CHAPTER 104 Sinusitis
ETIOLOGY
Sinusitis is a suppurative infection of the paranasal sinuses and often complicates the common cold and allergic rhinitis. The maxillary and ethmoid sinuses are present at birth, but only the ethmoidal sinuses are pneumatized. The maxillary sinuses become pneumatized at 4 years of age. Frontal sinuses begin to develop at 7 years of age and are not completely developed until adolescence. The sphenoid sinuses are present by 5 years of age. The ostia draining the sinuses are narrow (1 to 3 mm) and drain into the middle meatus in the ostiomeatal complex. The mucociliary system maintains the sinuses as normally sterile.
Obstruction to mucociliary flow, such as mucosal edema resulting from the common cold, impedes sinus drainage and predisposes to bacterial proliferation. In 90% of children with acute sinusitis, the bacterial causes are Streptococcus pneumoniae, nontypable Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus, and group A streptococcus. Anaerobes emerge as important pathogens in subacute and chronic sinusitis. Indwelling nasogastric and nasotracheal tubes predispose to nosocomial sinusitis, which may be caused by gram-negative bacteria (Klebsiella and Pseudomonas). Antibiotic therapy predisposes to infection with antibiotic-resistant organisms. Sinusitis in neutropenic and immunocompromised persons may be caused by Aspergillus and the Zygomycetes (e.g., Mucor, Rhizopus).
EPIDEMIOLOGY
The true incidence of sinusitis is unknown. The common cold is the major predisposing factor for developing sinusitis at all ages. Other risk factors include cystic fibrosis, immunodeficiency, human immunodeficiency virus (HIV) infection, nasogastric or nasotracheal intubation, immotile cilia syndrome, nasal polyps, and nasal foreign body. Sinusitis also is a frequent problem in immunocompromised children after organ transplantation.
CLINICAL MANIFESTATIONS
Clinical manifestations most commonly include persistent, mucopurulent, unilateral or bilateral rhinorrhea, nasal stuffiness, and cough, especially at night. Less common symptoms include a nasal quality to the voice, halitosis, facial swelling, facial tenderness and pain, and headache. Sinusitis may exacerbate asthma.
LABORATORY AND IMAGING STUDIES
Culture of the nasal mucosa is not useful. Sinus aspirate culture is the most accurate diagnostic method but is not practical or necessary. Transillumination may show evidence of fluid, but this is difficult to perform in children and is not reliable.
Plain x-ray and computed tomography may reveal sinus clouding, mucosal thickening, or an air-fluid level. Abnormal radiographic findings do not differentiate infection from allergic disease; computed tomography and magnetic resonance imaging often show abnormalities, including air-fluid levels, in the sinuses of asymptomatic persons. Conversely, normal radiographs have high negative predictive value for bacterial sinusitis.
DIFFERENTIAL DIAGNOSIS
The diagnosis usually is based on history and physical findings for longer than 10 to 14 days without improvement or increased severity of symptoms compared with the common cold.
TREATMENT
Amoxicillin administered for 7 days after resolution of symptoms is recommended for treatment of uncomplicated sinusitis. Alternative antibiotics for penicillin-allergic patients include cefuroxime axetil, cefpodoxime, clarithromycin, and azithromycin. For children at increased risk for resistant bacteria (antibiotic treatment in the preceding 1 to 3 months, day care attendance, age <2 years), and for children who fail to respond to initial therapy with amoxicillin within 72 hours, high-dose amoxicillin-clavulanate (80 to 90 mg/kg/day of amoxicillin and 6.4 mg/kg/day of clavulanate) is recommended. Failure to respond to this regimen necessitates referral to an otolaryngologist.
COMPLICATIONS AND PROGNOSIS
Complications include orbital cellulitis, epidural or subdural empyema, brain abscess, dural sinus thrombosis, osteomyelitis of the outer or inner table of the frontal sinus (Pott’s puffy tumor), and meningitis. These all should be managed with sinus drainage and broad-spectrum parenteral antibiotics. Sinusitis also may exacerbate bronchoconstriction in asthmatic patients.
Orbital cellulitis is a serious complication of sinusitis that follows bacterial spread into the orbit through the wall of the infected sinus. It typically begins as ethmoid sinusitis and spreads through the lamina papyracea, a thin, bony plate that separates the medial orbit and the ethmoid sinus. Orbital involvement can lead to subperiosteal abscess, ophthalmoplegia, cavernous sinus thrombosis, and vision loss. Manifestations of orbital cellulitis include orbital pain, proptosis, chemosis, ophthalmoplegia and limited extraocular muscle motion, diplopia, and reduced visual acuity. Infection of the orbit must be differentiated from that of the preseptal (anterior to the palpebral fascia) or periorbital space. Preseptal (periorbital) cellulitis usually occurs in children younger than 3 years of age; these children do not have proptosis or ophthalmoplegia. Periorbital cellulitis is associated with a skin lesion or trauma and usually is caused by S. aureus or group A streptococcus.
The diagnosis of orbital cellulitis is confirmed by a computed tomography scan of the orbit, which determines the extent of orbital infection and the need for surgical drainage. Disorders to be considered in the differential diagnosis are zygomycosis (mucormycosis), aspergillosis, rhabdomyosarcoma, neuroblastoma, Wegener granulomatosis, inflammatory pseudotumor of the orbit, and trichinosis. Therapy for orbital cellulitis involves broad-spectrum parenteral antibiotics, such as oxacillin and ceftriaxone.
More than half of children with acute bacterial sinusitis recover without any antimicrobial therapy. Fever and nasal discharge should improve dramatically within 48 hours of initiating treatment. Persistent symptoms suggest another etiology.