How sure can you be of this diagnosis?
Almost 100%. The presence of a hypointense T2 'dot' within the cyst is extremely characteristic.
What does this do represent?
An intraluminal nodule which macroscopically appears white and is often adherent to the cyst wall (although it may be free floating) is composed of solid tissue that represented desquamated cellular debris.
What is the usual T1 signal intensity of the cyst content?
50% are hyperintense (high protein content); 50% are hypointense
A cystic lesion measuring 9 x 10 x 12 millimetres occupies the anterior part of the pituitary fossa, displacing the normal pituitary tissue posteriorly and somewhat to the left. It is of low signal intensity on T1, does not enhance, and is of high signal intensity on T2 and demonstrates a 2 to 3 mm hypointense nodule anteroinferiorly.
The optic chiasm may be just contacted in the midline by the dome of the cyst. There is no evidence of extension into the cavernous sinuses.
Scattered throughout the white matter of both cerebral hemispheres, particularly in the frontal lobes, are regions of high T2 signal, which are non-specific but most likely relate to chronic small vessel ischaemic change.