Craniopharyngioma

            Craniopharyngiomas originate from epithelial remnants of Rathke's pouch, usually at the junction of the infundibulum and the pituitary gland. They are benign slow-growing tumors composed of both solid epithelial tissue and cystic components. The cysts contain variable amounts of cholesterol, keratin, necrotic debris, proteinaceous fluid and hemorrhage. Calcification is present in 75 to 85% of cases.

            Craniopharyngiomas have a variable appearance on MR, depending on their solid or cystic nature and the specific cyst contents. The solid lesions are hypointense on T1-weighted images and hyperintense on T2-weighted images. The cysts also have a long T2, but if they have a high cholesterol content or methemoglobin, shortening of T1 results in high signal intensity on T1-weighted images. Other features of craniopharyngioma include truncation of the dorsum sellae and upward growth into the third ventricle. Calcification is not reliably detected with MR, a disadvantage for differential diagnosis. Endnote  

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