Prognostic Value of Classifying Parapharyngeal Extension in Nasopharyngeal Carcinoma Based on Magnetic Resonance Imaging

Figure 1

Axial section through the nasopharynx showing the relationship between various anatomic sites of parapharyngeal extension surrounding the nasopharynx, which are divided by the three layers of the cervical fascia: deep (dark blue line), middle (bright green line), and superficial (orange line). Parapharyngeal extension includes involvement of the masticator space (MS, blue), prestyloid space (PSS, purple), carotid space (CS, green), retropharyngeal space (RPS, pink), prevertebral space (PVS, yellow), and parotid space (PS, brown). Compared with the anatomic masticator space, the staging masticator space (the region within the red line) excludes the medial and lateral pterygoid muscles but includes the retromaxillary fat pad. MP: medial pterygoid muscle; LP: lateral pterygoid muscle; M: masseter muscle; T: temporalis muscle; RT: retromaxillary fat pad.