Surgical Strategies for Nonenhancing Slow-Growing Gliomas With Special Reference to Functional Reorganization: Review With Own Experience

Abstract

Nonenhancing intrinsic brain tumors have been empirically treated with a strategy that has been adopted for World Health Organization (WHO) grade II gliomas (low-grade gliomas: LGGs), even though small parts of the tumors might have been diagnosed as WHO grade III gliomas after surgery. However, the best surgical strategy for nonenhancing gliomas, including LGGs, is still debatable.LGGs have the following features: slow growth, high possibility of histologically malignant transformation, and no clear border between the tumor and adjacent normal brain. We retrospectively examined 26 consecutive patients with nonenhancing gliomas who were surgically treated at Kanazawa University Hospital between January 2006 and May 2012, with special reference to functional reorganization, extent of resection (EOR), and functional mapping during awake surgery. These categories are closely related with the features of LGG, i.e. functional reorganization due to slow-growing nature, EOR with related malignant transformation, and functional mapping for delineating the unclear tumor border. Finally, we discuss surgical strategies for slow-growing gliomas that are represented by LGGs and nonenhancing gliomas. In conclusion, slow-growing gliomas tend to undergo functional reorganization, and the functional reorganization affects the presurgical evaluation for resectability based on tumor location related to eloquence. In the clinical setting, to definitely identify the reorganized functional regions, awake surgery is recommended. Therefore, awake surgery could increase the extent of the resection of the tumor without deficits, resulting in the delay of malignant transformation and increase in overall survival.

Intraoperative Functional Mapping and Monitoring during Glioma Surgery

“…Several reports have suggested that brain function plasticity occurs preoperatively in patients with low-grade gliomas, based on the findings of functional magnetic resonance imaging (fMRI) and positron emission tomography (PET). 82 – 88) Prior fMRI and PET studies have demonstrated activation of motor and language areas within and around the tumor. 89 , 90) These reports indicate that the infiltrative characteristics of low-grade gliomas may make it possible for the neurologic function to persist within the tumor, while the slow rate of tumor invasion likely promotes functional plasticity.…”

Initial Experience with Brain Mapping under Awake Craniotomy for Resection of Insular Gliomas of the Dominant Hemisphere

“…One proposed mechanism for enhancing extent of resection of dominant insular gliomas by intraoperative mapping is brain plasticity and functional reorganization of brain areas involved in important tasks (6,30). This has been previously demonstrated in gliomas of extra-insular locations (31).…”

The structure of activation of the language zone in patients with intracerebral tumors according to fMRI with respect to tumor location and the functional asymmetry profile

“…В настоящее время существует много работ, касающихся изучения перестройки речевой функциональной системы у больных с инсультами [8,[26][27][28], при оперативном лечении больных с фармакорезистентной эпилепсией [23,29], а также у больных с опухолями головного мозга [30,31]. Например, A. Thiel и соавт.…”