To modify the method of treating trigeminal neuralgia (TN) affecting the maxillary branch and to provide clinical evidence of an etiologic hypothesis of narrowing bone canal compression.Forty patients who met the inclusion and exclusion criteria were included, and those with bony compression of the affected infraorbital canal (IOC) were selected by preoperative computer measurement. Modified decompression of the IOC was performed through the maxillary sinus with the assistance of a piezoelectric device and an endoscope. The results of the operation were evaluated.Fourteen patients (35.00%) had bony compression of the affected IOC. During a mean follow-up period of 29.4 months, 11 patients (78.57%) had complete pain relief (excellent); 1 (7.14%) had moderate relief with carbamazepine administration. The success rate was 85.71% (12 of 14). The postoperative numbness rate was 35.71% (5 of 14).Narrowing of the IOC might be a reason some patients with TN have no intracranial neurovascular compression and have pain localized to the distribution of the maxillary branch. Modified decompression of the IOC through the maxillary sinus is a safe, highly effective, and minimally invasive method to treat these patients.