Anatomy and Location of the Sella Turcica
The sella turcica is a central landmark on the superior surface of the sphenoid body (Corpus). It features a complex topography surrounded by several key bony structures:
- Hypophysial fossa (Fossa hypophysialis) — the central depression housing the pituitary gland.
- Tuberculum sellae — forms the anterior boundary of the fossa. It features the middle clinoid process (Processus clinoideus medius).
- Dorsum sellae — forms the posterior boundary of the fossa. It extends laterally into the posterior clinoid processes (Processus clinoidei posteriores).
- Prechiasmatic sulcus (Sulcus prechiasmaticus) — leads to the sella anteriorly. Anterior to this is the jugum sphenoidale, separated by the Limbus sphenoidalis.
Laterally, the carotid sulci (Sulcus caroticus) run along the sides of the sphenoid body, bounded posteriorly by the Lingula sphenoidalis. Inside the sphenoid body lie the sphenoid sinuses, divided by the Septum sinuum sphenoidalium.
Contents and Relations of the Sella Turcica
Topographically, the sella turcica region is intimately related to critical endocrine and neurovascular structures:
- Pituitary gland — located within the hypophysial fossa. It is an endocrine organ weighing approximately 0.5 g, enveloped in a dense fibrous connective tissue capsule. It lies at the base of the brain and connects to the tuber cinereum via the pituitary stalk. The stalk contains the infundibulum, the cavity of which is a direct extension of the third ventricle.
- Cranial nerves and vessels — in sagittal projection, close to the bends 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 closely related to the region.
Diagnostic Imaging
Skull radiography evaluating the sella turcica and brain MRI are used to rule out organic lesions in endocrine disorders such as anovulatory infertility. When evaluating large pituitary tumors, T1-weighted MRI scans in the coronal and sagittal planes are utilized, frequently with contrast enhancement.
Pathologies of the Sella Turcica and Adjacent Structures
Pathological changes in the sella turcica region typically stem from neoplastic processes or cerebrospinal fluid dynamics abnormalities:
- Pituitary adenomas — tumors expanding within the sella turcica. They are classified as microadenomas (diameter < 10 mm) and macroadenomas (10 mm or greater). Large pituitary tumors, such as prolactinomas, can expand within and above the sella turcica, significantly enlarging the bony cavity, enhancing with contrast, and compressing the optic chiasm superiorly. This compression serves as the morphological basis for bitemporal hemianopsia.
- Empty sella syndrome — a rare condition involving a defect in the diaphragma sellae or an abnormally enlarged diaphragmatic hiatus. Chronic pulsations of cerebrospinal fluid lead to flattening and sclerosis of the pituitary gland. On imaging, the pituitary gland does not fill the entire sella turcica. This syndrome may occur secondarily following Sheehan syndrome, Simmonds disease, pituitary apoplexy, or radiation therapy.
- Suprasellar tumors — the most common include hypothalamic gliomas and craniopharyngiomas, which often present with hypopituitarism.