Brain Mapping Unit, Department of Psychiatry, Sir William Hardy Building, University of Cambridge, Cambridge, United Kingdom.
Academic Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, United Kingdom.
Neurosurgery. 2019 Jun 1;84(6):1201-1213. doi: 10.1093/neuros/nyy378.
Neurosurgical management of brain tumors has entered a paradigm of supramarginal resections that demands thorough understanding of peritumoral functional effects. Historically, the effects of tumors have been believed to be local, and long-range effects have not been considered.
To test the hypothesis that tumors affect the brain globally, producing long-range gradients in cortical function.
Resting-state functional magnetic resonance imaging (fMRI) data were acquired from 11 participants with glioblastoma and split into discovery and validation datasets in a single-center prospective cohort study. Fractal complexity was computed with a wavelet-based estimator of the Hurst exponent. Distance-related effects of the tumors were tested with a tumor mask-dilation technique and parcellation of the underlying Hurst maps.
Fractal complexity demonstrates a penumbra of suppression in the peritumoral region. At a global level, as distance from the tumor increases, this initial suppression is balanced by a subsequent overactivity before finally normalizing. These effects were best fit by a quadratic model and were consistent across different network construction pipelines. The Hurst exponent was correlated with graph theory measures of centrality including network robustness, but graph theory measures did not demonstrate distance-dependent effects.
This work provides evidence supporting the theory that focal brain tumors produce long-range gradients in function. Consequently, the effects of focal lesions need to be interpreted in terms of the global changes on functional complexity and network architecture rather than purely in terms of functional localization. Determining whether peritumoral changes represent potential plasticity may facilitate extended resection of tumors without functional cost.
神经外科对脑肿瘤的治疗已经进入了边缘切除的模式，这需要对肿瘤周围的功能影响有透彻的理解。从历史上看，人们认为肿瘤的影响是局部的，而没有考虑到远程影响。
检验肿瘤对大脑产生全局影响，导致皮质功能产生远程梯度这一假说。
在一项单中心前瞻性队列研究中，从 11 名胶质母细胞瘤患者中获取静息态功能磁共振成像 (fMRI) 数据，并将其分为发现数据集和验证数据集。使用基于小波的赫斯特指数估算器计算分形复杂度。使用肿瘤掩模膨胀技术和潜在赫斯特图的分割来测试肿瘤的距离相关效应。
分形复杂度显示出肿瘤周围区域存在抑制的半影。在全局水平上，随着与肿瘤的距离增加，最初的抑制被随后的过度活跃所平衡，最终恢复正常。这些效应最好用二次模型拟合，并且在不同的网络构建管道中是一致的。赫斯特指数与网络中心性的图论度量相关，包括网络鲁棒性，但图论度量没有表现出距离依赖性效应。
这项工作提供了支持以下理论的证据：即局灶性脑肿瘤会在功能上产生远程梯度。因此，局灶性病变的影响需要根据功能复杂性和网络结构的全局变化来解释，而不仅仅是根据功能定位来解释。确定肿瘤周围的变化是否代表潜在的可塑性，可能有助于在不影响功能的情况下扩大肿瘤切除范围。
