Comparison of Cochlear Implant Relevant Anatomy in Children Versus Adults

Hypothesis: To test whether there are significant differences in pediatric and adult temporal bone anatomy as related to cochlear implant (CI) surgery. Background: Surgeons rely upon anatomic landmarks including the round window (RW) and facial recess (FR) to place CI electrodes within the scala tympani. Anecdotally, clinicians report differences in orientation of such structures in children versus adults. Methods: Institutional review board approval was obtained. High-resolution computed tomographic scans of 24 pediatric patients (46 ears) and 20 adult patients (40 ears) were evaluated using software consisting of a model-based segmentation algorithm that automatically localizes and segments temporal bone anatomy (e. g., facial nerve, chorda tympani, external auditory canal [EAC], and cochlea). On these scans, angles pertinent anatomy were manually delineated and measured blinded as to the age of the patient. Results: The EAC and FR were more parallel to the basal turn (BT) of the cochlea in children versus adults (angle EAC:BT 20.55 degrees versus 24.28 degrees, p = 0.003; angle FR:BT 5.15degrees versus 6.88 degrees, p = 0.009). The RW was more closely aligned with the FR in children versus adults (angle FR:RW 30.43 degrees versus 36.67 degrees, p = 0.009). Comparing the lateral portion of the EAC (using LatEAC as a marker) to the most medial portion (using perpendicular to TM as a marker), the measured angle was 136.57 degrees in children and 172.20 degrees in adults (p < 0.001). Conclusion: There are significant differences in the temporal bone anatomy of children versus adults pertinent to CI electrode insertion.