Neurological Institute, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel.
Sagol Brain Institute, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel; Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.
Epilepsy Behav. 2021 Jul;120:107986. doi: 10.1016/j.yebeh.2021.107986. Epub 2021 May 6.
Electroencephalography-correlated functional magnetic resonance imaging (EEG-fMRI) allows imaging of brain-wide epileptic networks, and demonstrates that focal interictal epileptic activity is sometimes accompanied by bilateral functional activations. The corpus callosum (CC) facilitates bilateral spread of epileptic activity and at times targeted surgically for drug-resistant epilepsy (DRE). We hypothesized that focal epileptic networks are more unilateral in patients lacking intact CC.
We included focal DRE patients who underwent pre-surgical EEG-fMRI and had CC agenesis (group A, n = 5), patients who previously underwent anterior callosotomy as treatment for drop attacks and continued having seizures (group B, n = 6), and control group of patients with focal epilepsy and intact CC (group C, n = 9). Blood-oxygenation-level-dependent (BOLD) signal maps were generated for interictal epileptic discharges. To quantify bi-hemispheric distribution of epileptic networks, laterality indices were compared between groups. Anatomical and diffusion-weighted imaging demonstrated white matter pathways.
96% of studies demonstrated bilateral activations. Laterality indices were similar in groups A and C, whereas group B demonstrated a more bilateral network than group C (p = 0.028). Diffusion-weighted and anatomical imaging showed aberrant white matter pathways and larger anterior commissure in groups A and B. 68% of studies showed maximal activation cluster concordant with the presumed epileptic focus, 28% showed non-maximal activation at presumed focus.
Focal epileptic activity is associated with bilateral functional activations despite lack of intact CC, and is associated with stronger contralateral activation in patients after anterior callosotomy compared to controls. These findings disprove our initial hypothesis, and combined with white matter structural imaging, may indicate that the CC is not a sole route of propagation of epileptic activity, which might spread via anterior commissure. Our study demonstrates the utility of EEG-fMRI in assessing epileptic networks and potentially aiding in tailoring surgical treatments in DRE patients with callosal anomalies, and in callosal surgeries.
脑电图相关功能磁共振成像（EEG-fMRI）可对全脑癫痫网络进行成像，并证实局灶性癫痫发作间期活动有时伴有双侧功能激活。胼胝体（CC）有助于癫痫活动的双侧传播，有时会对药物难治性癫痫（DRE）进行靶向手术。我们假设，在 CC 完整的患者中，局灶性癫痫网络更倾向于单侧。
我们纳入了接受术前 EEG-fMRI 检查且存在 CC 发育不全的局灶性 DRE 患者（A 组，n=5）、之前因猝倒发作而行前部胼胝体切开术且持续发作的患者（B 组，n=6），以及胼胝体完整的局灶性癫痫患者（C 组，n=9）。为了生成癫痫发作间期放电的血氧水平依赖（BOLD）信号图，我们对其进行了比较。通过组间比较，确定偏侧指数来量化癫痫网络的双侧分布。解剖和弥散加权成像显示了白质通路。
96%的研究显示双侧激活。A 组和 C 组的偏侧指数相似，而 B 组的网络比 C 组更具双侧性（p=0.028）。弥散加权和解剖成像显示 A 组和 B 组存在异常白质通路和较大的前连合。68%的研究显示最大激活簇与假定的癫痫灶一致，28%的研究显示假定焦点处的非最大激活。
尽管缺乏完整的 CC，但局灶性癫痫活动与双侧功能激活相关，并且与前部胼胝体切开术后患者相比，对侧激活更强。这些发现推翻了我们最初的假设，并且结合白质结构成像，可能表明 CC 不是癫痫活动传播的唯一途径，它可能通过前连合传播。我们的研究证明了 EEG-fMRI 在评估癫痫网络方面的实用性，并可能有助于为存在胼胝体异常的 DRE 患者和胼胝体手术提供个体化的治疗。
