Abstract: Objective　To investigate the association between sudden deafness (SD) and morphological character of anterior inferior cerebellar artery loop and jugular bulb.　Methods　MRI scanning and three-dimensional reconstruction of inner ear was observed in 80 patients with sudden deafness of unilateral outset (80 ears) and 36 healthy adults (72 ears). The SD group consisted of patients with SD of unilateral outset (80 ears) and the control group consisted of healthy adults (72 ears). The primary endpoints: (1) whether anterior inferior cerebellar artery loop juts out into the internal auditory canal (IAC), (2) the spatial relationship between the anterior inferior cerebellar artery loop, the facial nerve and the cochleovestibular nerve, (3) the spatial relationship between the jugular bulb and surrounding structures.  Results　(1) Proportion of anterior inferior cerebellar artery loop jutting out into IAC did not differ in both groups: 35 ears (43.8%) in the SD group and 29 ears (40.3%) in the control group, P=0.665. (2) Neither did the proportion of different types that were classified by spatial relationship between the anterior inferior cerebellar artery loop, the facial nerve and the cochleovestibular nerve. 9 superior type (11.3%), 53 medial type (66.3%) , 11 inferior type (13.8%), 7 anterior type (8.8%)  and no posterior type could be observed in the SD group.  8 superior type (11.1%) , 46  medial type (63.9%), 11  inferior type (15.3%), 7 anterior type (9.7%) and no posterior type could be observed in the control group, P=0.771. (3) The proportion of jugular bulb types differed significantly between two groups. 2 were type I (2.5%) , 40 medial type Ⅱ(50.0%), 36type Ⅲ (45.0%) , 2 type Ⅳ(2.5%) in SD group. There were no type I, 19 type Ⅱ(26.4%) , 46 type Ⅲ (63.9%), 7 type Ⅳ (9.7%)  in the control group( P＜0.001).     Conclusion    Different jugular bulb subtypes are associated with higher risk of SD. Jugular bulb type Ⅱ is associated with high risk of SD among type I, Ⅲ and Ⅳ. Whether the anterior inferior cerebellar artery loop juts out into IAC and the relationship among the anterior inferior cerebellar artery loop, the facial nerve and the cochleovestibular nerve are not associated with higher risk of SD.

Key words: Sudden deafness;Anterior inferior cerebellar artery loop;Jugular bulb, Magnetic resonance image