Espiral AtlasSinus of sphenoid bone
sinus sphenoidalis
Study entry
Location
In the body of the sphenoid, and may extend into the wings.
Structure
Divided unequally by a bony septum. Because of this pneumatization, the body of the sphenoid is fragile: only thin bony plates separate it from the optic nerves, the optic chiasm, the hypophysis, the internal carotid arteries and the cavernous sinuses. They derive from a posterior ethmoidal cell that begins to invade the sphenoid at about 2 years; in some people, several cells do so, and then there are multiple sinuses, which open separately into the sphenoethmoidal recess.
Blood supply
Posterior ethmoidal arteries.
Innervation
Posterior ethmoidal nerves.
Source: cap. 8, «Senos paranasales»
Clinical correlation
Fractures of the orbit
A direct blow to the rim of the orbit fractures the sutures between the bones that form it. The medial and inferior walls are thin and can break with the rim intact, in «blowout» fractures. The medial wall can involve the ethmoidal cells and the sphenoidal sinus, and the floor can reach the maxillary sinus. The upper wall is stronger, but translucent: a pointed object can pierce it and reach the frontal lobe. Hemorrhage inside the orbit pushes the eyeball forward and causes exophthalmos. Infection can reach the cavernous sinus through the ophthalmic vein.
Tumors of the orbit
The optic nerve lies near the sphenoidal sinus and the posterior ethmoidal cell. A malignant tumor in these sinuses can erode the thin bony walls of the orbit and compress the nerve and the orbital contents. Tumors of the orbit cause exophthalmos. Tumors of the middle cranial fossa enter the orbit through the superior orbital fissure. Those of the temporal or infratemporal fossa enter through the inferior orbital fissure.
Sinusitis
The paranasal sinuses continue with the nasal cavities through openings. Infection can pass from the nasal cavity and inflame and swell the mucosa of the sinuses (sinusitis), with local pain. Sometimes several sinuses become inflamed (pansinusitis). Edema of the mucosa can block one or more openings to the nasal cavity.
Related clinical cases
- Fractures of the orbit
- Tumors of the orbit
- Sinusitis