The pituitary stalk, also known as the infundibulum or infundibular stalk, is largely outside the blood brain barrier like the rest of the pituitary and therefore normally enhances following the administration of gadolinium. It gradually tapers inferiorly, and superiorly is spread by the infundibular recess of the third ventricle.
There have been some studies looking at the range of normal sizes of the pituitary stalk. One study had a normal range of:
- 3.25 mm +/- 0.56 (SD) at the level of the optic chiasm
- 1.91 mm +/- 0.40 (SD) as the stalk enters the pituitary gland proper
in other words, 95% of patients should have a stalk that measures no more than:
- 4.4 mm at the level of the optic chiasm, and
- 2.7 mm just above the gland
- differential diagnosis of pituitary stalk abnormal enhancement