Research And Analysis With Relevant Examinations About Vestibular Function And Audiometry In Large Vestibular Aqueduct Syndrome

ObjectiveBy the means of recording and analyzing vestibular evoked myogenic potentials (VEMP) , subjective visual vertical(SVV),caloric test and pure tone audiometry(PTA) in large vestibular aqueduct syndrome(LVAS),we may reveal the function of saccule,utricle,vestibular (mainly the horizontal semicircular canal) and vestibular nerve in LVAS.We may also reveal the relationship between the function of vestibular and the characteristic of audiology..MethodsWe summarized and analyzed the results of the examination and clinical symptoms of 22 cases of LVAS (42 affected ear) and 20 cases of control group who were all underwent VEMP, SVV, caloric test and PTA.Results25 of 42(59.5%) affected ears witch were exited by VEMP showed high amplitude and/or low threshold; In the low-threshold group of VEMP, the mean value of vestibular aqueduct was (4.30±0.53) mm, 19 ears were easily influenced by the external factors or the fluctuations of internal cranial pressure caused by fever. And 30 of 42(71.4%) affected ears were exited by PTA showed mixed hearing loss with the feature of significant air-bone gap in low and intermediate frequency (below 2KHz).Compared with the control group ,LVAS patient group had no significant difference (P> 0.05) on P13, N23 average incubation period of VEMP examination, while the VEMP average amplitude and average thresholds were significantly different (P <0.01); And compared with the control group, LVAS patients group had no significant difference on SVV and caloric test in statistics (P> 0.05).Conclusions1. Most LVAS patients witch were exited by VEMP showed high amplitude and/or low threshold, and most affected ears witch were exited by PTA showed mixed hearing loss with the feature of significant air-bone gap in low and intermediate frequency. These may be caused by the existence of the "Third window".2. In LVAS patients group,the average value of vestibular aqueduct diameter is larger in the patients with lower VEMP threshold whose subjective hearing are affected by the external factors or the fluctuations of internal cranial pressure caused by fever more easily. But there's no correlation between the degree of the hearing loss with the mean value of vestibular aqueduct, neither with the characteristics of VEMP.3. Compared with the nomal group ,LVAS patient group had significant difference on VEMP examination, but had no significant difference on SVV and caloric test. Thus we can speculated that mutation of the large vestibular aqueduct may only affected the function of the balloon, but little affected the function of utricle and vestibular (mainly the horizontal semicircular canal).