Sella turcica

The sella turcica (literally Turkish Chair) is a saddle-shaped depression in the sphenoid bone of the human skull and of the skulls of other Hominidae including chimpanzees, orangutans, and gorillas.

Anatomy
The seat of the saddle is known as the hypophyseal fossa, which holds the pituitary gland. The hypophyseal fossa is located in a depression in the body of the sphenoid bone. Located anteriorly to the hypophyseal fossa is the tuberculum sellae.

Completing the formation of the saddle posteriorly is the dorsum sellae which is continuous with the clivus, inferoposteriorly. The dorsum sellae is terminated laterally by the posterior clinoid processes.

Pathological Significance
Since the sella turcica forms a bony caudal border for the pituitary gland, a pituitary tumor usually extends upward in the rostral direction into the suprasellar region. This can result in compression of the optic chiasm, which lies on top of the pituitary, enveloping the pituitary stalk. Compression of the optic chiasm can lead to bitemporal hemianopsia, and, when there is no relevant trauma, this clinical finding is pathognomonic for a pituitary tumor.

Some pituitary adenomas can extend inferiorly, growing downward and invading the sphenoid bone and cavernous sinus. Adenomas greater than 10mm (macroadenomas) can cause remodeling of the underlying sphenoid bone altering the shape of the sella turcica.

Clinical significance
Sella turcica is usually used as a reference point with nasion to establish the base of the skull in cephalometric analysis. This is commonly done prior to orthodontic treatment.