What signal intensity do colloid cysts usually exhibit on MRI?
Typically they demonstrate high T1 signal (can be variable) and only rarely have thin rim enhancement, but usually this represents enhancement of the adjacent and stretched septal veins. On T2 they are typically low signal, although again this is variable.
Look at the lesion on FLAIR. Does this mean it is filled with CSF like fluid?
No it is dark because it is intrinsically dark on T2 weighted images. Beware assuming something dark on FLAIR must represent attenuated fluid.
How do colloid cysts usually present clinically?
In the vast majority of cases, colloid cysts are found incidentally and are asymptomatic. Their position in the roof of the third ventricle immediately adjacent foramen of Monro can on occasion result in sudden obstructive hydrocephalus and can present with a thunderclap headache or unconscious collapse. The headaches tend to be positional, and patients may learn how to relieve symptoms.
The rounded structure at the foramen of Munro is confirmed. The content of the cyst is hyperintense on T1, hypointense on T2 and demonstrates no central enhancement or restricted diffusion.
The ventricles are a little prominent with likely a minor degree of hydrocephalus, although the degree of cerebral volume loss and expected ex-vacuo dilatation of ventricles does make this a little difficult to determine.