Specific Imaging Findings

Hemangioblastomas are typically located along the cerebellar surface and their classic appearance is a cystic mass with a mural nodule; however, solid masses with or without internal cysts are frequently encountered. The lesions are spherical and sharply demarcated, with the cystic component being usually CT hypodense, of very low T1 and high T2 signal. The signal of the cyst may vary, based on the protein content, and hemorrhage may be present. The solid tumor is T2 hyperintense and typically abuts the surface of the cerebellum and markedly enhances with contrast, whereas the cystic wall does not enhance. There is moderate to marked surrounding edema. Characteristic vascular flow-voids on MRI are present within larger lesions and best seen on T2WI. Solid portions have high diffusivity and are very bright on ADC maps. Perfusion studies reveal extremely high relative cerebral blood volume. While sporadic hemangioblastomas are found almost exclusively in the cerebellum, these tumors may occur anywhere throughout the CNS in patients with von Hippel–Lindau disease (VHL). The size of the lesion varies from punctate to several centimeters and post-contrast MR images are needed to detect small lesions. Catheter angiography of some hemangioblastomas shows characteristic tightly packed wide vessels and a nodule in the early arterial phase, resembling a “cherry attached to its stalk”. The constellation of MRI findings including intralesional flow-voids, contrast enhancement, increased diffusivity, and very high perfusion are diagnostic in most cases.