Characteristics of Poor Recordability of Intraoperative Neurophysiological Monitoring during Metastatic Spinal Tumor Surgery: A Multicenter Study

Abstract

Objectives

The objective of this study is to investigate the poor recordability characteristics of intraoperative neurophysiological monitoring (IONM) for metastatic spinal tumors, focusing on tumor status or preoperative muscle weakness.

Method

A total of 132 patients (age 65.3 ± 11.8 years; 82 men) with or without preoperative lower extremity muscle weakness were included in this study. The patients' background characteristics, the presence and degree of pre- and postoperative muscle weakness, and the IONM outcome, including the availability of transcranial motor evoked potential (Tc-MEP) recording and the occurrence of Tc-MEP alarms, were investigated. The data between the groups with and without preoperative muscle weakness were compared. Logistic regression analysis was performed to identify the risk factors for unrecordable Tc-MEP.

Results

Sixty-seven patients with muscle weakness had significantly more unrecordable Tc-MEP (19% vs. 5%, p = 0.009) than the 65 patients without muscle weakness. The highest percentage of recordable Tc-MEP in the group with muscle weakness was noted in the plantar muscle (72%). Multivariate analysis identified manual muscle test (MMT) score of ≤3 (odds ratio [OR] 4.529) and ventral spinal cord compression by metastatic tumor (OR 3.924) as independent significant factors for unrecordable Tc-MEP.

Conclusions

IONM for metastatic spinal cord tumors with muscle weakness had a high rate of unrecordable Tc-MEP. Additionally, Tc-MEP may not be detectable in cases of ventral spinal cord compression by a tumor; therefore, preoperative imaging should be thoroughly evaluated.