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DOI: 10.1055/s-0042-1757930
Stimulus for Simultaneous Multifrequency (SiMFy) oVEMP: A More Efficient Approach for Determining Otolith Tuning
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The frequency-tuning properties of the otolith system are driven by the mass and stiffness of the organs and can vary depending on several factors such as age and disease. Although vestibular evoked myogenic potential (VEMP) responses can be extremely variable in terms of amplitude, depending on the stimulus used, they can offer helpful insight into different disease processes. What is challenging is that, in the vestibular laboratory, clinicians are often attempting to gather as much diagnostic data as possible in a limited amount of time.
Over the last three decades, the contemporary vestibular assessment has expanded to include VEMPs, video head impulse testing, ocular torsion, and other assessments. It can be a challenge for clinicians to take a comprehensive case history in addition to completing a full vestibular diagnostic workup and counsel on results. Accordingly, techniques such as the monothermal warm caloric test have been developed and validated to shorten testing, yet keep the tests sensitive and specific.
With the addition of the ocular and cervical VEMP assessments to the vestibular test battery, novel information regarding the otolith system can now be obtained. In most instances, laboratories will test the VEMP at 500 Hz, which has been shown to generate the largest responses in normal subjects, and perhaps do a threshold search. However, it is well documented in the literature that testing at more than one frequency can provide the clinician with additional insight into the underlying pathophysiology of different inner-ear conditions.
Some of the earliest work investigating the frequency tuning of the VEMP comes from those investigators interested in the aging inner ear. For example, when the frequency tuning of the VEMP in young adults was compared to older adults, the best response was obtained from a higher frequency stimulus in the older group (Piker et al., 2013).[1]
More recently, the tuning of the VEMP has been shown to be altered in patients diagnosed with Ménière's Disease. In fact, it has been reported that patients with Ménière's Disease often demonstrate their largest amplitude responses using 1000 Hz stimuli rather than 500 Hz, which is typically the optimal stimulus frequency in patients with no history of otologic disease (Rauch, 2004).[2] The hypothesis is that, because of the presence of endolymphatic hydrops, the vestibular system becomes stiffer.
Another application for multifrequency VEMP testing can be found with patients presenting with superior semicircular canal dehiscence. This disorder occurs where there is a thinning or absence of the bony covering of the superior semicircular canal. Typically, these patients will demonstrate lower VEMP thresholds and larger amplitudes when tested at 500 Hz. One screening procedure set forth by Manzari and colleagues (2013)[3] showed that, in “normal” ears, a VEMP should not be present when a 4 kHz stimulus is used. In dehiscent ears, it is possible to record a measurable VEMP.
With compelling evidence emerging from numerous laboratories regarding the value of multifrequency testing, there is no question that we as clinicians should be using this method to help aid in the differential diagnosis of the vestibular disorder. In this issue of the Journal of the American Academy of Audiology, Singh and his team address this very issue.
Their technique, referred to as Simultaneous Multifrequency (SiMFy) Stimulus, is shown to be able to deliver a time-saving and reliable stimulus for the purpose of quickly mapping the tuning to the utricle. It is innovative work such as this that not only provides diagnostically useful information to the clinician, but also does it in an efficient manner. I encourage you to read this interesting article that is an excellent example of how clinical research can transform practice.
Publication History
Article published online:
18 November 2022
© 2022. American Academy of Audiology. This article is published by Thieme.
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References
- 1 Piker EG, Jacobson GP, Burkard RF, McCaslin DL, Hood LJ. Effects of age on the tuning of the cVEMP and oVEMP. Ear Hear 2013; 34 (06) e65-e73
- 2 Rauch SD, Zhou G, Kujawa SG, Guinan JJ, Herrmann BS. Vestibular evoked myogenic potentials show altered tuning in patients with Ménière's disease. Otol Neurotol 2004; 25 (03) 333-338
- 3 Manzari L, Burgess AM, McGarvie LA, Curthoys IS. An indicator of probable semicircular canal dehiscence: ocular vestibular evoked myogenic potentials to high frequencies. Otolaryngol Head Neck Surg 2013; 149 (01) 142-145 DOI: 10.1177/0194599813489494.