(097) Cochlear Implantation in Abnormal Cochlea by Transcanal Technique Our Experience

Introduction: To describe the clinical profile, operative findings, surgical technique, type of implant and complications encountered in implantation of abnormal cochlea by the transcanal technique and discuss the advantages of transcanal technique in abnormal cochlea

Methods: This is a retrospective study involving a tertiary referral centre in India amongst 275 patients between the ages of 1 years to 61 years who underwent cochlear implantation between January 2015 to December 2022 . After evaluation with HRCT and MRI the cochleovestibular malformations in this study were classified according to Sennaroglu classification.The. Cochlear ossification was graded from I-IV and the area of cochlear fibrosis was noted based on T2 weighted MRI images . Data was collected regarding the age , sex , hearing loss on audiological evaluation , radiological findings , intra operative findings, type of implant placed and complications if any .All the patients underwent cochlear implantation by transcanal approach .

Results: Amongst the 275 patients who underwent cochlear implantation during the study period there were 32 cases with abnormalities of cochlea. This included 14 patients (5.09%) with congenital malformations , 7 patients (2.54%) with cochlear fibrosis and 11 patients (4%) with cochlear ossification. The commonest cochlear malformation was Incomplete Partition 2 ( IP-II) which was present in 7 patients (50%) out of which 4 was associated with enlarged vestibular aqueduct.Out of the 7 patients with cochlear fibrosis, 4 patients had fibrosis only in the basal turn.Out of the 11 patients with cochlear ossification 6 patients (54.54%) had a grade 1 ossification, 1 patient had a grade 2 ossification and 4 patients had a grade 3 ossification. The type of implant were chosen depending on individual malformation or length of ossification and fibrosis.

Conclusions: In the past, inner ear anomalies were considered as a contraindication for cochlear implantation ,however it is now possible to implant most of these abnormal cochlea by careful planning, a modification of the surgical technique and the type of electrode used.