Low grade gliomas: functional mapping resection strategies, extent of resection, and outcome

The impact of surgery on outcome of adult patients with low-grade gliomas is controversial. Without prospective randomized treatment trials, one is primarily dependent on retrospective studies to address this issue. This paper reviews the recent clinical series of low-grade gliomas in which the association between extent of resection (EOR) and outcome could be analyzed. Functional stimulation mapping methods will be described to point out their critical role in maximizing the extent of resection while minimizing the risk associated with radical resection of low-grade gliomas. Studies from the CT-era analyzed with multivariate statistical methods were emphasized. The analysis of these studies points out that, for astrocytomas, there is no clear consensus that a greater EOR improves survival, but in most series under review, greater EOR significantly extended the survival of patients with oligodendroglioma. Unfortunately, there is little data which specifically analyzes and stratifies the outcome for other end-points such as time to progression, malignant degeneration, mortality and morbidity, and duration of high quality survival by EOR.