What is a Sphenoid Sinus?

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  • Written By: Mary McMahon
  • Edited By: O. Wallace
  • Last Modified Date: 11 September 2019
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The sphenoid sinus is an air-filled cavity which surrounds the sphenoid bone in the skull. Everyone has two sphenoid sinuses, with each sinus being around the size of a grape. These sinuses are asymmetrical in shape, and they drain into the back of the nose. Over the course of childhood and adolescence, the sphenoid sinuses grow and settle into their final shapes, with everyone having slightly different patterns in their sinuses; sometimes, sinus anatomy can even be used like a fingerprint to identify someone.

Each sphenoid sinus is located roughly in the middle of the skull, behind the nose and eyes. Like other sinuses in the face, the function of the sphenoid sinuses is not fully understood. They appear to lighten the weight of the skull, and may provide some cushioning from impacts to protect the brain, and they also provide a route for drainage of mucus. In rare cases, the sphenoid sinuses can become inflamed and infected, in a condition known as sinusitis.

When a patient has sphenoid sinusitis, he or she usually develops a headache which can be quite persistent and very painful. A dull pain may also emerge behind the eyes, and the patient can experience a fever and a distinctive nasal discharge. Treatment involves the application of anti-inflammatory drugs to resolve the inflammation, and antibiotics to kill microorganisms responsible. It may be necessary to culture fluids found in the sphenoid sinus to determine the cause of the inflammation.


The location of the sphenoid sinus is of interest to some surgeons because it can provide an avenue of entry for certain surgical procedures on the head. This sinus can also develop tumors, which can become cancerous and problematic because this sinus is in close proximity to the eyes and brain. Abnormalities such as swelling or an accumulation of fluid caused by an infection can be seen with the use of medical imaging studies such as MRI which can visualize the inside of the head.

Many people go a lifetime without experiencing problems in their sphenoid sinuses. In cases where problems like infections or tumors arise, diagnosis and treatment can be challenging because of the location of the sphenoid sinus. People with a history of sphenoid sinusitis and tumors should also be aware that recurrence is common, and when early symptoms are identified, it is a good idea to inform a doctor of any previous history of problems with the sphenoid sinuses, as this can save time on diagnosis.


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Post 4

My husband is suffering with trigeminal neuralgia and has been for several years. Recently an MRI showed that he has a diseased sphenoid sinus on the same side as the pain diagnosed as trigeminal neuralgia. e has had other procedures with no relief from the almost constant pain. He is now scheduled for sphenoid sinus surgery of the left sinus. Wish us well.

Post 3

my vision is a little blurred and i have eye pressure. does this mean i have that kind of sinus infection?

Post 2

@lovealot - Sphenoid sinus infection is quite rare. Only 3% of those who have sinus infection are the sphenoid type. The most common symptom is a bad head or eye ache that won't go away. Some patients may have blurred vision because the sinus is so near the optic nerve.

The doctor will probably have a CT taken. If it shows that the sphenoid sinus is filled with infectious material, then a specialist will do a surgical procedure. He inserts a fine surgical tool up the nose and gets up to the sinus and drains it. This is the scary part - he has to be very careful to avoid the optic nerve, the pituitary gland, arteries and other delicate body parts. This should take care of the infection.

Post 1

Wow! These sphenoid sinuses are the size of grapes, filled with air, are so different they can be used like a fingerprint ID. And the purpose is really not known. They must have served some purpose during the evolutionary process.

I guess these sinuses do have at least one function - it gives the surgeon a clear entrance into the brain and eye area.

So far, I haven't experienced sinusitis. Those head aches and eye aches must be awful. Thank goodness for antibiotics!

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