Sinusitis is a common disease affecting 35 million people annually in North America.1,2 It accounts for an estimated 2 to 3 billion dollars in health care costs annually3,4 and patients spend approximately 150 million for products prescribed or recommended for the treatment of the disease.5 Even so, sinus infections are among the most frequently misdiagnosed and misunderstood diseases in clinical practice. The dental clinician must be cognizant of the various diseases of the maxillary sinus and their possible presentations. In the dental office, both acute and chronic maxillary sinusitis of non-odontogenic origin may present as chronic orofacial pain or atypical odontalgia6,7,8 and will require appropriate medical referral. Sinusitis of an odontogenic origin is a well-recognized condition with a reported incidence of approximately 10 percent.9 Those cases of odontogenic maxillary sinusitis that appear resistant to conventional treatment should be referred appropriately to an otolaryngologist or oral and maxillofacial surgeon for management. To determine appropriate care for a patient presenting with maxillary sinusitis symptoms, the dental clinician must understand the anatomy, pathophysiology and microbiology of the maxillary sinuses.
ANATOMY
There are four paranasal sinuses in the human skull. They surround the nasal cavity and are named according to the bones in which they are located: maxillary, frontal, ethmoid, and sphenoid. They develop as nasal cavity invaginations during the third and fourth fetal month and aeration of the sinuses occurs following birth. In adolescence each sinus has attained adult dimensions. The sinuses are lined by pseudostratified columnar ciliated epithelium. The ciliary movement is spiral and toward the ostia, directing the secretory flow of mucous along with any contaminant to the nose for elimination.
The anatomic relationships of these sinuses are important particularly when infected, and account for the more rare intracranial and periorbital complications associated with sinusitis.10
The maxillary sinus is the largest of the sinuses and most relevant to dentists given its proximity to the posterior maxillary teeth (Fig. 1). Each cavity is the shape of a three-sided pyramid, with the apex toward the zygomatic process. The orbital floor forms the roof, the alveolar process forms the inferior boundary and the lateral nasal wall forms the medial wall of the sinus. The ostium that connects the maxillary sinus to the nasal cavity is situated on the anterior superior aspect of the medial wall. This opens to the middle meatus under the middle turbinate. The middle meatus and related anatomic structures, including the uncinate process, hiatus semilunaris and bulla ethmoidalis, are collectively referred to as the osteomeatal complex (OMC). This is the area where the frontal, maxillary and anterior group of ethmoid sinuses drain.
CLASSIFICATION AND PATHOPHYSIOLOGY
In 1996, the American Academy of Otolaryngology-Head and Neck Surgery established parameters for distinguishing the subtypes of sinusitis.11,12 Signs and symptoms associated with sinusitis are divided into major and minor groups (Table 1). The classification is based on the duration of disease and the presence of a specified combination of signs or symptoms determined by history and physical examination. The classification are acute (12 weeks) based on the presence of two or more major signs and symptoms; one major and two or more minor signs on examination.
Mucociliary function, ostium patency, oxygen exchange and mucosal blood flow may all be involved in the pathogenesis of sinusitis.13 Edema and mucosal thickening lead to inadequate drainage of the sinus. This produces stagnation of secretions, pH changes, epithelial damage and reduced oxygen tension which create an ideal environment for bacterial growth. The resultant bacterial products retained within the sinus then causes more mucosal thickening, alteration in the cellular architecture and ciliary dysfunction which may establish a pathogenic cycle of chronic infection.1
The modern concept of sinusitis is that most infections are rhinogenic in nature, with infection spreading secondarily to involve the larger sinuses.14 The most common precursors to bacterial sinusitis include viral upper respiratory infection, sinus obstruction from mucosal edema of inhalant allergies, and anatomic factors such as septal deviations, septal spurs or deformities of the osteomeatal complex.12,15 Less frequent causes include nasal polyps, hormone-based turbinate edema (pregnancy), medication side effects, and mucociliary dysfunction associated with cystic fibrosis and immune deficiencies.12,15 A number of systemic and local factors can influence sinus infection (Table 2).
Maxillary sinusitis of odontogenic origin may result from periapical infection, periodontal disease, perforation of the antral floor and mucosa with tooth extraction, and displacement of roots or foreign objects into the maxillary sinus during a dental or surgical procedure.16,17 The presence of odontogenic cysts, odontogenic tumours and certain metabolic diseases affecting the maxilla may also impact on the maxillary sinus (Table 3).
MICROBIOLOGY OF MAXILLARY SINUSITIS
In health the paranasal sinuses were initially thought to be sterile.18 This is highly controversial as many studies have documented the presence of normal flora in these air-filled cavities.13 Most cases of sinusitis are thought to be of bacterial etiology. The microbiology of acute and chronic sinusitis is thought to be different, and can also vary depending on the paranasal sinus involved. As with odontogenic infections, sinusitis is most often polymicrobial and mixed aerobic/anaerobic in nature (Table 4).
In acute sinusitis, Streptococcus pneumonia and Haemophilus influenzae have been identified as primary etiologic agents. Streptococcus pyogenes and Moraxella catarrhalis are less frequently involved. A multitude of other organisms, including coagulase positive and negative Staphylococci and Escherichia coli have been implicated in approximately 5% of sinus infections.
In chronic sinusitis the etiologic infectious organisms are highly variable,4 with anaerobic organisms isolated with increased frequency. Brook19 reported that 88% of culture positive cases contained anaerobes, and 32% were part of a mixed infection. Of the anaerobes approximately 50% exhibited beta lactamase activity. The predominant organisms include Bacteroides species, anaerobic cocci, Peptostreptococcus anacrobius, P.niger and Clostridium species.
In a review of infections of odontogenic pyogenic origin, most were considered to be mixed aerobic-anaerobic infections with the most common organisms including anaerobic streptococci, bacteroides, Proteus and coliform bacilli.20,21 These studies also demonstrate that Staphylococcus species are neither the cause of, nor involved in, most odontogenic infections. However, S. aureus is a common pathogen in nosocomial sinusitis and cases of sphenoidal or frontal sinusitis. Patients with cystic fibrosis and immotile cilia syndrome are predisposed to Pseudomonas aeruginosa and S. aureus infections.13 Patients with a history of IV drug abuse can be prone to infections with resistant bacterial species including MRSA.
CLINICAL PRESENTATION
It is important to accurately diagnose the type of sinusitis a patient has before initiating treatment as the bacteriology and management of each condition differs significantly. Patient evaluation should start with a thorough history and complete physical examination. A local examination can be performed to evaluate the nares and nasopharynx.
Acute sinusitis presents with rhinorrhea that is often purulent, unilateral or bilateral infra-orbital tenderness, nasal congestion or obstruction, dull headache, intermittent fever, and/or cheek swelling of less than three weeks duration.22 Additional signs can include tenderness with chewing, halitosis, and altered sense of smell.23
Chronic sinusitis is defined as signs and symptoms of sinusitis which persist for more than 12 weeks, four episodes of acute sinusitis of greater than 10 days duration per year, or both. Nasal polyposis is the classic indicator of chronic inflammation and may in fact represent a stage in the continuum of sinusitis. Nasal polyps may indicate a fulminant allergy requiring appropriate investigations and aggressive management, and in children is considered pathognomonic of cystic fibrosis.
The close proximity of the maxillary sinus floor to the root apices of the posterior maxillary teeth may lead to symptoms that suggest dental disease.24-26 Inflammation of the sinus lining can produce percussion sensitivity in the molar teeth. However, in the absence of concurrent pulpal disease these teeth will respond vital to pulp testing and will not exhibit thermal sensitivity. In addition, pain that varies with changes in head position is suggestive of sinusitis.
The dental practitioner must remain vigilant of the possibility of odontogenic infections spreading from the teeth into the neighboring maxillary sinus, producing symptoms of both dental and sinus disease. Lesions of the maxillary sinus may remain clinically asymptomatic, particularly when localized in the inferior portion of the antrum. When the free flow of fluid and gas through the ostium is blocked, pressure within the sinus increases and there is potential for considerable pain and discomfort. Pain from the maxilla may be referred to the face, eye, nose and oral cavity. Facial symptoms may include unilateral paresthesia, anaesthesia, and midface fullness. There can be a change in vision, diplopia, altered eyeball position, and epiphora. Nasal symptoms may include epistaxis, allergic rhinitis and postnasal drip. Intra-orally, in addition to tooth pain and sensitivity, paresthesia or anaesthesia of the gingiva and mucosa as well as a feeling of alveolar expansion or malocclusion may be experienced.
In contrast to adults, children rarely experience headache, facial pain and local tenderness with a sinus infection. The immature state of their immune systems and anatomically smaller nasal passages may predispose to infection.27 The most common indicator is a history of upper respiratory tract infection, low-grade fever and irritability, purulent nasal discharge and cough of more than 10 days duration. As such, most cases of pediatric sinusitis will present to their family physicians office.
EXAMINATION OF SINUSITIS
Transillumination and sinus ultrasonography has been used for many years in Europe with good results. Stafford, however, feels that these techniques has a lower sensitivity and specificity than plain film radiography, but may prove beneficial in pregnant patients, or in those for whom radiation exposure is contraindicated.22 Plain film radiography which often includes lateral, Water’s, Caldwell and basal projections provide adequate evaluation of all sinuses with the exception of the anterior ethmoids and the upper two thirds of the nasal cavity.28 These views can be obtained quickly, and are relatively inexpensive. Demonstration of an opacified sinus, or an air-fluid level is generally diagnostic and no further radiography is required (Figs. 2a & b).
The standard plain films, however, will not assist in determining the extent of involvement of the OMC or the anterior ethmoidal region which often contribute to the persistence or recurrence of sinusitis.28 Coronal CT scans provide a better view of all sinuses, and will often display the underlying cause of infection (Fig. 2c). Such scans allow the clinician to systematically identify and evaluate each sinus, as well as the OMC and contiguous anatomic structures such as the orbits and cranial base. The CT scan, despite its greater diagnostic ability, is a second line diagnostic tool. It is primarily indicated in recurrent disease despite medical therapy, suspicion of ethmoid or sphenoid disease, or to assist in the identification of anatomic abnormalities or evaulation of patients who have developed a complication from sinusitis such as abscess formation.14 Nasal endoscopy can often be used to complement CT scans. Endoscopy can be used to visualize and evaluate inflammatory changes within the nasal passage and swelling in the region of the middle meatus, and in particular in the area of the OMC, to acquire culture specimens and to rule out anatomic variations.24 Endoscopy utilizes rigid rod or flexible endoscopes, in conjunction with video cameras, to examine the nose and sinuses. The procedure is generally carried out in the office setting by an experienced otolaryngologist. Kennedy has stated that the widespread adoption of diagnostic nasal endoscopy is clearly the greatest single advance in the management of sinusitis in recent years, and the experience gained from it has helped to change surgical thinking with regard to chronic sinusitis.24
MANAGEMENT OF SINUSITIS
The management goals for the treatment of sinusitis include: control of infection and pain, reduction of tissue edema, facilitation of drainage and maintenance of sinus ostia patency.22,32 While the control of infection is important, one must always keep the other therapeutic goals in mind (Table 5). Since nasal cultures are often unreliable, antibiotic therapy must therefore be directed toward the most commonly described pathogens. Amoxicillin therapy is considered to be the first-line of treatment for acute bacterial sinusitis: an adequate dosage i.e., 40mg/kg/day is paramount (Table 6). Several studies have shown a mean bacteriological cure rate of greater than 90% with first-line therapies.29 Alternative agents include second and third generation cephalosporins such as cefaclor and ceftiroxime. When patients fail to respond to one of the first line agents, the likely cause is the presence of beta lactamase producing bacteria or resistant strains. Amoxicillin-clavulanate is highly effective against such resistant strains. In children, the combination of erythromycin and sulfisoxazole is often considered the agent of first choice. Acute sinusitis should be treated by at least a 14-day course since this gives the clinician the best opportunity to eliminate the organism completely and thus avoiding the development of chronic sinusitis. The extra few days of therapy may help ensure the complete eradication of the disease. Although no antibiotic has been approved in Canada specifically for the treatment of chronic sinusitis, amoxicillin-clavulanate is a good first choice. Clindamycin also provides good coverage, especially against the anaerobic species, however, there is a higher reported incidence of Clostridium diffucile infections versus other antibiotics.30 Alternatively, the addition of metronidazole to the penicillins will cover the spectrum of probable pathogens. Chronic sinusitis is inherently resistant to medical treatment and may require 4-6 weeks of antibiotic coverage. Studies have suggested that there is an underlying osteomyelitis and as such, six or more weeks of antibiotic therapy would be appropriate.31 Infections of the sinuses may spread beyond their cavities to the orbits and cranial cavity. Orbital and periorbital complications from sinusitis tend to occur in patients under the age of 6 although orbital complications in older children and adults tend to be more severe. Intracranial complications, albeit rare, can have devastating consequences.30,32
Many other pharmacologic adjuncts have been prescribed for the treatment of sinusitis. Topical vasoconstrictor agents such as phenylephrine HCL 0.5% and oxymetazoline HCL 0.05%, provide almost immediate symptomatic relief by shrinking inflamed nasal mucosa. Use of these agents for longer periods of time carries a high risk of rebound congestion. When decongestion is necessary for longer than three days, oral decongestants are advised.23 Topical corticosteroids will help to reduce inflammation at the sinus ostia, and therefore increase ostia diameter, however there does not appear to be any compelling scientific data to suggest their use in acute sinusitis.32,33 Their use may be considered in patients with allergic rhinitis or nasal polyps. The routine use of antihistaminic drugs should be reserved for patients who display signs of sinusitis in conjunction with those of allergy. Antihistamines are not indicated since there is little or no histamine produced in sinusitis and drying of the nasal mucosa may cause thickening of secretions, which is counterproductive to the goals of therapy. Finally, analgesics are often requested by patients with sinus infections. Combination products of non-steroidal anti-inflammatory drugs (NSAID) or acetaminophen with a decongestant are readily available as over the counter remedies. Concern over Reyes syndrome in children and gastrointestinal bleeding in adults may lead one to choose the acetaminophen products as first line drugs. Additionally, patients who have asthma and nasal polyps may display sensitivity to ASA and the NSAIDs and therefore should avoid such combination products.
The role of fungal elements in chronic sinusitis is being increasingly recognized. While pure ‘fungal ball’ type sinusitis is uncommon, fungi are often associated with aggressive eosinophillic inflammation at the mucosal level. The treatment can be problematic and requires management of the inflammation process as well as the associated pathogens. The search for an adequate topical anti-fungal preparation is ongoing.
Several non-pharmacologic measures have been advocated for treatment of acute sinusitis. While good scientific evidence concerning their effectiveness is lacking, they do provide short temporary symptomatic relief. Saline sprays or irrigation moistens the nasal and antral mucosa and may help liquify secretions. Steam inhalation will also liquify and soften nasal crusting as well as it will moisturize the dry inflammed mucosa. Spicy foods such as horseradish or garlic or astringents such as pine oil, eucalyptus and menthol may provide additional benefit by facilitating air flow and reducing stuffiness.32,33
For a recent and more comprehensive discussion of bacterial resistence patterns, as well as antibiotic and adjunctive drug action, dosage, cost, compliance and adverse reactions, the reader is referred to the article by Halpern et.al.34
Patients who are not responsive to therapuetic measures or develop recurrent infections and complications should be referred to the oral and maxillofacial surgeon or otolaryngologist for further investigation and treatment (Fig. 3). The surgical management of chronic sinusitis has evolved from conventional techniques such as antral lavage, intranasal antrostomy and Caldwell-Luc procedures to more modern endoscopic surgery called functional endoscopic sinus surgery (FESS). FESS allows for direct visualization and precise location of the abnormalities and restoration of normal drainage with minimal invasiveness. Results of FESS are good, with a reported success rate of 80-90% with few compilcations.35 It is one of the most common surgical procedures carried out in North America. The primary goal of surgical treatment is to re-establish drainage by removing the obstructive causes (such as poylps) and widening the natural ostia of the sinuses.
SUMMARY
The close proximity of the maxillary sinus to the oral cavity makes it a common clinical concern for medical and dental practitioners. For this reason, dentists should be familiar with the anatomy, physiology and pathology of this complex region. Sinusitis may often be mistaken for dental disease and one should be able to recognize, diagnose and adequately manage this common ailment. Under-treatment can lead to more chronic and recurrent illness.
Dr. Pynn is Oral and Maxillofacial Surgeon, Thunder Bay Regional Hospital, and Adjunct Professor, Lakehead University, Thunder Bay, ON.
Dr. Nish is Oral and Maxillofacial Surgeon, Hospital for Sick Children, Toronto, ON.
Dr. McCann is Oral and Maxillofacial Surgeon, Private Practice, Waterloo, ON.
Dr. Turner is Otolaryngologist, Chief of Surgery, Thunder Bay Regional Hospital, Thunder Bay, ON.
Dr. Irish is Associate Professor, Department of Otolaryngology and Surgical Oncology, University of Toronto, Wharton Head and Neck Centre, Princess Margaret Hospital, Toronto, ON.
Oral Health welcomes this original article.
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