Normal pituitary stalk size in children: CT study.

A retrospective study was undertaken of 1005 normal contrast-enhanced head computed tomographic (CT) scans in children to determine normal standards for pituitary stalk diameter, basilar artery diameter, and their ratio for age and gender. The pituitary stalk enlarges with age, and girls have larger stalks than do boys after age 8. The pituitary stalk-to-basilar artery ratio is easily estimated visually. Ratios greater than or equal to 1 are unusual in normal children. A ratio greater than or equal to 1 should prompt direct measurement of the stalk and comparison with age-matched normal values. If the stalk measurement is greater than 2 SD above the age-matched mean, it is presumably abnormal and deserves further evaluation for numerous possible pathologic conditions including histiocytosis X, pituitary adenoma, hypothalamic lesions, Rathke cleft cysts, metastases, sarcoidosis, hypothyroidism, and infection.