1Department of Neurosurgery.
2TUM Neuroimaging Center, and.
Neurosurg Focus. 2021 Jan;50(1):E9. doi: 10.3171/2020.10.FOCUS20774.
Tractography is a useful technique that is standardly applied to visualize subcortical pathways. However, brain shift hampers tractography use during the course of surgery. While intraoperative MRI (ioMRI) has been shown to be beneficial for use in oncology, intraoperative tractography can rarely be performed due to scanner, protocol, or head clamp limitations. Elastic fusion (EF), however, enables adjustment for brain shift of preoperative imaging and even tractography based on intraoperative images. The authors tested the hypothesis that adjustment of tractography by ioMRI-based EF (IBEF) correlates with the results of intraoperative neuromonitoring (IONM) and clinical outcome and is therefore a reliable method.
In 304 consecutive patients treated between June 2018 and March 2020, 8 patients, who made up the basic study cohort, showed an intraoperative loss of motor evoked potentials (MEPs) during motor-eloquent glioma resection for a subcortical lesion within the corticospinal tract (CST) as shown by ioMRI. The authors preoperatively visualized the CST using tractography. Also, IBEFs of pre- and intraoperative images were obtained and the location of the CST was compared in relation to a subcortical lesion. In 11 patients (8 patients with intraoperative loss of MEPs, one of whom also showed loss of MEPs on IBEF evaluation, plus 3 additional patients with loss of MEPs on IBEF evaluation), the authors examined the location of the CST by direct subcortical stimulation (DSCS). The authors defined the IONM results and the functional outcome data as ground truth for analysis.
The maximum mean ± SD correction was 8.8 ± 2.9 (range 3.8-12.0) mm for the whole brain and 5.3 ± 2.4 (range 1.2-8.7) mm for the CST. The CST was located within the lesion before IBEF in 3 cases and after IBEF in all cases (p = 0.0256). All patients with intraoperative loss of MEPs suffered from surgery-related permanent motor deficits. By approximation, the location of the CST after IBEF could be verified by DSCS in 4 cases.
The present study shows that tractography after IBEF accurately correlates with IONM and patient outcomes and thus demonstrates reliability in this initial study.
束路追踪技术是一种标准的用于可视化皮质下通路的有用技术。然而，脑移位会妨碍手术过程中的束路追踪。虽然术中磁共振成像（ioMRI）已被证明在肿瘤学中有益，但由于扫描仪、协议或头夹的限制，术中束路追踪很少进行。然而，弹性融合（EF）可以调整术前影像和基于术中影像的束路追踪。作者测试了以下假设：基于术中磁共振成像的 EF（IBEF）调整束路追踪与术中神经监测（IONM）和临床结果相关，因此是一种可靠的方法。
在 2018 年 6 月至 2020 年 3 月连续治疗的 304 例患者中，8 例患者在皮质脊髓束（CST）内皮质下病变的运动功能区胶质瘤切除术中出现术中运动诱发电位（MEPs）丢失，这在 ioMRI 中显示。作者在术前使用束路追踪可视化 CST。还获得了术前和术中图像的 IBEF，并比较了 CST 在皮质下病变中的位置。在 11 例患者（8 例术中 MEPs 丢失，其中 1 例在 IBEF 评估中也出现 MEPs 丢失，另加 3 例在 IBEF 评估中出现 MEPs 丢失）中，作者通过直接皮质下刺激（DSCS）检查 CST 的位置。作者将 IONM 结果和功能结果数据定义为分析的真实数据。
全脑最大平均±SD 校正值为 8.8±2.9（范围 3.8-12.0）mm，CST 为 5.3±2.4（范围 1.2-8.7）mm。在 IBEF 前 CST 位于病变内的 3 例，在 IBEF 后所有病例均位于病变内（p=0.0256）。所有术中 MEPs 丢失的患者均有与手术相关的永久性运动功能障碍。通过近似，在 4 例中可以通过 DSCS 验证 IBEF 后的 CST 位置。
本研究表明，IBEF 后的束路追踪与 IONM 和患者结果准确相关，因此在这项初步研究中证明了其可靠性。
