Deeper insertion of electrode array result in better rehabilitation outcomes - Do we have evidence?

To study the outcome analysis in cochlear implantees in relation to depth of insertion.

30 patients of non-syndromic congenital profound hearing loss in the age range of 2-12 years received cochlear implantation by a posterior tympanotomy round window approach. Depth of insertion was calculated using post-operative X-rays (modified Stenver's view) and categorized into four groups, viz. fair insertion (Group A <180°), good insertion (Group B 180-<270°), very good insertion(Group C 270-360°), excellent insertion (Group D >360°). The outcome analysis of each implantee was carried out in a follow up interval of every 3 months using Meaningful Auditory Integration Scale (MAIS), Infant Toddler Meaningful Auditory Integration Scale (IT-MAIS), Category of Auditory Performance (CAP), and Speech Intelligibility Rating (SIR).

Overall 30, 29, 25, and 22 patients have completed 3, 6, 9, and 12 months follow up respectively. The MAIS scores in Group C were significantly better than Group B at 6, 9, and 12 months (P<0.05). The mean CAP score of Group C was more than rest of the groups with significant difference between Group C and Group D at 12 months (P<0.05). The mean SIR scores were maximum in Group C with significant difference between Group C and Group B at 9 and 12 months (P<0.05).

The study demonstrates that insertion from 270° to 360° gives optimum hearing outcomes as compared to deeper insertion, although larger sample and long term follow-up is warranted for definite conclusions.