Cauda equina tumor surgery: how I do it

Intraoperative Monitoring for Cauda Equina Tumors: Surgical Outcomes and Neurophysiological Data Accrued Over 10 Years

Objective

Cauda equina tumors affect the peripheral nervous system, and the validities of triggered electromyogram (tEMG) and intraoperative neurophysiologic monitoring (IOM) are unclear. We sought to evaluate the accuracy and relevance of tEMG combined with IOM during cauda equina tumor resection.

Methods

Between 2008 and 2018, an experienced surgeon performed cauda equina tumor resections using tEMG at a single institution. A cauda equina tumor was defined as an intradural-extramedullary or intradural-extradural tumor at the level of L2 or lower. The clinical presentation, extent of resection, pathology, recurrence, postoperative neurological outcomes, and intraoperative tEMG mapping and IOM data were retrospectively analyzed.

Results

One hundred three patients who underwent intraoperative tEMG were included; 38 underwent only tEMG (tEMG-only group), and 65 underwent a combination of tEMG and multimodal IOM (MIOM group). There were no significant differences between the neurologic outcomes, extents of resection, or recurrence rates of the 2 groups. No significant therapeutic benefit was observed; however, the accuracy of intraoperative predetection improved with the combination of IOM and tEMG (accuracy: tEMG-only group, 86.8%; MIOM group, 92.3%). When the involved rootlet was resected despite the positive tEMG result, motor function worsened in 3 of 8 cases. The sensitivity and specificity of tEMG were 37.5% and 94.7%, respectively.

Conclusion

tEMG is an essential adjunctive surgical tool for deciding on and planning for rootlet resection. If the tEMG finding is negative, complete resection, involving the rootlet, may be safe. The accuracy may be further improved by using a combination of tEMG and IOM.

Tumors in the cauda equina: A SEER analysis of tumor types and predictors of outcome

Caudaequinatumors are histologically diverse. International Classification of Diseases for Oncology (ICD-O3) confers dedicated site code (C72. 1) for cauda equina. This code is excluded during analyses of other primary spinal cord tumors. In this retrospective study, the Surveillance, Epidemiology and End Results (SEER) data for primary cauda equina tumors (PCET, C72. 1) excluding the tumors of spinal meninges (C70. 1) from 1992 to 2015 were reviewed. Demographic characteristics, tumor types, and clinical outcomes were analyzed using univariable analysis. Overall survival was estimated using Kaplan-Meier methods and compared for age, histology and treatment type. 293 patients with PCET met inclusion criteria. The most common tumors comprised schwannoma (32%), myxopapillary ependymoma (21%), malignant ependymoma (22%). The median age at diagnosis was 50 years (range < 1 year to 98 years), 57% of patients were males. 77% of the patients underwent surgery. Median follow up time for these patients was 70 months. Of the 293 patients, 250 (85%) were living at the end of 2015. The cause of death was tumor or CNS related in 15 patients. 136 patients were followed for <5 years, of which 102 were censored and 34 died (11.6%) before 5 years. Using univariable analysis, age at diagnosis (Hazard Ratio, HR 1.05; confidence interval, CI 1.03-1.07; p < 0.001), malignant tumor type (HR 2.88, CI 1.15-7.19, p = 0.0239) and absence of surgical intervention (HR 2.54, CI1.26-5.11, p = 0.0092) were predictors of increased mortality. Although most patients did well, older age and lack of surgical intervention were associated with worse survival.

Utility of Intraoperative Monitoring in the Resection of Spinal Cord Tumors: An Analysis by Tumor Location and Anatomical Region

STUDY DESIGN

Retrospective review of institutional data.

OBJECTIVE

The aim of this study was to assess the utility of somatosensory-evoked potentials (SSEP) and transcranial electric motor-evoked potentials (MEP) in the resection of spine tumors and evaluate the ability of both single and multi-modal monitoring to predict postoperative neurological deficits.

SUMMARY OF BACKGROUND DATA

Although the utility of intraoperative monitoring (IOM) is well established in scoliosis and degenerative surgery, studies in spine tumor patients have been limited.

METHODS

A series of consecutive patients who underwent resection with the use of IOM at a single institution between August 2009 and March 2013 was identified. Demographic, clinical, and neuromonitoring data were collected preoperatively, during surgery, at the moment of discharge, and at a 6-month follow-up visit. Three cohorts were established based on the anatomical location of the tumor: intramedullary, intradural extramedullary, and extradural. Additional groupings were formed based on spinal region. Patients with significant changes in SSEPs or MEPs during surgery were identified and the rate of neurological deficits was assessed.

RESULTS

A total of 52 patients were analyzed. A change in SSEPs or MEPs was detected in 11 (21.2%) cases whereas 14 patients (26.9%) developed permanent postoperative deficits. SSEPs predicted deficits in the resection of intramedullary tumors (P = 0.015) (area under cover, AUC = 0.83), and intradural extramedullary tumors (P = 0.048; AUC = 0.70). MEP monitoring did not predict postoperative deficits in the resection of intramedullary (P = 0.21; AUC = 0.69) or intradural extramedullary tumors (P = 0.31; AUC = 0.63). Neither SSEPs nor MEPs predicted deficits for extradural tumors.

CONCLUSION

The efficacy of IOM in spine tumor resection is dependent on tumor location relative to the spinal cord and dura. The accuracy of SSEPs and their ability to predict postoperative deficits was greatest for intramedullary lesions. For this series, MEP and multi-modal monitoring did not confer a benefit in predicting permanent neurological deficits.

LEVEL OF EVIDENCE

4.