Surgical Outcomes and Prognostic Factors for Resectability of Intramedullary Spinal Cord Tumors Incorporating Intraoperative Neurophysiological Monitoring In Vietnam

Abstract

Background: Surgery is the preferred treatment for symptomatic intramedullary lesions. Intraoperative neurophysiological monitoring (IONM) has recently emerged as a crucial tool in spinal surgery, enhancing safety through real-time assessment of spinal cord function. Its use is particularly beneficial during intramedullary tumor resection, helping to reduce the risk of neurological impairment and improve postoperative outcomes.

Objective: Our study aims to evaluate the efficacy and outcomes of intraoperative neurophysiological monitoring for intramedullary tumor resection surgery in Vietnam and to identify some key predictive factors for tumor resectability.

Methods: A prospective study on 41 patients treated with neurosurgery using multimodal intraoperative neurophysiological monitoring between January 2022 and February 2024 at the Neurosurgery Center, Hanoi, Viet Nam.

Results: Gross total tumor resection was achieved in 26/41 patients (63.4%) with the mean tumor length was 49.9 mm. Among them, 21 cases (51.2%) were ependymoma, 15 cases (36.6%) were diffuse gliomas and 5 cases (12.2%) were other types (including hemangioblastoma, and metastases). Early outcomes assessed at 6 months using the modified McCormick Scale (MCS) revealed that 23.1 % showed no change, 76.9% patients demonstrated improvement. Univariate demonstrated intraoperative motor evoked potentials (MEPs) changes, tumor length and tumor transverse diameter were predictive factors for the resectability; preoperative McCormick Scale and somatosensory evoked potentials (SSEPs) changes were predictors for postoperative outcomes. Multivariate analysis revealed that tumor length was the only independent factor predicting tumor resectability.

Conclusion: Our study demonstrated the efficacy of IONM in improving surgical outcomes for patients undergoing intramedullary tumor resection. The outcomes of patients with intramedullary tumors post-surgery with IONM were significantly affected by the preoperative McCormick Scale and SSEPs changes during surgery. Predictive factors for resectability were tumor size in preoperative Magnetic Resonance Imaging (MRI) and intraoperative MEPs changes.

Keywords: Intraoperative neurophysiological monitoring; Somatosensory evoked potential.

Figure 1. Process flow diagram for method implementation

Figure 2. A 53-year-old female patient presented with intermittent numbness and weakness in the left limbs one year ago. Muscle strength in the left arm and leg was rated at 4/5, with numbness in the anterior and lateral aspects of the left thigh and the anterior aspect of the left calf. The McCormick scale prior to surgery was I. A. Preoperative MRI showed intramedullary heterogeneous mass with the solid portion extended from the C6 to T1 levels, measuring approximately 40 mm in length, strong and heterogeneous contrast enhancement (arrow). B. MRI follow-up at 1 month postoperative: a small area of residual heterogeneous enhancement was observed (arrow). C. Follow-up at 6 months postoperative: No residual enhancing components suggestive of a residual intramedullary tumor were seen. D. Macroscopic image during tumor resection surgery (tumor outlined in a dashed circle). E. At the initial assessment during surgery, at 1 minute and 14 seconds, the MEP waves were normal. F. At the assessment time of 1 hour 39 minutes 35 seconds, the MEP waves on the left side showed a complete loss of signal, with an amplitude reduction of 99%. G. At the assessment time of 1 hour, 55 minutes and 15 seconds the MEP waves on the left side showed recovery in amplitude after ceasing the procedure, flushing the surgical field, and increasing blood pressure.

Figure 3. Modified McCormick Scale and Muscle strength improvement postoperation