New Insights into Pre-, Intra- and Post-Operative Brain Mapping in Low- Grade Glioma Surgery: Towards a Longitudinal Study of Cerebral Plasticity

Surgery is currently the first treatment for low-grade gliomas (LGG). However, LGG often involves eloquent areas, in patients with no or mild preoperative deficit. Therefore, cortical and subcortical structures, essential, for brain functions must be preserved. Presurgical functional neuroimaging and tractography can show the relationships between eloquent regions and the tumor, but they have several limitations. Consequently, intraoperative electrical mapping is more and more used by neurosurgeons, to tailor the resection according to individual functional boundaries. Nonetheless, due to the invasive feature of LGG, the glioma removal is regularly incomplete to avoid postsurgical permanent deficit. The goal of this review is to provide new insights into cerebral plasticity, that is, the brains ability to reorganize its functional maps consecutively to slow-growing lesions like LGG. Longitudinal studies combining pre-, intra- and post-operative brain mapping methods may enable to analyze functional redistribution over time at the individual scale. Such plastic potential can open the door to multiple surgeries spaced by several months or years, with the aim to optimize the benefit/risk ratio of surgery, i.e. to increase the extent of resection of LGG before anaplastic transformation - thus to increase the overall survival - while preserving and even improving the quality of life.