Benign sinonasal masses and slow-growing neoplasms tend to remodel the nasal vault and facial bones, and this is particularly true of nasal polyps and inverted papillomas. However, when such benign masses press against the floor of the anterior cranial fossa and the walls of the sphenoid sinuses, simulated aggressive bone destruction rather than bone remodeling usually occurs. This type of bone destruction implies to the radiologist that a carcinoma may also be present, and this information could dissuade a surgeon from operating with an attempt at cure. In fact, about 90% of the time with inverted papillomas and in virtually all cases of nasal polyposis, no carcinoma is present. The computed tomographic (CT) scans and magnetic resonance images of 14 patients are used to demonstrate these changes. In addition, the CT scans of three patients with malignancies are shown to illustrate the similarity in the bony skull base changes.
Despite the plethora of information provided by magnetic resonance (MR) imaging that allows differentiation of some substances that are indistinguishable at computed tomography (CT), there are diagnostic problems. In particular, there are several quite disparate substances that all appear as either low signal intensity or signal void on T1-weighted images and even lower signal intensity or signal void on T2-weighted images. These substances include air, desiccated secretion, mycetomas, acute hemorrhage, calcium, bone, and enamel. When they are surrounded by material that has long T1 and T2 relaxation times, a not uncommon MR appearance in the sinonasal cavities, they may be impossible to differentiate from one another. The current explanations for the low signal intensities are presented, the similarities in the MR appearance are illustrated, and the use of CT to resolve diagnostic problems is discussed. CT appears to be the best modality for initially examining patients with suspected routine inflammatory disease or fungal infection.
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