The Optimal Head Position Following Intratympanic Injection: A Research Based on HRCT Reconstruction

Objective: This study aimed to investigate the optimal head position (OHP) following intratympanic injection, a critical intervention in treating inner ear disorders. Identifying OHP is essential to maximize drug retention in the middle ear, thereby significantly enhancing the therapeutic efficacy by mitigating the significant issue of injectate leakage through the eustachian tube (ET). Exploratory various positions of ET orifice and round window (RW) were investigated and associated with head movements. Methods: Twenty-two (10 males and 12 females) anonymized high-resolution computed tomography (HRCT) datasets of patients without structural ear disease were selected from January 2022 to December 2022 in the study. The subjects were categorized into two groups: children (≤18 years) and adult group (>18 years). The reconstruction of the ET orifice and RW from HRCT were analyzed using Mimics software and the distances from the center point of ET orifice or the center point of RW to the reference plane were defined as distance of ET orifice (D_ET) and distance of RW (D_RW). Results: In the supine position, the OHP for intratympanic injection was 23°of pronation and 24° of posterior extension, and the maximum distance between the ET orifice and RW (D_ET-RW) was 9.29 ± 2.13 mm. As the head position extended posteriorly beyond 43°, D_ET was relatively high compared with D_RW, resulting in the OHP a fully posteriorly extended 90° of the head being the optimal position with D_ET-RW of 2.13 ± 1.60 mm in the supine position, however, it is not realized in human beings. Moreover, the OHP had no obvious relevance corresponding to age following intratympanic injections. Conclusion: Our study suggested that OHP after intratympanic injections treatment consists of supine position, along with a slight pronation and posterior extension.