van Diessen Eric, Zweiphenning Willemiek J E M, Jansen Floor E, Stam Cornelis J, Braun Kees P J, Otte Willem M
Department of Pediatric Neurology, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands.
Department of Clinical Neurophysiology, VU University Medical Center, Amsterdam, The Netherlands.
PLoS One. 2014 Dec 10;9(12):e114606. doi: 10.1371/journal.pone.0114606. eCollection 2014.
Normal brain functioning is presumed to depend upon interacting regions within large-scale neuronal networks. Increasing evidence exists that interictal network alterations in focal epilepsy are associated with cognitive and behavioral deficits. Nevertheless, the reported network alterations are inconclusive and prone to low statistical power due to small sample sizes as well as modest effect sizes. We therefore systematically reviewed the existing literature and conducted a meta-analysis to characterize the changes in whole-brain interictal focal epilepsy networks at sufficient power levels. We focused on the two most commonly used metrics in whole-brain networks: average path length and average clustering coefficient. Twelve studies were included that reported whole-brain network average path length and average clustering coefficient characteristics in patients and controls. The overall group difference, quantified as the standardized mean average path length difference between epilepsy and control groups, corresponded to a significantly increased average path length of 0.29 (95% confidence interval (CI): 0.12 to 0.45, p = 0.0007) in the epilepsy group. This suggests a less integrated interictal whole-brain network. Similarly, a significantly increased standardized mean average clustering coefficient of 0.35 (CI: 0.05 to 0.65, p = 0.02) was found in the epilepsy group in comparison with controls, pointing towards a more segregated interictal network. Sub-analyses revealed similar results for functional and structural networks in terms of effect size and directionality for both metrics. In addition, we found individual network studies to be prone to low power due to the relatively small group differences in average path length and average clustering coefficient in combination with small sample sizes. The pooled network characteristics support the hypothesis that focal epilepsy has widespread detrimental effects, that is, reduced integration and increased segregation, on whole brain interictal network organization, which may relate to the co-morbid cognitive and behavioral impairments often reported in patients with focal epilepsy.
正常的脑功能被认为依赖于大规模神经元网络内相互作用的区域。越来越多的证据表明,局灶性癫痫发作间期的网络改变与认知和行为缺陷有关。然而,由于样本量小以及效应量适中,所报道的网络改变尚无定论且统计效力较低。因此,我们系统地回顾了现有文献并进行了荟萃分析,以在足够的效力水平上表征全脑发作间期局灶性癫痫网络的变化。我们关注全脑网络中两个最常用的指标:平均路径长度和平均聚类系数。纳入了12项研究,这些研究报告了患者和对照组的全脑网络平均路径长度和平均聚类系数特征。总体组间差异,量化为癫痫组和对照组之间标准化平均路径长度差异,对应于癫痫组平均路径长度显著增加0.29(95%置信区间(CI):0.12至0.45,p = 0.0007)。这表明发作间期全脑网络的整合性较低。同样,与对照组相比,癫痫组的标准化平均聚类系数显著增加0.35(CI:0.05至0.65,p = 0.02),表明发作间期网络的隔离性更强。亚分析在效应量和两个指标的方向性方面显示了功能和结构网络的类似结果。此外,我们发现由于平均路径长度和平均聚类系数的组间差异相对较小以及样本量小,个体网络研究容易出现效力不足的情况。汇总的网络特征支持这样的假设,即局灶性癫痫对全脑发作间期网络组织具有广泛的有害影响,即整合减少和隔离增加,这可能与局灶性癫痫患者经常报告的共病认知和行为障碍有关。