Esthesioneuroblastoma with intracranial extension. The authors present five cases of olfactory neuroblastoma with intracranial extension operated on in the Department of Neurosurgery in collaboration with otorhinolaryngologists. This tumor is most frequently reported as growing inside the nasal cavities, and it can extend to the paranasal sinuses. Cases presenting initially as intracranial tumors have been infrequently reported. At present, histological diagnosis of this tumor is aided by the use of electron microscopy and immunocytochemistry. Total resection combined with radiation therapy remains the most satisfactory treatment. 