Ultrasonographic prediction of the location of the proximal submandibular stones relative to the lingual nerve for the strategic transoral surgery

Abstract

Introduction Transoral surgical removal of the proximal submandibular stones has been performed to preserve the gland. Application of ultrasound could extend the indication of transoral surgery to the impalpable proximal stones. However, technical unfamiliarity of ultrasound scanning and anatomical complexity of proximal submandibular area can be hurdles for the general application of ultrasound guided transoral surgery. The objectives of this study were to assess the feasibility of preoperative ultrasonographic determination of the location of stone relative to the lingual nerve (LN) and to find optimal surgical approach for the proximal submandibular stones. Methods We retrospectively reviewed the medical records of 170 patients who were diagnosed as proximal submandibular stones and treated ultrasonography-guided transoral surgery from Mar 2011 to May 2018. Three patients had bilateral stones. The posterior edge of mylohyoid (PM) was used as the preoperative ultrasonographic criterion to classify the proximal submandibular stones into 3 types: stones anterior to PM (type I), stones crossing PM (type II), and stones posterior to PM (type III). The correlation between ultrasonographic and operative findings was investigated. Results Preoperative ultrasonography determined the proximal stones as type I in 40 (23.8%) cases, as type II in 69 (41.1%) cases, and as type III in 59 (35.1%) cases. According to the operative records, the stones were approached medially to the LN in 58 (34.5%) cases and laterally to the LN in 110 (65.5%) cases. In type 1 stones, 90% of stones were approached medially to the LN, while in type 2 and 3 stones, 78.3% and 88.1% of stones were approached laterally to the LN during transoral surgery, respectively. The surgical approaches were significantly different in relation to preoperative ultrasonographic classification of the proximal submandibular stones (P Conclusion Optimal transoral surgical approach relative to the lingual nerve can be selected based upon preoperative ultrasonographic findings of the proximal submandibular stones.