Sella turcica !

The sella turcica is the saddle-shaped hollow in the sphenoid bone at the centre of the skull base; it holds the pituitary gland, just below the optic nerves.

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What it is

The saddle-shaped hollow in the sphenoid.

What it does

Holds the pituitary gland, just below the optic chiasm.

Key facts

Where: Upper surface of the body of the sphenoid
Function: Houses the pituitary (hypophyseal fossa); enlarged by pituitary tumours

Relations

Contents: Pituitary gland in the hypophyseal fossa, roofed by the diaphragma sellae, a dural sheet pierced by the stalk; intercavernous sinuses in front of and behind the gland
In front: Tuberculum sellae and the groove for the optic chiasm, with an optic canal opening on each side; the anterior clinoid processes
Behind: Dorsum sellae with the posterior clinoid processes, continuing down as the clivus; behind it the basilar artery and the pons
Above: Diaphragma sellae, then the optic chiasm, the hypothalamus and the floor of the third ventricle
Below: Sphenoid sinus, separated by a floor that is normally thin
Lateral: Cavernous sinus on each side, with the internal carotid artery and III, IV, V1, V2 and VI

How to find it

It cannot be felt. It sits in the midline of the middle cranial fossa, on top of the body of the sphenoid bone, between the anterior and posterior clinoid processes; on a lateral skull X-ray it is the rounded dip above the sphenoid sinus.

Examination

Confrontation visual fields, one eye at a time: loss of the outer (temporal) half of the field in both eyes suggests a mass rising out of the sella onto the optic chiasm; formal perimetry maps the defect and is repeated to follow it

On imaging

MRI is the main study: thin coronal and sagittal T1 slices before and after contrast show the gland, stalk, chiasm and any cavernous sinus invasion. A lateral X-ray or CT shows the bony outline: an enlarged sella with a thinned or double floor suggests a slow-growing mass, and CT shows bone erosion and calcification.

Clinical notes

Empty sella is primary (a weak diaphragma, often with obesity and raised CSF pressure) or secondary (after surgery, radiotherapy or apoplexy shrinks a tumour); some people have hormone deficits
Masses in and around the sella: pituitary adenoma, craniopharyngioma (often calcified), Rathke cleft cyst, tuberculum sellae meningioma and, rarely, an internal carotid aneurysm
Long-standing raised intracranial pressure can thin the dorsum sellae, a classic sign on old skull X-rays

Anatomical variants

Sella turcica bridge: the anterior and posterior clinoid processes join over the fossa, seen on lateral X-rays; more common with some craniofacial and dental anomalies; reported frequency varies
Size and outline vary (oval, round or flat)

Development

The pituitary forms partly from Rathke's pouch rising from the roof of the primitive mouth; rarely its track persists as a craniopharyngeal canal through the body of the sphenoid, linking the sella to the nasopharynx.

Memory aid

Turkish saddle: the tuberculum sellae is the front of the saddle, the dorsum sellae the backrest, and the pituitary sits in the seat.

Test yourself

Think of the answer, then tap the question to see it.

What does the sella turcica hold, and what lies above and below it?

The pituitary gland; above, the diaphragma sellae and optic chiasm; below, the sphenoid sinus.

What shape does a pituitary adenoma take on MRI as it grows up out of the sella turcica?

A snowman or figure-of-eight shape, as it balloons the sella and pushes up through the diaphragma sellae.

What is an empty sella, and what condition can it signal?

The subarachnoid space bulges through the diaphragma sellae and flattens the pituitary; often incidental, sometimes a sign of idiopathic intracranial hypertension.

Which structures lie in the cavernous sinus on each side of the sella turcica?

The internal carotid artery and nerves III, IV, V1, V2 and VI.

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Educational information, not medical advice. For any symptom, see a health professional.

Its names

Official Latin (TA2): sella turcica TA2 589
Official Spanish (DeCS): Silla Turca DeCS D012658
English (TA2): Sella turcica
Also called: pituitary fossa

Sources: Terminologia Anatomica (TA2); DeCS; Empty Sella Syndrome; Anatomy, Head and Neck, Pituitary Gland; Anatomy, Head and Neck, Middle Cranial Fossa; 16.3 The Cranial Nerve Exam (OpenStax (Rice University), 2022) · adapted, CC BY 4.0.

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Representative model, for educational purposes only.