Sinus or skull osteoma seen by chance on a head scan

What the report means

Osteoma. A rounded, sharply outlined, dense bony lump. On CT it looks like compact, even bone. (Aksakal 2021)(Pons Escoda 2020)
Where it sits. Most sinus osteomas are in the frontal sinus above the eyes or the ethmoid sinuses between the eyes; the sphenoid and maxillary sinuses are rare sites. (Aksakal 2021)(Buyuklu 2011) Osteomas can also grow on the outside of the skull bones. (Pons Escoda 2020)
Ivory, mature or mixed. Words for what the bone looks like inside: solid outer bone only, bone with marrow in the middle, or a mix. (Pons Escoda 2020)
Size. Reports often give a size in mm. On dental cone beam CT scans the average osteoma was 3.43 mm across. (Semerci 2024)
CT shows bone best. CT is the main test for an osteoma; MRI is used when doctors want to look at nearby soft tissue, the eye socket or the brain. (Aksakal 2021)(Lygeros 2026)

How common it is, by age and sex

Up to 3 in 100 scans. Earlier studies found a sinus osteoma on 0.42% to 3% of X-rays and CT scans. (Aksakal 2021) In 18,867 sinus, face and brain CT scans, 176 people (0.92%) had one. (Aksakal 2021)
More on dental scans. In 499 dental cone beam CT scans done for tooth problems, 7% showed an osteoma, most often in the ethmoid sinuses. (Semerci 2024)
Age. People with an osteoma in the large CT study were aged 18 to 93, average 59.9. (Aksakal 2021) The dental scan study found no link with age. (Semerci 2024)
Sex. Earlier series found osteomas more often in men, from 1.08 to 2.6 men for each woman. (Aksakal 2021) The two newer studies found close to equal numbers in men and women. (Aksakal 2021)(Semerci 2024)
Mostly one. In the large CT study, 152 of 176 people had a single osteoma and 24 had more than one. (Aksakal 2021)

When it matters

Most cause nothing. About 10% of sinus osteomas cause symptoms; most are found by chance on CT. (Aksakal 2021) Skull vault osteomas mainly cause no symptoms. (Pons Escoda 2020)
Slow growth. Growth is usually about 0.3 to 1 mm a year, and many stay the same for decades. (Lygeros 2026) In 47 osteomas found by chance and scanned again a median of about 3 years later, growth averaged 0.42 mm a year. (Luo 2024)
Blocked drainage. Rarely, a sinus osteoma blocks the sinus drainage, grows or wears through nearby bone. Frontal and ethmoid osteomas are the ones most often linked to these problems, because they sit close to the eye socket and the base of the skull. (Lygeros 2026)
More than one osteoma. Several osteomas are often seen in Gardner syndrome, which goes with bowel polyps. (Aksakal 2021)(Pons Escoda 2020) People with familial adenomatous polyposis (FAP) can have osteomas. (MedlinePlus Genetics) See screenings for people with FAP.
Worry is real. See after an abnormal screening result.

Other things a head scan may show

The same scan may mention other chance findings, each with its own page: sinus thickening, arachnoid cyst and pineal cyst.

Who it applies to

Adults told that a head CT, MRI or dental cone beam CT done for another reason shows an osteoma in a sinus or the skull. Children, people already being seen for an osteoma, and a scan done because of symptoms from it are outside this page.

In the rare osteomas that cause trouble, the reported symptoms include headache, seizures, problems with vision such as double vision or loss of sight, a bulging eye, and new nerve problems such as weakness. (Lygeros 2026)(Aksakal 2021) Tell your doctor if you have any of these.

Routine age-based screening

An osteoma on a head scan does not replace the routine screenings for your age. See screenings by age and gender.

Where they differ:

How common it is. Figures range from 0.42% to 3% on X-rays and CT (Aksakal 2021) up to 7% on dental cone beam CT, which picks up very small osteomas. (Semerci 2024)
Men and women. Older series found more osteomas in men; the newer CT and cone beam CT studies found close to equal numbers. (Aksakal 2021)(Semerci 2024)
Growth rate. Averages range from 0.42 mm a year (Luo 2024) to 0.79 to 0.99 mm a year (Buyuklu 2011) and 1.61 mm a year in a small older study of osteomas that grew (range 0.44 to 6.0). (Koivunen 1997)
Follow-up. One group says some osteomas found by chance likely need no follow-up, with one scan at a year when growth could block frontal sinus drainage. (Luo 2024) Another says follow-up is necessary because of possible serious problems. (Buyuklu 2011) A review describes periodic scans for osteomas without symptoms. (Lygeros 2026)

Your doctor decides what your result means for you.

Questions people ask

Is a sinus osteoma cancer?

No. An osteoma is a benign, slow-growing growth made of mature bone. Most cause no symptoms and are found by chance on a CT scan. Your doctor decides what your result means for you. (Lygeros 2026) (Aksakal 2021)

How common is an osteoma on a head scan?

Earlier studies found a sinus osteoma on 0.42% to 3% of X-rays and CT scans. In 18,867 CT scans, 0.92% showed one. On 499 dental cone beam CT scans the figure was 7%, mostly very small ones. (Aksakal 2021) (Semerci 2024)

Does an osteoma keep growing?

Usually very slowly. A review gives about 0.3 to 1 mm a year, with many staying the same for decades. In one study of 47 osteomas found by chance, the average was 0.42 mm a year. (Lygeros 2026) (Luo 2024)

Will I need another scan?

Studies differ. One group says some osteomas found by chance likely need no follow-up, and suggests a single scan after a year when growth could block the frontal sinus drainage. Another group, which found growth in about half of rescanned osteomas, says follow-up is necessary. Your doctor decides. (Luo 2024) (Buyuklu 2011)

What does more than one osteoma mean?

Most people have a single osteoma. Several osteomas are often seen in Gardner syndrome, a form of familial adenomatous polyposis (FAP), which also causes many polyps in the bowel. (Aksakal 2021) (Pons Escoda 2020) (MedlinePlus Genetics)