Skull base involvement by a nasopharyngeal carcinoma shown by Tc-99m MDP SPECT but not by computed tomography

Purpose: Plain radiographs, computed tomography (CT), and more recently mag netic resonance imaging (MRI) are used routinely to stage carcinoma of the nasopharynx. Tc-99m methylene diphosphonate (MDP) SPECT is seldom used for local staging of the disease. Materials and Methods: Plain radiographs and CT were used to stage squamous carcinoma of the nasopharynx in a 50-year-old man with a left XII nerve pa lsy. Results: Findings of the plain radiographs were normal, whereas the CT scan revealed a nonhomogenous hyperdense mass in the nasopharynx but intact und erlying bone. Given the symptoms, a Tc-99m MDP planar scan was ordered and showed no enhanced uptake, but SPECT images obtained at the same time revea led markedly increased focal radiotracer uptake in the region of the tumor, indicating osseous involvement. Conclusion: Possible bony invasion with a nasopharyngeal carcinoma may be b etter shown with MDP SPECT than with planar isotope bone scans, plain radio graphs, or CT.