Internal auditory canal volume in normal and malformed inner ears.

Eur Arch Otorhinolaryngol

Department of Otorhinolaryngology-Head and Neck Surgery, Ruhr-University Bochum, St. Elisabeth-Hospital Bochum, Bochum, Germany.

Published: May 2023

AI Article Synopsis

  • * Researchers analyzed high-resolution CT scans of 128 temporal bones, measuring both the diameter and volume of the IAC, with results showing significant differences in measurements among different types of IEMs.
  • * The findings suggest that using volumetric measurements of the IAC can reduce variability and enhance classification of IEMs, underscoring the importance of radiological assessment for patients with severe hearing loss before cochlear implantation.

Article Abstract

Purpose: A narrow bony internal auditory canal (IAC) may be associated with a hypoplastic cochlear nerve and poorer hearing performances after cochlear implantation. However, definitions for a narrow IAC vary widely and commonly, qualitative grading or two-dimensional measures are used to characterize a narrow IAC. We aimed to refine the definition of a narrow IAC by determining IAC volume in both control patients and patients with inner ear malformations (IEMs).

Methods: In this multicentric study, we included high-resolution CT (HRCT) scans of 128 temporal bones (85 with IEMs: cochlear aplasia, n = 11; common cavity, n = 2; cochlear hypoplasia type, n = 19; incomplete partition type I/III, n = 8/8; Mondini malformation, n = 16; enlarged vestibular aqueduct syndrome, n = 19; 45 controls). The IAC diameter was measured in the axial plane and the IAC volume was measured by semi-automatic segmentation and three-dimensional reconstruction.

Results: In controls, the mean IAC diameter was 5.5 mm (SD 1.1 mm) and the mean IAC volume was 175.3 mm (SD 52.6 mm). Statistically significant differences in IAC volumes were found in cochlear aplasia (68.3 mm, p < 0.0001), IPI (107.4 mm, p = 0.04), and IPIII (277.5 mm, p = 0.0004 mm). Inter-rater reliability was higher in IAC volume than in IAC diameter (intraclass correlation coefficient 0.92 vs. 0.77).

Conclusions: Volumetric measurement of IAC in cases of IEMs reduces measurement variability and may add to classifying IEMs. Since a hypoplastic IAC can be associated with a hypoplastic cochlear nerve and sensorineural hearing loss, radiologic assessment of the IAC is crucial in patients with severe sensorineural hearing loss undergoing cochlear implantation.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC10066105PMC
http://dx.doi.org/10.1007/s00405-022-07676-1DOI Listing

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