The incidence of rare intradural spinal cord tumors is 3 to 10 per 100,000 of population. Open bilateral laminectomy with partial or total facet removal is the standard surgical access for gross total resection (GTR) of such intradural tumors. Retrospective studies in adults revealed that for patients operated with bilateral laminectomy as well with less invasive procedures, the risk of developing postoperative deformity or worsening preoperative deformity is still significant. The this study describes integration of Minimally invasive Spine Surgery (MISS) techniques with preoperative MRI data and intraoperative 3 dimensional fluoroscopic images with the aim of planning skin incision according to a precise transmuscular trajectory, thus tailoring tumor access with minimal bone resection in patients with intradural extramedullary lesions.

A retrospective review of 45 consecutive surgical cases of intradural tumors was carried out. Seven patients operated for intradural extramedullary tumors using the image merged guided MISS were selected. 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. After a 3D fluoroscopic image acquisition using the merged data, a skin incision was planned according to the chosen entry point and the transmuscular trajectory was optimised for tumor access. Under microscopic and neuronavigation guidance, tailored bone resection and lesion removal were carried out.

From December 2012 to August 2014, we performed MISS removal of intradural extramedullary spine tumors in seven patients, four male and three female as described above. Pre-operative Nurick score was 3 in three patients, 1 in two patients and 0 in other two cases. One patient presented with local hematoma that regressed in the immediate postoperative period. Follow up ranges from 2 to 14months (average 5.8months). Follow up neurological Nurick scores recording reveals a favorable neurological outcome with a score of 0 in six patients. Any 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 confirms GTR in all cases.

The goal of treatment of intradural extramedullary lesions ismaximum tumor resection, adapting surgical approach to minimise manipulation of neural structures and reducing bone resection without comprising tumor resection. Image merged guided MISS is a safe and feasible procedure for tumor removal in patients with intradural extramedullary tumors. In the present study, we demonstrate that this technique allows the surgeon to define entry point, to tailor transmuscular trajectory and tumor access while minimizing bone removal and achieving GTR of intardural lesions.