Frequency of meningioma as an incidental finding in neuroimaging study is increasing. It is important to characterize tumors that will grow to be symptomatic in order to select appropriate treatment and radiological follow-up because long-term observation may increase the risk of surgery due to enlargement of the tumors and aging of patients. [Methods]We reviewed 26 studies that analyzed natural courses in asymptomatic or untreated meningiomas. RESULTS: In time-growth rate analysis, nearly 70% of meningiomas showed radiological progression defined by a volume criteria and the rate approached plateau at 5–6 years. About half of incidental meningiomas presented a decelerating growth pattern or no growth while less than one-fourth of them grew exponentially. Growth pattern change could be affected by the length of follow-up period. Radiological progression, growth speed (annual volume change (AVC) or relative growth rate (RGR)) and symptomatic progression had each different factor related to their progression. Younger age, non-calcification and high intensity on T2 weighted image related to radiological progression and rapid growth speed but not to symptomatic progression. Tumors in men and lager size were likely to be symptomatic in meta-analysis. AVC (>= 2.1cm3/year) was the strongest indicator for symptom development. In the group of AVC >=2.1cm3/year, progression free rate was 69.3% at 3 years, and reached to 55.4% at 6 years whereas 100% in slower growth group. [Conclusion]Radiological features may not be useful for prediction of symptom development except for perifocal edema in a long term. This may be due to dynamic change of these radiological markers in a long term. Quantitative tumor size and growth speed especially AVC were important factors for decision of treatment.
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