The Effects of Age and the Middle Ear on the Frequency Tuning of the cVEMP and oVEMP.

Abstract

The featured article thismonth is a paper byour colleagues at James Madison University, Jha, Piker, and Romero. The title of the paper is “Effects of Age and Middle Ear on the Frequency Tuning of the cVEMP and oVEMP.” When a new method of assessment is developed, a flurry of activity normally occurs. This activity usually is focused on the determination of the optimal stimulating, subject, and recording variables. Also, we need to know what constitutes normal and abnormal performance on the new metric. The introduction to our profession of the cervical and ocular vestibular evoked myogenic potentials (cVEMP and oVEMP, respectively) was no exception. Clinical laboratories throughout the nation and the world contributed to this knowledge base. Among the many observations emanating from the international scientific community was that neither the cVEMP nor the oVEMP were present 100 percent of the time in “normal” subjects. In fact, Su and colleagues (2004)1 suggested that up to approximately 40 percent of “normal” individuals over the age of 60 years could be expected to fail to generate a cVEMP. Our group (Piker et al. 2013)2 and others have attempted to identify variables that are responsible for the absence of these evoked responses in “normal” subjects. Where the oVEMP is concerned, part of the explanation was attributable to the location of the inverting (i.e., reference) input (Piker et al. 2018).3 It was observed that, when the contralateral inverting electrodewasplaced immediately inferior to the non-inverting electrode input, there was a significant amount of reference contamination (i.e., cancellation of the evoked responsebecause the inverting electrode contained a significant amount of the non-inverting input). For the cVEMP, it was observed that the presence of the response often was absent when the stimulus was a 500Hz tone burst, but might be present when a higher frequency stimulus (e.g., a 750Hz or 1000Hz tone burst) was used as the evoking stimulus. When this observation was studied systematically, it was shown that subject age is a significant variable in the recording of VEMPs. In general, it was shown that older individuals (e.g.,>60 years) were more likely to generate VEMPs if the stimulus is>500Hz. It is significant that, for most clinical investigations, a 500Hz tone burst is the recommended stimulus frequency. This brings us to the current investigation. In this study, the investigators added to what we know by assessing the effect of tone burst frequency and middle ear status on the recording of cVEMP and oVEMP. They evaluated 107 subjects that were divided into three groups (young, middle-aged, and older adults). The researchers recorded VEMPs in response to 500Hz, 750Hz, and 1000Hz tone bursts. Further, theymeasured static admittance andmeasures ofmiddle ear resonant frequency. I am not going to give away the results of the study, but will say that they contribute significantly to our knowledge base on VEMP testing and have motivated me to alter my recording techniques.