In 1972, Douek wrote that ‘‘classification has an important place in medicine, as it forms the framework upon which diagnosis is made possible, etiology recalled and separated, and treatment decided. It remains, however, an intellectual system imposed onto a nature that has rarely rigid boundaries’.

Now, more than 30 years later, this statement is still valid. By acquiring new information about the natural history of rhinosinusitis based on novel imaging techniques such as MRI, CT scanning, and nasal endoscopy, new insights on the pathophysiology of the disease were gained.

Because of better culture techniques; and recent advances in histocytochemistry of inflammation; it became obvious that the classification of this disease needed to be adapted and redefined step-by-step.

Rhinosinusitis Versus Sinusitis

There exists a general agreement that rhinosinusitis can be defined as any inflammation of the paranasal sinus mucosa. Johnson and Ferguson stated that because the lining of the mucosa and the paranasal sinuses is continuous, an inflammation of the nasal cavity is usually associated with inflammation of the sinus lining.

The faculty of the staging and therapy group shared the same opinion and stated that the term rhinosinusitis is perhaps more precise than the term sinusitis.

The reasons are that sinusitis does not typically develop without prior rhinitis, isolated sinus disease without rhinitis is rare, the mucous membrane lining of the nose and the paranasal sinus is continuous, and two of the prominent features of sinusitis— nasal obstruction and drainage—are associated with rhinitis symptoms.

The Task Force on Rhinosinusitis (TFR) preferred the term rhinosinusitis as well. On occurrences in children, the members of the Consensus Panel on Pediatric Rhinosinusitis preferred to speak of rhinosinusitis since rhinitis and sinusitis are often a continuum of the disease.

Radiological Changes as Signs of Sinusitis

Havas et al. found abnormal appearances of the paranasal sinuses on CT scan in 42.5% of asymptomatic adults and Bolger et al. found a similar proportion of 41.7% in patients scanned for nonsinus reasons.

As a possible explanation, Bolger et al. suggested that these abnormalities could be induced by normal variations of the sinus mucosa, asymptomatic chronic sinus disease, and mild to moderately symptomatic undiagnosed chronic sinusitis.

In a CT scan study of children undergoing nonsinusitis evaluation, Diament et al. detected maxillary and ethmoidal thickening in ~50% of the patients.

Similar figures were found by Gordts et al. who demonstrated in an MRI study of a non-ENT population of adults (without any complaints and a blank surgical history) that there existed on 40% abnormalities of the mucosa, and in 45% of the cases in a non-ENT population of children.

All these imaging studies show us that imaging signs of sinusitis, in particular pathological mucosal swelling, can occur in completely asymptomatic adults and children. The meaning of these findings is unclear, and therefore, many clinicians claim that one has to treat patients and not CT or MRI scans.

The problem, however, remains that subclinical, silent, or asymptomatic sinusitis exists. Whether it needs to be diagnosed or treated in order to prevent manifest sinusitis is another question that has not been investigated yet.

Rhinosinusitis can be defined as any inflammation of the nasal and paranasal sinus mucosa, resulting in signs and symptoms. According to Pinheiro et al., classification of rhinosinusitis should be done along five axes:

1. Clinical presentation (duration: acute, subacute, and chronic).
2. Anatomical site of involvement (ethmoid, maxillary, frontal, and sphenoid).
3. Responsible microorganism (viral, bacterial, and fungal).
4. Presence of extra sinus involvement (complicated and uncomplicated).
5. Modifying or aggravating factors (e.g., atopy, immunosuppression, ostiomeatal obstruction, etc.).

According to these authors, a complete classification of sinusitis according to these five axes is essential to tailor the treatment for the particular situation.

As an example of this axes system, a possibility would be chronic, frontal, bacterial sinusitis complicated by frontal bone osteomyelitis and aggravated by immunosuppression due to diabetes mellitus.