Department of Neurological Surgery, St. Luke's-Roosevelt Hospital, New York, New York 10019, USA.
J Neurosurg Spine. 2010 Jun;12(6):623-8. doi: 10.3171/2010.1.SPINE09112.
Intramedullary spinal cord tumors can displace the surrounding neural tissue, causing enlargement and distortion of the normal cord anatomy. Resection requires a midline myelotomy to avoid injury to the posterior columns. Locating the midline for myelotomy is often difficult because of the distorted anatomy. Standard anatomical landmarks may be misleading in patients with intramedullary spinal cord tumors due to cord rotation, edema, neovascularization, or local scar formation. Misplacement of the myelotomy places the posterior columns at risk of significant postoperative disability. The authors describe a technique for mapping the dorsal column to accurately locate the midline.
A group of 10 patients with cervical and thoracic intramedullary spinal cord lesions underwent dorsal column mapping in which a strip electrode was used to define the midline. After the laminectomy and durotomy, a custom-designed multielectrode grid was placed on the exposed dorsal surface of the spinal cord. The electrode is made up of 8 parallel Teflon-coated stainless-steel wires (76-microm diameter, spaced 1 mm apart) embedded in silastic with each of the wires stripped of its insulating coating along a length of 2 mm. This strip electrode maps the amplitude gradient of conducted spinal somatosensory evoked potentials elicited by bilateral tibial nerve stimulation. Using these recordings, the dorsal columns are topographically mapped as lying between two adjacent numbers.
The authors conducted a retrospective analysis of the preoperative, immediate, and short-term postoperative neurological status, focusing especially on posterior column function. There were 8 women and 2 men whose mean age was 52 years. There were 4 ependymomas, 1 subependymoma, 1 gangliocytoma, 1 anaplastic astrocytoma, 1 cavernous malformation, and 2 symptomatic syringes requiring shunting. In all patients the authors attempted to identify the midline by using anatomical landmarks, and then proceeded with dorsal column mapping to identify the midline electrophysiologically. In the 2 patients with syringomyelia and in 5 of the patients with tumors, the authors were unable to identify the midline anatomically with any certainty. In 2 patients with intramedullary tumors, they were able to identify the midline anatomically with certainty. Dorsal column mapping allowed identification of the midline and to confirm the authors' anatomical localization. In 2 patients with intramedullary tumors, posterior column function was preserved only on 1 side. All other patients had intact posterior column function preoperatively.
Dorsal column mapping is a useful technique for guiding the surgeon in locating the midline for myelotomy in intramedullary spinal cord surgery. In conjunction with somatosensory evoked potential, motor evoked potential, and D-wave recordings, we have been able to reduce the surgical morbidity related to dorsal column dysfunction in this small group of patients.
脊髓内肿瘤可使周围的神经组织移位，导致正常脊髓解剖结构的扩大和变形。为避免损伤后柱，需要进行脊髓正中切开术进行切除。由于解剖结构的变形，脊髓正中切开术的中线定位往往很困难。由于脊髓旋转、水肿、新生血管形成或局部瘢痕形成，标准解剖标志在脊髓内肿瘤患者中可能具有误导性。脊髓正中切开术的错位会使后柱有发生术后严重残疾的风险。作者描述了一种用于描绘背柱以准确定位中线的技术。
一组 10 例颈胸段脊髓内病变患者接受了背柱定位，其中使用条状电极来定义中线。在椎板切除术和硬脊膜切开术后，将定制的多电极网格放置在脊髓暴露的背表面上。该电极由 8 根平行的聚四氟乙烯涂层不锈钢丝（直径 76 微米，间隔 1 毫米）组成，嵌入硅橡胶中，每根丝的绝缘涂层沿 2 毫米长被剥离。该条状电极描绘了由双侧胫骨神经刺激引起的传导性脊髓体感诱发电位的幅度梯度。使用这些记录，可以将背柱作为位于两个相邻数字之间的拓扑图进行映射。
作者对术前、即刻和短期术后神经状态进行了回顾性分析，特别关注后柱功能。患者中有 8 名女性和 2 名男性，平均年龄为 52 岁。有 4 例室管膜瘤、1 例室管膜下瘤、1 例神经节细胞瘤、1 例间变性星形细胞瘤、1 例海绵状血管畸形和 2 例因需要分流而有症状的脊髓空洞症。在所有患者中，作者均试图通过使用解剖标志来确定中线，然后进行背柱定位以电生理方式确定中线。在 2 例脊髓空洞症患者和 5 例肿瘤患者中，作者无法确定中线的解剖学位置。在 2 例脊髓内肿瘤患者中，作者能够准确地确定中线。背柱定位允许确定中线并确认作者的解剖定位。在 2 例脊髓内肿瘤患者中，仅 1 侧保留了后柱功能。所有其他患者术前均有完整的后柱功能。
背柱定位是脊髓内肿瘤手术中指导外科医生进行脊髓正中切开术确定中线的有用技术。结合体感诱发电位、运动诱发电位和 D 波记录，我们能够降低与这一小组患者后柱功能障碍相关的手术发病率。
