MR findings of subarachnoid dissemination of a pituitary adenoma

Although pituitary adenoma is a benign tumour, subarachnoid dissemination o ccurs rarely. We describe a case of pituitary adenoma with subarachnoid dis semination. After the third operation for pituitary adenoma, an extraaxial mass was demonstrated on MR images. On T-1 and T-2 weighted images, the sig nal intensities of the extraaxial mass were similar to those of the primary pituitary adenoma. On dynamic contrast T-1 weighted images, the time-inten sity curve of the extraaxial mass, which showed early and persistent signal intensity, was also similar to that of the primary pituitary adenoma. Thes e MR findings are considered to reflect the similar vascularity and stroma of the extraaxial mass and the primary pituitary adenoma.