• Clinical science



Sinusitis is an inflammation of the mucous membrane of the paranasal sinuses. It rarely occurs without concurrent inflammation of the nasal mucosa (rhinitis) and is therefore commonly referred to as rhinosinusitis. Sinusitis affects about one in eight adults in the United States, resulting in about 30 million diagnoses annually. While the etiology is typically viral, it may also be bacterial or fungal (especially in immunocompromised patients). The condition is usually self-limiting, but if it lasts longer than 12 weeks it is considered chronic. The primary symptoms are purulent rhinorrhea and facial pain (particularly when leaning forward). Antibiotic therapy is only indicated if a bacterial superinfection is suspected. Imaging and endoscopy is reserved for cases that persist or worsen despite initial antibiotic therapy. Local extension of the disease may occur in cases that are complicated or that have not received adequate treatment, potentially resulting in frontal bone osteomyelitis, meningitis, or brain abscess.




  • Sinusitis is one of the most commonly diagnosed conditions in the USA, affecting an estimated 35 million individuals per year.
  • Peak incidence: early fall to early spring
  • Sex: >


Epidemiological data refers to the US, unless otherwise specified.




  • Sinusitis is triggered by three factors: obstruction of sinus drainage pathways (sinus ostia), ciliary impairment, and altered mucus quantity and quality → stasis of secretions inside the sinuses → proliferation of various pathogens → sinusitis
  • Recurrent, untreated/complicated acute sinusitis may lead to chronic sinusitis.


Clinical features

Condition Sinusitis Rhinitis Additional features
Acute viral rhinosinusitis
  • Sneezing, nasal congestion, rhinorrhea, and post-nasal drip
  • Hyposmia/anosmia
Acute bacterial rhinosinusitis
  • Persistent symptoms ≥ 10 days without clinical improvement OR
  • ≥ 3 initial days of severe symptoms, fever (> 39°), facial pain, or purulent nasal discharge OR
  • Symptoms initially improve and then worsen after 5–6 days (double worsening)

Fungal rhinosinusitis

  1. Non-invasive
    • Allergic fungal: features of asthma and other atopic manifestations
    • Fungal mycetoma: unilateral complaints; usually involves the maxillary sinus
  2. Invasive
    • Acute fulminant rhino-orbital-cerebral mucormycosis: epistaxis and dark ulcers on the septum, palate and turbinates; acutely ill with altered mental status
Chronic rhinosinusitis
  1. Allergic fungal: See “Fungal rhinosinusitis” above.
  2. Chronic rhinosinusitis with nasal polyps: See nasal polyps.
  3. Chronic rhinosinusitis without nasal polyps: anatomical abnormalities (septal deviation, tumors), dental disease

Acute bacterial rhinosinusitis should be suspected in patients with a pre-existing viral URTI and symptoms that do not improve after 10 days or worsen after initial improvement!


Subtypes and variants

Nasal polyps

Primary ciliary dyskinesia

There is only 'take-out' service at Kartagener's restaurant because there is no dine-in (dynein)!

Kartagener syndrome is a subtype of primary ciliary dyskinesia characterized by the triad of situs inversus, chronic sinusitis, and bronchiectasis!



Diagnosis of acute cases is usually established clinically. However, imaging or endoscopy should be considered if symptoms fail to improve within 7 days of diagnosis or worsen during the initial management of acute bacterial rhinosinusitis.

  • Laboratory tests: to determine underlying condition if suspected (e.g., nasal cytology allergic rhinitis, HIV test, sweat chloride test for cystic fibrosis)
  • Imaging
    • X-ray of sinuses; (poor sensitivity): decreased transparency of sinus, air-fluid levels may be seen
    • CT of sinuses (imaging modality of choice)
      • Soft tissue swelling, mucoperiosteal thickening, and air-fluid levels
      • Bony erosions and extension in cases of invasive mucormycosis infection
      • Fungus balls in the case of chronic aspergillosis infection
    • MRI may be considered to confirm soft tissue extension in invasive disease.
  • Nasal endoscopy

A clinical diagnosis of chronic sinusitis should be confirmed with objective documentation of sinonasal inflammation, which may be accomplished using anterior rhinoscopy, nasal endoscopy, or computed tomography!



Condition General approach Additional treatment
Viral infection
Bacterial infection

Fungal infection



Orbital and intracranial necrotic spread is especially common in invasive fungal sinusitis!


We list the most important complications. The selection is not exhaustive.