Risk assessment of damage to the anterior superior alveolar nerve during endoscopic modified medial maxillectomy (EMMM)-usefulness of preoperative CT evaluation-

Abstract

Recently, endoscopic modified medial maxillectomy (EMMM) has been performed as treatment for tumors of the maxillary sinus. In EMMM, when the anterior wall of the maxillary sinus is preserved, injury to the anterior superior alveolar nerve (ASAN) is unlikely, in contrast to the case during the Caldwell-Luc and Denker's operations, which have been the conventionally adopted procedures. We encountered a case in which injury of the ASAN was confirmed during EMMM. The ASAN is located in a bony canal or sulcus structure in the anterior wall of the maxillary sinus, called the canalis sinuosus (CS). In many cases, the CS is detectable on high-resolution CT images. We performed CT image analysis of 40 maxillary sinuses in 20 patients (10 males, 10 females), to examine the CS structure and risk of ASAN injury during EMMM. In 10 sinuses, the total canal structure of the CS was identified, and in these cases, the canal was considered to be fully covered by the bone: such cases are considered to be at a lower risk for ASAN injury during EMMM. However, in 5 of these 10 sinuses, the CS was located in the septa of the maxillary sinus, which are usually removed during sinus surgery; therefore, the risk of injury to the ASAN is considered to be higher in such cases. In 25 sinuses, the canal structure of the CS was partially defective, and in 5 sinuses, the CS was undetectable. In the latter 30 sinuses, the ASAN is considered to be more exposed in the maxillary sinus, with a greater risk of injury to the nerve during EMMM.