The positional relationship between facial nerve and round window niche in patients with congenital aural atresia and stenosis

To investigate whether differences existing in the distance between facial nerve (FN) and round window niche opening among congenital aural atresia (CAA), congenital aural stenosis (CAS) and a normal control group and to assess its effect on the round window implantation of vibrant soundbridge, CT images of 10 normal subjects (20 ears), 27 CAS patients (30 ears) and 25 CAA patients (30 ears) were analyzed. The distances from the central point of round window niche opening to the terminal point of the horizontal segment, the salient point of pyramidal segment, the beginning point of the vertical segment, and the vertical segment of the facial nerve (abbreviate as OA, OB, OC, OE, respectively) were calculated based on three-dimensional reconstruction using mimics software. The results suggested that the pyramidal segment of the FN was positioned more closely to round window niche opening in patients with both CAA and CAS groups than that in control group, whereas there was no significant difference between CAA and CAS group (P < 0.05). The vertical portion of the FN was positioned more closely to round window niche opening in the CAA group than those in both the CAS and control groups with statistical significance (P < 0.05). Furthermore, the vertical portion of the FN was positioned more closely to round window niche opening in the CAS group than that in control group (P < 0.05). In conclusion, the dislocation between facial nerve and round window niche in patients with congenital auditory canal malformations could have significant effects on the round window implantation of vibrant soundbridge. Moreover, three-dimensional measurements and assessments before surgery might be helpful for a safer surgical approach and implantation of vibrant soundbridge.