Rathke’s cleft cyst is a non-neoplastic epithelium-lined cyst arising from the embryologic remnants of Rathke’s pouch. On imaging it is a well-defined non-enhancing midline cyst in the sellar region, arising between the anterior and intermediate lobes of the pituitary. 40% are purely intrasellar and 60% have suprasellar extension. Purely suprasellar lesions are rare. On CT it is typically non-calcified and of homogenous low density. Uncommonly it may be of mixed isodensity and low density, or contain small curvilinear calcifications in the wall.
On MRI the signal characteristics vary according to the cyst content which may be mucoid or serous. On T1, 50% are hyperintense and 50% are hypointense. On T2, 70% are hyperintense and 30% are iso or hypointense. 70% have a small non-enhancing intracystic nodule consisting of mucinous material; this feature is virtually pathognomic of a Rathke’s cleft cyst. There is no contrast enhancement of the cyst but a thin enhancing rim of adjacent compressed pituitary tissue may be seen.
The main differential differential diagnoses are craniopharyngioma, cystic pituitary adenoma and other non-neoplastic cysts such as an arachnoid cyst or epidermoid cyst.
Rathke’s cleft cysts are typically asymptomatic and are found in up to 1/3 of autopsies. If large, they may cause visual disturbance due to compression of the optic chiasm or pituitary dysfunction due to compression of adjacent pituitary tissue.
References:
1. Osborn A. & Preece M. Intracranial Cysts: Radiologic-Pathologic Correlation and Imaging Approach, Radiology 2006; 239:650-664
2. StatDx
3. eMedicine.com
Credit: Dr Donna D’Souza
http://www.radpod.org
