Sinusitis explained: types, causes, symptoms, diagnosis and treatment

What you will learn

Osmosis from Elsevier offers a concise, expert overview of sinusitis, including how sinus infections are classified, what causes them, typical symptoms, how they are diagnosed, and common treatments. The video explains the anatomy of the nasal cavities and paranasal sinuses, and highlights the differences between viral and bacterial infections, as well as when surgery may be considered.

• Types and duration: acute up to four weeks, subacute one to three months, chronic more than three months.
• Causes and features: mucus production, mucus drainage pathways, nasal polyps in chronic disease, environmental allergies.
• Diagnosis and treatment: CT or rhinoscopy for chronic cases; antibiotics for bacterial infections; decongestants, steroids for allergies; surgical options for recurrent cases.
• Key anatomy: goblet cells, cilia, nasal meatuses, four paranasal sinuses (maxillary, ethmoidal, sphenoidal, frontal).

Sinusitis overview and anatomy

Sinusitis is an inflammation of the paranasal sinuses that surround the nose. The paranasal sinuses act as small echo chambers to help amplify the voice and warm and humidify inspired air. They are lined by a mucosal epithelium with goblet cells that produce mucus, and by ciliated columnar cells that help move mucus draining into the nasal passages. The nasal cavity contains three nasal meatuses (superior, middle, and inferior), which drain mucus from the sinuses. The sphenoidal sinus drains to the sphenoethmoidal recess, above the superior meatus, while the ethmoid sinus drains into the superior, middle, and anterior meatuses. The maxillary and frontal sinuses drain into the middle meatus. This anatomy is central to understanding symptoms and drainage in sinusitis.

"The sphenoidal sinus drains to the sphenoethmoidal recess, which is a small space in the nasal cavity right above the superior meatus." - Osmosis

Classification and causes

Most sinusitis cases are acute and viral in origin, with rhinovirus and influenza-like viruses commonly implicated. Bacterial pathogens such as Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis can cause acute bacterial sinusitis. Subacute sinusitis lasts one to three months, while chronic sinusitis persists for more than three months and may be associated with environmental allergies, fungi exposure in some immunocompromised individuals, or nasal polyps that lead to chronic inflammation and hyperplasia.

"Most cases of sinusitis are acute and are the result of a viral infection." - Osmosis

Symptoms and diagnosis

Symptoms center on mucus buildup, facial pain, pressure, fever if infection is present, and changes in voice, smell, or taste. Diagnosis for acute sinusitis is mainly symptom-based, while subacute or chronic sinusitis may benefit from CT imaging or rhinoscopy, where a camera is inserted into the nose to directly visualize the nasal passages and sinuses. In chronic cases, imaging can reveal mucus or pus blocking drainage pathways.

"In subacute or chronic sinusitis it can be helpful to get a CT scan or rhinoscopy, which is when a tube that has a camera is inserted into the nose to directly see the nasal passages in the sinuses." - Osmosis

Treatment and management

Acute sinusitis due to bacterial infection is commonly treated with antibiotics. Decongestants help reduce swelling and promote drainage. If underlying allergies or nasal polyps are present, steroids or allergy medications can be beneficial. Chronic or recurrent sinusitis may require surgical intervention to open poorly draining sinuses and restore drainage into the nasal cavity. For many patients, management includes addressing mucus buildup, controlling allergies, and improving sinus drainage to relieve symptoms and reduce recurrence.

"The main treatment for acute sinusitis is antibiotics. In addition, it can be helpful to use decongestants to help reduce swelling and promote better drainage." - Osmosis

Summary of key anatomy and drainage

Goblet cells produce mucus to trap particles, and cilia move mucus toward the nasal cavity. The three nasal meatuses and the drainage patterns of the sphenoidal, ethmoid, maxillary, and frontal sinuses are essential for understanding symptoms and the effects of congestion during a cold. When drainage is blocked, mucus accumulates, promoting symptoms and sometimes infection.