Spinal intradural extramedullary tumors: microscopic keyhole resection with the focus on intraoperative neurophysiological monitoring and long-term outcome.

OBJECTIVE: Spinal schwannomas (SS) and spinal meningiomas (SM) account for most intradural extramedullary (IDEM) tumors. These tumors are usually benign lesions, which generally respond favorably to surgical excision. Few studies up to now tried to determine the long-term outcome after minimally invasive surgery (MIS) with multimodal intraoperative neurophysiological monitoring (IONM) for IDEM tumors. The aim of this study was to present one of the largest case series with special regard to IONM findings and long-term outcome after MIS-keyhole surgery with a tubular retractor system. METHODS: Between January 2013 and August 2018, 87 patients with IDEM tumors who underwent tumor removal surgery via MIS-keyhole approach under multimodal IONM were retrospectively reviewed. The neurological status was assessed using a modified McCormick grading scale pre- and postoperatively. Multimodal IONM consisted of motor evoked potentials (MEP), somatosensory evoked potentials (SEP), and electromyography (EMG). Both short-term and long-term clinical evaluations as well as patients' medical files were retrospectively analyzed. RESULTS: Surgeries were performed for resection of SS in 49 patients and SM in 38 patients. Tumor locations were cervical in 16.1%, thoracic in 48.3%, thoracolumbar in 4.6%, lumbar 31%. Critical IONM changes were detected in 9 operations (10.3%) in which there were 2 SEPs, 5 MEPs, and 2 EMG events. Three IONM changes (2 MEPs, 1 EMG) were turned out to be transient change in nature since they were resolved in a short time when immediate corrective actions were initiated. Six patients with permanent IONM changes (2SEPs, 3MEPs, 1EMG event), all deficits had resolved during hospitalization or on short -term follow-up evaluation. Sensitivity, specificity, and positive and negative predicted values of IONM were 100, 96, 67, and 100%, respectively. Gross total resection rate was 100%, and a stable or improved McCormick grade exhibited in all patients. No tumor recurrence and no spinal instability were found in the long-term follow-up evaluation (mean 5.2 ± 2.9 years postoperatively). Overall, 94% of patients were either satisfied or very satisfied with their operation, and 93% patients reported excellent or good general clinical outcome according to Odom's criteria. CONCLUSION: MIS-keyhole surgery with multimodal IONM for IDEM tumors enables a high level of satisfaction and a satisfying long-term clinical and surgical outcome.

Microscopic Keyhole Technique for Surgical Removal of Thoracic Spinal Meningiomas.

OBJECTIVE: The aim of this study was to evaluate the safety and efficacy of the microscopic minimally invasive keyhole technique for surgical resection of thoracic spinal meningiomas. METHODS: Seventeen consecutive patients with thoracic spinal meningiomas were included in the series from May 2015 to August 2017. All patients were treated using a microscopic keyhole technique through a tubular retractor system. The demographic data and perioperative variables were recorded. At last follow-up, clinical outcome was assessed using the visual analog scale for pain and the American Spinal Injury Association scale for motor and sensory outcome. RESULTS: All patients underwent microscopic keyhole surgery and complete resection was achieved. Mean operative time was 153.2 minutes (range 115-300 minutes). Mean blood loss during surgery was 110.3 mL (range 50-175 mL). No infection or aggravation of spinal cord injury occurred after operation, except for 2 patients who had postoperative cerebrospinal fluid leakage that recovered after conservative treatment. The mean duration of hospital stay was 6.8 days (range 5-10 days). At the last follow-up, all patients had a reduced level of pain as suggested by an average visual analog scale score that improved from 7.6 to 0.2. The American Spinal Injury Association grade improved or remained normal in all patients except 1. No evidence of tumor recurrence or secondary spinal deformity was observed in any patients during the postoperative follow-up period, and spinal stabilities were found to be satisfactory. CONCLUSIONS: Based on our results, the microscopic minimally invasive keyhole technique can be used safely and effectively for resection of thoracic spinal meningiomas.