Background: The optimal insertion route for an electrode array in hearing preservation cochlear implantation (CI) surgery is still tentative. Both cochleostomy (CO) and round window (RW) techniques are used today. In the present study we analyzed size variations and topographic anatomy of the ‘hook' region of the human cochlea to better comprehend the Testo effects of various electric array insertion modes. Material and Methods: Size variations of the cochlear ‘hook' region were assessed in 23 human, microdissected temporal bones by measuring the distances between the oval and round windows, also outlining the spiral ligament/spiral lamina. Influence of size variations on spiral ligament position and fundamentals for different surgical approaches were evaluated in a subset of ‘small' and ‘large' cochleae performing different types of CO. In addition, the relationship between the microdissected accessory canal housing the inferior cochlear vein and the RW was analyzed. Results: The lateral vestibular wall and the cochlear ‘hook' displayed large anatomic variations that greatly influenced the size of the potential surgical area. Results showed that only very inferiorly located CO entered the scala tympani without causing trauma to the spiral ligament and spiral lamina. An inferior approach may challenge the inferior cochlear vein. Conclusion: Preoperative assessment of the distance between the round and oval windows may direct the surgeon before CI hearing-preservation surgery. CO techniques, especially in ‘small' ears, may lead to frequent damage to the inner ear structures. In those cases with substantial residual hearing, CI surgery may be better performed through a RW approach. i 2014 S. Karger AG, Basel

Addams-Williams J, Munaweera L, Coleman B, Shepherd R, Backhouse S: Cochlear implant electrode insertion: in defence of cochleostomy and factors against the round window membrane approach. Cochlear Implants Int 2011;12(suppl 2):S36-S39.
Adunka O, Unkelbach MH, Mack M, Hambek M, Gstoettner W, Kiefer J: Cochlear implantation via the round window membrane minimizes trauma to cochlear structures: a histologically controlled insertion study. Acta Otolaryngol 2004;124:807-812.
Adunka OF, Buchman CA: Scala tympani cochleostomy I: results of a survey. Laryngoscope 2007;117:2187-2194.
Adunka OF, Radeloff A, Gstoettner WK, Pillsbury HC, Buchman CA: Scala tympani cochleostomy II: topography and histology. Laryngoscope 2007;117:2195-2200.
Adunka OF, Pillsbury HC, Buchman CA: Minimizing intracochlear trauma during cochlear implantation. Adv Otorhinolaryngol 2010;67:96-107.
Adunka OF, Dillon MT, Adunka MC, King ER, Pillsbury HC, Buchman CA: Cochleostomy versus round window insertions: influence on functional outcomes in electric-acoustic stimulation of the auditory system. Otol Neurotol 2014;35:613-618.
Atturo F, Barbara M, Rask-Andersen H: Is the human round window really round? An anatomical study with clinical implications. Otol Neurotol 2014;35:1354-1360.
Banfai P, Hortmann G, Kubik S, Wustrow F: Projection of the spiral cochlear canal on the medial wall of the tympanic cavity with regard to the cochlear implant. Scand Audiol Suppl 1979;11:157-170.
Basura GJ, Adunka OF, Buchman CA: Scala tympani cochleostomy for cochlear implantation. Oper Tech Otolaryngol Head Neck Surg 2010;21:218-222.
Briggs RJ, Tykocinski M, Stidham K, Roberson JB: Cochleostomy site: implications for electrode placement and hearing preservation. Acta Otolaryngol 2005;125:870-876.
Bruce IA, Bates JE, Melling C, Mawman D, Green KM: Hearing preservation via a cochleostomy approach and deep insertion of a standard length cochlear implant electrode. Otol Neurotol 2011;32:1444-1447.
Erixon E, KFbler S, Rask-Andersen H: Cochlear implantation and hearing preservation: Results in 21 consecutively operated patients using the round window approach. Acta Otolaryngol 2012;132:923-931.
Gantz BJ, Turner C: Combining acoustic and electrical speech processing: Iowa/nucleus hybrid implant. Acta Otolaryngol 2004;124:344-347.
Gstoettner W, Kiefer J, Baumgartner WD, Pok S, Peters S, Adunka O: Hearing preservation in cochlear implantation for electric acoustic stimulation. Acta Otolaryngol 2004;124:348-352.
Havenith S, Lammers MJ, Tange RA, Trabalzini F, della Volpe A, van der Heijden GJ, Grolman W: Hearing preservation surgery: cochleostomy or round window approach? A systematic review. Otol Neurotol 2013;34:667-674.
Kang BJ, Kim AH: Comparison of cochlear implant performance after round window electrode insertion compared with traditional cochleostomy. Otolaryngol Head Neck Surg 2013;148:822-826.
Li P, Wang H, Northrop C, Merchant S, Nadol J: Anatomy of the round window and hook region of the cochlea with implications for cochlear implantation and other endocochlear surgical procedures. Otol Neurotol 2007;28:641-648.
Rask-Andersen H, Stahle J, Wilbrand H: Human cochlear aqueduct and its accessory canals. Ann Otol Rhinol Laryngol Suppl 1977;86(suppl 42):1-16.
Skarzynski H, Lorens A, Piotrowska A, Anderson I: Preservation of low frequency hearing in partial deafness cochlear implantation (PDCI) using the round window surgical approach. Acta Otolaryngol 2007;127:41-48.
Stidham KR, Roberson JB Jr: Cochlear hook anatomy: evaluation of the spatial relationship of the basal cochlear duct to middle ear landmarks. Acta Otolaryngol 1999;119:773-777.
Von Ilberg C, Kiefer J, Tillein J, et al: Electric-acoustic stimulation of the auditory system. New technology for severe hearing loss. ORL J Otorhinolaryngol Relat Spec 1999;61:334-340.
Webb RL, Clark GM, Shepherd RK, Franz BK, Pyman BC: The biologic safety of the Cochlear Corporation multiple electrode intracochlear implant. Am J Otol 1988;9:8-13.
Wilbrand HF, Rask-Andersen H, Gilstring D: The vestibular aqueduct and the paravestibular canal. An anatomic and roentgenologic investigation. Acta Radiol Diagn (Stockh) 1974;15:337-355.
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.