Olfactory neuroblastoma: MR evaluation.

PURPOSE To evaluate MR in the diagnosis and staging of olfactory neuroblastoma. METHODS Five patients with histologically proved olfactory neuroblastomas were studied by MR. Four also had CT scans. RESULTS The extent of disease delineated by MR agreed with surgical findings and surgical staging of the tumor in all five patients. All cases of olfactory neuroblastomas originated in the nasal cavity and involved the ethmoid sinuses. In three of the five cases, the tumors extended to the anterior skull base. In one case MR correctly suggested skull base involvement missed on CT. Lesions were isointense to hyperintense with muscle on T1-weighted scans. Compared with fat on T2-weighted scans, olfactory neuroblastomas were variable in signal intensity. Enhancement was minimal to moderate in all cases. CONCLUSION In the evaluation of olfactory neuroblastoma, MR is most useful in delineating the extent of the tumor and may be more accurate than CT. However, the signal intensity characteristics of olfactory neuroblastomas may overlap other tumors.