Normal membranous labyrinth
Dilated membranous labyrinth in Meniere's disease (Hydrops)
There have been several hypotheses offered concerning why VEMP testing might be useful in diagnosing Meniere's disease, or the related problem of endolymphatic hydrops. These trains of thought result in several conjectures that are in part conflicting and also are somewhat illogical. Fife et al (2017) stated that "All 8 studies on Meniere disease are class II, most of which were downgraded because of spectrum bias". In other words, the studies are not the best. Fife et al concluded "There is insufficient evidence that either cVEMP or oVEMP may be used to diagnose Meniere disease".
The logic about Meniere's and VEMP's is as follows:
One can also broadly criticize all studies of VEMPs in that the core dogma driving the enthusiasm in doing VEMP tests is implausible. The core dogma is that things are very simple, allowing one to make diagnostic inferences. While not emphasized much in the literature, VEMP tests likely involve input from many senses, and are not confined to saccule or utricle inputs as has been suggested. It is also implausible that the wiring is "unilateral". Thus we have a large clinical database that has not produced very impressive results, perhaps based on an oversimplified idea about how the ear is wired up to the nervous system.
In our own (large) clinical experience, we have not found cVEMP's to be of any use in Meniere's disease. However, others have reported different experiences.
It has been reported that low amplitude of cVEMPs may be found in the affected ear (Waele, 1999) and a substantial proportion of subjects show no cVEMP, or a higher threshold (Rauch et al, 2004), or a lower amplitude ratio (Kim et al, 2013; Jariengprasert et al, 2013; Egami et al, 2013)-- this is hypothesis 1 from above. Absent cVEMPs in advanced disease may represent collapse of the saccule. The abnormalities are not impressive -- for example, Kim et al reported about 20-30% sensitivity. Egami et al (2013) wrote that "the sensitivity and specificity of VEMPs in diagnosing MD were not high". Kigma and Wit (2011) similarly stated "The diagnostic value of VEMP amplitude asymmetry measurement in individual patients is low, because of the large overlap of the VEMP amplitude asymmetry range for unilateral Meniere patients with that for normal subjects."
cVEMP amplitudes can be increased in early Meniere's disease, as well as fluctuate oppositely to hearing, perhaps due to saccular dilatation (Young et al, 2002) -- hypothesis 2 from above.
One might also logically suppose that there should be a point in which the saccule is normal in size, in the middle. It seems to us that these observations just suggest that cVEMP's can be any size in Meniere's disease -- big, normal or small, and that they are unlikely to be useful for diagnosis.
Rauch and associates have reported that cVEMP's show different "tuning" in Meniere's disease -- hypothesis 3 from above. The idea seems to be that as patients with Meniere's have a low-tone hearing loss, they might also show alteration at low-tones in VEMP's. In our opinion, this is not a very logical idea as the cochlea and saccule have very different mechanical organizations. Nevertheless, in several papers, Rauch and colleagues showed that the 500 hz tone-burst cVEMP has the lowest threshold, and that this "favoring" of 500 hz over 250 and 1K is largely lost in persons with Meniere's disease (Rauch et al, 2004). It is our feeling that in addition to being a dubious idea, this is simply impractical. It is just too difficult to obtain cVEMP thresholds at 3 frequencies.
It has been proposed that cVEMPs that increase on glycerol loading or furosemide injection are suggestive of Meniere's disease (Shojaku et al, 2002; Seo et al, 2003). This idea expresses the opposite idea as hypothesis 2. We would like to see confirmation of this by others. If enlarged cVEMPs are due to saccular dilatation (hypothesis 2), one would expect the opposite effect.
Rauch et al reported that threshold differences in cVEMPs, particularly at 250 hz, were about 80% accurate in detecting the side of lesion in persons already known to have Meniere's disease from audiometric and clinical data (Rauch et al, 2004). Lacking a pathological "gold standard" diagnosis, however, it is difficult to know how to interpret this observation.
Osei-Lah and others (2008) reported that the mean interaural amplitude difference ratio is significantly higher in stable Meniere's disease as compared to acute Meniere's disease. Thresholds and latencies were not useful. We are not sure what this means.
VEMP's may be useful in monitoring low-dose gentamicin treatment for Meniere's disease though, because VEMP's are reduced in this situation (Helling et al, 2007; Picciotti et al, 2005: Gode et al, 2011). So far, we have seen some confirmation of this idea. Look here for a case illustration. We tentatively think that it is a good idea to get a VEMP prior to ITG, and another one if there appears to be a treatment failure. On the other hand, a VHIT test may do equally as well, and it is quicker/easier. Some report that IT gentamicin has little effect on the utricle/saccule. We are dubious about this, but there it is.
Some report that oVEMPS are useful in Meniere's disease. As of 2016, it is too early to know about this for sure, but it seems unreasonable that oVEMPs should work but cVEMPs not work. It is always easier to get positive papers published than negative papers. For the time being, we think that oVEMPs are probably ineffective as a diagnostic tool for Meniere's disease.
Winters et al (2011) reported lower amplitudes and thresholds in AC oVEMPs, in MD compared to normal controls. Johnson et al (2016) reported that Meniere's patients exhibit elevated thresholds in the affected ear compared with the unaffected ears, but not with controls. There were a number of other puzzling findings. Overall, they concluded that there was overlap in results from Meniere's patients compared to normal controls. This seems very reasonable.
Winters et al (2011) suggested that oVEMPS in Meniere's patients generally showed lower amplitudes and higher frequencies than normal subjects, and also that the best stimulus in MD patients was 1000 hz.
Above is a FAR/OVEMP test for a patient who does NOT have Meniere's disease. The response at 1000 hz is larger than 500 on the left, and the same on the right. The ratios are 1.24 on the left and 0.94 on the right. This is higher than the criteria suggested by Singh/Barman (see below), and by their criteria would be called Meniere's disease. We use exactly the same equipment and protocol of Singh/Barman. But this patient doesn't have Meniere's disease ...
Singh and Barman (2016) reported that the Frequency-Amplitude Ratio (FAR) was extremely effective in separating patients with Meniere's from normal controls. This involves presenting the same stimulus, in terms of 125 SPL, at two different frequencies (e.g. 500 and 1000). They reported that the ratio of 1000/500 was only 0.61 +- 0.23 in normal subjects, while it averaged 1.60 (+- .70) for the affected ear of individuals with Meniere's disease. For the receiver operating characteristic, they said that the sensitivity was 90% for the 1000/500 pair, using a criterion of positive for a FAR > 0.92. We find this amazing -- it is rare that any test performs at a sensitivity of 90% and 100% specificity ! Furthermore, we have no idea why oVEMPs should be stronger at 1000 hz in Meniere's than in normal subjects. One would think that there would be a stronger oVEMP, for the same SPL, at frequencies close to the resonance of the middle ear (about 2000), and thus one would guess that oVEMPs would be strongest at about 2000. The Singh/Barman paper above does not provide this kind of data, and in particular, do not present the absolute values for the oVEMP -- just the ratios. They did consider the idea that the resonance would predict more energy at higher frequencies. Perhaps there is a "ceiling" effect in normal subjects, that goes away in damaged ears ? A lot more work needs to be done here. Overall, we find this idea very dubious -- there is no real rationale for VEMPs to be larger at high frequencies in Meniere's disease -- the utricle is not like the cochlea and does not have "low tone hearing loss".
Murofushi et al (2016) found normal oVEMPs in 2 patients with low-tone hearing loss, implying that hydrops does not affect the oVEMP. This is just too few patients to draw any conclusions at all.
Taylor et al (2011) compared AC, and BC VEMPS (both cVEMP and oVEMP) and reported higher sensitivity for AC (33%) vs. BC. Huang et al (2011) also found that air conducted VEMPS, especially cVEMPS (45%), were the most sensitive study for Meniere's disease. Bone conducted cVEMPS and oVEMPS were only 25% sensitive. These observations are not consistent with the idea that these responses are wired unilaterally, as BC is a more effective way of delivering stimulus than AC, but might make sense if one took the more reasonable approach that BC is a "sloppier" stimulus that excites everything (i.e. auditory, utricle, saccule, canals, proprioception), which is less specific for unilateral disease than AC which does not excite to any great extent the canals or proprioception.
There have also been occasional papers about delayed endolymphatic hydrops, which in essence is a variant of Meniere's.
Okhi et al (2002) reported on "VEMPS" in contralateral DOH. 5 of 9 ears with profound hearing loss had no VEMP. On the contralateral side, 6 also had no VEMP's, but in 4 patients who had the glycerol test, 2 regained their VEMP.
Okhi wrote a second paper in 2002 on patients with ipsilateral DOH. Hm. They reported that VEMPs were nearly all normal on the contralateral, normal side. No surprises here.
Young et al (2002), suggested that retained VEMPs after profound hearing loss might predict future development of DEH.
As of 2017, there is little evidence that any type of VEMP is sufficiently sensitive to be useful for diagnosis of Meniere's disease. Their main role is to diagnose other illnesses that might be confused with Meniere's, and possibly to predict whether gentamicin injection for Meniere's was effective.