Ultrasonographic Localization of Parotid Gland Tumor Relative to the Facial Nerve Using Stensen's Duct Criterion

Abstract

During the preoperative evaluation of parotid gland tumors, one of the main concerns is to determine the location of the tumors in relation to the facial nerve. This study aims to assess the value of ultrasound for determining the location of parotid gland tumors in relation to the facial nerve using Stensen's duct. This is a retrospective cross-sectional study at a single institute. The subjects who underwent preoperative ultrasound and parotidectomy for parotid gland tumors were included. The subjects with incomplete operative records or no reference standard for the location of parotid gland tumor were excluded. The primary predictor was ultrasound tumor location, which was defined as the location of parotid gland tumors determined by preoperative ultrasound as to whether the tumors were superficial or deep to the facial nerve. The operative records were used as the reference standard for the location of parotid gland tumors. The primary outcome was diagnostic performances of preoperative ultrasound in predicting the location of parotid gland tumors, which were calculated by comparing ultrasound tumor location to the reference standard. Covariates were sex, age, type of surgery, tumor size, and tumor histology. Data analysis involved descriptive and analytic statistics; P<.05 was considered statistically significant. One hundred and two of 140 eligible subjects met inclusion and exclusion criteria. There were 50 male and 52 female, with a mean age of 53.3years. Ultrasound tumor location was classified as deep in 29 subjects, superficial in 50, and indeterminate in 23. The reference standard was deep in 32 subjects and superficial in 70. Indeterminate ultrasound tumor location results were grouped as either deep or superficial to make every possible cross table in which ultrasound tumor location results were presented as a dichotomy. The mean sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the ultrasound to predict the deep location of parotid tumors were 87.5, 82.1, 70.2, 93.6, and 83.8%, respectively. Stensen's duct on ultrasound can be a useful criterion to determine the location of parotid gland tumor relative to the facial nerve.