Computed tomography of cerebellar hemangioblastomas.

Ten patients with proven cerebellar hemangioblastomas were studied by computed tomography (CT). Angiography was obtained in seven cases. Eight patients had a cyst and a nodule, one presented with a nodule only, and one with a cyst only. Some morphological features on CT were found particularly helpful in establishing the histological diagnosis of this tumor. All cysts in this series had either a nonenhancing wall or a thin, discontinuous enhancement rim. The remarkable thinness of the cyst is a helpful feature in differentiating between hemangioblastomas and ring enhancement due to metastases. All hemangioblastoma nodules are near the pia, particularly the tentorial surface or the occipital surface of the cerebellum. The nodules in this series were isodense with brain before and enhanced significantly after contrast medium injection, matching or exceeding the density of the straight sinus. In three cases, a large vessel leading to the nodule could be identified on CT. In only one of 10 cases was there a central lucency in the enhancing nodule. The CT density of the hemangioblastoma cyst correlated with the size of the nodule, i.e., the larger the nodule, the denser the cyst on precontrast studies. Compared to cerebellar astrocytomas, hemangioblastomas are not calcified and tend to have relatively small nodule associated with a large cyst. For a given size cyst, the nodule in an astrocytoma is usually larger.