Nerve · Head

Posterior ethmoidal nerve

Nervus ethmoidalis posterior

A slender branch of the nasociliary nerve that supplies the air cells at the back of the ethmoid bone and the lining of the sphenoid sinus — deep sinus territory behind and below the eye. It leaves the orbit through the posterior ethmoidal foramen, high on the medial wall in the seam between the frontal and ethmoid bones, and disappears straight into the sinus system without ever reaching skin. It is the least constant branch of the nasociliary nerve and is frequently absent, its territory then covered by its neighbours. Its interest is regional rather than personal: it is one of the few named nerves that gives the deep sinuses behind the nose any sensory voice at all.