Diagnostic Value of 3D Segmentation in Understanding the Anatomy of Human Inner Ear Including Malformation Types

Abstract

Objective: To understand the anatomical and dimensional variations of the human inner ear using 3-dimensional (3D) segmentation within the Middle East population. Design: Retrospective study. Setting: King Abdullah Ear Specialist Center (KAESC) Riyadh, Saudi Arabia. Participant: Forty computed tomography (CT) images of patients with sensorineural hearing loss who underwent cochlear implant (CI) were taken for analysis. Main outcome Measures: Three-dimensional images showing the anatomical variations of the inner ear including various pathological conditions, cochlear parameters including basal turn diameter (“A” value), “B” value which is perpendicular to “A” value, cochlear height, length, and width of the internal auditory canal (IAC), intercochlear spacing, and electrode angular insertion depth (AID). Results: Out of 40 CT image data sets, 12 had normal inner-ear anatomy (NA), 4 with enlarged vestibular aqueduct syndrome (EVAS), 8 with only 2 turns of the cochlea (2TL), 7 with incomplete partition (IP) type II, 5 with cochlear hypoplasia, 1 with common cavity, and 3 with abnormal IAC. Taking the NA, EVAS, 2TL, and the IP type II cases altogether, age of the patient had no correlation with the “A” value; however, the “A” value had a linear correlation with the “B” value. The age of the patient had an increasing logarithmic correlation with the IAC length and the intercochlear spacing. The “A” value did not have any meaningful correlation with the cochlear height. Three data sets showed asymmetric inner-ear malformation types on either side of the ears. All these 40 cases were implanted with various CI electrode array variants and the corresponding postoperative plain film X-ray images showing the electrode AID are given separately in figures. Conclusions: Three-dimensional segmentation of the inner ear from the temporal bone CT is a valuable clinical and training tool for surgeons and radiologists especially in difficult cases which will certainly help to understand the overall anatomical and dimensional variations.