Rathke cleft cyst intracystic nodule: a characteristic magnetic resonance imaging finding.

OBJECT: The fluid content of Rathke cleft cysts (RCCs) displays variable appearances on magnetic resonance (MR) images and can appear indistinguishable from other intrasellar or suprasellar cystic lesions. Intracystic nodules associated with individual RCCs have been noted, but to date their significance has not been fully explored. METHODS: The authors retrospectively reviewed MR imaging studies obtained in patients harboring intrasellar or suprasellar lesions that were consistent with RCCs to identify the presence and imaging characteristics of intracystic nodules. An intracystic nodule was present in nine (45%) of 20 patients with an RCC. All intracystic nodules were clearly visible and displayed a characteristic low signal intensity on T2-weighted MR images. The nodule was only visualized on T1-weighted images in four cases, in which it exhibited a consistent high signal intensity similar to that of the cyst fluid. The nodules did not enhance following the intravenous administration of a contrast agent. CONCLUSIONS: Although it is difficult to differentiate RCCs from other sellar cystic lesions because of the variable signal intensities displayed on MR images, the intensity of the intracystic nodule seems consistent on T1- and T2-weighted images, and the nodule is always clearly visible on T2-weighted images. With a nonenhancing cystic lesion that does not cause significant symptoms in the patient, the identification of an intracystic nodule with a characteristic signal intensity will aid in the diagnosis of RCC and the selection of conservative management.