The first interest is diagnostic: the presence of the IDH1Arg132His mutation allows the diagnosis of glioma. This information is particularly valuable in patients not amenable to biopsy, because of the location of the tumor considered at risk, the general condition of the patient or the co-morbidities and medications. We hope also with these parameters to better monitor patient's follow-up, and to have a new method to differentiate tumor recurrence and radionecrosis or post-radiation leukoencephalopathy.