Sphenoidal sinuses

The sphenoidal sinuses (or sphenoid) contained within the body of the sphenoid vary in size and shape; owing to the lateral displacement of the intervening septum they are rarely symmetrical.

The following are their average measurements: vertical height, 2.2 cm.; transverse breadth, 2 cm.; antero-posterior depth, 2.2 cm.

Relations
When exceptionally large they may extend into the roots of the pterygoid processes or great wings, and may invade the basilar part of the occipital bone.

Each sinus opens into the roof of the nasal cavity via aperatures on the posterior wall of the sphenoethmoidal recess. The aperatures are located high on the anterior walls of the sinuses themselves.

Because only thin shelves of bone separate the sphenoidal sinuses from the nasal cavities below and hypophyseal fossa above, the pituitary gland can be surgically approached through the roof of the nasal cavities by first passing through the anterioinferior aspect of the sphenoid bone and into the sinuses, followed by entry through the top of the sphenoid bone into the hypophyseal fossa.

Innervation
The mucous membrane is innervated by the posterior ethmoidal nerves, and the orbital branches of the pterygopalatine ganglion.

Infection
A potential complication of sphenoid sinusitis is cavernous sinus thrombosis.

Development
They are present as minute cavities at birth, but their main development takes place after puberty.