59. Longitudinal changes in outcomes of transcranial motor evoked potential monitoring during intra- and extramedullary spinal cord tumor surgeries

BACKGROUND CONTEXT

The use of transcranial motor evoked potential (Tc-MEP) has been recognized as an indispensable tool in high-risk spine surgeries, particularly in cases involving spinal tumors, ossification of the posterior longitudinal ligament, and spinal deformities. These surgeries have an increased likelihood of intraoperative spinal cord and nerve root injuries.

PURPOSE

Given the significance of Tc-MEP in mitigating these risks, this research undertakes a comprehensive analysis of the annual changes in the precision of Tc-MEP monitoring, the incidence of postoperative paralysis, and the success rate of rescue interventions during surgeries for intramedullary spinal cord tumors (IMSCT) and extramedullary spinal cord tumors (EMSCT).

STUDY DESIGN/SETTING

Prospective multicenter study.

PATIENT SAMPLE

We examined data spanning 5 years, from 2017-2022, covering 163 IMSCT patients (92 male, 71 female, average age 48, BMI 23.2) and 754 EMSCT patients (325 male, 429 female, average age 58, BMI 23.2). These patients were treated in 17 prominent domestic institutions, all affiliated with the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

OUTCOME MEASURES

We assessed the Tc-MEP monitoring results, postoperative incidence of a de novo paralysis, and the rescue rate (number of rescue cases / number of true-positive + rescue cases).

METHODS

We established an alarm threshold when the Tc-MEP waveform in one or more limbs exhibited a decrease of 70% or more from the baseline. A postoperative disability was determined as a one-grade decline in muscle strength immediately after the procedure. From 2010, the committee convened regular meetings to assess and enhance waveform judgment protocols, with a focus on evaluating true-positive and rescue cases. The rescue case was defined as a patient with recovered TcMEP amplitudes after certain procedures and without a de novo paralysis.

RESULTS

For IMSCT resection surgeries, Tc-MEP monitoring results were: Sensitivity/Specificity/Positive predictive value/Negative predictive value: 95%/83%/75%/97% (2017-18, n=58), 89%/73%/42%/97% (2019-20, n=52), and 64%/67%/35%/87% (2021-22, n=53). Postoperative paralysis incidence/rescue cases/rescue rate were: 33%/3 cases/14% (2017-18), 17%/2 cases/20% (2019-20), and 21%/2 cases/22% (2021-22), indicating a gradual decline in postoperative paralysis over the years. For EMSCT resection surgeries, Tc-MEP monitoring results were: Sensitivity/Specificity/Positive predictive value/Negative predictive value: 88%/91%/47%/99% (2017-18, n=205), 87%/85%/27%/99% (2019-20, n=261), and 67%/93%/37%/98% (2021-22, n=288). Postoperative paralysis incidence/rescue cases/rescue rate were: 8%/7 cases/33% (2017-18), 6%/15 cases/54% (2019-20), and 5%/11 cases/52% (2021-22), showcasing an annual increase in the rescue rate and a decline in the incidence of postoperative paralysis.

CONCLUSIONS

The study underscores the importance of proactive interventions and accurate judgments concerning Tc-MEP waveform alterations. By adopting a rigorous and standardized approach across multiple institutions, we've seen not just an uptick in the success of rescue procedures but also a substantial reduction in incidences of postoperative paralysis. This inter-institutional collaboration and commitment to refining practices have yielded encouraging results in safeguarding patient well-being during high-risk spinal surgeries.

FDA Device/Drug Status

This abstract does not discuss or include any applicable devices or drugs.