Low attenuation lesions in the midline posterior fossa: differential diagnosis.

A wide variety of cystic appearing or low attenuation lesions in the midline posterior fossa can so closely resemble one another as to render specific histologic diagnosis from CT scans alone fraught with error. Absorption coefficients often overlap and are too nonspecific to infer consistently accurate histologic diagnosis. It is virtually impossible to separate cystic from noncystic, benign from malignant, and neoplastic from non-neoplastic lesions by absorption coefficients alone.