Abstract： Objective To investigate MR imaging features of endolymphatic sac and vestibular aqueduct in patients with large vestibular aqueduct syndrome (LVAS) and its correlation with hearing loss.Methods MR imaging findings of LVAS were analyzed in 31 cases (62 ears) retrospectively.MR imaging features were grouped into 4 types.In the first type,the signals of endolymphatic and vesitibular aqueduct were hypointense without any hyperintense area.In the second type,the signals of endolymphatic sac and vestibular were hyperintense which were confined within vestibular fissure.In the third type,the area from vestibular aqueduct backward out of the edge of the petrous bone was hyperintense,but its lower boundary was above posterior semicircular.In the fourth type the area which was hyperintense was below the posterior semicircular.To avoid errors in visual inspection,the hyperintense and hypointense area of endolymphatic and the signal intensity of vestibular aqueduct and cerebrospinal fluid (CSF) were measured.The differences of signal intensity among the vestibular endolymphatic sac between the high-signal areas and lowsignal areas were compared with paired t-test.The correlation of the endolymphatic sac MRI classification and degree of hearing loss was analyzed by corrected Chi-square test and Spearman correlation analysis.Result Ten ears belonged to type Ⅰ (moderate hearing loss in 1 ear,severe in 4 ears,profound in 5 ears),17 ears belonged to type Ⅱ ( moderate hearing loss in 1 ear; severe in 5 ears,profound in 11 ears),23 ears to type Ⅲ (moderate hearing loss in 3 ear,severe in 5 ears,profound in 15 ears) and 12 ears belonged to Ⅳ(mild hearing loss in 1 ear,moderate in 1 ear,severe 3 ear,profound in 7 ears).The boundary between hyperintense and hypointense area was clear,and the signal intensity ratios was 2.02 ± 0.06.The signal ratios of hyperintense and hypointense area to vestibular and CSF were 0.95 ±0.12,0.49 ±0.10,0.99 ± 0.08 respecitively.So there was statistical significant difference between hyperintense and hypointense area ( t =- 24.966,P ＜ 0.05 ),but there was no statistical significant difference between hyperintense area and vesitbular( t =-24.966,P ＞ 0.05).There was no difference of hearing loss between different MRI types ( likelihood ratio =5.02,P ＞ 0.05 ).Conclusions Not only endolymphatic sac enlarged but also perilymph herniated into skeletal fissures of vestibular aqueduct in patients with LVAS.The signal intensity of the endolymphatic sac did not show significant correlation with degree of hearing loss.