Improvement of Stapedial Muscle Reflex Threshold by Acoustic Sensitivity of the Saccule

Acoustic sensitivity of the human vestibular system has long been established and can be demonstrated by means of the cervical vestibular evoked myogenic potential (cVEMPs). The objective of this cross-sectional study is to investigate the possibility that the acoustic sensitivity of the saccule improves stapedial muscle reflex threshold. Twenty healthy persons and twenty-five patients as having unilateral benign paroxysmal positional vertigo (BPPV) investigated in our audiology department (Hamadan, Iran). The assessments consisted of pure-tone audiometry, tympanometry, stapedial muscle reflex testing, video-nystagmography, and cVEMPs. We compared findings among the three groups (the healthy, the affected and the unaffected ears of the patients with unilateral BPPV). The affected ears had delayed latencies of first waveform (p13-n23) of the cVEMPs with normal ipsilateral stapedial muscle reflex threshold to 1000, 2000 and 4000 Hz, but delayed to 500 HZ. The healthy and the unaffected ears had normal findings. Multiple comparisons of mean p13 and mean n23 latencies between three groups were significant (Pp13 = 0.037, Pn23 = 0.041, ANOVA). Comparisons of mean p13 and mean n23 latencies in the affected ears vs the healthy ears were significant (Pp13 = 0.044, Pn23 = 0.046, Tukey HSD). Then, saccular afferents may give rise to a response in excitation of the stapedius and acoustic sensitivity of the saccule improves stapedial muscle reflex threshold to low frequency. Consequently, the new application of cVEMPs test is the prediction of the possibility of ipsilateral stapedial muscle reflex to 500 HZ.