What is a reasonable differential for this lesion?
Colloid cyst, central neurocytoma, subependymal giant cell astrocytoma, intraventricular meningioma, intraventricular astrocytoma.
What is the usual appearance of a colloid cyst?
Density is variable, but usually they are hyperdense on CT.
A nodule is located at the foramen of Monro which is well-defined and homogeneously isodense to brain and has a maximal diameter of 1.2 cm measured. There is no evidence of acute haemorrhage or calcification within this lesion. No enhancement. Asymmetry of the lateral ventricles is within normal limits. There is no evidence of uncal or tonsillar herniation.