Image Merge Assisted Minimally Invasive Resection of Intradural Extramedullary Tumors: A Retrospective Series of Eight Cases

Abstract

Introduction Intradural extramedullary spinal tumors are rare lesions, with a prevalence of 3 to 10 per 100,000 in general population. Open bilateral laminectomy with partial or total facet removal is the standard surgical access for gross total resection (GTR) of such tumors. Studies in patients operated with laminectomy, the risk of developing postoperative deformity, particularly in the cervical spine, is still significant, accounting of 20 to 60% of patients treated with laminectomy. In addition, ventrolateral or ventrally placed tumors are often not easily accessible through a standard translaminar approach. In the present series, preoperative MRI data and intraoperative three-dimensional (3D) fluoroscopic images are manually merged in the operating room. Minimally invasive surgical techniques through a tubular retractor system are then used to resect the tumor. The merged images are used to plan the ideal trajectory to the lesion, thus, facilitating tumor access while minimizing bone and soft tissue resection in these patients. Methods A retrospective chart review of 45 consecutive surgical cases of intradural tumors over a 7-year period was performed. Eight patients operated for intradural extramedullary tumors using the image merge technique. Preoperative MRI and intraoperative 3D fluoroscopic data were manually merged using Synergy Cranial 2.2 software and Stealth Merge 1.2. Accuracy of manual image merging was verified with anatomic landmarks as references. Using these merged images, a trajectory from skin to tumor is planned to facilitate microsurgical tumor resection. The trajectory chosen defines the skin incision, and the type and extent of bone resection. Following 3 to 4 cm skin incision, a transmuscular expandable retractor is “docked” onto the spine. Bone drilling is tailored to the tumor margins using the merged images. From this point on, standard microsurgical resection is performed, followed by dural closure. Results From December 2012 to September 2014, five male and three female patients underwent tubular resection of intradural extramedullary spine tumors with the image merge assistance. Preoperative Nurick score was 3 in three patients, 1 in two patients, and 0 in remaining three patients. Follow-up neurological Nurick scores recording reveal a favorable neurological outcome with a score of 0 in seven patients. Follow-up ranges from 2 to 14 months (average, 5.8 months). No patient showed postoperative neurological deterioration. Only one patient with a resected L1 Schwannoma complains of postoperative radicular pain, which is responsive to medical treatment. MRI confirmed GTR in all cases. Conclusion In this small series, image merge assisted minimally invasive resection of intradural extramedullary lesions achieves maximum tumor resection while minimizing spinal cord manipulation and tailoring bone resection to reduce the risk of postoperative instability. This appears to be a safe and feasible procedure for such lesions.