Introduction
Rhinosinusitis refers to a group of diseases, mainly the inflammation and infection, which affect the mucosa of the nose and paranasal sinuses (PNS). There are various factors involved in the pathogenesis of chronic rhinosinusitis (CRS), which include both host and environmental components. Because of the complex interplay of factors affecting the nose and PNS, there has been significant debate and confusion in the classification and terminology used to describe rhinosinusitis.
The prevalence and incidence of the condition is showing an increasing trend worldwide with about 31 million people suffering from it in USA alone. Though we don’t have sufficient demographic data about the exact incidence of CRS in India, a rough estimate reveals that about 15% of the population suffers from it.
The chronicity of the condition also renders it one of the common causes of frequent absenteeism from work and school. Consequently it not just has health implications but also affects the economic and quality of life aspects of the affected patients.
This introductory chapter will attempt to familiarize the readers with the various terminologies used to define and describe this condition and mention some commonly used staging methods. It will also touch up on the prevalence trends and describe the economic and quality of life impacts of this disease.
Classification and Associated Terminology
Though rhinosinusitis is a very common problem encountered by otolaryngologists, there are no clear-cut definitions. Extrinsic factors like bacterial, viral and fungal infections and allergy (both IgE and non-IgE–mediated) and several intrinsic factors like genetic, autoimmune or structural causes all contribute to CRS. Hence, various terminologies and modes of classification have been used to define and quantify the condition.
Classification Based on Duration of Symptoms
Taking the time frame of the clinical presentation as a differentiating factor, rhinosinusitis can be essentially classified into acute rhinosinusitis, recurrent acute rhinosinusitis (RARS), CRS, acute exacerbation of CRS (AECRS) and subacute rhinosinusitis.1,2
Acute rhinosinusitis is usually bacterial in nature, is of sudden onset, and usually follows an upper respiratory tract infection (URTI). The symptoms are similar to those of URTI and last for a minimum of 5–7 days to a maximum of <4 weeks. RARS is defined by four or more episodes of rhinosinusitis every year with each episode lasting for more than 7–10 days and no symptoms or signs during the refractory period which could be indicative of any ongoing or CRS.3 CRS occurs when the duration of symptoms is >12 weeks. There can be occasional worsening of symptoms suggestive of an acute exacerbation and with treatment of the acute attack the symptoms return to baseline CRS. This is termed as AECRS. Subacute rhinosinusitis encompasses those with rhinosinusitis lasting for 4–12 weeks. The disease in some of these patients completely resolves in due course of time while in others it progresses to CRS.
Classification Based on Presence/Absence of Polyps/Fungal Infection
The previous classification of rhinosinusitis is simple but does not take into account the underlying mechanisms that could impact the behavior of the disease. The presence or absence of polyps and emergence of fungal infection in CRS requires different modes of treatment and has different clinical outcomes. Recognizing the need for evidence-based classification guidelines, a workshop of the AAO-HNS and other related societies came to a consensus and divided rhinosinusitis into four groups, namely acute bacterial rhinosinusitis (ABRs), CRS with polyps, CRS without polyps (chronic hypertrophic rhinosinusitis) and allergic fungal rhinosinusitis (AFRS).4
This classification suggests that CRS can present with or without polyps and it is essential to differentiate between these two variants as their clinical presentation and disease outcome are totally different. Patients of CRS with polyps and hypertrophic rhinosinusitis have different mechanisms of pathophysiolgy and therefore require different modes of treatment. The patients with polyps are more likely to manifest with eosinophilia, asthma, and aspirin sensitivity whereas the hypertrophic rhinosinusitis are more likely to have bacterial infections.5 Cases with hypertrophic rhinosinusitis have a better response to medical treatment and corticosteroids,6 but the postoperative recurrence and relapse of disease is much higher. In patients with polyps, the response to intensive medical treatment is not as good as those without polyps7 but the post-operative recurrence is much less in those with polyps only. Though further studies are required to define the benefits of different modalities of treatment such as surgery, anti-inflammatory therapy, and allergen immunotherapy between these groups,8 the difference in behavior of the disease warrants an incorporation of these factors into the classification of the condition.
The spectrum of diseases caused by fungal presence in nose and PNS encompasses a relatively benign colonization, AFRS9 due to fungal balls and invasive fungal rhinosinusitis, a potentially life-threatening condition. These are described in detail in the chapter on fungal rhinosinusitis.
Classification Based on Histological Markers
Kountakis et al10 further examined the correlation of severity of CRS with molecular, cellular, and histological markers to identify the characteristics which affect objective measurements. They also studied other disorders that could co-exist with CRS. Based on the results they have proposed a classification of CRS as follows:
Staging for Severity of Chronic Rhinosinusitis
Interest in surgical management of CRS has increased because of widespread usage of endoscopes and CT imaging, which offer a better visualization of disease and structures and facilitate better treatment modalities. Any assessment of a medical or surgical therapeutic response requires a method of quantifying the disease severity which has to be widely accepted by the practicing rhinologists. Consequently the necessity for a good staging system for the non-neoplastic sinus disease has arisen.
Types of Chronic Rhinosinusitis Staging
Several workers have used endoscopic or CT findings or a combination of both to reach a numerical value for the staging. CT scan findings have been the basis of staging methods proposed by Friedmann et al,25 Levine and May11 as well as Gliklich and Metson.12 Kennedy13 has proposed a staging based on prognostic factors such as the number and type of sinuses involved, unilateral or bilateral disease, presence, or absence of polyps and anatomical abnormalities. The staging system proposed by Benninger et al14 has used endoscopic findings such as presence and severity of polyps, edema, scarring, crusting, and discharge to assign a number score.
The most popularly used staging system to facilitate treatment strategies15 is the Lund-Mackay scoring. It has various parameters including symptom score, endoscopy score, radiologic score, and a score based on surgery performed. However, the radiologic scoring has become widely used for its simplicity as it does not require radiology training, is unambiguous, and has minimal interobserver variability.16 This staging system is described in detail in the chapter on diagnosis of CRS.
