Causes and Risk Factors
- Sinusitis is often caused by a viral infection, such as the common cold.
- Underlying conditions like allergies or structural problems in the nose can increase the risk of sinusitis.
- People with lesser immunity against bacteria by birth are more prone to sinusitis.
- Recurrent episodes are more likely in individuals with asthma, cystic fibrosis, and poor immune function.
- Most cases of sinusitis are caused by a viral infection, not bacteria.
- Acute sinusitis is usually caused by viral infections, such as rhinoviruses, coronaviruses, and influenza viruses.
- Bacterial infections can also cause acute sinusitis, with Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis being common culprits.
- Fungal invasion can lead to acute sinusitis, especially in individuals with diabetes or immune deficiencies.
- Chronic sinusitis can be caused by various diseases, including anatomic derangements, allergic rhinitis, asthma, cystic fibrosis, and dental infections.
- Smoking and secondhand smoke are associated with chronic sinusitis.

Signs and Symptoms
- Common symptoms of sinusitis include thick nasal mucus, a plugged nose, and facial pain.
- Other signs and symptoms may include fever, headaches, a poor sense of smell, sore throat, and frequent coughing.
- Acute sinusitis may be accompanied by a green nasal discharge that may contain pus or blood.
- Chronic sinusitis can lead to nasal congestion, facial pain, headache, night-time coughing, and an increase in asthma symptoms.
- Anosmia, the loss of the sense of smell, is often associated with chronic sinusitis.

Diagnosis
- In early stages, an ENT doctor can confirm sinusitis using nasal endoscopy.
- Diagnostic imaging is usually not needed in the acute stage unless complications are suspected.
- In chronic cases, confirmatory testing is recommended through direct visualization or computed tomography.
- The unnecessary and ineffective treatment of viral sinusitis with antibiotics is common.
- Sinusitis is classified into several categories based on the duration of symptoms, including acute, recurrent acute, subacute, chronic, and acute exacerbation of chronic sinusitis.
- Roughly 90% of adults have had sinusitis at some point in their lives.
- Bacterial and viral sinusitis can be distinguished through watchful waiting.
- Diagnostic methods include noting local tenderness and dull pain, CT and nuclear isotope scanning, and microbial culture.
- Chronic sinusitis can be part of a spectrum of diseases affecting the respiratory tract and is often linked to asthma.

Treatment
- Initial treatment for acute sinusitis is watchful waiting.
- If symptoms do not improve in 7-10 days or get worse, an antibiotic may be used.
- Pain killers such as naproxen, nasal steroids, and nasal irrigation can help with symptoms.
- Amoxicillin or amoxicillin/clavulanate is recommended as the first-line antibiotic treatment.
- Surgery may be used in people with chronic sinusitis or those who do not respond to medications.
- Treatment for sinusitis includes surgical drainage and administration of antimicrobial therapy.
- Surgical debridement is rarely required after an extended course of parenteral antimicrobial therapy.
- Chronic sinusitis is managed by controlling inflammation and reducing the incidence of infections.
- Medications are the first line of treatment, but surgery may be necessary if medications are ineffective.
- Antifungal treatments have had mixed results in treating chronic sinusitis associated with fungi.

Complications and Prognosis
- Complications of sinusitis are rare but can be life-threatening.
- Infection of the brain is the most dangerous complication, particularly in the frontal and sphenoid sinuses.
- Sinus infection can spread to the orbit, causing periorbital cellulitis, abscesses, and orbital cellulitis.
- Sinusitis may extend to the central nervous system, causing cavernous sinus thrombosis, meningitis, and brain abscesses.
- Other complications include sinobronchitis, maxillary osteomyelitis, and frontal bone osteomyelitis.
- Odontogenic sinusitis (ODS) can occur when an infection or complication of a dentistry procedure involves the maxillary sinus.
- Sinus infections can spread to other sinuses, including the ethmoid, frontal, and sphenoid sinus.
- Infections may involve the orbit, causing orbital cellulitis and potentially leading to blindness.
- Sinus infections can also result in central nervous system complications such as meningitis, brain abscess, and cavernous sinus thrombosis.
- Ethmoid sinusitis can lead to infection of the eye socket, resulting in the loss of sight and accompanied by fever and severe illness.
- 46% of sinusitis cases without antibiotics are cured after one week.
- 64% of sinusitis cases without antibiotics are cured after two weeks.
- 24 to 31 million sinusitis cases occur annually in the United States.
- Chronic sinusitis affects approximately 12.5% of people.