Suprasellar cystic lesion (differential diagnosis)

Located in the posterior aspect of the suprasellar cistern is an elongated ovoid mass which measures 12 x 11 x 13mm (AP x CC x trans). The lesion is hypointense on T2 (more intense than CSF), mildly hyperintense on FLAIR (compared to adjacent medial temporal lobe) and of intermediate signal intensity on T1 (less intense than brain). In the posterior right aspect there are two small rounded foci low T2 and slightly high T1 signal, most likely representing accretion of cellular debris (a common finding in epithelial lined cysts, especially Rathke's cleft cysts, but also sometimes seen in colloid cysts and pineal cysts for example). There is no appreciable contrast enhancement of these foci all the wall. The lesion appears separate from the pituitary gland which is normal, and the posterior pituitary bright spot is in a normal location. The lesion abuts the posterior margin of the infundibulum which remains midline. The superior border of the lesion abuts but does not significantly displace the optic chiasm and optic tracts.

The inferior anterior margin abuts the posterior clinoid processes. No significant susceptibility demonstrated on gradient echo imaging. No restricted diffusion evident.

The remainder of the imaged brain appears unremarkable.

IMPRESSION

The suprasellar lesion has minimal mass effect and is most in keeping with a purely suprasellar Rathke's cleft cyst albeit in an unusual location. The differential diagnosis includes other cysts (e.g. neurenteric cysts), hypothalamic hamartoma or a craniopharyngioma; the latter is thought unlikely given lack of T1 fluid hyperintensity, and lack of any enhancing component.