Sphenoid Sinus

What is the sphenoid sinus?

Your sphenoid sinuses are a pair of air-filled cavities inside your skull. They’re one of four paranasal sinuses (or just “sinuses,” as most people call them). Your paranasal sinuses are your: frontal sinuses, ethmoid sinuses, sphenoid sinuses and maxillary sinuses. They’re all arranged around your nasal cavity. Of all your sinuses, your sphenoid sinus is the farthest back in your skull.

Your sphenoid sinuses make mucus that clears germs and allergens out through your nose. Rarely, they can get infected. When this happens, it’s important to seek treatment to prevent the infection from spreading to nearby structures, like your brain or eye sockets.

What does the sphenoid sinus do?

Your sphenoid sinus makes mucus that traps and flushes out germs that might otherwise make you sick. The mucus also keeps the lining of your nasal cavity warm, moist and healthy. In this way, your sphenoid sinuses help humidify the air you breathe.

Doctors are still learning about all the jobs your sphenoid sinus does. Other potential functions include:

• Reducing the weight of your skull (as the sphenoid sinus is a hollow cavity within bone)
• Absorbing some of the impact during head injuries (which can prevent skull bones from breaking)
• Helping shape the sound of your voice (as sound reverberates, or echoes, more in air-filled spaces)

Where are the sphenoid sinuses located?

Your sphenoid sinuses are inside your sphenoid bone. It’s a butterfly-shaped bone that’s between the bones in your face and other bones deeper in your skull. Your sphenoid sinuses are located behind the upper part of your nasal cavity, just about in the center of your head.

Your sphenoid sinuses are close to key structures. They’re near your:

• Internal carotid artery, the main artery that carries blood to your brain
• Optic nerve, which helps your eyes communicate with your brain so you can see
• Pituitary gland, which makes hormones that regulate several body functions

Surgeons sometimes use the sphenoid sinus to access the pituitary gland and remove tumors. During transsphenoidal surgery, a surgeon can look through your nose and into your sphenoid sinus using a small telescope. This access point prevents surgeons from having to make incisions (cuts) on your face or scalp to remove tumors.

What is its structure?

You have two sphenoid sinus cavities: a left sphenoid sinus and a right sphenoid sinus. They’re separated by a thin bony wall. But the wall isn’t a straight vertical line that divides your sinuses evenly. This means that your left and right sphenoid sinuses aren’t mirror images of each other. Instead, one may be much bigger than the other. Their size varies depending on your age, sex and ethnicity.

The mucus from your sphenoid sinuses drains into the sphenoethmoidal recess. This structure sits inside another one called the superior meatus. It’s located in the back of your nose, just in front of your sphenoid sinus. Parts of your ethmoid sinus also drain here.

What are the common conditions and disorders that affect this body part?

Germs or allergens that get trapped in your sphenoid sinuses can cause inflammation, or tissue swelling. Inflammation in your sphenoid sinuses is called sphenoid sinusitis. The swelling can block your sinus passages and cause germs to get stuck. This can lead to a sinus infection. Usually, when your sphenoid sinuses are infected, nearby sinuses like your ethmoid and frontal sinuses are involved, too.

Although it’s rare for just your sphenoid sinuses to get infected, it can happen. Most sphenoid infections are caused by bacteria. Rarely, fungi play an infectious role. Bacterial infections of the sphenoid sinus can be serious without treatment because these sinuses are so close to your brain and optic nerves.

An infection in your sphenoid sinus can lead to:

• Brain abscess (pus in your brain)
• Damaged cranial nerves (the nerves inside your brain)
• Meningitis (an infection of the membranes surrounding your brain and spinal cord)

Benign, precancerous and cancerous growths can also form in your sphenoid sinus, but these are rare.

Symptoms something isn’t working right

Since your sphenoid sinus is deep within your skull, it doesn’t usually cause symptoms typical of sinus infections, like a stuffy or runny nose. Symptoms of a sphenoid sinus infection, inflammation, or growth are more likely to cause:

• Double vision (diplopia)
• Facial pain or numbness (The area affected depends on which cranial nerves are impacted.)
• Headaches
• Sensitivity to light (photophobia)
• Vision loss

How can I stay healthy?

The same steps you take to prevent colds and allergic reactions, in general, can protect your sphenoid sinuses. Getting enough sleep, exercising regularly and eating nutritious foods can help reduce your risk of getting sick. Good handwashing hygiene and taking precautions around people who are sick help, too.

If you suspect your sphenoid sinuses are clogged, there are things you can do to help clear them. You can try:

• Nasal irrigation, to wash away debris
• Using a humidifier to moisten dry, irritated tissue
• Taking NSAIDs to ease inflammation
• Using a nasal steroid spray, such as fluticasone, to reduce inflammation and assist in sinus drainage

As these sinuses are so close to important structures, it’s important to see a healthcare provider if you’re experiencing signs of sphenoid sinusitis. They may need to drain your sphenoid sinuses to prevent the infection from spreading.

While most sinus infections eventually clear on their own, if two weeks have passed and things aren’t better, it’s time to see a healthcare provider.