The natural history of asymptomatic meningiomas in Olmsted County, Minnesota.

To define the natural history of asymptomatic meningioma found incidentally on a neuroimaging study, we performed a retrospective analysis of 35 such patients. There were 32 women and three men, with a mean age of 67 years and a mean follow-up of 74 months. Four tumors had progressed on subsequent imaging, and one patient developed symptoms related to the meningioma. Noncalcified tumors were more likely to progress than calcified tumors.