The sella may not be completely filled with tissue. When the sella is partially filled with CSF in the suprasellar cistern, it is referred to as an empty sella (Fig. 20-4). A partially empty sella is a common incidental finding and usually should be considered a normal variation in anatomy. The empty sella may be related to incomplete formation of the diaphragma sella, allowing CSF into the pituitary fossa (see Chap. 11). A partially empty sella can be seen in association with pseudotumor cerebri, hydrocephalus, previous pituitary surgery, or a previous pituitary mass that has shrunk. It can also be seen after irradiation, after trauma, or as sequela of apoplexy. Occasionally, an empty sella is associated with a CSF leak or fistula. The term empty sella syndrome has been used to describe a variable clinical constellation of findings, such as headache, endocrine dysfunction, and visual disturbances, which are seen in association with a partially empty sella.15

With an empty sella, the sellar bony margins may be expanded, forming an oval or J shape on plain radiograph or
CT. It is often of normal size. The CSF spaces extend into the sella; the pituitary gland may be normal, small, or large in size. The optic nerve, optic chiasm, and optic tracts may herniate into the empty sella. The main finding is visualization of the pituitary stalk extending into the fossa, which is the best way to distinguish an empty sella from a cystic mass.