Sphenoid sinus

Last revised by Craig Hacking on 3 May 2023

The sphenoid sinus is the most posterior paranasal sinus.

The sphenoid sinuses are paired spaces formed within the body of the sphenoid bone, communicating with the roof of the nasal cavity via the sphenoethmoidal recess in its anterior wall. The two hemisinuses are separated by a septum which may or may not be in the midline. It usually lies anteroinferior to the sella.

A large sinus can show a number of ridges and depressions related to closely adjacent structures. These can include the pituitary gland, optic nerve, and internal carotid artery.

Pneumatization types have been subdivided 4:

  • conchal
  • lateral recess
  • presellar
  • sellar (which can be incomplete or complete)

Lymphatic drainage occurs via afferent vessels leading into the retropharyngeal nodes

With respect to optic nerve (CN II) relationship:

  • type 1: adjacent to sphenoid sinus
  • type 2: indenting the sinus
  • type 3: traversing the sinus
  • type 4: adjacent to posterior ethmoid sinus

Pneumatization of the sphenoid sinus starts at around 2 years of age and it develops more slowly than the other paranasal sinuses.

It is important to look for and report the type of pneumatization of this sinus and to report its relationship with adjacent neurovascular structures, especially the presence of dehiscence. In particular, the close proximity of the optic canal and carotid canal to the sphenoid sinus are important aspects to consider when planning sphenoid sinus surgery.5

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