Pituitary Stalk Cysts

Cysts of the pituitary stalk represent the major differential diagnosis of an inflammatory or tumoral thickened pituitary stalk. Most seem to originate from the Rathke pouch. They can extend from the sella or be limited to the pituitary stalk. They usually demonstrate a T2W hyperintensity, more rarely a T2W hypointensity and are isointense or slightly hyperintense on T1W images. Hyperintensity on FLAIR is a useful clue to eliminate a deep posterior recess of the third ventricle. As Rathke cleft cysts, they can present a punctiform T2 hypointense nodule. Importantly, they displace the neural tissue peripherally. The diagnosis of benign pituitary cysts must be severely questioned if irregular contours or unusual signals or in case of hormonal disturbance.