A Study of Relationship between the Acoustic Sensitivity of Vestibular System and the Ability to Trigger Sound-Evoked Muscle Reflex of the Middle Ear in Adults with Normal Hearing

Introduction & The vestibular system is sound sensitive and the sensitivity is related to the saccule. The vestibular afferents are projected to the middle ear muscles (such as the stapedius). The goal of this research was studying the relationship between the vestibular hearing and the sound-evoked muscle reflex of the middle ear to 500 HZ. This study was a cross sectional-comparison done in audiology department of Sheikholreis C‍‍linic (Hamadan، Iran). The study groups consisted of thirty healthy people and thirty patients with benign paroxysmal positional vertigo. Inclusion criteria of the present study were to have normal hearing on pure tone audiometry، acoustic reflex، and speech discrimination scores. Based on ipsilateral acoustic reflex test at 500HZ، they were divided to normal and abnormal groups. Then they were evaluated by cervical vestibular evoked myogenic potentials (cVEMPs) and finally classified in three groups (N) Normal ear، (CVUA) Contra lateral vertiginous ear with unaffected saccular sensitivity to sound، (IVA) Ipsilateral vertiginous ear with affected saccular sensitivity to sound. Thirty affected ears (IVA) with decreased vestibular excitability as detected by ab-normal cVEMPs، revealed abnormal findings of acoustic reflex at 500HZ. Whereas، both un-affected (CVUA) and normal ears (N) had normal results. Multiple comparisons of mean values of cVEMPs (p13،n23) and acoustic reflex at500HZ among the three groups were sig-nificant. The correlation between acoustic reflex at 500HZ and p13 latencies was significant. The n23 latencies showed significant correlation with acoustic reflex at 500HZ. The vestibular sensitivity to sound retains the ability to trigger sound-evoked re-flex of the middle ear at 500 HZ.