Specific Imaging Findings

Olfactory neuroblastoma (ONB, also known as esthesioneuroblastoma – ENB) typically arises in the roof of the nasal cavity and from there it characteristically grows in both superior and inferior directions with intracranial extension and spread through the nasal cavity, paranasal sinuses, and orbits. The tumors are T1 and T2 iso- to hypointense compared to the gray matter and usually exhibit prominent contrast enhancement. Diffusion of water in ONBs is lower compared to the brain, seen as dark signal intensity on ADC maps. In the periphery of the intracranial lesions, adjacent to the brain parenchyma, MRI may show well-defined ovoid to round cysts with T1, T2, and diffusion signal characteristics similar to the CSF. These peripheral or marginal cysts are a very characteristic and specific feature of ONB; however, in many cases they are not present, especially with smaller tumors. Large ONBs may be heterogenous with irregular necrotic areas and create a significant mass effect with surrounding vasogenic edema in the brain parenchyma. On CT the tumors tend to be iso- to slightly hyperdense. MRI is the imaging modality of choice as a small intracranial extension of the lesion may not be appreciated on CT. Dural masses in a distant non-contiguous location are a feature of recurrent ONBs.

Pertinent Clinical Information

ONB most commonly presents with nonspecific symptoms of nasal obstruction and epistaxis, followed by headache, visual disturbances and anosmia. There is a bimodal age distribution with the tumors primarily involving patients in their second and sixth decades of life. Overall 5-year survival is approximately 65%.