Congenital malformation of the oval window: experience of radiologic diagnosis and surgical technique.

The aim of this study was to introduce and discuss the method of preoperative radiological diagnosis to the congenital absence or atresia of the oval window (OW), and the method of surgical treatment. From July 2010 through August 2014, patients with normal external canal and tympanic membrane but conductive hearing loss underwent high resolution CT scan (HRCT). The multi-planar reformation (MPR), a post-processing protocol, was used. The patients with diagnosis of OW atresia and malformed stapes preoperatively underwent surgical treatment. The vestibular drilled-out and promontory drilled-out technique was used to reconstruct the ossicular chain. In the preoperative radiological diagnosis, six patients (ears) were noted to have congenital absence or atresia of the oval window with malformed facial nerve (class 4) and two patients (ears) were found to have footplate fixation (class 2). In the surgical treatment of eight ears, the malformed structure was identified and the ossicular chain reconstruction was made in six ears. The coronal HRCT CT imaging and the MPR post-processing technique can provide us practical and definite information for surgical treatment, especially in the discrimination of OW atresia and the fixed stapedal footplate. The promontory drill-out technique, fenestration in the bottom of the basal turn, provides us a new method in the hearing reconstruction when the area of OW was fully covered by malformed facial nerve. This technique was first reported in the literature.