Decoding Age-Linked Masseter Vestibular Evoked Myogenic Potential Changes in Healthy, Aging Individuals

The primary objective of this study was to assess how age influences masseter vestibular evoked myogenic potential (mVEMP) parameters by utilizing 500-Hz tone burst stimuli delivered through air conduction.

The study involved 110 participants ranging from 15 to 60 years of age, grouped into five categories, all of whom had no previous issues related to their vestibular system. The participants were exposed to 500-Hz tone burst stimuli at 125 dB SPL through ER-3A inserts. These stimuli were presented to one ear at a time, with alternating polarity. A Tukey's honestly significant difference test was conducted to compare rectified and unrectified amplitude, along with latencies (P11 and N21) and the asymmetric ratio across all age groups. Additionally, a multivariate analysis of variance was performed to assess the impact of sex on the study variables.

All 110 participants (220 ears) in the study provided mVEMP responses, encompassing 100% of the subjects. The results revealed a significant reduction in both amplitude and latency extension for the P11 and N21 peaks. Interestingly, P11 latency was also prolonged in the youngest participants (Group 1), suggesting ongoing maturation of the system even beyond the age of 16 years. Moreover, a significant sex difference was observed in the P11 latencies. However, there were no substantial sex differences (p > .05) in N1 peak latency, peak-to-peak amplitude, rectified amplitude, and asymmetric ratio.

Changes in structure occur due to degeneration, and the quantity of vestibular sensory hair cells gradually diminishes with age. The rate of decline is faster in semicircular canals compared to end organs, as observed by Merchant et al. (2000). Following a linear degeneration starting at the age of 40 years, a continuous reduction in sensory cells and primary neurons takes place until approximately 40% of vestibular sensory cells are lost by the age of 75 years and insufficient maturation can lead to prolonged peaks and reduced amplitudes compared with those that are considered normal. Therefore, it is crucial to consider the age of the participants when making diagnoses and incorporate relevant correction factors based on age-related reference data.