Where is the main abnormality located and what complication is evident?
A large pineal region mass is present which results in hydrocephalus, due to compression of the aqueduct.
Look carefully. Is a second related abnormality present?
Yes, most easily seen on sagittal images, a second smaller but similar mass is present in the floor of the third ventricles / suprasellar region.
What should be your favoured diagnosis?
Germ cell tumour has a tendency to involve these two sites simultaneously.
What would initial management consist of?
Given the marked degree of hydrocephalus, placement of shunt or ventricular drain is required (which occurred prior to MRI).
A large lobulated mass is centered on the pineal gland, engulfing the pineal calcifiation. It is somewhat hyperdense compared to adjacent brain. A further smaller mass is seen in the floor of the third ventricle. The midbrain is distorted, compressed and demonstrates low density suggestive of oedema. Obstructive hydrocephalus is present.