Preoperative evaluation of cochlear implantation through the round window membrane in the facial recess using high-resolution computed tomography.
PURPOSE
We evaluated the risk of cochlear implantation through the round window membrane in the facial recess through a preoperative analysis of the angle between the facial nerve-round window and the cranial midline using high-resolution temporal bone CT.


METHODS
Temporal bone CT films of 176 patients with profound sensorineural hearing loss at our hospital from 2013 to 2015 were reviewed. The preoperative temporal bone CT scans of the patients were retrospectively analysed. The vertical distance (d value) from the leading edge of the facial nerve to the posterior wall of the external auditory canal and the angle (α value) between the line from the leading edge of the facial nerve to the midpoint of the round window membrane and the median sagittal line on the round window membrane plane were measured. Based on intraoperative observation, the round window membrane was divided into complete round window membrane exposure (group A), partial exposure (group B), and unexposed (group C) groups, and statistical analysis was performed.


RESULTS
The α value could be effectively measured for all 176 patients (62.60 ± 7.12), and the d value could be effectively measured for 95 cases (5.53 ± 1.00). An analysis of the correlation between the α and d values of these 95 cases found a negative correlation. Of the 176 cases, one-way analysis of variance (ANOVA) showed that the differences among the groups were significant [P = 0.000 (< 0.05)].


CONCLUSION
The angle (α value) between the line connecting the leading edge of the facial nerve to the midpoint of the round window and the median sagittal line measured in preoperative CT scans was associated with the difficulty of intraoperatively exposing the round window membrane. When the α value was larger than a certain degree, the difficulty of exposing the round window membrane was increased. In such cases, the surgeon should fully expose the round window membrane during surgery, which could result decrease the likelihood of complications.
['Xie|Li-Hong|LH|', 'Tang|Jie|J|', 'Miao|Wen-Jie|WJ|', 'Tang|Xiang-Long|XL|', 'Li|Heng|H|', 'Tang|An-Zhou|AZ|']
D000293:Adolescent D002648:Child D002675:Child, Preschool D019929:Cochlear Implantation D004424:Ear Canal D005154:Facial Nerve D005260:Female D006319:Hearing Loss, Sensorineural D006801:Humans D007223:Infant D008297:Male D011300:Preoperative Care D012189:Retrospective Studies D012405:Round Window, Ear D013701:Temporal Bone D014057:Tomography, X-Ray Computed
Cochlear implantation Round window membrane Facial nerve Temporal bone high-resolution computed tomography