Significance of round window niche drilling for cochlear implant surgery

Deepak Dalmia, Sanjaya Kumar Behera

Indian Journal of Otology 2017 23(3):141-145

Aim: The aim of this study is to determine the extent of round window niche (RWN) drilling for optimal visualization of the round window membrane (RWM) during cochlear implant surgery. Materials and Methods: This is a prospective study of 38 candidates between 1 and 8 years for cochlear implant surgery from March 2014 to March 2016. We classified the visibility of RWM and its cover by RWN on the surgical view through the posterior tympanotomy during surgery into four types (1) Type 1 - fully visible, (2) Type 2-2/3rd (75%–99%) of RWM visible, (3) Type 3 - ½–2/3rd (50%–74%) of RWM visible, and (4) Type IV - ¼th–½ (25%–49%) of RWM visible. Extent of drilling of RWN into (1) drilling of anterosuperior and superior lip, (2) drilling of anterosuperior, superior, and posterosuperior lip, (3) drilling of the anterior lip with anterosuperior, superior, and posterosuperior lip, and (4) drilling of the posterior lip with Type III drilling. Results: Type-4 RWN is the most common and Type-1 least common. The extent of drilling most commonly performed was Type IV drilling of anterosuperior, superior, and posterosuperior and anterior and posterior lip of RWN. Conclusion: Sufficient drilling of the bony overhang is essential for complete exposure of RWM for insertion of electrodes without any hindrance.

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