Anatomy of the middle-turn cochleostomy

Brandon Isaacson, Peter S. Roland, Charles G. Wright

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Middle-turn cochleostomies are occasior ally used for cochlear implant electrode placement in patients with labyrinthitis ossificans. This study evaluates the anatomic characteristics of the middle-turn cochleostomy and its suitability for placement of implant electrodes, Methods: Ten cadaveric human temporal bone were dissected using a facial recess approach. A middleturn cochleostomy was drilled 2 mm anterior to the oval window and just inferior to the cochleariform process. The preparations were then stained with osmium tetroxidce and microdissections were performed. The location of the cochleostomy on the cochlear spiral and its path through the various cochlear compartments were evaluated in all 10 specimens. A Cochlear Corporation depth gauge was inserted in five of the specimens and insertion trauma, number of contact rings, and depth of insertion were recorded. Results: Eight of the 10 cochleostomies were placed at approximately 360° on the cochlear spiral, near the transition between the basal and middle turns. In one case, the cochleostomy was found to enter the cochlear apex and in another it entered scala vestibuli of the proximal basal turn. The cochleostomy entered scala media in six bones and scala vestibuli in four specimens. A depth gauge was inserted in five specimens. The number of contacts placed within the cochlear lumen ranged from four to nine. There was evidence of insertional trauma to the lateral wall of the cochlear duct, basilar membrane, and Reissner's membrane, but no evidence of fractures to the osseous spiral lamina or modiolus. Conclusion: This study demonstrates that electrodes inserted via a middle-turn cochleostomy are likely to enter scala vestibuli and have access to the middle-and apical-cochlear turns. It is also possible that the electrode could be directed into the descending portion of the basal turn depending on cochleostomy orientation. Middle-turn cochleostomy seems to be a viable alternative for electrode placement when preservation of residual hearing is not a concern.

Original languageEnglish (US)
Pages (from-to)2200-2204
Number of pages5
Issue number12
StatePublished - Dec 1 2008


  • Cochlear implant
  • Human cochlea
  • Labyrinthitis ossificans

ASJC Scopus subject areas

  • Otorhinolaryngology


Dive into the research topics of 'Anatomy of the middle-turn cochleostomy'. Together they form a unique fingerprint.

Cite this