IDH1 and astrocytoma (excluding glioblastoma): We, and others, have shown that preoperative non-invasive magnetic resonance spectroscopy at 3- or 7-Tesla may provide the neurosurgeon with information on IDH status of diffuse gliomas33; however, to the best of our knowledge, this currently does not allow distinction between IDH-mutant astrocytomas and oligodendrogliomas.