Fujiwara RJ, Ishiyama G, Lopez IA, Ishiyama A. Morphometric Analysis and Linear Measurements of the Scala Tympani and Implications in Cochlear Implant Electrodes.
Otol Neurotol 2023;
44:e343-e349. [PMID:
36893208 PMCID:
PMC10175138 DOI:
10.1097/mao.0000000000003848]
[Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/10/2023]
Abstract
HYPOTHESIS
The objective of this study was to perform detailed height and cross-sectional area measurements of the scala tympani in histologic sections of nondiseased human temporal bones and correlate them with cochlear implant electrode dimensions.
BACKGROUND
Previous investigations in scala tympani dimensions have used microcomputed tomography or casting modalities, which cannot be correlated directly with microanatomy visible on histologic specimens.
METHODS
Three-dimensional reconstructions of 10 archival human temporal bone specimens with no history of middle or inner ear disease were generated using hematoxylin and eosin histopathologic slides. At 90-degree intervals, the heights of the scala tympani at lateral wall, midscala, and perimodiolar locations were measured, along with cross-sectional area.
RESULTS
The vertical height of the scala tympani at its lateral wall significantly decreased from 1.28 to 0.88 mm from 0 to 180 degrees, and the perimodiolar height decreased from 1.20 to 0.85 mm. The cross-sectional area decreased from 2.29 (standard deviation, 0.60) mm 2 to 1.38 (standard deviation, 0.13) mm 2 from 0 to 180 degrees ( p = 0.001). After 360 degrees, the scala tympani shape transitioned from an ovoid to triangular shape, corresponding with a significantly decreased lateral height relative to perimodiolar height. Wide variability was observed among the cochlear implant electrode sizes relative to scala tympani measurements.
CONCLUSION
The present study is the first to conduct detailed measurements of heights and cross-sectional area of the scala tympani and the first to statistically characterize the change in its shape after the basal turn. These measurements have important implications in understanding locations of intracochlear trauma during insertion and electrode design.
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