Locating the scala media in the fixed human temporal bone for therapeutic access

Objective: To investigate the location of the scala media in relation to the round window niche in human temporal bones. Design: Ten human temporal bones were investigated by radical mastoidectomy and promontory drill-out. Setting: Temporal bone laboratory. Outcome measures: The distance from the scala media to the anterior edge of the round window niche, measured by Fisch's stapedectomy measuring cylinders. Results: The scala media was identified at the transection point of a vertical line 1.6 to 2.2 mm (mean = 1.8 mm; standard deviation = 0.2) anterior to the anterior edge of the round window niche and a horizontal line 0.2 mm inferior to the lower border of the oval window. Conclusion: This report demonstrates the point of entry into the scala media via the promontory in fixed temporal bone models, which may provide a site of entry for stem cells and gene therapy insertion.