Prediction of Location of the Parotid Tumors that Cross Over Anatomical Criteria for Facial Nerve on Computed Tomography

Abstract

Background and Objectives To find more accurate way to determine the location of parotid tumors that cross anatomical criteria for the facial nerve (FN). Subjects and Method Two hundred patients were included in the study and retrospectively studied. Five anatomical criteria were used to predict the location of parotid tumors on computed tomography (CT). Deep portion of tumors was measured and then, cutoff value was obtained after receiver operator curve analysis. The location of tumor was predicted by using the cutoff value and by the conventional way, in which the side where most of the tumor is located is determined as the tumor site. Results The parotid tumors were located in superficial lobes in 148 cases, and in deep lobes in 52 cases by operative record. The tumors that cross the anatomical criteria were defined as 'crossing tumor.' The cutoff values for prediction of 'crossing tumor' location on CT were 6.7 mm for anatomical line, 6.4 mm for FN line, 11.2 mm for retromandibular vein, 4.9 mm for Utrecht line and 3.8 mm for Conn's arc. The accuracy of 5 anatomical criteria for 'crossing tumor' was between 55.9% and 81.6% when the cutoff value was used, whereas the accuracy was between 25.7% and 68.9% when conventional way was used. Conclusion In cases of 'crossing tumor,' the cutoff value obtained by measurement of deep portion of tumor can be applied to improve the diagnostic performance for the prediction of tumor location.