Imaging and anatomical features of ethmomaxillary sinus and its differentiation from surrounding air cells.

OBJECTIVE: The aim of this study was to investigate the imaging anatomical characteristics and clinical significance of the ethmomaxillary sinus (EMS).

METHODS: The study included a total of 280 ENT Outpatient Department patients with nasal symptoms whose paranasal sinus CT scans were analyzed from January 2012 to December 2016. The anatomical imaging characteristics of EMS were observed.

RESULTS: EMS was observed in 23 of 280 patients, with an incidence of 8.2%. Bilateral EMS appearance in 17 cases (73.9%) was significantly higher than that of unilateral EMS in 6 cases (26.1%) (P < 0.01). EMS occurs when there are anterior or anterior-inferior cells of the posterior ethmoidal sinus (PEs) extending toward the maxillary sinus (MS) and entering the MS through the maxillary hiatus rather than spreading from outside of the MS. EMS is surrounded by five walls, and the main position of EMS was invariably located in the posterior-superior corner of the MS and draining to the superior nasal meatus (SNM). EMS must be differentiated from SNM, sphenoid sinus, and retromaxillary pneumatization of PEs, because they may appear between the MS and the orbital floor.

CONCLUSION: EMS was not a rare variation that should be careful identification during endoscopic sinus surgery. Accurately confirming EMS is the key to completely opening and removing lesions in the MS and EMS.