Normal Variations of the Sella Turcica on Thin-Section Tomography : Concerning the Sellar Floor and the Sphenoid Sinus

Normal variations of the sella turcica on thin-section tomography were studied in 40 normal clinical cases who had no abnormal lesions in the sella turcica and the sphenoid sinus, and in 50 normal dry skulls. Tomography of the sella turcica was performed with hypocycloidal motion at 2 mm intervals in anteroposterior and lateral projections. The author investigated the shape of the sellar floor and the sphenoid sinus and its septa. In the relationship between the sellar floor and the pneumatization of the sphenoid sinus, the sellar height of the major and extensive sellar type was smaller than the height of the conchal and presellar type of sphenoidal pneumatization. In the relationship between the sellar floor and the sphenoid septum, 34 of 68 cuts which had lateral septum or double septa had an asymmetric sellar floor. Twenty-three of 48 cases on frontal tomograms and 24 of 44 cases on lateral tomograms had a downward V-shaped projection of the sellar floor at the site of the attachment of the septum. The sellar floor was concave in 57.0%, flat in 41.1% and convex in 1.9% on the frontal tomograms. Fourteen of 90 cases had different sellar floor shapes on every tomographic cut of the frontal tomograms and eight of 14 cases had asymmetric sellar floors. Fifty-eight cases had concave sellar floors, of which the maximum measurement was 2.4 mm. Twenty-five cases had lateral depression of the sellar floor, the maximum measurement of which was below 2.5mm in ordinary cases and the maximum degree of the angle of the sellar floor was below 10 degrees in those cases who had the same degree of pneumatization in the sphenoid sinus. The thickness of the lamina dura on the anterior and posterior sellar floor was thinner than that on the inferior sellar floor. Localized expansion of the sellar floor was seen in 29 cases and localized thinning was seen in 22 cases. On the other hand, localized expansion associated with thinning of the sellar floor was seen in only four cases and this finding never exceeded one tomographic cut. Therefore, the presence of pituitary microadenoma might be suspected when localized expansion associated with thinning of the sellar floor is seen more than two tomographic cuts