The distribution of MRI scans has increased the chance of diagnosing asymptomatic FLAIR high-signal lesions. Herein, we retrospectively analyzed 14 asymptomatic FLAIR high-signal lesions to evaluate their natural course. Fifteen symptomatic(epilepsy)patients with FLAIR high-signal lesions were also analyzed as controls. As a result, all symptomatic patients underwent surgery and were diagnosed with lower-grade gliomas(n=14)and a dysembryoplastic neuroepithelial tumor(n=1). Among the 14 lower-grade gliomas, 11 gliomas were isocitrate dehydrogenase(IDH)-mutant. As previously reported, these results showed that FLAIR high-signal lesions with epilepsy are closely associated with IDH-mutant gliomas. On the other hand, 12 of the 14 asymptomatic patients showed no changes in the size of the lesion and symptoms during the follow-up period. Only 2 patients(14.3%)revealed increased lesions within 38 and 25 months, who were diagnosed with high-grade gliomas. Although there was no difference in the apparent diffusion coefficient value between asymptomatic and symptomatic lesions, low-intensity T1WI on MRI might be useful to discriminate lower-grade gliomas from non-tumor lesions. In conclusion, there is no need for immediate surgery for true asymptomatic lesions; however, we must undergo routine follow-up MRI scans.