Sinusitis in detail with treatment

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Sinusitis (Rhinosinusitis) - A Detailed Overview

Definition

Sinusitis - more accurately called rhinosinusitis - is inflammation of the mucous membranes lining the paranasal sinuses and nasal cavity. The term "rhinosinusitis" is preferred because sinusitis almost never occurs without concurrent nasal mucosal inflammation. It affects approximately 12% of adults in the U.S. annually and is one of the most common reasons for antibiotic prescriptions, though most cases are viral and self-limiting. - Goldman-Cecil Medicine, p. 4164; Rosen's Emergency Medicine, p. 966

Anatomy of the Paranasal Sinuses

Four paired sinuses are involved:

Maxillary sinuses - most commonly affected; drain via the ostiomeatal complex
Ethmoid sinuses - anterior and posterior groups; key in most CRS cases
Frontal sinuses - above the eyebrows; drain via nasofrontal duct
Sphenoid sinuses - deep, near the cavernous sinus and optic nerve

Classification by Duration

Type	Duration
Acute rhinosinusitis (ARS)	< 4 weeks
Subacute	4-12 weeks
Chronic rhinosinusitis (CRS)	> 12 weeks
Recurrent acute	≥ 4 episodes/year, each < 4 weeks

Etiology and Pathophysiology

Viral Acute Rhinosinusitis (Most Common)

The vast majority of ARS is viral. Common culprits include rhinovirus (most common), adenovirus, influenza, and parainfluenza. Viral infection causes mucosal edema, mucus stasis, and ciliary dyskinesia - which creates an environment conducive to secondary bacterial superinfection. - Rosen's Emergency Medicine, p. 966

Acute Bacterial Rhinosinusitis (ABRS)

Bacterial superinfection complicates roughly 0.5-2% of viral ARS episodes. The most common bacteria are:

Streptococcus pneumoniae (most common, ~20-35%)
Non-typeable Haemophilus influenzae (~20-35%)
Moraxella catarrhalis (~3-20%)

The "double sickening" phenomenon - initial improvement followed by worsening - strongly suggests secondary bacterial infection. - Goldman-Cecil Medicine, p. 4165

Chronic Rhinosinusitis (CRS)

CRS differs fundamentally in microbiology and pathophysiology:

Staphylococcus aureus, Pseudomonas aeruginosa, and anaerobic bacteria are most often cultured
Characterized by loss of bacterial diversity with overgrowth of a pathologic species
Two phenotypes:
- CRS with nasal polyps (CRSwNP) - eosinophilic, TH2-driven inflammation
- CRS without nasal polyps (CRSsNP) - neutrophilic/mixed inflammation
Odontogenic infection (tooth root infection of maxillary molars) is a common cause of unilateral maxillary CRS - Goldman-Cecil Medicine, p. 4165

Structural Predisposing Factors

Nasal septal deviation
Concha bullosa (pneumatized middle turbinate)
Accessory ostia
Oroantral fistula
Infraorbital ethmoid air cells > 3mm - Rosen's Emergency Medicine, p. 966

Fungal Sinusitis

Non-invasive (fungus ball/mycetoma): typically in immunocompetent patients; most common in maxillary sinus
Invasive fungal sinusitis: in immunocompromised patients; caused by Aspergillus spp., Mucor, Fusarium; life-threatening; eschar on nasal septum/turbinates is a warning sign
Acute Aspergillus sinusitis of ethmoid/sphenoid can progress to cavernous sinus thrombosis - Goldman-Cecil Medicine, p. 335; Scott-Brown's Otorhinolaryngology

Clinical Features

Symptoms

The diagnosis of rhinosinusitis requires:

Nasal obstruction/congestion OR purulent nasal discharge (anterior or posterior)
PLUS: facial pain/pressure OR reduced/loss of smell (hyposmia/anosmia)

Additional symptoms may include:

Sore throat, hoarseness, cough
Headache, fatigue, malaise
Fever (especially in bacterial disease)

Site-Specific Pain

Maxillary sinusitis: cheek pain, tooth pain (upper molars), pain worsens on bending forward
Frontal sinusitis: forehead pain, worse in morning
Ethmoid sinusitis: periorbital/medial canthal pain
Sphenoid sinusitis: vertex or diffuse headache, retro-orbital pain

Distinguishing Viral vs. Bacterial

No single symptom reliably distinguishes viral from bacterial; the time course is key:

Bacterial ABRS is diagnosed when symptoms persist ≥ 10 days without improvement, OR
Symptoms worsen after initial improvement ("double worsening") - Rosen's Emergency Medicine, p. 966; 2025 AAO-HNS Guideline

Note on "sinus headaches": Goldman-Cecil highlights that virtually all patients complaining of "sinus headaches" in the context of chronic symptoms actually have atypical migraine (bilateral distribution, maxillary/ophthalmic trigeminal branches, often with vasomotor features). Chronic sinusitis rarely causes headaches.

Diagnosis

Clinical Diagnosis

ABRS: clinical diagnosis based on time course (as above)
No imaging needed for straightforward ABRS per 2025 AAO-HNS guidelines - only order if a complication or alternative diagnosis is suspected

Endoscopy

Nasal endoscopy can directly visualize turbinate swelling, purulent discharge, polyps, and structural abnormalities. Endoscopically guided cultures are the best method to confirm bacterial infection.

CT Scan

Gold standard imaging for CRS
Findings: mucosal thickening, air-fluid levels, ostiomeatal complex obstruction, opacification
Indicated: atypical presentation, CRS, suspected complications, pre-operative planning
Not indicated for routine acute sinusitis - Rosen's Emergency Medicine, p. 967

Culture

Gold standard = sinus puncture culture (painful, not routine)
Nasal swabs correlate poorly with sinus pathogens
Endoscopy-guided middle meatal cultures are practical and reasonably accurate

Additional Testing (CRS workup)

Allergy testing (skin prick or serum IgE) - relevant for CRSwNP
Immune function testing (IgG subclass, complement) - for recurrent disease
CT sinuses - mandatory before surgery

Complications

Rare but serious - escalate urgently if suspected:

Complication	Signs
Orbital cellulitis/abscess	Periorbital edema, proptosis, painful/limited eye movement
Intracranial abscess	Severe headache, altered consciousness, focal neurology
Meningitis	Nuchal rigidity, photophobia, fever
Cavernous sinus thrombosis	Proptosis, chemosis, cranial nerve (III, IV, V, VI) palsies
Pott's puffy tumor	Frontal soft-tissue swelling with subperiosteal abscess
Osteomyelitis	Especially frontal bone; requires 8-12 weeks of antibiotics

Frontal and ethmoid sinusitis carry the highest risk of orbital and intracranial spread. Failure to recognize early signs within 24 hours of hospitalization is indefensible. - Scott-Brown's Otorhinolaryngology, p. 495

Treatment

1. Viral Acute Rhinosinusitis (Symptomatic Management)

Since most ARS is viral and self-resolving, treatment is supportive:

Agent	Dose/Route	Evidence
Intranasal corticosteroid (e.g., fluticasone, mometasone)	2 sprays each nostril once daily	Recommended - reduces mucosal edema
Saline nasal irrigation	1-2 sprays each nostril every 4 hours	Recommended - clears secretions
Paracetamol/acetaminophen	650 mg q6-8h (or 15 mg/kg in children)	For pain/fever
Ibuprofen	400-800 mg q8h (10 mg/kg children)	For pain/fever
Oral decongestants	Not routinely recommended	Insufficient evidence
Antihistamines	Not routinely recommended unless allergic symptoms present
Systemic corticosteroids	Not recommended for acute sinusitis

Rosen's Emergency Medicine, p. 967

2. Acute Bacterial Rhinosinusitis (ABRS) - Antibiotics

Antibiotics should only be prescribed if ABRS criteria are met (≥10 days without improvement or double worsening). The benefit is modest: cure rates at 7-15 days are only slightly higher with antibiotics vs. placebo. A watchful waiting approach for 7 days is acceptable for well-appearing, otherwise healthy patients.

First-Line Antibiotics (2025 AAO-HNS Guideline):

Amoxicillin 500 mg TID OR amoxicillin-clavulanate 875/125 mg BID for 5-7 days

Prefer amoxicillin-clavulanate if:

Age > 65 years
Recent antibiotic use
Smoker
Diabetes mellitus
Healthcare worker (higher resistance risk)
Symptoms not isolated to maxillary sinus

Second-Line (Penicillin allergy):

Doxycycline 100 mg BID (preferred in allergy)
Levofloxacin or moxifloxacin - effective but reserve for cases without alternatives due to side-effect profile (tendinopathy, QT prolongation, neurotoxicity)

Avoid:

Macrolides (azithromycin) - increasing S. pneumoniae resistance
TMP-SMX
Second/third-generation cephalosporins (increased resistance)

Reassess if no improvement after 3-5 days of appropriate antibiotic therapy - reconsider diagnosis and rule out complications. - Rosen's Emergency Medicine, p. 967-968; 2025 AAO-HNS Guideline

3. Chronic Rhinosinusitis (CRS) Treatment

CRS management is stepwise:

Step 1 - Medical Management:

Intranasal corticosteroids (INCSs) - cornerstone therapy; reduce polyp size and symptoms
Saline nasal irrigation (large-volume, high-pressure)
Oral antibiotics for exacerbations (based on culture if possible)
Short course oral corticosteroids (for CRSwNP with significant obstruction)
Treat underlying allergic rhinitis

Step 2 - If refractory:

Culture-directed antibiotics
Long-term low-dose macrolides (e.g., azithromycin 3x/week) - anti-inflammatory rather than antimicrobial role in CRSsNP
Allergy immunotherapy if allergy-driven

Step 3 - Biologics (CRSwNP): A new 2025 AAO-HNS recommendation now specifically directs clinicians to educate patients about biologic therapy for CRS with polyps:

Dupilumab (anti-IL-4Rα) - most evidence; approved for CRSwNP; shown comparable to surgery in some outcomes in a 2024 meta-analysis (PMID: 39149992)
Mepolizumab (anti-IL-5), benralizumab, omalizumab (anti-IgE for allergic CRSwNP) - also options

Step 4 - Surgery (Functional Endoscopic Sinus Surgery, FESS):

Indicated when maximal medical therapy fails (typically after 12 weeks)
Goals: restore sinus drainage, remove polyps, widen ostia
A 2025 AAO-HNS surgical guideline provides evidence-based criteria (PMID: 40424072)
Post-operative medical therapy (INCSs, saline irrigation) is essential to maintain results

4. Complicated Sinusitis (Orbital/Intracranial Extension)

Hospitalization, IV antibiotics
Surgical drainage of abscesses
Frontal osteomyelitis: 8-12 weeks of antibiotics minimum
Early ENT + ophthalmology ± neurosurgery consultation
MRI with contrast preferred over CT for orbital/intracranial complications

5. Fungal Sinusitis Treatment

Type	Treatment
Fungus ball	Surgical removal; no antifungals needed
Allergic fungal sinusitis	FESS + systemic corticosteroids ± antifungals
Invasive fungal (Aspergillus, Mucor)	Urgent surgical debridement + systemic antifungals (voriconazole for Aspergillus; amphotericin B for Mucor); reverse immunosuppression if possible

Pediatric Considerations

A 2025 Italian consensus (PMID: 40140854) highlights that:

Children with acute sinusitis also primarily have viral disease
Watchful waiting is appropriate in mild-to-moderate cases
Amoxicillin-clavulanate remains first-line when antibiotics are needed
Intranasal corticosteroids are beneficial in children with allergic predisposition

The Harriet Lane Handbook notes azithromycin 500 mg (or weight-based) daily x 3 days as an option for sinusitis in penicillin-allergic patients, though this should be contextualized given resistance concerns.

Key 2025 Guidelines Summary (AAO-HNS)

The 2025 AAO-HNS Clinical Practice Guideline on Adult Sinusitis (published July 2025, updating the 2015 version) includes 14 key recommendations:

Distinguish ABRS from viral ARS - strong recommendation
Do not obtain routine imaging for ABRS unless complications suspected
Use amoxicillin ± clavulanate as first-line for 5-7 days
Reassess at 3-5 days if no improvement
Offer intranasal corticosteroids for all rhinosinusitis
New 2025: Educate patients about biologics (dupilumab, etc.) for CRSwNP
Evidence-based criteria for when to refer for surgery

Quick Reference Summary

ACUTE VIRAL ARS:    Symptomatic only → INCS + saline + analgesics
ACUTE BACTERIAL:    Amoxicillin ± clavulanate 5-7 days (only if ≥10 days or double worsening)
CHRONIC (CRSsNP):  INCS + saline → culture-based ABX → low-dose macrolide → FESS
CHRONIC (CRSwNP):  INCS + saline + OCS bursts → biologics (dupilumab) → FESS
COMPLICATED:        IV ABX + surgical drainage + specialist input
INVASIVE FUNGAL:    Urgent debridement + antifungals + reverse immunosuppression

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