The Enlarged Sella and the Intrasellar Cistern

Abstract

Discussion Pneumoencephalography combined with tomography has shown that in some patients an enlarged sella is not occupied by tumor but by an extension of the subarachnoid space into the sella. We are reporting 12 cases of this sort, in which such an "empty sella" was found as a primary entity in the absence of prior surgical or radiation therapy. These will be analyzed and compared to similar cases described in the literature. Materials Our patients, 8 women and 4 men, ranged in age from twenty-four to sixty-eight years (Table I). Initial roentgenograms of the skull had been obtained for evaluation of trauma to the head in 2 instances, cerebrospinal fluid rhinorrhea in 1, seizures in 1, acute sinusitis in 1, dizziness in 1, and headaches, visual problems, or both in 4. Clinical evidence of acromegaly in the remaining 2 patients initiated their diagnostic workup. No prior history of endocrine problems that might have been related to an intrasellar tumor was obtained in the other 10 patients. Three patients had visual complaints. In 1, a perineural cyst surrounding the intraorbital portion of the optic nerve was subsequently found. In the other 2 patients, no significant objective visual loss was noted. Roentgenograms of the skull showed enlargement of the sella in all of the patients. The sella dimension was below the level ofenlargement was of the balloon type, i.e., the widest anteroposterior the diaphragma sellae. Slight truncation of the dorsum sellae was noted in one patient. At pneumoencephalography, significant findings were limited to the sellar region. Air entered the sella with the head extended in the sitting position or in the brow-up position. With change in position of the head, air was demonstrated to leave and usually re-enter the sella freely, and a fluid level was seen when air partially filled the intrasellar cistern. These maneuvers established that the air entered the sella from the subarachnoid space and not from the third ventricle. Tomograms of the sellar area and anterior third ventricle were obtained in the lateral projection and, in most instances, in the anteroposterior projection as well. Autotomography was used in 1 patient, linear tomography in 3, and hypocycloidal tomography in 8. The pituitary gland was usually seen as a crescentic soft-tissue shadow adjacent to the floor of the sella (Fig. 1). The configuration of the sella and its relation to the anterior third ventricle were traced for all 12 patients (Fig. 2). A line drawn from the infundibular recess to the center of the sella indicates approximately the course of the infundibular stalk. In each instance, this line crossed the plane of the diaphragma sellae well behind its center. This observation and the free entry and exit of air from the sella suggest that the diaphragma sellae consisted of a very narrow rim.