MR of malignant nasosinusal neoplasms. Frequently asked questions.

ABSTRACT

This paper focuses on the role of MR imaging of malignant neoplasms through a particular layout that emphasizes (a) the rationale for the application of imaging; (b) the factors influencing the selection of sequences, planes and their proper arrangement; (c) the correlation between MR findings, imaging staging and clinical decision making. Since in most cases surgery is the treatment of choice, the precise assessment of the local extent and spread of tumour plays a key role in planning the surgical approach and influences either the therapy and the prognosis. However, the degree of spatial/anatomical detail required in treatment planning significantly differs between surgery and radiotherapy. Planning of the examination technique focuses on (a) assembling sequences and planes in the shortest time possible; (b) the solution of specific problems distinction between neoplasm and retained secretions within nasosinusal cavities; staging of submucosal spread toward the anterior cranial fossa, the orbit, the pterygo-palatine and superior orbital fissures. Since the most effective barrier to spread of neoplasms beyond sinusal walls does not depend on the mineral content of bone, but on the periosteum, assessment of the integrity of periorbita or dura mater is an essential information. Although MR cannot detect focal erosions of the thin sinusal walls, it reliably demonstrates both residual barriers (periorbita and dura), even though the bone has been completely destroyed. However, the final decision concerning orbital exenteration is made according to intraoperative staging. MR imaging can accurately precise the degree of anterior cranial fossa involvement. Furthermore, since either MR and CT accurately indicate the need to perform an anterior craniofacial resection and adequately exclude neoplastic invasion requiring orbital exenteration, more comparative studies are required to demonstrate that MR preoperative staging of nasosinusal malignancies is cost-effective.