Atypical CT and MR appearance of a Rathke cleft cyst.

A 1 0-year-old boy had a 4-year history of growth retardation , a 10month history of polyuria and polydipsia, and recent onset of frontal headaches. Physical examination revealed a small , prepubescent boy without neurologic or visual-field deficits. His growth curve fell below the fifth percentile for height and weight, and the bone age was delayed. CT showed a round sellar mass that bulged into the suprasellar cistern . The lesion was of mixed attenuation, but mostly hyperdense and noncalcified, and it failed to show contrast enhancement (Fig. 1 ). On MR, the mass was hyperintense on T1-weighted images, diminished in signal intensity on intermediate-weighted images, and became isointense on T2-weighted images. A prominent area of signal void was noted centrally on the T2-weighted image. The cyst displaced the optic chiasm anterosuperiorly and obscured the pituitary stalk. At craniotomy, a cyst containing gray-brown gelatinous material was excised completely. Histologically, the cyst was lined with ciliated epithelium and contained scattered foci of inflammation with hemosiderin deposition, diagnostic of a Rathke cleft cyst.