Differential Involvement of Lateral Semicircular Canal and Otolith Organs in Common Vestibular Disorders

[An analyzation on the characterization of frequency tuning of vestibular evoked myogenic potential in patients with unilateral vestibular hypofunction]

Objective: To explore the value of adding 1 kHz cervical vestibular evoked myogenic potential（cVEMP） and ocular vestibular evoked myogenic potential（oVEMP） in the auxiliary diagnosis of unilateral vestibular hypofunction. Methods:A retrospective analysis of 84 patients with unilateral vestibular hypofunction receiving two or more vestibular function tests was conducted,29 cases of unilateral Ménière's disease, 27 cases of benign paroxysmal positional vertigo （BPPV）, 8 cases of idiopathic sudden sensorineural hearing loss （ISSHL） with vertigo, and 20 cases of ISSHL without vertigo were included. SPSS 25.0 software was used for statistical analysis to observe the difference of frequency amplitude ratio （FAR） at 500 Hz/1 kHz of cVEMP and oVEMP between the experimental and control groups. Results:①The cVEMP elicitation rates were 95.24% （80/84） and 98.81% （83/84） for 500 Hz and 1 kHz, respectively; and the oVEMP elicitation rates were 78.57% （66/84） and 91.67% （77/84） for 500 Hz and 1 kHz, respectively. ②Except for the lateral difference of FAR in oVEMP of the posterior semicircular canal BPPV group and cVEMP of the horizontal semicircular canal BPPV group （P<0.05）, no significant lateral difference was observed in the other disease groups （P>0.05）. Conclusion:In patients with unilateral vestibular hypofunction, cVEMP and oVEMP showed different frequency tuning changes in different semicircular canal BPPV groups. Additionally, 1 kHz cVEMP and oVEMP as regular stimulation frequencies in clinical test, which has certain clinical reference significance for determining the diagnosis and prognosis of BPPV on the weak ear and in different semicircular canal involvement.

High frequency hearing loss may act as a screening index evaluating otolith function in vertigo patients with normal semi-circular canal function

Objective

To investigate whether otolith dysfunction is related to hearing impairment in vertigo patients with normal semicircular canal function, and to clarify the types of hearing impairment that may be related to otolith organ damage.

Methods

The demographic data, pure tone threshold audiometry (PTA) results (air-conduction), data of bithermal and video-head impulse test (vHIT), and vestibular evoked myogenic potential (VEMP) results (reaction threshold, P1–N1 amplitude) of patients with vertigo in outpatient clinic from April 2017 to January 2020 were collected. The clinical records of 51 vertigo patients with normal semicircular canal function were included in this study. Low-frequency, speech-frequency, high-frequency, full-frequency PTA were defined as the average of PTA in different frequency bands, respectively (low: 0.125, 0.25, 0.5 kHz; speech: 0.5, 1, 2 kHz, high: 4, 8 kHz, full 0.125–8 kHz). The correlations between hearing impairment in different frequency bands and otolith function impairment were analyzed.

Results

The mean thresholds of 51 patients (102 ears) in low-PTA, speech-PTA, high-PTA, full-PTA were 20.95 ± 6.01, 21.92 ± 6.90, 40.12 ± 17.47, 26.97 ± 8.53 dB nHL, respectively. Among 102 ears, 87 ears (85.3%) could elicit c-VEMP waveforms and 65 ears (63.7%) had o-VEMP waveforms. The mean threshold and P1–N1 amplitude of c-VEMP were 83.10 ± 6.96 dB nHL and 176.79 ± 103.10 uV, while those of o-VEMP were 87.92 ± 5.99 dB nHL and 21.45 ± 32.22 uV. The mean threshold in high-PTA was significantly linearly correlated with c-VEMP threshold (P = 0.01) and P1–N1 amplitude (P = 0.028). There were not significant linear correlations between the mean threshold in each frequency band of PTA and o-VEMP threshold (low-PTA: P = 0.266, speech-PTA: P = 0.33, high-PTA: P = 0.311) or P1–N1 amplitude (low-PTA: P = 0.414, speech-PTA: P = 0.069, high-PTA: P = 0.08).

Conclusions

There is a positive linear correlation between saccule dysfunction and high-frequency hearing impairment in vertigo patients with normal semi-circular canal function. High frequency hearing loss can be expected in patients who have saccular damage. It suggests that high frequency hearing loss in PTA may act as a screening index that otolith organ function should be comprehensively evaluated.