Anatomy of the Sinuses

 

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The sinuses are spaces filled with air in some of the bones of the skull. Air passes in and out of these cavities, and mucus drains through them and out of the nose. They also reduce the weight of the skull and give our voices a nicer sound.

The sinus cavities are different than the nasal cavity.  The nasal cavity is the space that we breath through.  It contains two major structures: the septum which is the wall that separates the two nasal passageways and the turbinates which curl off the sides of the nasal cavity.  The turbinates are what swell and block the nose on and off.  The sinus cavities drain into the nasal cavity.

There are four main pairs of sinus cavities in the face:
 

• Maxillary - in the cheekbones
• Ethmoid - between the eye sockets
• Frontal - in the forehead and above the eyebrows
• Sphenoid - deep in the head at the back of the nose

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The mucous membrane in the nose and sinuses is our personal air conditioner. It warms, moistens, and cleans the air. The mucous membrane creates a clear, wet, slightly sticky mucus that gathers any dust, smoke, bacteria, or virus particles that may have been in the air. Tiny hairs along the membrane called cilia act as tiny oars, moving the mucus along much like a conveyor belt through the sinuses and out the nose.

When the mucus containing the unwanted particles reaches the nose and throat, the body prompts us to swallow, spit, sneeze, or cough it out of the body. When a cold or allergy prevents the cilia from moving the mucus through, the nose becomes blocked.

The mucous membrane is also one of the body's front-line defense systems. It releases chemicals that help to destroy bacteria and viruses before they can attack.

If a virus, bacteria, allergen or other irritant is strong enough to prevent the mucous membrane and cilia from doing their job, blockages can occur in any of sinus openings.

Sinusitus

Chronic sinusitis can be a miserable condition that significantly impairs your quality of life.  It begins with an inflammation of the mucous membranes in your sinuses. The inflammation causes fluid buildup eventually plugging the sinus cavity and preventing normal mucus drainage. Most cases of sinusitis are acute, meaning they resolve in less than four weeks. However, when the condition recurs or endures longer than 12 consecutive weeks, you've developed a case of chronic sinusitis.

 Cause

Anything that inflames the membranes of the sinus cavity or blocks the sinus passageways from draining normally.  Once the sinuses become blocked, they fill with secretions and the oxygen content fall.  These are conditions that allow bacteria to grow and then increase the inflammation and symptoms.

• infections of the upper respiratory tract (viral infections or a “cold”)
• allergies
• molds and fungus in sinuses
• anatomical problems such as a deviated nasal septum
• nasal packing
• diseases (e.g. cystic fibrosis) or medications (e.g. antihistamines) that change the normal nasal secretions
• diseases (e.g. HIV) or drugs (e.g. chemotherapy) that affect the immune system
• nasal or facial trauma
• extremes of temperature and humidity
• poor air quality
• foreign objects placed in the nose
• diseased teeth
• tumors

Fungi are present in virtually everyone. However, sufferers of chronic sinusitis may react to the fungi by producing cytokines or elevated levels of eosinophils in the sinuses. Cytokines are compounds that cause or regulate inflammation and other immune responses. Eosinophils are a type of white blood cell that can cause inflammation in the sinuses. This reaction may trigger the inflammation that leads to chronic sinusitis in some people.
 

Symptoms
The signs and symptoms of chronic sinusitis are similar to acute sinusitis, except they last longer and often cause more significant fatigue. Chronic sinusitis usually does not cause fever.
 

• pain and pressure in the cheeks, across the forehead and behind the eyes, sometimes localized to one side
• aching in your upper jaw and teeth
• drainage of a thick yellow or greenish discharge from the nose or down the back of the throat
• difficulty breathing through the nose
• reduced sense of smell or taste
• sore throat
• cough
• fatigue

Diagnosis
Because the symptoms of chronic sinusitis can resemble those of colds or allergies, chronic sinusitis can be difficult to diagnose. Tell your doctor as much as possible about your symptoms.
 

• Nasal endoscopy. A thin, rigid tube (endoscope) with a fiber-optic light inserted through your nose allows your doctor to visually inspect the inside of your nose, but not inside your sinuses.
• Imaging studies. Images taken using computerized tomography (CT) or magnetic resonance imaging (MRI) can show details of your sinuses and nasal area. These may identify a deep inflammation or physical obstruction that is difficult to detect using an endoscope.
• Nasal and sinus cultures. Laboratory tests are generally unnecessary for diagnosing chronic sinusitis. However, in cases in which the condition fails to respond to treatment or is progressing, tissue cultures may help pinpoint the cause, such as identifying a bacterial pathogen.
• An allergy test. If your doctor suspects that the condition may be brought on by allergies, an allergy skin test may be recommended. A skin test is safe and quick and can help pinpoint the allergen that's responsible for your nasal flare-ups.

A doctor's approach to treating chronic sinusitis will aim to clear the nasal passages and also eliminate the underlying cause.
 

CT Scans: The image on the left is two radiologic views of the sinuses at different depths in the head. The image on the right demonstrates the appearance of abnormal sinuses which now are filled with swollen tissue and trapped secretions. The sinuses which are black are filled with air and are considered normal. The abnormal sinsues are all gray. •click to enlarge images

Treatment

• antibiotics. A course of antibiotics can help eliminate sinusitis caused by a bacterial infection. Your doctor may prescribe antibiotic therapy for 10 days, or until you've been symptom-free for seven days.
• corticosteroids (Prednisone and Medrol). Your doctor may prescribe corticosteroids to reduce swelling if you have severe inflammation of your sinuses. Corticosteroids may be delivered through the nose, such as Flonase, Beconase or Nasacort, or taken orally, as in the case of prednisone.
• decongestants. Taken orally or in the form of a nasal spray, decongestants shrink the swollen mucosa and give temporary relief by helping to drain the sinuses. Examples of nasal sprays are Afrin, Dristan or NeoSynephrine, while a common oral decongestant is Sudafed.
• antihistamines  Allegra, Zyrtec, Claritin, Benadryl and other antihistamines can help dry up nasal secretions, but some doctors are concerned that they may worsen a sinus condition.
• moisture and humidification. Flushing the nasal cavity with isotonic saline nasal sprays can help loosen dried mucus and cleanse the nose and sinuses of bacteria. Hypertonic (very salty) irrigations may have the advantage of being a natural decongestant.
• immunotherapy. If allergies are contributing to the sinusitis, stimulating the antibodies that block the body's reaction to specific allergens may help alleviate the condition.

In cases that continue to resist treatment or medication, endoscopic sinus surgery  may be an option. For this procedure, the doctor uses an endoscope, a thin, flexible tube with an attached light, to explore your sinus passages. Then, depending on the source of obstruction, the doctor may use various tools to remove tissue or shave away a bone or polyp that is causing nasal blockage. Enlarging a narrow sinus opening may also be an option to promote drainage.

Another treatment method that may become more common is balloon sinuplasty which helps open the drainage from the frontal sinuses by inserting and then inflating a balloon where it can safely crush some of the obstructing bony chambers. The procedure is less invasive than traditional sinus surgery. However, it is relatively new and long-term results are still unclear.

Prevention

You can reduce your risk of developing chronic sinusitis by:

• Good hygiene. Wash your hands frequently, especially before meals, to avoid contracting viral, bacterial or fungal infections.
• Carefully managing allergies. Work with your doctor to get symptoms quickly under control.
• Treating cold symptoms immediately. Drink plenty of fluids and keep your nasal passages clear when you contract a cold. Use decongestants and try to prevent a cold from lingering.
• Avoiding cigarette smoke and polluted air. These contaminants can irritate and inflame your nasal passages.
• Using a humidifier. Adding moisture to the air can keep your nasal passages clear.
• Taking care to prevent asthma attacks. Try to eliminate potential triggers of an asthma attack. Limit exposure to allergens, tobacco smoke and other causes.

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