Floating Myodil--a new sign of fat in the ventricles.

A case in which a remarkable series of CT studies demonstrated a dermoid cyst is reported. There was leakage of fat into the ventricular system which caused hydrocephalus due to adhesions partly obstructing the fourth ventricular outlets. The latter was confirmed by a ventriculogram using Myodil which dissolved in, or combined with, the fat produced by the tumour. This resulted in a high attenuation substance of lower specific gravity than CSF, which appeared to cause acute ventriculitis.