What are the causes and treatment options for sinusitis in adults?

Causes of Sinusitis in Adults

Sinusitis in adults is most commonly caused by viral upper respiratory infections, with bacterial superinfection occurring when symptoms persist beyond 10 days or worsen after initial improvement. 1

Primary Infectious Causes

Viral Pathogens

• Viral upper respiratory tract infections are the most common precipitant of sinusitis, occurring when viruses infect the sinuses during a cold and cause the sinus lining to swell, blocking drainage channels and causing mucus and pus accumulation. 1, 2
• Most acute sinus infections are viral, with the majority of patients improving within 2 weeks without antibiotics. 3

Bacterial Pathogens

• Acute bacterial rhinosinusitis (ABRS) develops in two distinct patterns: (1) persistent symptoms without improvement for at least 10 days, or (2) "double worsening" where symptoms worsen within 10 days after initial improvement. 1
• The primary bacterial pathogens in acute sinusitis are Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. 4
• In chronic sinusitis, anaerobic bacteria and Staphylococcus aureus predominate. 4
• Many of these organisms have developed beta-lactamase resistance, requiring amoxicillin-clavulanate rather than amoxicillin alone. 4

Predisposing Anatomic and Mechanical Factors

• Conditions affecting sinus ostia patency, including anatomic obstruction (deviated nasal septum, nasal polyps), directly cause sinusitis by preventing proper drainage. 1, 2
• Nasal polyps are present in 20% of patients with chronic rhinosinusitis and cause obstruction leading to recurrent infections. 3
• Dental infections, particularly periapical infections of maxillary molar teeth, are important causes of maxillary sinusitis due to the proximity of tooth roots to the sinus floor. 1

Underlying Medical Conditions

Allergic and Inflammatory Conditions

• Respiratory allergies are a known predisposing factor by causing mucosal inflammation and ostial obstruction. 1, 2
• Allergic rhinitis provides ongoing inflammation that can lead to or augment acute bacterial sinusitis. 1
• Eosinophilic nonallergic rhinitis was found in 26% of patients with chronic sinusitis. 1

Systemic Diseases

• Immunodeficiency states (congenital or acquired including HIV) increase susceptibility to recurrent sinusitis. 1, 2
• Cystic fibrosis should be considered in patients with nasal polyps or Pseudomonas colonization. 1
• Ciliary dyskinesia and immotile cilia disorders impair mucociliary clearance. 1
• Asthma is associated with chronic rhinosinusitis and represents a modifying factor in management. 1

Other Contributing Factors

• Gastroesophageal reflux disease (GERD) has been suggested as a cause, with medical treatment of GERD resulting in significant improvement in sinusitis symptoms. 1
• Prolonged nasotracheal intubation can lead to nosocomial sinusitis. 2
• Pseudomonas aeruginosa has emerged as a pathogen in immunocompromised patients and those with nasal tubes or catheters. 4

Treatment Approach Based on Etiology

Viral Rhinosinusitis (Symptoms <10 days, not worsening)

• Symptomatic relief only—no antibiotics indicated as viral sinusitis does not benefit from antibacterial therapy. 1
• Options include analgesics, saline irrigation, and intranasal corticosteroids. 1

Acute Bacterial Rhinosinusitis

• Amoxicillin-clavulanate 875 mg/125 mg twice daily for 5-10 days is first-line therapy for most adults, providing coverage against beta-lactamase-producing organisms. 5, 4
• For penicillin allergy, use doxycycline or a respiratory fluoroquinolone (gatifloxacin, moxifloxacin). 1, 4
• Intranasal corticosteroids as adjunctive therapy reduce symptoms more effectively than antibiotics alone. 1, 3
• Reassess at 3-5 days if no improvement and consider switching antibiotics. 1

Chronic Rhinosinusitis (Symptoms >12 weeks)

• Topical intranasal corticosteroids are the treatment of choice, significantly decreasing inflammation, congestion, and improving airflow. 1, 3
• Saline nasal irrigation provides mechanical removal of infectious debris. 1
• Short courses of oral steroids may be needed for severe cases, followed by maintenance with topical steroids. 3
• Longer duration antibiotic therapy may be required for chronic infectious sinusitis, with attention to anaerobic pathogens. 1

Critical Pitfalls to Avoid

• Do not obtain radiographic imaging for uncomplicated acute rhinosinusitis unless complications (orbital involvement, intracranial extension) or alternative diagnoses are suspected. 1
• Do not prescribe antibiotics for symptoms lasting less than 10 days unless severe presentation with high fever and purulent discharge. 1
• Do not substitute two 250 mg/125 mg tablets for one 500 mg/125 mg tablet of amoxicillin-clavulanate, as they contain the same amount of clavulanic acid and are not equivalent. 5
• Assess patients with recurrent or chronic sinusitis for modifying factors including allergic rhinitis, immunodeficiency, cystic fibrosis, and anatomic abnormalities before repeated antibiotic courses. 1, 6