Detailed evaluation of the risk of infraorbital nerve injury in postoperative maxillary cyst surgery.

OBJECTIVE: Postoperative maxillary cyst (POMC) develops as a delayed complication after radical surgery. The infraorbital nerve (ION) is a terminal branch of the trigeminal nerve and is one of the low-frequency collateral injuries that may occur in maxillary sinus surgery. The risk of ION injury may increase during POMC surgery due to anatomical variations: however, this has not yet been examined in detail. Therefore, we herein investigated variations in the ION in POMC cases with a focus on its relationship with the aperture site of the cyst, to clarify the risk of injury. METHODS: A multifacility retrospective study was conducted between May 2014 and December 2023 on patients who underwent POMC surgery in Kagawa Medical University or Japanese Red Cross Asahikawa Hospital. Preoperative coronal CT images were reviewed from the viewpoint of anatomical variations in the ION and the risk of nerve injury. RESULTS: Eighty-four patients (95 sides), including 11 bilateral cases, were eligible. The presence of several risk factors for nerve injury was evaluated. The following outcomes were noted: contact between the opening site and ION (27.4 %), bony erosion of the infraorbital canal (35.8 %), descent of the ION from the orbital floor (16.8 %), and obscuration of the nerve run (17.9 %). The risk of injury was classified based on the results of imaging evaluations as follows: no risk (69 cases, 72.6 %), low risk (16 cases, 16.8 %), moderate risk (6 cases, 6.3 %), and high risk (4 cases, 4.2 %). A retrospective review revealed that ION injury occurred in only 1 patient (1.4 %) who was categorized as high risk. CONCLUSION: Although the overall risk of ION injury is not very high, it is important to note that it may occur in some cases without precautions. Therefore, detailed CT with a focus on the ION to preoperatively assess the risk of nerve injury is important.