Sellar Cysts and “Empty Sella”: Myths or Reality

The differential diagnosis of space-occupying sellar lesions traditionally incorporated the so-called “empty sella” as the second most frequent abnormality associated with an enlarged sella turcica, following pituitary adenoma. However, to avoid confusion three entities must be differentiated: sellar cysts and primary and secondary forms of an “empty sella turcica”.

Briefly, primary empty sella is the result of an incomplete or incompetent sellar diaphragm. While ideally the diaphragm fits snugly around the infundibulum at its entry site into the pituitary, minor or larger innate defects of the diaphragm are frequently observed in serial autopsy or imaging studies, leading to herniations of the arachnoid of the opticochiasmatic cistern into the intrasellar space. Consequently, CSF pulsations are transmitted into this herniation. Compression of the pituitary and sellar enlargement can occur. There are large variations in the amount of herniation, from a small anterior arachnocele within a sella of normal size to a pronounced sellar enlargement and thinning of the gland, that are almost unidentifiable even in sophisticated imaging. The term “empty sella” is a bit misleading. While pathologists saw the sella to be empty, in reality the sella was filled with CSF. Thus, in the past, cisternography was used to diagnose empty sella and to differentiate it from intrasellar cysts. To date, MRI and CT are the imaging methods of choice. The typical feature of empty sella is the infundibulum sign. Clinical presentation includes hormonal disturbances, headache, deterioration of vision, and most of all, the incidental radiographic finding. Systematic investigations of hormonal secretion show nontumorous, functional hyperprolactinemia as the most frequent abnormality. Various degrees of hypopituitarism can occur. Correction of prolactin secretion by dopamine agonists and substitution of hypopituitarism are standard therapeutic procedures. The treatment of primary empty sella generally is nonsurgical, unless CSF leak occurs from extreme thinning and expansion of the sellar floor. Since the leak is difficult to occlude, the authors recommend trans-sphenoidal reconstructions of the sellar floor, occlusion of the sphenoid sinus by an autologous transplant, and insertion of a lumboperitoneal shunt. Chiasmapexy was not found necessary in our experience since on long-term observation, visual field constriction and impairment of vision spontaneously improved in several patients.

After both trans-sphenoidal or transcranial surgeries of pituitary tumors and also after irradiation or medical shrinkage of adenomas, secondary empty sella can be observed. This is the result of the resection cavity left after tumor excision. A pronounced empty sella is the ideal finding after resection of a large pituitary adenoma and indicates total tumor resection. However, when the intrasellar space is completely filled by CSF there might be residual tumor within the cavernous sinus or skull base. Any alteration that was described with primary empty sella can also be encountered in a secondary empty sella, including cisternal and optic nerve herniation.

The clinical and radiological features of sellar cysts and their differential diagnosis are briefly reviewed. In summary, we will review the typical clinical and imaging features of primary and secondary empty sella and discuss the pathophysiology, guidelines for management, and differential diagnosis of cystic pituitary lesions.