High resolution CT appearances of the normal pituitary stalk and in pituitary microadenomas

The size of the pituitary stalk (PS) was measured on axial 1 - 2 mm slice post-enhancement CT scans in 20 patients: 5 had raised serum pituitary hormone levels and positive CT findings for microadenoma, 14 had normal serum pituitary hormone levels and one an ACTH secreting bronchogenic carcinoma. The upper limit diameter of 'normal' PS was found to be 3 mm at the level of the dorsum sellae. Enlargement of the PS was seen in all 5 patients who were confidently diagnosed clinically and radiologically as having pituitary microadenomas. Furthermore, the ratio of the diameter of the PS to that of the basilar artery (BA) was greater than 1 in this group, and less than one in the control group. Therefore, detection of the PS enlargement may help in the diagnosis in patients with pituitary microadenomas. (author)