Preoperative prediction of the location of parotid gland tumors using radiographic anatomical landmarks

Abstract

(J Korean Assoc Oral Maxillofac Surg 2012;38:38-43) Introduction: The location of parotid gland tumors in the superficial or deep lobes can affect the time and difficulty of operations. Therefore, accurate preoperative evaluation of the tumor location is important for surgical outcomes. Materials and Methods: A total of 16 patients with parotid gland tumors and who underwent a parotidectomy between April 2003 and March 2011 were retrospectively reviewed in terms of demographic background, tumor location, surgical treatment, and treatment outcomes. Tumor location was estimated by four landmarks on contrast enhanced computerized tomography scans, which were Conn's arc, the facial nerve (FN) line, the Utrecht line, and the retromandibular vein. Tumor location was confirmed by relative position depending on the facial nerve during surgery. It was assumed positive since the tumor lies in the superficial lobe of the parotid gland, the sensitivity, specificity, positive predictive value, negative predictive value, and efficiency of each landmark were evaluated. Results: Our result revealed that the facial nerve line had a sensitivity of 83.3%, specificity of 100%, positive predictive value of 100%, negative predictive value of 71.4%, and efficiency of 87.5%. Some would be more efficient preoperative evaluation methods of the relationship of parotid gland tumors to the facial nerve than others. Conclusion: In our study, the FN line was found to be the most reliable analysis method.

Correlation between preoperative predictions and surgical findings in the parotid surgery for tumors

“…Some previous publications indicate high sensitivity and specificity (up to 100 %!) of CT based preoperative location of the parotid tumor [ 1 , 2 , 8 ]. We understand it as a wrong interpretation of statistical reports.…”

“…Various landmarks were used in computed tomography (CT) and magnetic resonance imaging (MRI) investigations for precise localization of the tumor and of the facial nerve. Among these landmarks, the facial nerve line (FNL) is the line between the lateral surface of the posterior belly of m. digastricus and the lateral surface of the cortex of the ramus part of the mandible [ 1 , 2 ]. The Utrecht line (UL) runs from the most dorsal point of the ipsilateral half of the first vertebra to the most dorsal point of the retromandibular vein [ 3 , 4 ].…”

“…Definitely some disagreement exists on the question which landmark or line is the most reliable for preoperative diagnostics. While some authors name FNL as the most reliable landmark [ 2 , 3 ], the other suggest UL [ 1 ] or the Stensen’s duct [ 6 ]. These landmarks are presented at the Fig.…”