Sella turcica

Structure and topography of the sella turcica

The sella turcica is the central structure on the upper surface of the body of the sphenoid bone (Corpus). It has a complex relief and is surrounded by several bony structures:

• Hypophysial fossa (Fossa hypophysialis) is a depression in the center of the sella that houses the pituitary gland.
• Tuberculum sellae (Tuberculum sellae) bounds the fossa anteriorly. It bears the middle clinoid process (Processus clinoideus medius).
• Dorsum sellae (Dorsum sellae) bounds the fossa posteriorly. Extending from it are the posterior clinoid processes (Processus clinoidei posteriores).
• Prechiasmatic sulcus (Sulcus prechiasmaticus) leads to the sella anteriorly. Anterior to it lies the jugum sphenoidale (Jugum sphenoidale), which is separated by a border—the Limbus sphenoidalis.

On the sides of the sella, along the lateral surfaces of the body of the sphenoid bone, run the carotid sulci (Sulcus caroticus), bounded posteriorly by the Lingula sphenoidalis. Inside the body of the bone are the sphenoidal sinuses, divided by a septum (Septum sinuum sphenoidalium).

What is located inside and above the sella turcica?

Topographically, the region of the sella turcica is associated with endocrine and neural structures:

• Pituitary gland is located in the hypophysial fossa. It is an endocrine organ weighing about 0.5 g, covered by a capsule of dense fibrous connective tissue. It lies on the inferior surface of the brain and is connected to the tuber cinereum (tuber cinereum) via the pituitary stalk. Inside the stalk runs the infundibulum (infundibulum), the cavity of which is a continuation of the third ventricle.
• Cranial nerves and vessels — in the sagittal projection, in close proximity to the bend of the internal carotid artery, the oculomotor (CN III), trochlear (CN IV), abducens (CN VI) nerves, and branches of the trigeminal nerve (CN V) are visualized.

Clinical significance in diagnostics

Skull radiography evaluating the sella turcica and brain MRI are used to rule out organic lesions in endocrine anovulatory infertility. When describing a large pituitary tumor, T1-weighted MRI scans in the coronal and sagittal planes are used; some images are obtained with contrast enhancement.

Pathologies of the sella turcica and adjacent structures

Changes in the region of the sella turcica are associated with neoplastic processes or cerebrospinal fluid circulation disorders:

• Pituitary adenomas are tumors that fill the sella turcica. Microadenomas (diameter up to 10 mm) and macroadenomas (10 mm and larger) are distinguished. A large pituitary tumor, such as a prolactinoma, can be located inside the sella turcica and extend above it, significantly expanding the sella turcica, taking up contrast medium, and displacing the optic chiasm upward with stretching. This serves as the morphological substrate for bitemporal hemianopsia.
• Empty sella syndrome is a rare pathology associated with a defect of the diaphragma sellae or an excessively large opening for the pituitary stalk. Constant cerebrospinal fluid pressure leads to atrophy and sclerosis of the pituitary gland. On radiographs, the pituitary gland does not occupy the entire sella turcica as it normally does. The syndrome may develop secondarily against the background of Sheehan and Simmonds syndromes, pituitary adenoma infarction, or radiation therapy of the pituitary gland.
• Suprasellar tumors — the most common are gliomas and craniopharyngiomas of the hypothalamus. They cause adenohypophyseal hypofunction.

Class and exam questions

What else to study on this topic

• Sphenoid bone
• Pituitary gland
• Pituitary adenoma
• Empty Sella Syndrome
• Optic chiasm

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.