Chronic sinusitis is persistent inflammation of the paranasal sinus mucosa lasting more than 12 weeks. It is characterized by persistence of symptoms despite maximum medical therapy (antibiotics, nasal steroids, saline irrigation). It has two main phenotypes: with nasal polyps (CRSwNP) and without nasal polyps (CRSsNP). Imaging characteristically shows mucosal thickening, sclerotic bone changes (osteoneogenesis), polypoid mucosal changes, and ostiomeatal complex obstruction. CT is the gold standard imaging modality for anatomic mapping and assessment of disease extent prior to endoscopic sinus surgery (ESS).
Age Range
10-80
Peak Age
40
Gender
Equal
Prevalence
Very Common
Chronic sinusitis is a multifactorial disease involving ostiomeatal obstruction, mucociliary dysfunction, biofilm formation, and immune dysregulation. Persistent inflammation leads to goblet cell hyperplasia, submucosal fibrosis, and neovascularization in the sinus mucosa — these changes are reflected as persistent mucosal thickening on CT. Chronic inflammation creates reactive osteoneogenesis and sclerosis in sinus bony walls through periosteal stimulation — this finding is the most important radiologic criterion distinguishing it from acute sinusitis. In the polyp phenotype (CRSwNP), eosinophilic inflammation and Type 2 immune response predominate, forming edematous polypoid masses in the mucosa; in the non-polyp phenotype (CRSsNP), neutrophilic inflammation and fibrotic remodeling are predominant. Long-standing obstruction can lead to mucous retention, secondary infection, and progressive bone remodeling within the sinus, potentially setting the stage for mucocele formation.
Reactive bone thickening and sclerosis in sinus walls is the most specific and distinguishing CT finding of chronic sinusitis. While bone structures are normal in acute sinusitis, new bone formation develops as a result of prolonged periosteal stimulation in chronic sinusitis. This finding allows acute-chronic differentiation even without clinical duration information. Bone sclerosis is most prominently seen in maxillary sinus walls and bilateral symmetric involvement is common. Smooth, homogeneous sclerosis suggests a benign inflammatory process, while irregular bone destruction should suggest malignancy or invasive fungal infection.
In chronic sinusitis, reactive bone sclerosis and thickening is seen in the sinus walls. This osteoneogenesis is a result of chronic periosteal stimulation and is characterized by the white, dense appearance of the sinus walls. Bone thickening is most prominently seen in the medial and inferior walls of the maxillary sinus. Normal sinus wall thickness is 1-2 mm, while in chronic sinusitis it can reach 3-5 mm or more. Sclerosis is usually homogeneous and smooth — irregular or aggressive bone changes should suggest malignancy or invasive fungal sinusitis. This finding is the most reliable radiologic criterion for differentiating chronic from acute sinusitis.
Report Sentence
Bony sclerosis and osteoneogenesis secondary to chronic inflammatory changes is noted in bilateral maxillary sinus walls.
In chronic sinusitis, mucosal thickening typically demonstrates a polypoid character — smooth-bordered, round or lobulated contoured mucosal protrusions extend into the sinus lumen. Polypoid changes are most commonly seen in ethmoid sinuses and around the middle meatus. On CT, they appear homogeneous at soft tissue density (30-50 HU). Antrochoanal polyp is a special form — originating from the maxillary sinus, it extends through the natural ostium into the nasal cavity and choana, and is unilateral. The Lund-Mackay scoring system standardizes disease extent by scoring each sinus as 0 (normal), 1 (partial), or 2 (complete opacification) (total score 0-24, OMC scored separately).
Report Sentence
Polypoid mucosal thickening is noted in bilateral ethmoid sinuses and around the middle meatus, consistent with chronic rhinosinusitis.
The Lund-Mackay scoring system standardizes disease extent in chronic sinusitis. Six regions on each side are evaluated: anterior ethmoid (0-2), posterior ethmoid (0-2), maxillary (0-2), frontal (0-2), sphenoid (0-2), and ostiomeatal complex (0 or 2). Each region is scored as normal (0), partially opacified (1), or completely opacified (2). Total score ranges from 0-24. A Lund-Mackay score ≥4 is associated with endoscopic sinus surgery indication. Correlation with systemic diseases is important — the triad of asthma, aspirin sensitivity, and nasal polyposis (Samter's triad/AERD) is associated with high Lund-Mackay scores.
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The Lund-Mackay score is calculated as 16/24 bilaterally, consistent with extensive chronic sinusitis; bilateral ostiomeatal complexes appear obstructed.
Chronic sinusitis secretions show variable signal on MRI T2-weighted sequences — this feature differs from the homogeneously T2 hyperintense secretions of acute sinusitis. Low-protein serous secretions are T2 hyperintense, while high-protein or desiccated secretions are T2 hypointense. Very thick desiccated mucus or fungal debris can be markedly hypointense on T2 ('T2 blackout') — this should not be confused with tumor or air. Polypoid mucosal changes generally appear T2 hyperintense because the edematous stroma has high water content. MRI is superior to CT particularly in differentiating chronic sinusitis from sinonasal tumors, identifying fungal sinusitis, and evaluating orbital/intracranial complications.
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Variable signal intensity secretions and polypoid mucosal thickening are noted in the right maxillary sinus on MRI T2-weighted sequences, consistent with chronic sinusitis.
On contrast-enhanced T1 MRI, a characteristic 'peripheral enhancement' pattern is seen in chronic sinusitis. The thickened mucosa shows intense circumferential enhancement, while retention material in the sinus lumen does not enhance. This pattern is called the 'tramline sign' and reflects the enhancement difference between mucosa and luminal content. It is critically important in differential diagnosis from sinonasal tumors — tumors show solid enhancement, while peripheral/mucosal enhancement is expected in inflammatory disease. Polypoid changes may show mild-moderate homogeneous enhancement. In benign tumors such as inverted papilloma, a 'cerebriform' (resembling brain convolutions) enhancement pattern can be distinguishing.
Report Sentence
Peripheral mucosal enhancement is noted in bilateral maxillary sinuses on contrast-enhanced T1 MRI, with non-enhancing luminal secretions; findings are consistent with chronic sinusitis.
Anatomic variants predisposing to chronic sinusitis should be evaluated on CT. Concha bullosa (pneumatized middle turbinate) can narrow the OMC — prevalence is 14-53%. Septal deviation can affect nasal airflow and sinus drainage. Haller cell (infraorbital ethmoid cell) is located at the maxillary sinus ostium level and can narrow the infundibulum. Paradoxical middle turbinate (convexity facing laterally) contributes to OMC obstruction. Agger nasi cell hypertrophy can block frontal recess drainage. Onodi cell (posterolateral to the sphenoid sinus or adjacent to the optic nerve) is critical to identify preoperatively for surgical complication risk. These variants should be reported as 'danger zones' in endoscopic sinus surgery planning.
Report Sentence
Left concha bullosa and rightward nasal septal deviation are noted; both anatomic variants are considered predisposing factors for chronic sinusitis.
Bone scintigraphy (Tc-99m MDP) can show increased radiopharmaceutical uptake in the sinus region in chronic sinusitis. This finding reflects increased bone turnover (osteoblastic activity) and is consistent with chronic inflammation. Bone scintigraphy is not routinely used in chronic sinusitis but can complement CT in cases with suspected osteomyelitis (frontal bone, maxilla). SPECT/CT fusion imaging improves anatomic localization. FDG PET-CT can show moderately increased FDG uptake in chronic inflammation — this should not be confused with malignancy (SUVmax is generally <5 in inflammation vs >5-8 in malignancies).
Report Sentence
Increased radiopharmaceutical uptake is noted in bilateral maxillary sinus regions on bone scintigraphy, consistent with chronic inflammatory bone changes.
Criteria
Symptoms ≥12 weeks, no polyps on endoscopy. Neutrophilic inflammation predominant. Symptoms of nasal obstruction, facial pain, postnasal drip.
Distinct Features
Mucosal thickening on CT is usually smooth and concentric, bone sclerosis is prominent, polypoid changes are minimal. Frequently predisposed by local anatomic factors (septal deviation, concha bullosa).
Criteria
Symptoms ≥12 weeks, bilateral nasal polyps on endoscopy. Eosinophilic inflammation predominant, Type 2 immune response. Prominent hyposmia/anosmia. May be associated with asthma, aspirin sensitivity.
Distinct Features
Bilateral diffuse polypoid mucosal thickening on CT, dominant ethmoid sinus involvement, opacification of the olfactory cleft (correlating with hyposmia/anosmia), infundibular widening (from polyp pressure). Bone sclerosis may be less prominent than in CRSsNP.
Criteria
Triad of nasal polyposis + asthma + aspirin/NSAID intolerance. Most severe form of CRSwNP. High recurrence rate. Arachidonic acid metabolism disorder (leukotriene overproduction).
Distinct Features
Diffuse opacification of all sinuses on CT (high Lund-Mackay score 18-24), neo-osteogenesis in ethmoid region, expansion/remodeling of sinus walls. Rapid recurrence after surgery is expected. Good response to biologic therapy (dupilumab).
Criteria
Unilateral chronic maxillary sinusitis originating from dental pathology. Dental etiology should be investigated in cases unresponsive to standard medical therapy. Dental factors contribute in 10-40% of all chronic maxillary sinusitis cases.
Distinct Features
Unilateral maxillary sinus opacification + dental pathology adjacent to sinus floor on CT. Thin-section coronal CT best shows the relationship between dental apex and sinus floor. Periosteal reaction and focal bone defect should be sought in the sinus floor. Oroantral fistula can be better evaluated with cone-beam CT (CBCT).
Distinguishing Feature
Bone sclerosis and osteoneogenesis are ABSENT in acute sinusitis — bony walls are of normal thickness and density. Air-fluid level is characteristic of acute process and is not expected in chronic sinusitis. Clinical duration <4 weeks vs chronic >12 weeks.
Distinguishing Feature
Sinonasal polyposis is characterized by bilateral, diffuse, multinodular polypoid masses that usually also fill the nasal cavity. On contrast MRI, polyps show peripheral enhancement with non-enhancing central portion (edematous stroma). Important in differential diagnosis from tumors.
Distinguishing Feature
AFS shows hyperdense mucin (>60 HU) within sinuses, sinus expansion, and bone remodeling. T2 hypointense mucin ('T2 blackout') on MRI is characteristic. Chronic sinusitis shows low-moderate density secretions without significant bone remodeling.
Distinguishing Feature
Inverted papilloma is usually unilateral and shows a 'cerebriform' (resembling brain convolutions) enhancement pattern on contrast MRI — this pattern differs from the peripheral/homogeneous mucosal enhancement of chronic sinusitis. Focal bone remodeling/erosion may be seen in inverted papilloma. Surgical removal is required due to malignant transformation risk (5-15%).
Urgency
routineManagement
surgicalBiopsy
Not NeededFollow-up
Maksimum medikal tedaviye (topical nazal steroid, serum fizyolojik irrigasyon, kısa kür antibiyotik) yanıtsız olgularda endoskopik sinüs cerrahisi (ESS) planlanır. Preoperatif BT cerrahi yol haritası olarak zorunludur. Postoperatif takip endoskopik muayene ile yapılır; rekürrens için BT tekrarlanabilir.Chronic sinusitis management follows a stepwise approach: first-line maximum medical therapy (topical nasal steroid — mometasone/fluticasone, saline irrigation, short-course antibiotics, oral steroid course in CRSwNP), second-line endoscopic sinus surgery (ESS). Pre-ESS non-contrast sinus CT is mandatory as a surgical roadmap — anatomic variants, disease extent, critical structures (lamina papyracea, anterior ethmoid artery, optic nerve, internal carotid artery, skull base — fovea ethmoidalis) should be reported. Biologic therapies in CRSwNP (dupilumab — anti-IL4Rα, omalizumab — anti-IgE, mepolizumab — anti-IL5) are increasingly used as surgical alternatives.
Functional endoscopic sinus surgery (FESS) is considered when chronic sinusitis is refractory to medical treatment. Bone destruction requires malignancy exclusion. Bilateral involvement with polyps warrants investigation of allergic/immunologic etiologies.