Let's call a spade a spade and sinuses what they really are: abandoned sink holes in our faces. So much for intelligent design.
What a stupendously stupid design, a swim bladder over and under each eye, that inflates and deflates with air and in so doing can capture every spindle of nerve fiber from mandibular molars to jaw, to cheeks to temples, giving rise to tension and pressure like childbirth, like Zeus giving birth to Athena through his skull.
There's a great drawing of that in D'Aulaires' Book of Greek Mythology. Zeus, on his throne subdued by agony, clutching not at a lightening bolt, but at his temples. See what facial pain can do to a God? Let alone a mere mortal.
I understand now how foxes caught by the foot in fur traps might gnaw through their own bones to escape.