The Empty Sella Syndrome

Abstract

The term empty sella syndrome denotes the presence of an enlarged sella containing a remodeled pituitary gland flattened against its posterior and inferior walls. The designation “empty” is a misnomer, since the sella is filled partially by the compressed pituitary gland and partially by cerebrospinal fluid (CSF). The condition results from extension or herniation of the arachnoid membrane into the pituitary fossa, due to an inherent weakness of the diaphragma sella. This weakness, probably congenital, permits herniation of a small arachnoid diverticulum filled with CSF into the fossa. As the diverticulum gradually enlarges, it occupies more volume within the sella, pushing the pituitary to a corner and thus giving the illusion of an empty sella turcica. Since the early description of this entity in the 1960s,¹ the empty sella syndrome has been recognized with increasing frequency. The prevalence rate of empty sella syndrome in adults is estimated at approximately 6%.² Minor degrees of empty sella syndrome may not cause sufficient distortion or enlargement of the sella to be detected radiologically. Thus, the reported prevalence rate of radiologically evident empty sella syndrome underestimates the true incidence of this entity. Zull and Falko³ estimated that the empty sella syndrome accounts for 35% of radiologically demonstrable sellar enlargements. Thus, the empty sella syndrome runs a close second to pituitary tumors as a cause for sellar enlargement. The importance of recognizing empty sella syndrome resides in its superficial resemblance to pituitary tumors. In some cases, the roentgenographic and hormonal manifestations of the empty sella syndrome can be almost identical to those of pituitary tumors.