The target sign: a CT finding in tumors of the corpus callosum.

An unusual computed tomography finding, the "target sign," is demonstrated in a patient with a corpus callosum tumor mass extending to the right lateral ventricle. The central low attenuation of the "target" is produced by the isolated part of the dilated lateral ventricle surrounded by tumor tissue, the dense area of the "target." The diagnosis of the tumor of the corpus callosum and the explanation of the "target sign" was made by polytome pneumoencephalography.