Sinusitis is an inflammatory state of the paranasal sinuses, usually preceded by nasal cavity inflammation. Classification is time dependent. Acute sinusitis lasts less than three weeks, chronic sinusitis more than three months with sub-acute in the intermediate stage.
The true incidence of sinusitis is difficult to gauge because it is thought that there is significant over diagnosis. In the US there are 1,200 cases diagnosed per 10,000 person-years whereas in the UK there are only 250. Complications are very rare and hospitalisation in the UK occurs in 25 cases per 10,000.
Sinus cavities are a pair of air-filled bony pockets lined by a mucus-producing ciliated columnar epithelium. Clearance is via small 1-2.5mm openings or ostia into the nasal cavity.
The largest two sinuses are the frontal (supra orbital) and maxillary (behind the cheeks).
The frontal, maxillary and frontal ethmoid sinuses drain into a common middle meatus within the nasal cavity and are susceptible to being jointly inflamed. The posterior ethmoid and sphenoid sinuses have a separate draining area below the superior turbinate.
Acute sinusitis involves an initial impairment of mucus drainage followed by secondary bacterial colonisation. Commonly, the initial insult is a viral infection following a URTI. Infection of related tissue, such as tonsils, can result in a spreading of the infection.
The top three bacteria infecting the sinuses are Streptococcus pneumoniae (31 per cent), Haemophilus influenzae (21 per cent) and in children Moraxella catarrhalis (19 per cent).
Other cases include a variety of bacteria ranging from Staphylococcus aureus to Gram-negatives such as Escherichia coli and other anaerobes.
Chronic sinusitis is not caused by bacterial infection but can be complicated by it. Chronic sinusitis is marked by a chronic thickening of the mucus membranes and blockage of the ostia.
Local pressure secondary to polyps, cancerous growth and nasogastric tubes can directly block the ostia. Other causes include allergic rhinitis, vasomotor rhinitis, trauma, cystic fibrosis affecting mucus viscosity and hormonal changes associated.
A clinical diagnosis aide has been designed based on a systematic review of the literature by the American Academy of Otolaryngology (see box). The major features are facial pain or tenderness, nasal blockage, purulent discharge, anosmia and fever.
Minor features include pain (head or dental), local symptoms (bad breath, feeling of pressure behind the ears, cough) and fatigue.
A biphasic course, where patients have initial cold symptoms and then while getting better the congestion and discomfort return, makes the diagnosis more likely.
Symptoms in children are less specific. Useful pointers include an absence of response to antihistamines and tenderness over the external face of the sinuses.
An important but rare complication is periorbital cellulitis. This presents with cellulitis affecting the eyelids.
An urgent ENT referral should be made as IV antibiotics, monitoring of visual acuity and rarely surgical intervention for orbital decompression may be required.
Specialist investigations in primary care are not cost-effective or required. A diagnosis should be made on clinical grounds alone.
Trans-sinus illumination has a poor inter-operator reliability. Nasal swab cultures do not correlate well with direct sinus aspiration. Sinus X-rays are limited because only 60 per cent of patients with clinical symptoms have signs such as opacification, air-fluid level or mucosal thickening greater than 6mm. CT scans have a role to play in diagnosing chronic sinusitis in a secondary care setting.
Symptoms lasting more than seven days, worsening after five days or that are severe should be treated with antibiotics. Amoxicillin has been shown to be as effective as other broader-spectrum antibiotics.
In 10 per cent of maxillary sinusitis, there is a dental origin. When this is suspected the addition of metronidazole and a dental review to exclude an abscess is indicated.
Intranasal decongestants should be limited to seven days to avoid rebound rhinitis. Chronic sinusitis may respond to topical antihistamines or steroids, but outcomes are poor except in children where symptoms spontaneously resolve after the age of six to eight years.
An ENT referral should be sought if symptoms are repeated. Surgical options range from irrigation and placement of drainage tubes to obliteration of sinus tissue. Functional endoscopic sinus surgery has reported lower complication rates and aims to reopen sinus ostia.
Dr Hashmi is a former GP in London working as a consultant in family medicine in Jeddah, Saudi Arabia
Criteria for sinusitis diagnosis
Two major, or one major and two minor features must be present
- Facial discomfort (feeling of congestion or fullness)
- Nasal obstruction
- Purulent nasal discharge or postnasal drip
- Decreased or absent sense of smell
- Bad breath
- Dental pain
- A feeling of pressure or fullness in the ears
- Prodigy Guidance: Sinusitis (2006). www.neli.org.uk
- MeReC Bulletin. The management of common infections in primary care. Volume 17(3). November 2006. www.npc.co.uk/MeReC_Bulletins .