Paranasal sinus osteomas are common benign tumors, usually found incidentally.
For a general discussion, please see the main osteoma article.
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Epidemiology
Osteomas are commonly found in patients undergoing imaging of the sinuses, appearing in up to 3% of CT examinations of the paranasal sinuses 1. They are most frequently diagnosed in 20-50 years olds, and there is a male predilection (M:F = 1.5-2.6:1) 1.
Clinical presentation
Most paranasal sinus osteomas are asymptomatic and are found incidentally when imaging the sinuses either for sinonasal symptoms or for unrelated complaints. Osteomas may become symptomatic in one of two ways:
direct mass effect
obstruction of normal sinus drainage
Three possible mechanisms for pain are suggested: local effect, referred pain via the trigeminal nerve, and a prostaglandin E-2 mediated mechanism 5. There can be a significant inversely proportional discrepancy between the size of the lesion and the symptoms; do not simply assume because the lesion is small it does not account for the patient's symptoms.
Some osteomas are large and exophytic. They may be palpable (as is the case with skull vault osteomas) or compress structures, such as the content of the orbit 1-3. Rarely an osteoma may encroach upon the brain, and may even result in erosion of the dura with resultant CSF leak, pneumocephalus or intracranial infection (meningitis, cerebral abscess) 1,2,4.
More frequently they may impair normal drainage of one or more paranasal sinuses thereby resulting in acute or chronic sinusitis or even mucocele formation 1,3.
Pathology
Location
The distribution of osteomas within the paranasal sinuses is 1-3
frontal sinuses: 80%
ethmoidal air cells: ~15%
maxillary sinuses: ~5%
sphenoid sinus: rare 2
Associations
rhinosinusitis: occurs in ~30% although a causal link has not been established 1
Radiographic features
Parasinus osteomas are seen either with a sinus or less commonly exophytically growing out of a sinus. See the main osteoma article for more details.
Treatment and prognosis
In asymptomatic cases excision is not necessarily indicated, and management varies from surgeon to surgeon. If sinonasal symptoms are present, then they can initially be managed medically (as if the osteoma is not present). In cases where the osteoma is thought to be responsible for symptoms (e.g. mucocele) then resection is required. Some surgeons prefer to excise all osteomas. Excision may be performed either endoscopically or externally.
Differential diagnosis
General imaging differential considerations include:
fibrous dysplasia: especially in less dense ground-glass osteomas
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other osteogenic tumors
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more frequently of the maxilla (rather than maxillary sinus or mandible)
younger patients
more aggressive appearance and rapid growth
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usually of the alveolar portions of the mandible or maxilla