Intracranial fetus-in-fetu: CT diagnosis.

The authors present a case of fetus-in-fetu in which the CT findings are compatible with an earlier description by Nocera et al., i.e., a "round or tubular collection of very low density fat surrounding a central bony structure (probably one of the legs)." Additionally, sonography showed a heterogeneous mass with limb-like structures in the left lateral ventricle. Plain films can confirm the presence of a vertebral column and identify specific bony structures, but CT is a valuable aid in cases where plain films were not obtained or are inconclusive.