ACUTE AND CHRONIC SINUSITIS

Definitions
Sinusitis can be broadly defined as inflammation of one or more of the
paranasal sinuses. Classically, sinusitis is characterized as the following:

Acutedsymptoms last less than 4 weeks 
Subacutedsymptoms last 4 to 8 weeks
Chronicdsymptoms last longer than 8 weeks
Recurrentdthree or more acute episodes a year
Acute sinusitis can be further defined as an infection of the paranasal
sinuses, with accompanying symptoms present for more than 10 days and
less than 4 weeks.

To fully define chronic sinusitis has been difficult. Because of the variation in clinical expression of the disease, and the discordance between patient symptoms and objective findings, no one set of diagnostic criteria has been agreed on by all clinicians. Furthermore, before much of the microbiologic

or pathologic data regarding this disease had been shown, chronic sinusitis was thought to be a chronologic extension of acute sinusitis. However, it is now thought that chronic sinusitis is a much different disease. In contrast to acute sinusitis, most chronic sinusitis is not an infectious disease and is better thought of as an inflammatory disease, much akin to asthma.


Acute sinusitis


Several factors promote the development of acute sinusitis. 

In most cases, bacterial sinusitis is preceded by a viral upper respiratory infection, which in turn leads to sinus inflammation and obstruction of the OMC. As a result, drainage and ventilation of the maxillary, anterior ethmoid, and frontal sinuses are compromised. Once this occurs, both the pH and oxygen content  decrease, the cilia are less functional, mucosa are damaged, and the microenvironment becomes more susceptible to infection. Approximately 0.5% to 2% of viral sinusitis progress into bacterial infections . 

To distinguish between bacterial and viral sinusitis can be difficult. Typically viral sinusitis resolves in 7 to 10 days , whereas bacterial sinusitis remains persistent  Rhinovirus is the most common viral pathogen and is easily transmissible.


In a study of healthy volunteers, 95% of individuals challenged with intranasal rhinovirus drops became infected, and three quarters of them became symptomatic. Within 10 hours, newly replicating virus was found in the nasal secretions . 

As confirmed by sinus puncture, Streptococcus pneumoniae, Haemophilus influenza, and Moraxella catarrhalismake up the majority of the community acquired bacterial pathogens.

 One possible mechanism for introduction of pathogens from the nasal passages into the sinuses may  actually be through nose blowing. This processes creates a negative intranasal pressure with such force that nasal fluid is propelled from the middle meatus into the sinus cavity .