Improved visualization of the chorda tympani nerve using ultra-high-resolution computed tomography

Background: Recognition of the anatomical course of the chorda tympani nerve (CTN) is important for preventing iatrogenic injuries during middle-ear surgery. Purpose: This study aims to compare visualization of the CTN using two computed tomography (CT) methods: conventional high-resolution CT (C-HRCT) and ultra-high-resolution CT (U-HRCT). Materials and methods We performed a retrospective visual assessment of 59 CTNs in normal temporal bones of 54 consecutive patients who underwent both C-HRCT and U-HRCT. After dividing CTN into three anatomical segments (posterior canaliculus, tympanic segment, and anterior canaliculus), two neuroradiologists scored the visualizations on a four-point scale. Results: On C-HRCT, the visual scores of the posterior canaliculus, tympanic segment, and anterior canaliculus were 3.5 +/- 0.7, 1.6 +/- 0.6, and 3.1 +/- 0.7, respectively. The respective values were significantly higher in all segments on U-HRCT: 3.9 +/- 0.2, 2.4 +/- 0.6, 3.5 +/- 0.6 (p < 0.01). Although the difference in scores between methods was greatest for the tympanic segment, the visual score on U-HRCT was lower for the tympanic segment than for the anterior and posterior segments (p < 0.01). Conclusion: Ultra-high-resolution CT provides superior visualization of the CTN, especially the tympanic segment.