Sinusitis
The paranasal sinuses are four pairs of air filled cavities within the bones of the face, above and around the eyes and nose, named the maxillary, ethmoid, frontal and sphenoid sinuses. They are connected to the nasal cavity by small openings and are lined by the same mucous membrane that lines the nasal passages and the rest of the respiratory system.
Air passes in and out of the sinuses and mucous produced by the mucous membrane is able to drain into the back of the nasal cavity. Mucous helps to remove dust, bacteria and other air pollutants from the sinuses and nasal cavity.
What is sinusitis?
Sinusitis, also known as sinus infection, inflammatory sinus disease or rhinosinusitis, is the inflammation of the mucosal lining of one or more of the sinuses. The inflammation causes congestion which leads to the build up of pressure causing symptoms such as pain, nasal discharge, post nasal drip, headache, fever, reduced sense of smell and a feeling of fullness of the face.
What causes sinusitis?
The inflammation can be caused by infection or allergies. Usually the infection that causes sinusitis is bacterial or viral, although fungal infections can also cause the condition.
Obstructions within the sinuses or nasal cavity such as anatomic variants, deviated septum, nasal polyps or tumours, can lead to sinusitis by preventing the normal drainage of mucous and creating a breeding ground
for infection.
What is the difference between acute and chronic sinusitis?
Acute sinusitis commonly occurs as the result of a cold, a bacterial or viral infection, or allergies. Symptoms may last up to four weeks. There may be repeated occurrences but symptoms are absent in between episodes.
Chronic sinusitis is considered present if a patient has continuous symptoms for more than three months. The sinuses may become narrowed or closed completely due to chronic infection and inflammation. Ongoing allergies and environmental irritants such as cigarette smoke may also be a causative factor.
How is sinusitis diagnosed?
The diagnosis of sinusitis can be difficult as its symptoms can mimic those of a common cold. In order to make an accurate diagnosis a full medical history is taken including an assessment of the nature and duration of symptoms. A physical examination is performed including looking into the ears, throat and nose.
Imaging of the sinuses is best achieved by a CT examination of the sinuses which allows high resolution cross sectional views of the sinuses in all three planes to be analysed. CT of the sinuses has replaced plain x-rays and the CT miniseries as the investigation of choice and does not require contrast injection.
Chronic sinusitis is demonstrated on CT by mucosal thickening within the sinuses which may obstruct the drainage pathways and extend into the nasal passages as nasal polyps.
Acute sinusitis may be diagnosed on CT if there is fluid within the sinuses forming a dependent level with air above. This can often occur superimposed upon a background of chronic sinusitis.
How is sinusitis treated?
Antibiotics are used to treat acute bacterial sinusitis. Longer courses may be needed for cases of recurrent or chronic sinusitis. Steroid medications such as prednisone may be prescribed in order to treat cases of chronic sinusitis.
Surgery may be recommended for cases where medical treatment has not been effective or an obstructive lesion has been demonstrated by CT. Functional endoscopic sinus surgery (FESS) aims to improve airflow and drainage between the sinuses and the nasal cavity by correcting structural abnormalities such as a deviated septum, removing obstructions such as polyps and by removing areas of diseased tissue.
Picture 1: Sagittal view of the frontal, ethmoid and sphenoid sinuses with normal aeration
Picture 2:Coronal view of the maxillary sinuses with moderate chronic sinusitis
Picture 3: Coronal view of the maxillary and ethmoid sinuses with severe chronic sinusitis and nasal polyposis
