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What is sinusitis?

What is sinusitis?

Sinusitis is the inflammation of the paranasal sinuses, which are cavities in the bones of the face in connection with the nasal cavity (the space inside the nose). Amongst the cells that lines the sinusitis, there are cells that produces mucus, and cells with hair like structures that clears the mucus.

Sinusitis can be acute or chronic. Acute sinusitis is often the case when a “cold” is lasting longer than usual, together with some tenderness below the eye, fever and headaches. In this situation, there is usually some accumulation of mucus (may look yellow because of infection ) in the spaces behind the nose. Chronic sinusitis is diagnosed if these symptoms persist usually for over 3 weeks.

What causes sinusitis?

Acute sinusitis is usually the result of a secondary bacterial infection, that commonly follows a viral infection involving the nose and throat. Bacterial infections are often the cause for exacerbations in chronic sinusitis as well. During the course of a infection, the lining of the inside of the nose can become swollen, obstructing the normal movement of air in the cavities. This causes an increase in mucus secretion which can get infected, when invaded by bacteria.

Factors that predispose individuals to develop sinusitis, include:

  • Allergic rhinitis (hayfever) – which makes up 25-28% of the cases.
  • abnormal shape of the inside of the nose
  • nasal polyps (extra tissue on the lining of the nasal cavity)
  • swimming
  • smoking
  • abnormal immune system
  • cystic fibrosis


Both acute and chronic sinusitis causes pain around the eyes (where the sinuses are), yellow coloured (infected) nasal discharge and blocked nose. Fever may or may not be present. In severe cases of sinusitis, there may be complications such as orbital cellulitis (infection spreading around the eyes) and spread to the brain and surrounding blood vessels.

Sinusitis can sometimes present as a non-specific generalised toothache from the affected side. Patients are sometimes convince that they have a dental problem.


Sinusitis is a prevalent disease that affects >14% of the population in most countries at any one time. It is also more common in patients in hospital who are critically ill, where 25-75% would have sinusitis as diagnosed by radiological imaging.


Sinusitis should be suspected when cold symptoms lasts for more than 7 to 10 days, accompanied by features such as facial pain, discharge from the nose or into the back of the throat. Examination of the nose provides evidence to suggest sinusitis. Chronic sinusitis may not have the characteristic symptoms and hence X-rays can be useful in making the diagnosis. X-rays can show thickening of the lining of the sinuses and the presence of fluid or abnormal masses.

  1. Rhinoscopy – this is the use of a flexible tube of fibreoptics to look directly at the sinuses, and is used when chronic sinusitis is suspected. It can also show the presence of polyps (extra, abnormal growth of a tissue lump) and other structural abnormalities. This can be done at a clinic under local anaesthetic spray inside the nose.
  2. Computerised tomography (CT) – CT can confirm the diagnosis and are also used to exclude other causes such as tumours. It also has a role in staging chronic sinusitis and to assess the response to treatment. It also has a very useful role in diagnosing complications (such as the spreading of infection into the back of the eye).
  3. Other diagnostic aids – Nasal smears may be useful to confirm the allergic component of the problem.


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Written by Dr. Ozair (CEO of SignSymptom.com) as physician writers are physicians who write creatively in fields outside their practice of medicine.

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