Radioanatomic study of the skull base and septum in Asians: implications for using the nasoseptal flap for anterior skull base reconstruction

Abstract

Objectives: To assess the feasibility of using the nasoseptal flap (NSF) for covering the anterior skull base defect in Asians, and to compare the results with Caucasians. Materials and Methods: A retrospective radioanatomic analysis was conducted in one hundred Korean adult patients. Septal, and skull base dimensions were measured and the feasibility of the NSF in reconstructing a full anterior skull base defect was evaluated according to gender and different age groups. Scans of 49 Caucasian patients were analyzed in the same protocol for a comparative study. Results: Among various septal dimensions, length of the septum was significantly different in Koreans when compared to Caucasians. Skull base dimensions such as anterior skull base length and width at the level of the anterior ethmoidal artery were different between the two ethnic groups. Individual differences between the anterior width of the hypothetical NSF and the anterior margin of the skull base defect (2.8±3.1 vs 6.4±4.8) and the difference between the hypothetical NSF length and the length of the flap needed for full coverage of the defect were significantly smaller in Korean patients (7.2±3.8 vs 13.1±5.6), leading to a statistically higher chance of flap insufficiency. The insufficiency was more often found in female patients. Additionally, there was significant difference of septum height at the level of the anterior ethmoidal artery for Korean male, female, and as a whole between each age group, while Caucasians did not show any difference in septal dimensions among each age group. For skull base dimensions, Korean male showed significant difference of the length for anterior wall of sella, while Caucasian male and as a whole showed significant difference of skull base width at sphenoethmoidal junction level. However, these results did not significantly affect the feasibility of NSF for reconstruction of anterior skull base defect. Conclusions: The risk of NSF insufficiency for covering the anterior skull base defect in Koreans is higher relative to Caucasians, and is accentuated in female patients. Efforts to increase the size of the NSF as well as efforts to avoid intraoperative shrinkage of the NSF should be considered to compensate for the relatively small NSF in Asians.