During the last decade, three manuscripts have been published that classified pediatric rhinosinusitis. The Lusk et al. guidelines were an extension of the TFR guidelines of the AAO-HNS using the same classifications.

The Clement report consisted of an International Consensus Meeting (ICM), primarily of otorhinolaryngologists, and the Wald et al. clinical practice guideline was a consensus of the Subcommittee on Management of Sinusitis and Committee on Quality Improvement of the American Academy of Pediatricians (SMS/CQI-AAP).

The three classifications of pediatric rhinosinusitis are similar, and therefore, their definitions and classification can be discussed together:

1. Acute rhinosinusitis in children is defined as an infection of the sinuses mostly introduced by a viral infection, where complete resolution of symptoms (judged on a clinical basis only) without intermittent URTI may take up to 12 weeks (ICM).

Acute sinusitis can be further subdivided into severe and nonsevere. The SMS/CQI-AAP guideline (71) introduces the concept of acute bacterial rhinosinusitis (ABRS) complicating an acute viral rhinosinusitis.

ABRS is an infection of the paranasal sinuses, lasting less than 30 days, in which symptoms resolve completely. According to Mucha et al. the diagnosis of ABRS should be considered after a viral URI, when symptoms worsen after five days, are present for longer than 10 days, or are out of proportion to those seen with most viral infections.

To cover the duration gap between acute and chronic, the SMS/ CQI-AAP guideline also introduced the concept of ‘‘subacute bacterial sinusitis’’ in children as an infection of the paranasal sinuses lasting between 30 and 90 days in which symptoms resolve completely.

The term subacute sinusitis was not recommended by the ICM in Brussels, as the difference between acute and subacute is very arbitrary and it does not imply a different therapeutic approach in children.

2. Recurrent acute rhinosinusitis in children are episodes of the bacterial infection of the paranasal sinuses separated by intervals during which the patient is asymptomatic. According to the SMS/ CQI-AAP guideline, these episodes last less than 30 days and are separated by intervals of at least 10 days.

3. Chronic rhinosinusitis in children is defined as a nonsevere sinus infection with low-grade symptoms that presents longer than 12 weeks.

4. Finally, recurrent acute rhinosinusitis in children has to be differentiated from chronic rhinosinusitis with frequent exacerbations (ICM) or acute bacterial sinusitis superimposed on chronic sinusitis (SMS/CQI-AAP).

These are patients with residual respiratory symptoms who develop new respiratory symptoms. When treated with antimicrobials, these new symptoms resolve, but the underlying residual symptoms do not.

The members of the ICM noted that medical treatment such as antibiotics and nasal steroids may modify symptoms and signs of acute and CRS, and it is sometimes difficult to differentiate infectious rhinosinusitis from allergic rhinosinusitis in a child on clinical grounds alone.

According to the SMS/CQI-AAP, a viral infection in children induces a diffuse mucositis and predisposes to a bacterial infection of the sinuses in 80% of cases whereas in 20% of the cases an allergic inflammation is responsible for the bacterial superinfection.

In conclusion, an internationally well-accepted classification of rhinosinusitis in adults as well as in children that is based on duration of signs and symptoms exists.

However, there still exists much controversy concerning the classification of fungal sinusitis. This classification is controversial because it is based on the eventual cause of CRS, which is still not well understood.