Characterizing the impact of advancing age on 500 Hz tone-burst evoked ocular-vestibular evoked myogenic potentials

Clinical significance of posterior expansion of the utricular endolymphatic space

BACKGROUND

Posterior expansion of the utricular endolymphatic space (ES) is a finding occasionally observed, and often occurs in bilateral ears. The clinical significance of posterior expansion of the utricular ES is not clear.

OBJECTIVES

To investigate the clinical significance of posterior expansion of the utricular ES detected on magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Among 957 patients who underwent contrast-enhanced MRI to investigate the presence of endolymphatic hydrops (EH), clinical findings in cases with posterior expansion of the utricular ES were evaluated and the significance of their existence is considered.

RESULTS

Posterior expansion of the utricular ES was detected in 30 ears from 20 cases (7 males, 13 females; mean age 48.7 years). The ears with posterior expansion had a significantly lower incidence of vestibular EH than those without, and this tendency was more prominent in cases in bilateral ears. Some cases with posterior expansion had vestibular symptoms and were diagnosed with Ménière's disease, although EH was not detected in their vestibules.

CONCLUSION AND SIGNIFICANCE

Posterior expansion of the utricular ES was associated with Ménière's disease without vestibular EH. Posterior expansion of the utricular ES might not be associated with the formation of EH but may occur independently.

Influence of the Electrode Montage to Detect Ocular Vestibular Evoked Myogenic Potentials

OBJECTIVE

To compare ocular vestibular evoked myogenic potentials (oVEMPs) obtained with three different electrode montages (infra-orbital vs belly-tendon vs chin) in a group of healthy subjects. To assess the electrical activity recorded at the level of the reference electrode in the belly-tendon and chin montages.

STUDY DESIGN

Prospective study.

SETTING

Tertiary referral center.

PATIENTS

Twenty-five healthy adult volunteers.

INTERVENTIONS

Each ear was tested separately via air-conducted sound (500 Hz Narrow Band CE-Chirps at 100 dB nHL) for recording contralateral myogenic responses. Recording conditions were randomized.

MAIN OUTCOME MEASURES

n1-p1 amplitudes values, interaural amplitude asymmetry ratios (ARs) and response rates.

RESULTS

The belly-tendon electrode montage (BTEM) produced larger amplitudes than the chin ( p = 0.008) and the IOEM (infra-orbital electrode montage; p < 0.001). The chin montage displayed larger amplitudes than the IOEM ( p < 0.001). The interaural amplitude asymmetry ratios (ARs) were not affected by the different electrode montages ( p = 0.549). In 100% of cases, oVEMPs were detected bilaterally with the BTEM which is higher than with the chin and the IOEM ( p < 0.001; p = 0.020, respectively). We did not record any VEMP when placing the active electrode on the contralateral internal canthus or the chin and the reference electrode on the dorsum of the hand.

CONCLUSIONS

The BTEM increased the amplitudes recorded and response rate in healthy subjects. No positive or negative reference contamination was observed with the belly-tendon or chin montages.

Effects of aging on ocular vestibular-evoked myogenic potential using ER-3A insert earphone and B81 bone vibrator

Purpose

Aging is a process associated with degeneration and dysfunction of peripheral vestibular system or apparatus. This study aimed to investigate the influence of aging on ocular vestibular-evoked myogenic potential (oVEMP) response rates and recording parameters using the B81 bone vibrator and compare them with air conduction stimuli (ACS) oVEMP response characteristics.

Methods

In 60 healthy participants aged 10–71 years (mean age 39.9; 29 male participants), the oVEMP response was elicited using a B81 bone vibrator and an ER-3A insert earphone. The effects of age and stimulus on oVEMP response rates and recording parameters were evaluated.

Results

Response rates and amplitudes declined with aging using either ACS or bone-conducted vibration (BCV) stimulation, particularly in individuals over 60 years of age, whereas thresholds increased and N1 latencies were prolonged. BCV showed fewer risks of absent oVEMP response than ACS (p = 0.002). BCV acquired higher amplitudes (p &lt; 0.001), lower thresholds, and shorter N1 and P1 latencies (all p &lt; 0.001) than ACS.

Conclusions

The absence of an oVEMP response may be attributed to aging rather than a concurrent vestibular disorder. B81-BCV likely produces higher mechanical drives to the vestibular hair cells at safer and non-traumatic levels compared with ACS and therefore may be more likely to evoke a response in the elderly cohort, whose vestibular function and mechanical sensitivity have declined. Thus, B81-BCV stimulation is more effective and safer to elicit oVEMPs, and it should be recommended when ACS fails in the clinic, particularly in the elderly population.

B81 Bone Vibrator-Induced Vestibular-Evoked Myogenic Potentials: Normal Values and the Effect of Age

Objective

To define the normal values and examine the influence of aging on B81 bone vibrator-induced cervical vestibular-evoked myogenic potentials (B81-cVEMPs) and ocular vestibular-evoked myogenic potentials (B81-oVEMPs).

Methods

Seventy healthy subjects, divided into seven groups according to their ages, were enrolled in this study. The 4–9-, 10–19-, 20–29-, 30–39-, 40–49-, 50–59-, and 60–70-year-old participants were divided into groups I–VII, respectively. B81-cVEMP and B81-oVEMP were recorded in each group.

Results

The B81-cVEMP response rates for groups I–VII were 100, 100, 100, 100, 95, 95, and 75%, respectively, with significant differences only between groups I–VI and group VII (p = 0.047, p &lt; 0.05). The B81-oVEMP response rates for groups I–VII were 100, 100, 100, 100, 70, 65, and 40%, respectively, with significant differences only between groups I–IV and groups V–VII (p = 0.020, p = 0.008, p = 0.000; p &lt; 0.05). The threshold, P13, and N23 latencies of B81-cVEMP positively correlated with age (r = 0.756, p = 0.000; r = 0.357, p = 0.003; r = 0.316, p = 0.009; p &lt; 0.05). The raw amplitudes and corrected amplitudes negatively correlated with age (r = −0.641, p = 0.000; r = −0.609, p = 0.000, p &lt; 0.05). For B81-oVEMP, the corrected amplitudes negatively correlated with age (r = −0.638, p = 0.000, p&lt;0.05), but the threshold and N10 latency positively correlated with age (r = 0.768, p = 0.000; r = 0.334, p = 0.009, p &lt; 0.05). Moreover, the interaural asymmetry ratio did not significantly correlate with age for B81-cVEMP and B81-oVEMP.

Conclusion

As age increased, the B81-cVEMP response rate decreased, the thresholds increased, P13 and N23 latencies were prolonged, and the raw amplitude and corrected amplitude decreased. The B81-oVEMP response rate and corrected amplitude decreased, the thresholds increased, and N10 latency was prolonged with age. These changes are probably due to the occurrence of morphological and functional changes in the vestibular system with aging. Therefore, we suggest establishing different reference values according to different age groups when evaluating the VEMP results in patients with vestibular diseases.

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

BACKGROUND

Upward shift in the air conducted (AC) frequency tuning of vestibular evoked myogenic potentials (VEMPs) as an effect of aging is hypothesized to be due to the microstructural stiffening changes in the inner ear. However, with an AC stimulus, it may be possible that the shift in the frequency tuning of VEMPs as an effect of aging may also be due to contributions from the middle ear.

PURPOSE

The main aim of this study was to examine the effects of age on the frequency tuning of the cervical VEMP (cVEMP) and ocular VEMP (oVEMP) and determine the role of middle ear transmission characteristics in shaping these effects.

RESEARCH DESIGN

Standard group comparison.

STUDY SAMPLE

One-hundred seven participants divided in three groups: young adult, middle-age, and older adults with "normal" middle ear and negative history of neurological or vestibular complaints.

DATA COLLECTION AND ANALYSES

Middle ear measures included static admittance and middle ear resonant frequency. cVEMP and oVEMPs were elicited with AC tone bursts at 500, 750, and 1,000 Hz.

RESULTS

No significant effect of age was observed on any of the middle ear measures. There was a significant effect of age on the amplitude of the cVEMP, but this effect was frequency specific. The age-related reduction in cVEMP corrected amplitude was only observed when the eliciting stimulus was 500 or 750 Hz, with no significant effect observed with a 1,000 Hz stimulus. For the oVEMP, the effects of age were apparent at all stimulus frequencies. We also observed a general upward shift in the frequency tuning of both the cVEMP and oVEMP for middle-age and older adults, with 750 and 1,000 Hz yielding higher response rates and larger amplitudes among middle-aged and older adults. Measurements of middle ear did not significantly contribute to the observed findings.

CONCLUSIONS

The upward shift in frequency tuning of VEMPs among middle age and older adults could be due to the changes in the vestibular system and not from the middle ear. These results support the use of different frequency stimuli (i.e., 750 or 1,000 Hz) to elicit a VEMP if a response is absent using a 500 Hz stimulus, especially in patients over the age of 40.