Imaging description

Incidental sellar and suprasellar masses are common on MRI. The most common entity accounting for incidental sellar/suprasellar lesions is Rathke’s cleft cyst (RCC), followed by non-functioning pituitary adenomas. RCCs are benign cysts arising from the remnants of the Rathke’s pouch and are found in up to one-third of autopsy populations [1]. RCCs measuring >2mm are found in 4% of an autopsy series [2]. They are most commonly located within the sella in the pars intermedia region in midline, although they can extend into the suprasellar region when they are large, and rarely occur in the suprasellar region without a sellar component (Figs. 50.1, 50.2).

The majority of RCCs will have increased T1 signal, with some showing isointense T1 signal and occasionally hypointense T1 signal. About 70% of RCCs will show markedly hyperintense T2 signal, but decreased T2 signal is characteristic of this entity and, when present, allows differentiation from other mass lesions (Fig. 50.3). Most asymptomatic lesions will not enhance. When enhancement is present it is thin, smooth, and limited to the cyst capsule. Enhancement of RCC may be secondary to rupture of the cyst causing inflammatory reaction, and it is more commonly seen in symptomatic patients. Occasionally, non-enhancing small nodule(s) may be present within the RCC, and these may move depending on the patient’s position (Fig. 50.4).