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Rhinosinusitis
Viral infection often precedes
bacterial colonization
BY Rajiv K. Bhalla, MD and Erin D.
Wright, MD
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Rhinosinusitis is a concomitant inflammation
of the mucosal surfaces of the nose and paranasal sinuses (Figure
1). The condition is very common and is estimated to affect
16% of the adult population annually in the U.S.1
We would expect similar numbers in Canada, where chronic rhinosinusitis
is more frequent in women than in men, and this sex difference is
consistent across age groups. The prevalence increases with age
but levels off after 60. In women -- but not in men -- the incidence
has been found to be higher in the eastern regions and among native
Canadians as compared to immigrants and those living in central
or western Canada. Cigarette smoking and low income are associated
with a higher occurrence of rhinosinusitis in both sexes, but there's
no relationship with alcohol consumption or a lack of regular exercise.2
What
causes sinusitis?
The etiologic factors are wide and varied, and can be congenital
or acquired. Hereditary causes include ciliary dyskinesias, cystic
fibrosis, cleft palate and immunoglobulin deficiencies. Acquired
causes range from infections, allergy, environmental pollutants,
trauma and barotraumas, to iatrogenic mechanisms such as dental
procedures and nasogastric intubation.
The common theme is a failure of normal mucociliary
clearance. This promotes stagnation and subsequent colonization
by bacterial pathogens, which further reduces mucociliary function.
The initial insult may be fairly innocuous -- a viral infection
or severe and persistent rhinitis may be enough to trigger the chain
of events necessary for the development of acute rhinosinusitis.
This is especially true if anatomic variants, prior trauma or ciliary
dyskinesias are present. Mucosal congestion and edema, an acidic
intrasinus pH and negative intraluminal pressure due to obstruction
of the sinus ostia all spark a vicious cycle of ciliary dysfunction,
stagnation of secretions and poor lymphatic drainage. These conditions
promote an anaerobic environment and subsequent bacterial overgrowth.
When
do you suspect it?
Rhinosinusitis can be acute, subacute, recurrent acute or
chronic. The diagnosis in the office setting isn't always straightforward.
Patients frequently attribute almost all types of facial pain to
their sinuses. The differential diagnosis may include dental pain,
mid-face tension headaches, migraine, temporomandibular joint dysfunction
and trigeminal neuralgia, among others. If the individual presents
with facial pain, you should seek a history that corroborates a
sinus etiology. A premorbid event, such as an upper respiratory
tract infection, increases the probability of sinusitis. Symptoms
such as green nasal discharge, heaviness, congestion or throbbing
in the sinuses, a vertex headache, fever, hyposmia and maxillary
alveolar pain make acute rhinosinusitis most likely. A specific
inquiry regarding migraine or neck complaints may raise the suspicion
for alternative causes of the pain, as would a history of lancinating
pain or aches that occur, for example, in cold weather. An acute
sinus headache is, in fact, very rare.3
Acute rhinosinusitis, by definition, settles
completely within 4 weeks -- from onset to resolution. Subacute
rhinosinusitis will present with similar features as acute rhinosinusitis,
but episodes typically last from 4-12 weeks, followed by complete
resolution. Chronic rhinosinusitis is defined by a green nasal discharge
present on most days, and is associated with facial heaviness, throbbing
or congestion in the region of the paranasal sinuses -- without
complete resolution in a 3-month period. Three or more episodes
of acute rhinosinusitis in a year constitute recurrent acute rhinosinusitis.4
What
are the offending pathogens?
The initial insult in acute or subacute rhinosinusitis is
likely to be a viral upper respiratory infection. Typical viruses
are the rhinovirus, coronavirus, influenza A or B, parainfluenza,
respiratory syncytial virus, adenovirus and enterovirus.5
Bacterial infections are unlikely to be the cause of a common cold.
Inflammation and congestion occurs not only in the nasal passages,
but also within the sinuses themselves. Indeed, the distinction
between the mucosal surfaces of the nose and sinuses is an artificial
one, which explains the use of the term rhinosinusitis.
Mucous stasis, viral immunosuppression and
secondary bacterial colonization promote a purulent discharge along
with the other symptoms already mentioned. Bacterial pathogens are
those normally associated with upper respiratory tract infections
-- Streptococcus pneumoniae, Haemophilus influenzae and Moraxella
catarrhalis are the most likely candidates (see
Figure 2). Staphylococcus aureus is unusual, as are fungal
infections. Anaerobes may be prevalent in chronic rhinosinusitis.
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