Minimum fascia-tumor distance as an independent predictor for deep lobe parotid tumors and postoperative facial palsy.

OBJECTIVES: To evaluate the clinical utility of ultrasound (US)-measured minimum fascia-tumor distance (MFTD) as a predictor of deep lobe tumor location and postoperative temporary facial nerve (FN) injury in benign parotid tumors. METHODS: This retrospective study included adult patients with benign parotid tumors who underwent preoperative US followed by parotidectomy. MFTD was defined as the shortest distance between the tumor and the parotidomasseteric fascia. Receiver operating characteristic analysis was used to determine optimal cutoff values. Univariable and multivariable logistic regression analyses were performed. Internal validation was conducted. RESULTS: A total of 97 patients were included. The mean MFTD was significantly greater in deep lobe than superficial lobe tumors (3.58 ± 2.44 mm vs. 1.21 ± 1.47 mm, P < 0.001). The optimal cutoff value was 3.25 mm according to the Youden index. Multivariable logistic regression analysis identified MFTD > 3.25 mm as an independent predictor of deep lobe tumors (adjusted odds ratio [aOR], 26.462; P < 0.001) and postoperative FN injury (aOR, 6.775; P = 0.003). Female sex (aOR, 5.205; P = 0.011) was also associated with postoperative FN injury. These associations remained consistent after internal validation. Analyses using continuous MFTD values demonstrated similar findings. CONCLUSION: US-measured MFTD is a useful parameter for distinguishing deep lobe parotid tumors and serves as an independent predictor of postoperative FN injury. Incorporation of MFTD into preoperative assessment may improve surgical planning.