MR imaging findings in colloid cysts of the sellar region: comparison with colloid cysts of the third ventricle and Rathke's cleft cysts.

RATIONALE AND OBJECTIVES

To identify magnetic resonance (MR) imaging characteristics allowing specific preoperative discrimination between colloid cysts (CCs) of the sellar region and third ventricle (CC3rdv) versus Rathke's cleft cysts (RCCs).

MATERIALS AND METHODS

MR imaging data of 38 patients with histologically proven CCs/CC3rdv and RCC underwent retrospective analysis with respect to signal intensity and heterogeneity on T1- and T2-weighted images, presence of the dot sign, enhancement, size, location, and accompanying infundibular stalk abnormalities.

RESULTS

Thirteen patients had CCs, 12 had CC3rdv, and 13 had RCCs. Signal intensity on T1-weighted images was partly or entirely hyperintense (n = 8), iso- or mixed iso/hypointense (n = 5) in CCs; hyperintense (n = 8), isointense, or mixed hypo/isointense (n = 3) in CC3rdv and hyperintense (n = 9); or mixed (n = 4) in RCCs. On T2-weighted images, signal intensity was hypointense (n = 12) or hyperintense (n = 1) in CCs, hypointense (n = 9) or hyperintense (n = 2) in CC3rdv, and hypointense (n = 5) or iso/hyperintense (n = 8) in RCCs. T2-weighted images were unavailable in two patients. Only one questionable enhancement was found in CCs, whereas an enhancing rim was consistently seen in RCCs. The dot sign was present in 7 CCs, 8 CC3rdv, and 4 RCCs. Mean cyst diameters were 12.6 mm for CCs and 14.5 mm for RCCs. RCCs showed more frequent and even solely suprasellar extent contrary to CCs.

CONCLUSION

Cyst wall enhancement was found in all RCCs but in none of the CCs, making this feature a reliable discriminator between the two. Complementary, suprasellar extension was more frequent in RCCs, whereas signal hypointensity on T2w was more common in colloid cysts.