Rathke's Cleft Cyst: MRI

CASE REPORT: 52year female with known sellar lesion for MRI ( with no prior details) shows- Complex heterogeneously enhancing lesion with deferentially enhancing (subtly, moderate, intense) components seen in sella-suprasellar region with unremarkable bony sella, infundibulum, sphenoid. Lunar shaped normal size intensely enhancing pars distalis component of pituitary with poorly defined posterior pituitary. Thin walled regular T1 hyper & T2 low signal mild enhancing mural nodule containing component in sella –suprasellar region causing compression of optic chiasma with normal cavernous sinus & ICA flow voids. Findings likely suggesting Rathke’s cleft cyst with mass effect on optic chiasma & anterior pituitary

Teaching Points by Dr MGK Murthy,  Dr GA Prasad

Rathke's cleft cysts are congenital, non-neoplastic sellar and suprasellar cysts derived from from failure of obliteration of the lumen of Rathke's pouch, which develops as a rostral outpouching of the primitive oral cavity during the third or fourth week of gestation. The epithelium of Rathke's cleft cyst is a vestige of Rathke's pouch that is the precursor of the anterior lobe, intermediate lobe, and pars tuberalis of the pituitary gland. A Rathke's pouch has an anterior and a posterior wall and a central embryonic cleft. The anterior wall of the pouch proliferates to form the anterior lobe of the pituitary gland and the pars tuberalis; the posterior wall becomes the pars intermedia. The residual lumen of the pouch is reduced to a narrow Rathke's cleft, which generally regresses .  It is the persistence and enlargement of this cleft that is said to be the cause of the symptomatic Rathke's cleft cyst. Alternatively, other investigators have suggested that Rathke's cleft cyst originates directly from neuroepithelial tissue, metaplasia of anterior pituitary cells, or endoderm.

 In general, Rathke's cleft cysts are less than 3 mm in diameter and are usually asymptomatic. Symptoms, when present, result from compression of optic chiasm, hypothalamus, or pituitary gland.

MR findings – nonenhancing cyst in sella – suprasellar location with variable fluid signal in T1/T2  with T1 hyperintese signal in 50% & T2 iso to hypointense in 30% & T2 hyperintensein70%, . In ~75% of cases, a small non-enhancing intracystic T1 hyperintense & T2 hypointese nodule can be identified which is virtually pathognomonic of a Rathke's cleft cyst. Thin enhancing rim of surrounding compressed pituitary tissue may be apparent.

Differential- cystic craniopharyngioma, cystic pituitary adenoma. Cyst aspiration and partial removal of Rathke's cleft cyst is regarded to be sufficient, and few recurrences have been reported.