal analysis, the cVEMP can be considered a sound-induced or vibration-induced temporal modulation of electromyographic variance. Several attempts have been made to explain the cVEMP on the basis of a model using a modulation of the sum of motor-unit action potentials as an input [5–7]. The first showed that, in contrast with other evoked potentials (e.g. brainstem auditory evoked potentials or vestibular evoked responses), the cVEMP is the result of an interruption of activity and not that of summed synchronized neural action potentials [5]. From subsequent studies [6,7], it became clear that the cVEMP and associated variance modulation is most likely composed of at least two components: a main component of inhibitory nature and at least one minor component of excitatory nature. At present, the iterative model developed based upon deconvolution techniques seems to make it possible to estimate the modulation of motor-unit potentials that underlie any cVEMP. Two functions of time are incorporated into this model: the temporal modulation of the motor unit action potential rate of all contributing motor units (rate component) and the motor unit action potential of an average motor unit. The rate modulation accounts for the p13–n23 inhibitory cVEMP component and is much stronger than the second, nonvestibular, n34–p44 excitatory component related to the summing of synchronized activity.

FIGURE 1

FIGURE 1

Box 1

Box 1

In contrast to the cVEMP, the oVEMP is a mainly crossed reflex that is typically excitatory in nature (Fig. 2) [8▪,9]. Recent recordings of the responses of single motor units of the inferior oblique and inferior rectus extraocular muscles in humans showed that the n10 oVEMP peak is produced by increased activity of the inferior oblique muscle [8▪]. Although the inferior rectus was also activated by sound and vibration, this activity occurred about 5 ms later than that in the inferior oblique muscle.

FIGURE 2

FIGURE 2

The cVEMP is now used in many contexts, in most cases to assess inner ear function in patients with vestibular dysfunction. Although it requires cooperation from the patient (i.e. activation of the SCM muscle by lifting the head or turning it forcefully to one side), the test is relatively easy to perform. For this reason, it is becoming more widely used to test paediatric populations [10–13], and the first reports of oVEMPs in children are also starting to emerge (for example [14]). Given the novelty and potential of the oVEMP, there has been a rush to test this reflex in clinical and experimental contexts, particularly in comparison to the cVEMP. With this surge in popularity has come an increase in complexity of the VEMP field, in part due to the variety of methods available to evoke these reflexes.

A major current theme in VEMP research that attempts to deal with this complexity is the investigation of VEMPs in patients with vestibular neuritis. As vestibular neuritis can affect the two portions of the vestibular nerve independently, the disease is currently used as a model to identify which nerve division (superior or inferior) carries the afferents responsible for each type of VEMP (i.e. VEMPs recorded from the eye muscles versus the neck muscles and VEMPs evoked with air-conducted sound versus bone-conducted vibration). Sound and vibration are thought to activate the otolith organs relatively selectively [15,16], but recent research points to possible additional activation of semicircular canal afferents [17,18]. As utricular afferents (and some saccular afferents) course through the superior nerve division and most saccular afferents travel through the inferior division, it is thought that differential dysfunction of one nerve division may indicate the likely involvement of the saccule and utricle in cVEMPs and oVEMPs. This question is very important given the early stage of development of the oVEMP as a clinical test and will hopefully result in greater understanding of the basis of these reflexes.

Back to Top | Article Outline

OCULAR VESTIBULAR EVOKED MYOGENIC POTENTIAL ORIGINS

Two initial studies of patients with suspected superior vestibular neuritis (SVN) established that oVEMPs evoked by vibration of the forehead are typically asymmetric or absent in SVN [19,20]. The patients were recruited based on abnormal horizontal canal responses on caloric or head impulse testing (HIT) but present sound-cVEMPs, suggesting that there was at least partial dysfunction of the superior vestibular nerve and preservation of the inferior nerve. The same pattern of results has more recently been found for the sound-oVEMP (Fig. 2) [21,22▪,23▪▪,24]. As the pattern of oVEMP abnormality in these patients matches that of the horizontal canal (whose fibres travel in the superior nerve), it suggests that the oVEMP is also produced predominantly by vestibular afferents in the superior vestibular nerve. This approach is promising, but caution is warranted due to possible heterogeneity in disease extent, severity and rate of recovery in vestibular neuritis, not only between patients but also particularly within the same patient. The fact that cVEMPs are the only available clinical measure of saccular function makes them valuable, but at the same time there is no independent measure of saccular function against which they can be judged. To test the origin and diagnostic efficacy of any VEMP in vestibular neuritis, patients would ideally be recruited and classified based only on clinical criteria and the function of the three canals and not VEMPs.

A recent article by Shin et al.[23▪▪] came close to this ideal by recruiting patients based on clinical inclusion and exclusion criteria, the result of clinical HIT in different canal planes and the direction of spontaneous nystagmus (although their criteria for SVN did also include present sound-cVEMPs). Most of their patients with SVN had abnormal sound-oVEMPs, whereas the patients with inferior vestibular neuritis (IVN) had normal sound-oVEMPs but impaired sound-cVEMPs. This pattern of abnormality supports another study of patients with suspected IVN, which showed that most patients with abnormal sound-cVEMP had symmetric vibration-oVEMP [25]. IVN is more difficult to definitively diagnose than SVN, and preferably includes a positive HIT for the posterior canal, as the sound-cVEMP can sometimes be absent in normal individuals, particularly with advancing age. In addition, an isolated cVEMP abnormality should also be interpreted with caution when the background muscle contraction is not known, as it could be the result of underactivation of the SCM muscle.

There is now agreement that both sound-oVEMPs and vibration-oVEMPs originate in the superior division of the vestibular nerve. The greater number of utricular fibres in this division means that a large oVEMP asymmetry is likely to predominantly reflect a utricular lesion. In contrast, it is not yet known what role the fibres from the anterior hook region of the saccule may play in this reflex. Although short-latency sacculo-ocular projections have been shown to be relatively weak [26], several studies have demonstrated their existence (for example [27–30]). Given the different directional sensitivities and physical properties of the two otolith organs, it has been suggested that these properties may render them differentially sensitive to VEMP stimuli delivered with different direction or frequency, and that under some circumstances the oVEMP could reflect saccular function [31]. It is hoped that future studies will determine the function of the sacculo-ocular projections and the conditions under which the saccule contributes to the control of gaze and possibly the oVEMP.

Back to Top | Article Outline

CERVICAL VESTIBULAR EVOKED MYOGENIC POTENTIAL ORIGINS

Although it would seem that the projections underlying the cVEMP are well established, new evidence has refocused attention on cVEMP pathways. Animal data on the vestibular projections to the neck muscles show that the saccule has only an ipsilateral inhibitory projection to the SCM, whereas the utricle (and probably also the canals) shares this projection and has an additional excitatory projection to the contralateral SCM [2,32]. Interestingly, in up to about 40% of normal volunteers, the sound-cVEMP consists of a bilateral response, an inhibition (p13–n23) in the ipsilateral SCM and a small excitation (n12–p20) in the contralateral SCM [3] (Fig. 1). In light of the animal data, this suggests that the sound-cVEMP often receives input from other vestibular organs, likely the utricle, especially with increasing stimulus intensity. The crossed response is characteristic of patients with superior canal dehiscence (Fig. 3), although it is not known whether it originates in the utricle or superior canal or both in these patients [33,34]. In practice, it is thought that the saccular contribution to the ipsilateral response is dominant and a sound-cVEMP asymmetry is likely to reflect saccular dysfunction.

FIGURE 3

FIGURE 3

In contrast, studies of the vibration-cVEMP show differential patterns of reflex activation with different vibration stimuli. It has recently been suggested that stimulation at the forehead with 500 Hz tone bursts produces normal cVEMPs in patients with SVN and that the saccule is, therefore, responsible for all cVEMPs [35]. In contrast, earlier studies showed that the vibration-cVEMP (evoked by forehead taps with a tendon hammer) was abnormal in SVN patients, suggesting that the superior nerve is indeed important [36]. A more recent study by Govender et al.[22▪] produced similar results and showed that cVEMPs evoked by taps delivered laterally to the mastoid were correlated with oVEMPs rather than sound-cVEMPs, again suggesting an origin in the superior nerve and utricle. The reason for this seemingly differential effect of different stimuli is not yet known; however, given the strength of utriculo-collic projections in general [37▪▪], and the role of utricular afferents in compensating for roll tilt of the head, it is not surprising that the utricle may play an important role in the vestibulo-collic reflex.

Back to Top | Article Outline

VESTIBULAR EVOKED MYOGENIC POTENTIALS IN VESTIBULAR DYSFUNCTION

A complementary approach to investigating VEMP origins and diagnostic efficacy has been comparison of VEMPs with established tests of vestibular function in patients with vestibular dysfunction. As expected for a test of superior nerve otolith afferents, the oVEMP appears to be most correlated with subjective visual vertical (SVV) and caloric responses, rather than sound-cVEMPs [38–40]. However, the correlation between SVV and oVEMP is only expected during the acute stage of vestibular loss, as performance on the former test improves over time due to vestibular compensation, while the oVEMP remains abnormal. This is a clear advantage of the oVEMP. Additionally, Valko et al.[41] showed that oVEMPs may also perform better than SVV during eccentric rotation, a test that can detect SVV abnormalities even in cases of chronic vestibular loss.

VEMPs have their clearest role in diagnosis of superior semicircular canal dehiscence (SSCD) and other ‘third window’ disorders, in which it is well documented that the sound-cVEMP has a characteristically low threshold. Shortly after the introduction of the oVEMP, it became clear that this new reflex showed even greater abnormality in SSCD patients: a low threshold and a reliably high amplitude (Fig. 3) [42,43▪]. Although the sound-cVEMP is often large in SSCD, there is significant overlap of amplitude with the normal range, thought to be because the inhibitory nature of the cVEMP makes it susceptible to saturation at high intensity. As the n10 oVEMP peak is an excitatory reflex [8▪], it is probably not prone to such saturation effects. New evidence suggests that a midline vibration stimulus produces similar results to sound stimulation for both cVEMPs and oVEMPs, suggesting that this stimulus could also be useful in diagnosis [44▪]. Although it is thought that VEMPs from the dehiscent labyrinth are enhanced partly due to activation of superior canal afferents, a recent case report provided evidence that VEMPs can still be abnormal even with dysfunction of the superior canal [45]. This demonstrates that otolith receptors are indeed abnormally stimulated in SSCD, but does not rule out concomitant canal activation.

The altered mechanical properties of the labyrinth in patients with SSCD lead to interesting changes in the preferred frequency, or tuning, of both cVEMPs and oVEMPs. In normal individuals, the sound-cVEMP is maximal at frequencies around 400–800 Hz, and new evidence has shown that the normal sound-oVEMP has very similar tuning [43▪,46–48]. In contrast, the normal vibration-cVEMP and oVEMP have a lower preferred frequency, closer to 100 Hz [49,50▪]. In contrast to normal individuals, frequency tuning studies in SSCD patients have shown broader tuning curves for both reflexes, with the sound-cVEMP tending to tune downwards and the sound-oVEMP upwards [43▪]. This high-frequency enhancement of the oVEMP to sound and vibration is preserved when patients are tested with stimulus intensities closer to threshold, suggesting that they are related to mechanical changes within the dehiscent labyrinth and an altered pattern of receptor activation, rather than being a simple consequence of stimulating far above threshold [51]. A consequence of the broader tuning is that higher frequencies may separate patients from controls better than the more commonly used 500 Hz stimulus [43▪]. The altered VEMP tuning returns to normal after resurfacing of the superior semicircular canal [52].

Similar tuning changes can be seen in patients with Ménière's disease, a very different type of vestibular disorder, but one that is also thought to produce changes in the mechanical properties of the labyrinth. Previous research has established that the sound-cVEMP in patients with Ménière's disease has higher frequency tuning than in controls (for example [53]). Recent studies have shown that this is also true of the sound-oVEMP [47,54,55]. Apart from the tuning shift, the sound-oVEMP also shows lower mean amplitudes and higher rates of abnormality in Ménière's disease compared to control groups, sometimes exceeding the performance of the sound-cVEMP [56,57,58▪]. However, data from normal individuals show that the sound-oVEMP has a higher threshold than the sound-cVEMP, thus care should be taken when comparing rates of abnormality across these reflexes [57,59].

Back to Top | Article Outline

CONCLUSION

Current evidence supports an origin primarily in the ipsilateral saccule for the sound-cVEMP and the contralateral superior nerve (probably mainly the utricle) for sound-oVEMPs and vibration-oVEMPs, suggesting that the reflexes can provide additional diagnostic information about the function of the otolith organs. Future research should aim to investigate the possible contributions of the semicircular canals to the reflexes and further delineate the vestibulo-collic and vestibulo-ocular projections in humans. In addition to their clinical utility, these reflexes can also be used to investigate the vestibular system and its properties. Many of the recently published oVEMP studies shed new light on the vestibulo-ocular reflex, including the behaviour of single extraocular muscle units to vestibular stimulation with sound and vibration [8▪] and the ability of the otoliths to respond to vibration of different directions, even up to quite high frequencies [60,61▪,62]. Continued development of the cVEMP and oVEMP over time will likely lead to increased understanding of the vestibular system and its response to sound and vibration as well as new opportunities in the diagnosis of disorders of vestibular function.

Back to Top | Article Outline

Acknowledgements

S.M.R. was funded by the National Health and Medical Research Council of Australia (Grant #617504).

Back to Top | Article Outline

Conflicts of interest

There are no conflicts of interest.

Back to Top | Article Outline

REFERENCES AND RECOMMENDED READING

Papers of particular interest, published within the annual period of review, have been highlighted as:

  • ▪ of special interest
  • ▪▪ of outstanding interest

Additional references related to this topic can also be found in the Current World Literature section in this issue (p. 107).

Back to Top | Article Outline

REFERENCES

1. Colebatch JG, Halmagyi GM. Vestibular evoked potentials in human neck muscles before and after unilateral vestibular deafferentation. Neurology 1992; 42:1635–1636.
2. Kushiro K, Zakir M, Ogawa Y, et al. Saccular and utricular inputs to sternocleidomastoid motoneurons of decerebrate cats. Exp Brain Res 1999; 126:410–416.
3. Welgampola MS, Colebatch JG. Vestibulocollic reflexes: normal values and the effects of age. Clin Neurophysiol 2001; 112:1971–1979.
4. Colebatch JG, Rothwell JC. Motor unit excitability changes mediating vestibulocollic reflexes in the sternocleidomastoid muscle. Clin Neurophysiol 2004; 115:2567–2573.
5. Wit HP, Kingma CM. A simple model for the generation of the vestibular evoked myogenic potential (VEMP). Clin Neurophysiol 2006; 117:1354–1358.
6. Lütkenhöner B, Rudack C, Basel T. The variance modulation associated with the vestibular evoked myogenic potential. Clin Neurophysiol 2011; 122:1448–1456.
7. Lütkenhöner B, Basel T. Deconvolution of the vestibular evoked myogenic potential. J Theor Biol 2012; 294:87–97.
8▪. Weber KP, Rosengren SM, Michels R, et al. Single motor unit activity in human extraocular muscles during the vestibulo-ocular reflex. J Physiol 2012; 590:3091–3101.

New evidence of the myogenic origin of the oVEMP is described in this study. Single motor unit recordings from the inferior oblique and inferior rectus muscles in humans showed that the n10 oVEMP peak originates in the inferior oblique muscle. The study shows the behaviour of single extraocular motor units to vestibular stimulation in humans for the first time.

9. Suzuki J-I, Tokumasu K, Goto K. Eye movements from single utricular nerve stimulation in the cat. Acta Otolaryngol 1969; 68:350–362.
10. Jafari Z, Malayeri SA. The effect of saccular function on static balance ability of profound hearing-impaired children. Int J Pediatr Otorhinolaryngol 2011; 75:919–924.
11. Wiener-Vacher S. VEMP. In: O’Reilly R, Morlet T, Cushing S, editors. Manual of pediatric balance disorders. San Diego, CA: Plural Publishing Inc.; 2013.
12. Zhang D, Fan Z, Han Y, et al. Benign paroxysmal vertigo of childhood: diagnostic value of vestibular test and high stimulus rate auditory brainstem response test. Int J Pediatr Otorhinolaryngol 2012; 76:107–110.
13. Zhou G, Gopen Q. Characteristics of vestibular evoked myogenic potentials in children with enlarged vestibular aqueduct. Laryngoscope 2011; 121:220–225.
14. Chou CH, Hsu WC, Young YH. Ocular vestibular-evoked myogenic potentials via bone-conducted vibration in children. Clin Neurophysiol 2012; 123:1880–1885.
15. Curthoys IS, Kim J, McPhedran SK, Camp AJ. Bone conducted vibration selectively activates irregular primary otolithic vestibular neurons in the guinea pig. Exp Brain Res 2006; 175:256–267.
16. Murofushi T, Curthoys IS. Physiological and anatomical study of click-sensitive primary vestibular afferents in the guinea pig. Acta Otolaryngol 1997; 117:66–72.
17. Xu Y, Simpson I, Tang X, Zhou W. Acoustic clicks activate both the canal and otolith vestibulo-ocular reflex pathways in behaving monkeys. J Assoc Res Otolaryngol 2009; 10:569–577.
18. Zhu H, Tang X, Wei W, et al. Click-evoked responses in vestibular afferents in rats. J Neurophysiol 2011; 106:754–763.
19. Iwasaki S, Chihara Y, Smulders YE, et al. The role of the superior vestibular nerve in generating ocular vestibular-evoked myogenic potentials to bone conducted vibration at Fz. Clin Neurophysiol 2009; 120:588–593.
20. Manzari L, Tedesco A, Burgess AM, Curthoys IS. Ocular vestibular-evoked myogenic potentials to bone-conducted vibration in superior vestibular neuritis show utricular function. Otolaryngol Head Neck Surg 2010; 143:274–280.
21. Curthoys IS, Iwasaki S, Chihara Y, et al. The ocular vestibular-evoked myogenic potential to air-conducted sound; probable superior vestibular nerve origin. Clin Neurophysiol 2011; 122:611–616.
22▪. Govender S, Rosengren SM, Colebatch JG. Vestibular neuritis has selective effects on air- and bone-conducted cervical and ocular vestibular evoked myogenic potentials. Clin Neurophysiol 2011; 122:1246–1255.

This study examined cVEMPs and oVEMPs in patients with vestibular neuritis using a variety of stimulation methods, including air-conducted sound, impulses (i.e. controlled taps given with a minishaker) delivered to the mastoids and forehead taps. The results confirmed that sound-oVEMPs originate in the superior vestibular nerve and showed that this nerve portion is also important for vibration-cVEMPs.

23▪▪. Shin B-S, Oh S-Y, Kim JS, et al. Cervical and ocular vestibular-evoked myogenic potentials in acute vestibular neuritis. Clin Neurophysiol 2012; 123:369–375.

In this study, patients with acute vestibular neuritis were recruited using well documented clinical criteria and careful observation of spontaneous nystagmus. On the basis of these results, their head impulse test results and their sound-cVEMP reflexes, patients were classified as having SVN or IVN. The authors showed that the sound-oVEMP is abnormal in patients with SVN and normal in patients with IVN.

24. Lin C-M, Young Y-H. Identifying the affected branches of the vestibular nerve in vestibular neuritis. Acta Otolaryngol 2011; 131:921–928.
25. Manzari L, Burgess AM, Curthoys IS. Ocular and cervical vestibular evoked myogenic potentials in response to bone-conducted vibration in patients with probable inferior vestibular neuritis. J Laryngol Otol 2012; 126:683–691.
26. Isu N, Graf W, Sato H, et al. Sacculo-ocular reflex connectivity in cats. Exp Brain Res 2000; 131:262–268.
27. Chan YS, Hwang JC, Cheung YM. Crossed sacculo-ocular pathway via the Deiters’ nucleus in cats. Brain Res Bull 1977; 2:1–6.
28. Goto F, Meng H, Bai R, et al. Eye movements evoked by selective saccular nerve stimulation in cats. Auris Nasus Larynx 2004; 31:220–225.
29. Fluur E, Mellström A. Saccular stimulation and oculomotor reactions. Laryngoscope 1970; 80:1713–1721.
30. Hwang JC, Poon WF. An electrophysiological study of the sacculo-ocular pathways in cats. Jap J Physiol 1975; 25:241–251.
31. Govender S, Colebatch JG. Ocular vestibular evoked myogenic potential (oVEMP) responses in acute vestibular neuritis. Clin Neurophysiol 2012; 123:1053–1057.
32. Fukushima K, Peterson BW, Wilson VJ. Vestibulospinal, reticulospinal and interstitiospinal pathways in the cat. Progr Brain Res 1979; 50:121–136.
33. Watson SRD, Halmagyi GM, Colebatch JG. Vestibular hypersensitivity to sound (Tullio phenomenon): structural and functional assessment. Neurology 2000; 54:722–728.
34. Brantberg K, Löfqvist L, Franson P-A. Large vestibular evoked myogenic potentials in response to bone-conducted sounds in patients with superior canal dehiscence syndrome. Audiol Neurootol 2004; 9:173–182.
35. Curthoys IS. Interpretation of clinical tests of peripheral vestibular function. Laryngoscope 2012; 122:1342–1352.
36. Brantberg K, Tribukait A, Fransson P-A. Vestibular evoked myogenic potentials in response to skull taps for patients with vestibular neuritis. J Vestib Res 2003; 13:121–130.
37▪▪. Uchino Y, Kushiro K. Differences between otolith- and semicircular canal-activated neural circuitry in the vestibular system. Neurosci Res 2011; 71:315–327.

This article provides a comprehensive review of the authors’ large body of research on the projections from individual vestibular organs to the central nervous system. Their data on vestibulo-ocular and vestibulo-collic projections provide important information on the projections likely to underpin the cVEMP and oVEMP.

38. Lin K-Y, Young Y-H. Correlation between subjective visual horizontal test and ocular vestibular-evoked myogenic potential test. Acta Otolaryngol 2011; 131:149–155.
39. Huang C-H, Wang S-J, Young Y-H. Correlation between caloric and ocular vestibular evoked myogenic potential test results. Acta Otolaryngol 2012; 132:160–166.
40. Murofushi T, Nakahara H, Yoshimura E, Tsuda Y. Association of air-conducted sound oVEMP findings with cVEMP and caloric test findings in patients with unilateral peripheral vestibular disorders. Acta Otolaryngol 2011; 131:945–950.
41. Valko Y, Hegemann SCA, Weber KP, et al. Relative diagnostic value of ocular vestibular evoked potentials and the subjective visual vertical during tilt and eccentric rotation. Clin Neurophysiol 2010; 122:398–404.
42. Welgampola MS, Myrie OA, Minor LB, Carey JP. Vestibular-evoked myogenic potential thresholds normalize on plugging superior canal dehiscence. Neurology 2008; 70:464–472.
43▪. Taylor RL, Bradshaw AP, Halmagyi GM, Welgampola MS. Tuning characteristics of ocular and cervical vestibular evoked myogenic potentials in intact and dehiscent ears. Audiol Neurotol 2012; 17:207–218.

The study explores the changes in frequency tuning caused by superior canal dehiscence. In dehiscent ears, the additional window in the labyrinth produces a broadening of tuning curves, with the oVEMP becoming more sensitive to high frequencies. A consequence of this is that higher frequency stimuli (1–2 kHz) may prove better for diagnosis. The authors also reported age-related changes in VEMP tuning in normal individuals, highlighting the importance of using age-matched controls in VEMP studies.

44▪. Manzari L, Burgess AM, McGarvie LA, Curthoys IS. Ocular and cervical vestibular-evoked myogenic potentials to 500 Hz Fz bone-conducted vibration in superior semicircular canal dehiscence. Ear Hear 2012; 33:508–520.

The data presented in this study show that vibration-cVEMPs and vibration-oVEMPs (evoked with a forehead 500 Hz stimulus) are also abnormal in patients with superior canal dehiscence, similar to sound-evoked VEMPs. These data differ from previous reports of forehead taps and mastoid vibration, which show lower rates of abnormality in superior canal dehiscence.

45. Manzari L, Burgess AM, MacDougall HG, Curthoys IS. Enhanced otolithic function in semicircular canal dehiscence. Acta Otolarygol 2011; 131:107–112.
46. Park HJ, Lee IS, Shin JE, et al. Frequency-tuning characteristics of cervical and ocular vestibular evoked myogenic potentials induced by air-conducted tone bursts. Clin Neurophysiol 2010; 121:85–89.
47. Winters SM, Berg ITB, Grolman W, Klis SFL. Ocular vestibular evoked myogenic potentials: frequency tuning to air-conducted acoustic stimuli in healthy subjects and Ménière's disease. Audiol Neurotol 2012; 17:12–19.
48. Zhang AS, Govender S, Colebatch JG. Tuning of the ocular vestibular evoked myogenic potential (oVEMP) to AC sound shows two separate peaks. Exp Brain Res 2011; 213:111–116.
49. Todd NPM, Rosengren SM, Colebatch JG. A utricular origin of frequency tuning to low-frequency vibration in the human vestibular system? Neurosci Lett 2009; 451:175–180.
50▪. Zhang AS, Govender S, Colebatch JG. Tuning of the ocular vestibular evoked myogenic potential to bone-conducted sound stimulation. J App Physiol 2012; 112:1279–1290.

This study on frequency tuning of the vibration-oVEMP in normal individuals compared the reflex across a very wide range of frequencies. The stimulus intensities were carefully matched across frequency, either by holding the peak stimulus force or the peak initial head acceleration constant. The preferred frequency found for both methods was around 100 Hz for both forehead and mastoid stimulation.

51. Zhang AS, Govender S, Colebatch JG. Tuning of the ocular vestibular evoked myogenic potential (oVEMP) to air and bone conducted sound stimulation in superior canal dehiscence. Exp Brain Res 2012; 223:51–64.
52. Zhang AS, Govender S, Colebatch JG. Superior canal dehiscence causes abnormal vestibular bone-conducted tuning. Neurology 2011; 77:911–913.
53. Timmer FC, Zhou G, Guinan JJ, et al. Vestibular evoked myogenic potential (VEMP) in patients with Ménière's disease with drop attacks. Laryngoscope 2006; 116:776–779.
54. Sandhu JS, Low R, Rea PA, Saunders NC. Altered frequency dynamics of cervical and ocular vestibular evoked myogenic potentials in patients with Ménière's disease. Otol Neurotol 2012; 33:444–449.
55. Taylor RL, Zagami AS, Gibson WPR, et al. Vestibular evoked myogenic potentials to sound and vibration: characteristics in vestibular migraine that enable separation from Menière's disease. Cephalagia 2012; 32:213–225.
56. Huang C-H, Wang S-J, Young Y-H. Localization and prevalence of hydrops formation in Ménière's disease using a test battery. Audiol Neurotol 2011; 16:41–48.
57. Taylor RL, Wijewardene AA, Gibson WPR, et al. The vestibular evoked-potential profile of Ménière's disease. Clin Neurophysiol 2011; 12:1256–1263.
58▪. Winters SM, Campschroer T, Grolman W, Klis SFL. Ocular vestibular evoked myogenic potentials in response to air-conducted sound in Ménière's disease. Otol Neurotol 2011; 32:1273–1280.

This study on oVEMPs in patients with Ménière's disease, who were staged according to formal criteria, examined reflex threshold in addition to amplitude. The results showed a high rate of oVEMP abnormality for affected ears and an intermediate rate for clinically unaffected ears compared to control ears.

59. Rosengren SM, Govender S, Colebatch JG. Ocular and cervical vestibular evoked myogenic potentials produced by air- and bone-conducted stimuli: comparative properties and effects of age. Clin Neurophysiol 2011; 122:2282–2289.
60. Cai KY, Rosengren SM, Colebatch JG. Cervical and ocular vestibular evoked myogenic potentials are sensitive to stimulus phase. Audiol Neurootol 2011; 16:277–288.
61▪. Holmeslet B, Westin M, Brantberg K. Ocular vestibular evoked myogenic potentials: skull taps can cause a stimulus direction dependent double-peak. Clin Neurophysiol 2011; 122:391–397.

This study highlights the direction sensitivity of the oVEMP. It explores the potential mechanisms responsible for the changes in reflex polarity and latency that occur with different directions of head vibration.

62. Jombik P, Spodniak P, Bahyl V. Direction-dependent excitatory and inhibitory ocular vestibular-evoked myogenic potentials (oVEMPs) produced by oppositely directed accelerations along the midsagittal axis of the head. Exp Brain Res 2011; 211:251–263.
Keywords:

otolith; vestibular evoked myogenic potential; vestibulo-collic reflex; vestibulo-ocular reflex

© 2013 Lippincott Williams & Wilkins, Inc.