Effects of age, gender, and frequency.
First one needs to consider what should be recorded. In our view, the most important parameter is simply amplitude. This differs from the situation with cVEMPs, where threshold is probably the most important. The reason for this is that amplitudes grow remarkably with the most important reason to do oVEMPs, SCD, and using amplitude as the main outcome variable is very successful in identifying SCD.
|oVEMP amplitudes in persons at Chicago Dizziness and Hearing, excluding those with diagnosis of SCD (n=1902 ears). Date of data set is 8-2019|
In our clinical practice in Chicago we have done many oVEMPs. In the data shown above, the median oVEMP amplitude is 3 uV, while the mean is 4.4. The mean is larger than the median because oVEMP amplitudes are skewed towards higher values. In other words, the distribution above is not a "normal" distribution and for this reason, one needs to discuss the distribution in non-parametric terms.
The graph above has roughly an order of magnitude more subjects than the studies reported below. It includes everyone who was tested, presenting with dizziness or hyperacusis, excluding those with a diagnosis of SCD. The average age of these individuals was 53.5. We use the Bio-Logic Navpro device, 500 AC Hz tone bursts. This data shows that less than 2% of our dizzy patients had oVEMP amplitudes > 20uV.
|No. Subjects||Age range||N1-P1||SD||Comment|
|Murnane et al, 2011||47||18-34||6||From figure 2 of their paper|
|Piker et al, 2011||50||8-88||10||From figure 2, C of their paper|
|Chihara et al, 2007||10||23-59||7.0||1||Small "n", unreasonable SD.|
|Rosegren et al (2011)||100||3.78||Methods did not involve commercial equipment.|
|Versino et al, 2015||
|Very small response compared to more recent studies.|
The take-home message here is that normal subjects have their strongest oVEMP amplitudes at 500 Hz.
Piker et al (2013) described the frequency and age dependence of oVEMPs.
Subfigure C above from Piker et al.'s paper shows peak-peak amplitudes as a function of both age and frequency. Note that amplitudes at the best frequency, 750, range from about 5 to 15. Clearly 750 Hz is the best frequency for oVEMPs in normal subjects, and clearly oVEMP amplitude drops by roughly a factor of 3 between "young adult" and "old adult". It would seem imprudent to use an "absolute" criterion for amplitude, such as are recommended for SCD, given that they are so strongly dependent on age.
Murame et al (2011) reported a similar dependence of amplitude on frequency, with the best response being at 500 Hz (about 6uV). Overall, a rather close match to Piker's middle age results, although a little lower overall. Murame et al used a GN Otometrics EP200 device to obtain their responses.
Curiously, Rosengren et al (2011), reported very low amplitudes for oVEMPs elicited by tone bursts in 100 subjects, with the mean being 3.78 uV p-p. This may be related to their methodology.
The take-home message is that oVEMPs, like cVEMPs, decrease greatly with age, roughly dropping by a factor of 2 between 20 and 60.
As cVEMPs clearly have a strong dependence on age, and the presumed reason for this is that the otoliths deteriorate with age, one would expect that oVEMP amplitude would also decline greatly with age. So it is logical that oVEMPs are reduced in older persons, just as are cVEMPs.
In our clinical practice in Chicago we have done many oVEMPs. In the data shown above, the average oVEMP amplitude is shown by decade. The graph above has roughly an order of magnitude more subjects than the studies reported below. It includes everyone who was tested, presenting with dizziness or hyperacusis, excluding those with a diagnosis of SCD.
The previously referenced paper of Piker et al (2015) also support this observation. According to Piker et al (2015), "VEMPs in response to air conduction stimuli are bilaterally absent in a large percentage of older patients complaining of dizziness who otherwise have normal vestibular and auditory testing for their age. In combination with other abnormal vestibular findings, an absence of VEMP responses may be of value. However, the functional consequence of an isolated bilaterally absent VEMP is not known and may provide minimal information to an older patient's diagnostic picture. In cases where the response is bilaterally absent, a more intense AC stimulus should be used or bone conducted vibration should be considered."
Li, Layman, Carey and Agrawal (2015) recorded oVEMPs using head taps (rather than sound). This method is not used in the clinic at this time (2018), and thus this oVEMP data is mainly of historical interest. Potentials were very large (compared to those for other methods), and averaged about 25uV for persons less than 50 (there were only 12 of these). The average potential for persons 80 and above was about 11. While the numbers here are not very useful, as they are for an discarded methodology, this paper shows that oVEMP potentials are highly age dependent. It appears that "young adults" for Piker's study had about half the amplitudes as the <50 group in Li et al's study. Oddly, individuals of Black ethnicity had larger oVEMP amplitudes on average than whites (18.5 vs. 12.2). Looking at their graphics, this may be related to some outliers with very large potentials. The study design did not include temporal bone CT scans, which would be needed to exclude SCD. In our opinion, it is unlikely that there is this much of a racial difference with oVEMP amplitudes, and this question needs to addressed again.
Rosengren et al (2011) reported "There was a significant, moderate correlation between age and amplitude for the AC click oVEMP and contralateral BC tone burst oVEMP only, indicating that the responses became smaller with increasing age (clicks r = 0.33, P = 0.009; BC tone bursts r = 0.41, P = 0.001). In as much as more recent papers (as well as our clinical data) find much higher amplitudes of oVEMPs in general, it would seem to us that technique must have advanced since 2011.
Contrary to the assertion that oVEMP amplitudes decline with age, Versino et al (2015), found almost no dependence of oVEMP amplitude on age in roughly 50 normal subjects, even though the amplitudes were clearly smaller in older patients. This was likely just an insufficient sample as they comment about the immense variability of oVEMP amplitudes. This paper is also difficult to interpret as amplitudes were roughly an order of magnitude smaller (about 1 uV), compared to the much larger oVEMP amplitudes reported in the rest of the literature.
Sung et al (2010) reported that the mean AC oVEMP amplitude was significantly larger in males than females. This was a study comparing only 10 males and females, in Taiwan. The average in males was 11.8+-6.2, and in females, 7.4+-3.2. Based on this small sample, they suggested that amplitudes should not be used for reporting of oVEMPs.
We just don't agree, based on many more subjects than this study. Data gathered in our clinical practice in Chicago suggested that women have slightly higher average oVEMP amplitudes than men, 4.6 uv versus 4.27 for men. This is based on 310 males and 458 females, with an average age of 53.4. One would expect higher average oVEMPs in youth, and lower in seniors.
The take home message here is that amplitude ratios are normed similarly to caloric tests, but it doesn't really matter much because diagnoses of SCD are made from amplitude. It may be that asymmetry in oVEMPs does matter, but so far clinical data has not been forthcoming.
|No. Subjects||Age range||Mean AR(%)||SD||Mean + 2SD (%)|
|Murnane et al, 2011||47||18-34||18.6||11.6||41.8|
|Piker et al, 2011||50||8-88||14||10.0||34|
|Chihara et al, 2007||10||23-59||19.3||8||35.3|
|Park et al, 2010||20||24-34||31||6||43|
(first version of data table courtesy of Ploy Maroongroge, Au.D., as of 2017)
This literature base is not impressive -- there were a little less than 130 normal subjects here in the world literature, and their ages are a bit variable. We think 35% is a reasonable pick for asymmetry ratio.
With respect to the latency, the mean latency (according to Kantnor and Gurkov, 2012) ranges from 13.3 to 17.9. Rosengren et al (2011) studied 61 subjects at 132 dB SPL (somewhat high), and suggested mean latency was 15.4+-1.3. At this writing, latency does not seem a very useful quantity.