Faust Katharina, Vajkoczy Peter
Department of Neurosurgery, Charité University Hospital, Berlin, Germany.
J Neurosurg. 2016 May;124(5):1343-52. doi: 10.3171/2015.3.JNS141584. Epub 2015 Oct 2.
OBJECT Visual field defects (VFDs) due to optic radiation (OR) injury are a common complication of temporal lobe surgery. The authors analyzed whether preoperative visualization of the optic tract would reduce this complication by influencing the surgeon's decisions about surgical approaches. The authors also determined whether white matter shifts caused by temporal lobe tumors would follow predetermined patterns based on the tumor's topography. METHODS One hundred thirteen patients with intraaxial tumors of the temporal lobe underwent preoperative diffusion tensor imaging (DTI) fiber tracking. In 54 of those patients, both pre- and postoperative VFDs were documented using computerized perimetry. Brainlab's iPlan 2.5 navigation software was used for tumor reconstruction and fiber visualization after the fusion of DTI studies with their respective magnetization-prepared rapid gradient-echo (MP-RAGE) images. The tracking algorithm was as follows: minimum fiber length 100 mm, fractional anisotropy threshold 0.1. The lateral geniculate body and the calcarine cortex were employed as tract seeding points. Shifts of the OR caused by tumor were visualized in comparison with the fiber tracking of the patient's healthy hemisphere. RESULTS Temporal tumors produced a dislocation of the OR but no apparent fiber destruction. The shift of white matter tracts followed fixed patterns dependent on tumor location: Temporolateral tumors resulted in a medial fiber shift, and thus a lateral transcortical approach is recommended. Temporopolar tumors led to a posterior shift, always including Meyer's loop; therefore, a pterional transcortical approach is recommended. Temporomesial tumors produced a lateral and superior shift; thus, a transsylvian-transcisternal approach will result in maximum sparing of the fibers. Temporocentric tumors also induced a lateral fiber shift. For those tumors, a transsylvian-transopercular approach is recommended. Tumors of the fusiform gyrus generated a superior (and lateral) shift; consequently, a subtemporal approach is recommended to avoid white matter injury. In applying the approaches recommended above, new or worsened VFDs occurred in 4% of the patient cohort. Total neurological and surgical morbidity were less than 10%. In 90% of patients, gross-total resection was accomplished. CONCLUSIONS Preoperative visualization of the OR may help in avoiding postoperative VFDs.
目的 视辐射（OR）损伤所致视野缺损（VFDs）是颞叶手术的常见并发症。作者分析术前对视束进行可视化是否会通过影响外科医生对手术入路的决策来减少这一并发症。作者还确定颞叶肿瘤引起的白质移位是否会根据肿瘤的形态遵循预定模式。方法 113例颞叶轴内肿瘤患者术前行弥散张量成像（DTI）纤维束示踪。其中54例患者术前和术后均使用电脑视野计记录VFDs。将DTI研究与其各自的磁化准备快速梯度回波（MP-RAGE）图像融合后，使用Brainlab公司的iPlan 2.5导航软件进行肿瘤重建和纤维可视化。追踪算法如下：最小纤维长度100 mm，各向异性分数阈值0.1。外侧膝状体和距状皮质用作纤维束种子点。与患者健康半球的纤维束示踪相比，观察肿瘤引起的视束移位。结果 颞叶肿瘤导致视束移位，但无明显纤维破坏。白质束的移位遵循取决于肿瘤位置的固定模式：颞外侧肿瘤导致纤维向内侧移位，因此建议采用外侧经皮质入路。颞极肿瘤导致向后移位，总是包括迈耶袢；因此，建议采用翼点经皮质入路。颞内侧肿瘤产生向外上移位；因此，经外侧裂-经脑池入路将最大程度地保留纤维。颞中心肿瘤也引起纤维向外移位。对于那些肿瘤，建议采用经外侧裂-经脑桥入路。梭状回肿瘤产生向上（和向外）移位；因此，建议采用颞下入路以避免白质损伤。在应用上述推荐的入路时，4%的患者队列出现了新的或加重的VFDs。总的神经和手术并发症发生率低于10%。90%的患者实现了大体全切。结论 术前对视束进行可视化可能有助于避免术后VFDs。
