CHRONIC SINUSITIS AND NASAL POLYPOSIS
- Imaging should be used only in an appropriately triaged group of patients who have a clinical diagnosis of chronic rhinosinusitis.
- Imaging can identify underlying causative or alternative conditions that may significantly affect medical and surgical decision making.
- Imaging is critical in identifying the extent of disease and complications such as mucoceles and excluding orbital and intracranial complications of chronic sinusitis.
Sinusitis is an inflammation of the paranasal sinus mucoperiosteal lining. Rhinosinusitis is currently the preferred term for this condition because the nasal mucosa is almost always simultaneously involved when sinusitis occurs.1–4 An otolaryngology Rhinosinusitis Task Force has defined acute sinusitis as lasting up to 4 weeks, subacute sinusitis lasting >4 weeks but >12 weeks, and chronic sinusitis when symptoms last <12 weeks. Recurrent acute sinusitis is defined as more than four episodes per year with complete resolution between infections. Acute and subacute infectious rhinosinusitis is discussed in Chapter 84. Chronic rhinosinusitis (CRS) and the often related sinonasal polyposis are the subjects of this chapter. Other considerations in this chapter include the frequent association of this disease with mucocele formation and fungal colonization.
The pathophysiology of CRS is poorly defined, but many mediators of inflammatory disease have been identified as part of the disease process, establishing CRS as a predominantly inflammatory disease. Contributing factors are described in the following Pathophysiology section.
Chronic sinusitis, once felt to be infectious, is now felt to be due to an infectious etiology less commonly, although patients may have had their disease incited by infection or have become infected as a result of the chronic obstruction within the paranasal sinuses. Patients with a history of allergy, occupational or vasomotor rhinitis, nasal polyps, or anatomic obstruction such as septal deviation and concha bullosa will be predisposed to chronic infections. Rhinosinusitis is more common in immune-deficient patients; in those with ciliary motility problems such as Kartagener syndrome; and in those with mucous blanket problems, such as cystic fibrosis (CF) patients.
The term chronic rhinosinusitis is now preferred to describe this condition. The presence of CRS requires two or more of the following symptoms: mucopurulent drainage, nasal obstruction, or some combination of facial pain, pressure, and/or fullness; hyposomia; fever; cough; dental pain; and fatigue. There should also be endoscopic presence of inflammation and evidence of rhinosinusitis on imaging.
Common complications of chronic sinusitis are superimposed acute sinusitis and, in children, adenoiditis with secondary serous or purulent otitis media. Dacryocystitis and laryngitis may also occur as complications of chronic sinusitis in children. Other complications include osteomyelitis and mucocele formation.
Orbital complications (Chapter 84) include preseptal and postseptal cellulitis, subperiosteal abscess, orbital cellulitis, orbital abscess, and cavernous sinus thrombosis. Intracranial complications (Chapter 84) include meningitis, epidural abscess, subdural abscess, and brain abscess.
Nasal polyps arise from any portion of the nasal mucosa or paranasal sinuses as the end result of various sinonasal disease processes. The most common mucosal polyps are benign nasal cavity inflammatory lesions that arise from the mucosa of the nasal cavity or the paranasal sinuses often at the outflow tract of the sinuses. These have an inflammatory etiology, but the exact mechanisms are uncertain, as discussed in the following Pathophysiology section.
Multiple polyps often occur in patients with chronic sinusitis, allergic rhinitis possibly associated with allergic fungal sinusitis (AFS), and CF. Polyps are associated with both nonallergic disease and allergic disease. The term polyp may be used to describe any of a number of benign or malignant tumors or congenital lesions, but that is not the sense of the term in this chapter, although those conditions may enter the differential diagnosis.
Prevalence and Epidemiology
CRS affects about 10% to 15% of the population in the United States, making it more common than any other chronic condition. Its incidence is increasing for unknown reasons.
Rhinosinusitis is more common in children, likely secondary to the increased frequency of upper respiratory tract infections and asthma in the pediatric population.
Multiple inflammatory nasal polyps typically occur in those patients older than 20 years and are more common in those over 40 years. Nasal polyps are uncommon in children younger than 10 years except in those with CF.
The incidence worldwide is the same as that in the United States. Males are at least twice as likely to have inflammatory polyps as females.
Symptoms of CRS overlap with other disease processes, and there may be poor correlation between symptoms and endoscopic and imaging findings. Patients with uncomplicated rhinosinusitis can have rhinorrhea, nasal congestion, facial pressure and pain, diminished sense of smell, and perhaps fever. Less directly correlating symptoms include headache, ear pain or fullness, bad breath, dental pain, cough, fever, and fatigue.
Small polyps may not produce symptoms, only being seen during anterior rhinoscopy. Small polyps may also block the outflow tract of the sinuses, causing chronic or recurrent acute sinusitis symptoms.
Larger and/or more extensive polyps may cause nasal airway obstruction, postnasal drainage, headaches, snoring, and rhinorrhea. Disorders of olfaction suggest that polyps obstructing airflow into the olfactory cleft, rather than chronic sinusitis alone, are present. Epistaxis may occur, and it always creates a concern for a more serious nasal cavity lesions.
Extensive polyposis or a single large polyp obstructing the nasal cavities and/or nasopharynx can cause obstructive sleep symptoms and chronic mouth breathing. Mucoceles as a complication may alter craniofacial structure, especially in children. Proptosis, hypertelorism, and diplopia may be presenting complaints. Compression on the optic nerve is rare, and neurologic symptoms are extremely rare in the absence of a complicating intracranial infection.
The sinuses are divided into anterior and posterior groups that drain into the middle meatus anteriorly and into the sphenoethmoidal recess and superior meatus posteriorly. The anatomy is discussed in detail in Chapter 78, and the physiology of sinonasal mucus clearance related to this anatomy is considered in the following material and also in Chapter 83 on endoscopic sinus surgery (ESS).
The paranasal sinuses are lined with a pseudostratified columnar (respiratory) epithelium that is continuous with the nasal mucosa. The mucoperiosteal sinus and nasal lining produces mucous secretions that trap bacteria, and both the mucus and bacteria are transported along a mucous blanket through the sinus ostia to be swallowed or expectorated. This is a normal process in sinuses that are air filled and communicate with the nasal passages through patent ostia.
Pathology and Patterns of Disease
The pathophysiology of CRS is poorly defined, but many mediators of inflammatory disease have been identified as part of the disease process, establishing CRS as a predominantly inflammatory disease. Contributing factors in some patients include allergy; immunodeficiency; autoimmune disease; colonizing fungi that produce an ongoing eosinophilic inflammation; persistent infection including biofilms, osteitis, and bacterial supertoxins; upper airway intrinsic factors; chemical irritation; and metabolic abnormalities such as aspirin sensitivity.
All of these factors may disrupt the mucociliary transport system as described in Chapter 83 and 84 and encourage bacterial growth that contributes to increased mucosal inflammation.
The pathogenesis of nasal polyposis is unknown. Polyp development is most basically linked to chronic inflammation; thus, conditions leading to chronic inflammation in the nasal cavity can lead to nasal polyps. Such processes include bronchial asthma, CF, allergic rhinitis, AFS, CRS, primary ciliary dyskinesia, aspirin intolerance, alcohol intolerance, Churg-Strauss syndrome and Young syndrome and nonallergic rhinitis with eosinophilia syndrome (NARES), autonomic nervous system dysfunction, and genetic predisposition conditions may be contributing factors.
Polyps are lobulated, bulging, or protruded regions of the nasal or sinus mucosa that are displaced by underlying edematous stroma, often in combination with some degree of mucosal inflammation (Figs. 85.1 and 85.2). Inflammatory changes likely first occur in the lateral nasal wall or sinus mucosa as the result of a viral bacterial or bacterial “trigger” that begins the inflammatory response, with that process possibly being enhanced by turbulent airflow. The initiating incident may not be established.
Polyps most typically arise at contact areas within the middle meatus that create turbulent airflow, with the narrowing and related turbulence then exacerbated by mucosal inflammation (Fig. 85.1). It is thought that anatomic abnormalities that lead to narrowing of the middle meatus may increase the risk of polyp formation. Ulceration or prolapse of the submucosa occurs along with epithelial repair and new gland formation. A polyp can then form from the mucosa because of the heightened, ongoing inflammatory process of epithelial cells, vascular endothelial cells, and fibroblasts. This cycling process releases mediators that produce conditions favorable for water retention that increases the volume of the polyps (Fig. 85.2). Vasomotor imbalance may contribute by increasing vascular permeability and impairing vascular regulation within the polyp stroma, resulting in more marked edema. This factor is reflected in the cell-poor stroma of the polyps that is also poorly vascularized and lacks vasomotor control. Patients with CF have a cellular defect that supports the theory of water retention as a contributing factor to polyp formation (Fig. 85.2).
Mucocele formation requires the obstruction of a draining ostium, complete opacification of a sinus, or an individual air cell within a sinus complex (Figs. 85.3–85.10). These conditions are most typically encountered in patients with CRS and especially in those with nasal polyposis. A prior history of either trauma or previous sinus or facial surgery is commonly encountered. In fact, patients with CRS and nasal polyposis may have very extensive mucoceles involving one or more sinus on either or both sides. The mucoceles can be sources of very significant consequences, including ocular motility disturbances, proptosis, hypertelorism, compressive optic neuropathy, and facial deformity. They may also become acutely infected, forming a mucopyocele that can lead to acute orbital and intracranial complications as discussed in Chapter 84.