MR Imaging of Nonmalignant Polyps and Masses of the Nasopharynx and Sphenoid Sinus after Radiotherapy for Nasopharyngeal Carcinoma

Coronal T1-weighted postcontrast MR image in a 71-year-old man, 11 years after radiation therapy, with a contrast enhancing polyp (arrow) with less enhancing stellate areas centrally, arising at the junction of the sphenoid sinus and roof of the nasopharynx where there is an osteoradionecrotic bony defect.

A, Coronal and (B) axial T1-weighted postcontrast MR image in a 40-year-old man with a 5-cm rapidly growing contrast-enhancing polyp with a more central area of reduced contrast enhancement radiating to the periphery, 2 years after treatment with conventional radiation therapy plus a stereotactic radiation therapy boost. Inflammatory changes and retained secretions are present in the sphenoid sinus.

Coronal T1-weighted postcontrast MR image in a 42-year-old woman with enhancing polyps in the left lateral wall of the nasopharynx and sphenoid sinus and a large defect in the sphenoid sinus floor, 11 years after conventional radiation therapy and 3 years after a nasopharyngectomy for local tumor recurrence (A). These polyps remained static before rapidly increasing in size on MR imaging 32 months later to form a large heterogeneous mass in the nasopharynx expanding into the sphenoid sinus and nasal cavity. On the T2-weighted image, the mass shows heterogeneous mixed signal intensity (B), and on the T1-weighted image postcontrast there is heterogeneous enhancement (C) with a less enhancing stellate area centrally in the nasal cavity component (D).

A, Coronal T1-weighted postcontrast MR image in a 69-year-old man with osteoradionecrosis causing a large defect in the sphenoid sinus floor and a nonenhancing mass (arrow) within the sphenoid sinus that also shows thickened enhancing mucosa in the roof of the sinus (arrowheads), 5 years after radiation therapy (“rhinolith” at surgery). B, Coronal T2-weighted MR image in the same patient showing the mass is of low-intermediate signal intensity (arrow) and radiation-induced injury in the white matter of the inferior aspects of both temporal lobes.

A, Axial T1-weighted postcontrast MR image in a 39-year-old man with a heterogeneous enhancing mass causing expansion of the sphenoid sinus (arrows) 4 years after radiation therapy. B, Axial T2-weighted MR image in the same patient showing a heterogeneous mass (arrows) with foci of very low T2 signal intensity presumed to be old hemorrhage.