Sinusitis
Sinusitis is inflammation of the paranasal sinuses, the air-filled spaces within the bones surrounding the nose and eyes. It is one of the most common conditions affecting the head and face and may result from infection, allergies, structural abnormalities, or other factors that interfere with normal sinus drainage. Sinusitis may be acute, lasting a few weeks, or chronic, lasting 12 weeks or longer. Imaging is not required for most uncomplicated cases but may be useful when symptoms are persistent, severe, recurrent, or difficult to diagnose.
What is it?
The paranasal sinuses are hollow, air-filled spaces located in the bones around the nose, cheeks, forehead, and between the eyes. These sinuses are lined with mucus-producing tissue that normally drains through small openings into the nasal cavity.
Sinusitis develops when this lining becomes inflamed or swollen, blocking normal drainage pathways and allowing mucus to accumulate. The trapped mucus may become infected, although many cases are caused by viral infections or allergies rather than bacteria.
Sinusitis is typically categorized based on symptom duration:
Acute sinusitis lasts up to 4 weeks and often follows a viral upper respiratory infection
Subacute sinusitis lasts 4–12 weeks
Chronic sinusitis lasts longer than 12 weeks and may involve ongoing inflammation, recurrent infections, nasal polyps, or structural abnormalities
Certain factors—including allergies, asthma, smoking, immune disorders, and a deviated nasal septum—may increase the risk of chronic or recurrent sinus disease.
CT is the preferred imaging test when sinusitis is chronic, recurrent, severe, or unresponsive to treatment because it provides detailed visualization of sinus anatomy, sinus blockage, mucosal thickening, drainage pathways, and structural abnormalities. CT imaging is also commonly used before sinus surgery to map anatomy and guide treatment planning.
MRI is usually reserved for situations where complications are suspected, such as spread of infection into the orbit or brain, fungal sinus disease, or possible tumors. Most uncomplicated sinus infections do not require imaging.
Important to Know
Most cases of acute sinusitis are viral and improve with supportive treatment such as saline rinses, hydration, decongestants, and pain relievers. Antibiotics are generally reserved for cases with signs suggesting bacterial infection, including symptoms lasting more than 10 days without improvement, worsening symptoms after initial improvement, or severe symptoms with fever and facial pain.
Chronic sinusitis often requires a combination of therapies that may include intranasal corticosteroids, allergy treatment, prolonged medication courses, and, in some cases, sinus surgery.
Imaging is most valuable when symptoms persist despite treatment, when recurrent sinus infections occur, or when complications are suspected. Evaluation by an otolaryngologist (ENT specialist) is common in chronic or difficult-to-treat cases.
Red flag symptoms include high fever, severe facial swelling, vision changes, double vision, eye redness or bulging, severe headache, neck stiffness, confusion, or signs of infection spreading beyond the sinuses. These symptoms require immediate medical evaluation.