Sinus

What is a sinus?

A sinus is a hollow, air-filled cavity. For the purposes of this article, a sinus will referred to those hollow cavities that are in the skull and connected to the nasal airway by a narrow hole in the bone (ostium). Normally all are open to the nasal airway through an ostium. Humans have four pair of these cavities each referred to as the:

1. frontal sinus (in forehead),
2. maxillary sinus (behind cheeks),
3. ethmoid sinus (between the eyes), and
4. sphenoid sinus (deep behind the ethmoids).

The four pair of sinuses are often described as a unit and termed the "paranasal sinuses." The cells of the inner lining of each sinus are mucus-secreting cells, epithelial cells and some cells that are part of the immune system (macrophages, lymphocytes, and eosinophils).

Functions of the sinuses include humidifying and warming inspired air, insulation of surrounding structures (eyes, nerves), increasing voice resonance, and as buffers against facial trauma. The sinuses decrease the weight of the skull.

Picture of the anatomy of the sinuses

What is a sinus infection?

A sinus infection occurs when a pathogenic microorganism (virus, bacterium, or a fungus) grows within a sinus and causes intermittent blockage of the sinus ostium. Drainage of mucus and pus often occur when the blockage is relieved. The drainage usually goes from the nasal passages to the throat or out the nostrils. Such infections also cause inflammation (an influx of immune cells and swelling of the sinus tissue) of one or more sinuses. This can to block the openings of the sinuses and leads to discomfort.

Inflammation of the air cavities within the passages of the nose (paranasal sinuses) is referred to as sinusitis. Sinusitis can be caused by infection, but can also be caused by allergy and irritation of the sinuses.

Sinusitis is one of the more common conditions that can afflict people throughout their lives. Sinusitis commonly occurs when environmental pollens irritate the nasal passages, such as with hay fever. Sinusitis can also result from irritants, such as chemicals or the use and/or abuse of over-the-counter (OTC) nasal sprays, and illegal substances that may be snorted through the nose. About 30 million adults have "sinusitis."

2011 is a year that sinus infections are getting much lay press as sinus infections have been reported in several sports figures in basketball and baseball. The sinus infections have been reported to alter the ability of the athletes to play at their peak performance. One young (18yr old) professional baseball player reportedly died from a bacterial sinus infection that spread to his brain. Also, about 15 trauma victims of the May tornado disaster in Joplin, Missouri developed fungal infections that are rarely seen (some of them in the sinuses).

Sinus infection facts

• Sinus infections are caused by infections from a pathogenic microorganism (virus, bacterium, or fungus), which grows within a sinus and causes intermittent blockage of the sinus ostium.
• Most people do not transmit sinus infections; most clinicians agree that except for rare instances, sinus infections are not contagious but arise from mainly viruses and bacteria that, by chance, contaminate a person who sinuses support their proliferation because of minor, and rarely, major abnormalities in the person's sinus tissue (for example, swelling, inflammation, abnormal mucus production, and rarely, facial or nasal trauma).
• Sinusitis is inflammation of the air cavities within the passages of the nose. Sinusitis can be caused by infection, but also can be caused by allergies and chemical or particulate irritation of the sinuses.
• Sinusitis may be classified in several ways such as acute sinus infection, subacute sinus infection, chronic sinus infection, infected sinusitis, and noninfectious sinusitis.
• Sinus infection symptoms include sinus headache, facial tenderness, pressure or pain in the sinuses, fever, cloudy discolored drainage, and feeling of nasal stuffiness, sore throat, and cough.
• Bacterial infection of the sinuses is suspected when facial pain, pus-like nasal discharge, and symptoms that persists for longer than a week and are not responding to over-the-counter nasal medications.
• Sinus infection is generally diagnosed based on patient history and physical examination by a health care practitioner.
• Bacterial sinusitis is usually treated with antibiotic therapy.
• Early treatment of allergic sinusitis may prevent secondary bacterial sinus infections.
• Home remedies for sinus infections include OTC medications such asTylenol, decongestants, and mucolytics. Nasal irrigation can be accomplished with a Neti-pot or rinse kit (nasal bidet).
• Rare fungal infections of the sinuses (for example, zygomycosis) constitute a medical emergency.
• Complications of a sinus infection that may develop are meningitis, brain abscess, osteomyelitis, and orbital cellulitis.
• There are no fungal vaccines available to prevent fungal sinus infections.

What causes sinus infections?

Sinus infection may be caused by anything that interferes with airflow into the sinuses and the drainage of mucus out of the sinuses. The sinus openings (ostea) may be blocked by swelling of the tissue lining and adjacent nasal passage tissue, for example with common colds, allergies, and tissue irritants such as OTC nasal sprays, cocaine, and cigarette smoke. Sinuses can also become blocked by tumors or growths that are near the sinus openings.

The drainage of mucous from the sinuses can also be impaired by thickening of the mucous secretions, by decrease in hydration (water content) of the mucous brought on by disease (cystic fibrosis), drying medications (antihistamines), and lack of sufficient humidity in the air. The epithelial cells have small hairlike fibers, called cilia, which move back and forth to help the mucus move out of the sinuses. These small cilia may be damaged by many irritants, especially smoke. This can prevent them from assisting the mucus in draining from the sinuses.

Stagnated mucus provides an environment for bacteria, viruses and in some circumstances (for example, AIDS or immunodepressed persons) fungus to grow within the sinus cavities. In addition, the microbes themselves can initiate and exacerbate sinus blockage. The most commonly infected sinuses are the maxillary and ethmoid sinuses.

Rarely, immunodepressed or victims of multiple traumas in disasters such as tsunamis, hurricanes, earthquakes, or tornadoes may breathe in fungi from the soil or water. Eventually, in a few days to over a week, the fungi can grow and cut off blood supply to almost any type of tissue, especially in the nose and eyes. These infections, although rare, are serious and can be deadly and require immediate medical and surgical care. Although the fungal infection may resemble common bacterial sinusitis initially, it is a disease termed zygomycosis or mucormycosis.

What are the types of sinusitis?

Sinusitis may be classified in several ways, based on the time span of the problem (acute, subacute, or chronic) and the type of inflammation (either infectious or noninfectious).

• Acute sinus infection (also termed acute sinusitis caused by infection) is usually defined as being of less than 30 days duration.
• Subacute sinus infection as being over 1 month but less than 3 months.
• Chronic sinus infection as being greater than 3 months duration.

There is no medical consensus on the above time periods.

• Infected sinusitis usually is caused by uncomplicated virus infection. Less frequently, bacterial growth causes sinus infection and fungal sinus infection is very infrequent. Subacute and chronic forms of sinus infection usually are the result of incomplete treatment of an acute sinus infection.
• Noninfectious sinusitis is caused by irritants and allergic conditions and follows the same general time line for acute, subacute and chronic as infectious sinusitis.

What are the signs and symptoms of sinus infection?

Commonly the symptoms of sinus infection are headache, facial tenderness, pressure or pain, and fever. However, as few as 25% of patients may have fever associated with acute sinus infection. Other common symptoms include:

• cloudy, discolored nasal drainage,
• a feeling of nasal stuffiness,
• sore throat, and
• cough.

Some people notice an increased sensitivity or headache when they lean forward because of the additional pressure placed on the sinuses. Others may experience tooth or ear pain, fatigue, or bad breath. In noninfectious sinusitis, other associated allergy symptoms of itching eyes and sneezing may be common, but may include some of the symptoms listed above for infectious sinusitis. Nasal drainage is usually clear or whitish-colored in people with noninfectious sinusitis.

With rare fulminant fungal infections, there may be ulceration, with sharply defined edges and a black, necrotic center in the nasal area. Some fungal infections cause a dark, black-appearing exudates. This requires immediate medical evaluation.

How is sinus infection diagnosed?

Sinus infection is most often diagnosed based on a history and examination made by a doctor. Because plain X-ray studies of the sinuses may be misleading and procedures such as CT and MRI scans, which are much more sensitive in their ability to diagnose sinus infection, are so expensive and not available in most doctors offices, most cases of sinus infection are initially diagnosed and treated based on clinical findings on examination. These physical findings may include:

• redness and swelling of the nasal passages,
• purulent (pus like) drainage from the nasal passages (the symptom most likely to clinically diagnose a sinus infection),
• tenderness to percussion (tapping) over the cheeks or forehead region of the sinuses, and
• swelling about the eyes and cheeks.

Occasionally, nasal secretions are examined for secreted cells that may help differentiate between infectious and allergic sinusitis. Infectious sinusitis may show specialized cells of infection (polymorphonuclear cells) while allergic sinusitis may show specialized cells of allergy (eosinophils). Physicians prescribe antibiotics if bacterial infection is suspected. Antibiotics are not effective against viral infections; many physicians then treat the symptoms.

If sinus infection fails to respond to the initial treatment prescribed, then more in-depth studies such as CT or MRI scans may be performed.Ultrasound has been used to diagnose sinus infections in pregnant women, but is not as accurate as CT or MRI. Rhinoscopy, a procedure for directly looking in the back of the nasal passages with a small flexible fiber optic tube, may be used to directly look at the sinus openings (ostea) and check for obstruction of these openings by either swelling or growths.

It may sometimes be necessary to perform a needle aspiration (needle puncture) of a sinus to get infected material to culture to determine what pathogen is actually causing the sinus infection. Cultures of the nasal passages are rarely helpful in determining what bacteria or fungus is causing a sinus infection since the nasal passages are often colonized by non-infecting bacteria. The needle puncture procedure is usually done by an otolaryngologist when treatments have failed to alleviate the disease. The procedure is uncomfortable and requires local anesthesia; some patients require general anesthesia. The sinus is aspirated, the contents sent for culture and staining, and the sinus may be flushed with a saline solution. This is technically the most accurate way to diagnose infectious sinusitis.

In addition, both rigid and flexible endoscopy has been used to obtain diagnostic material from sinuses. Unfortunately, these procedures are also uncomfortable and need to be done by an otolaryngologist who may need to sedate the patient. Some investigators suggest that endoscopy specimens are comparable to those obtained by needle puncture.

Fungal infections are usually diagnosed by such biopsy procedures and tissue removed by a surgeon, or by fungal culture and microscopic identification by a microbiologist or pathologist trained to identify fungi.