[The CT image features of ethmomaxillary sinus and their significance in endoscopic surgery]

Objective: To investigate the prevalence and radiographic characteristics of ethmomaxillary sinus (EMS) in chronic rhinosinusitis (CRS) patients by CT scan, as well as their endoscopic surgical significance in antrostomy. Methods: A retrospective analysis of 111 CRS patients who were prepared for surgery in Department of Otorhinolaryngology Head and Neck Surgery of Peking University People's Hospital from February to December of 2017 was performed. In all CRS patients, 79 patients were bilateral CRS and 32 were unilateral. The patients were divided into two groups according to whether they had history of surgery. Only the sides with CRS were analyzed. There were 98 patients (167 sides) in the non-surgical history group and 13 patients (23 sides) in the surgical history group. The prevalence of EMS in CRS sides in the two groups was counted by analyzing the CT images. The CT image features and anatomical variations associated with EMS in CRS sides in the non-surgical history group were also analyzed. SPSS 22.0 software was used for statistic analysis. Results: The prevalence of EMS in CRS sides was 21.7% (5/23) in the surgical history group and 12.0% (20/167) in the non-surgical history group. No statistically significant difference in the prevalence of EMS was found between the two groups (χ(2)=0.940, P>0.05). The medial-lateral diameters of the EMS ranged from 8.50 to 14.10 mm with an average of (10.38±1.69) mm (Mean±SD). The shape of the bony septum between the EMS and maxillary sinus was divided into three types: convex toward to the EMS (2 sides), convex toward to maxillary sinus (5 sides) and flat (13 sides). The Lund-Mackay (LM) scores of the maxillary sinuses in patients with and without EMS showed no statistically significant difference (1.60±0.50 vs 1.40±0.62, Z=1.285, P>0.05). The EMS obstructed the drainage of maxillary sinus posteriorly, medially and superiorly. All the EMS in diseased sides were dissected endoscopicly to improve drainage. In the non-surgical history group, the EMS coexisting anatomic variations were the Onodi cell (7/20), Haller cell (3/20), concha bullosa (6/20) and maxillary sinus hypoplasia (3/20). Conclusions: There is relatively high prevalence of the EMS in CRS patients. This is adjacent to the orbit, overpneumatizes laterally and obstructs the drainage of the maxillary sinus. Complete dissection of the EMS is helpful to improve the drainage of maxillary sinus.