The Prognostic Value of Intraoperative Neuromonitoring by Combining Somatosensory- and Motor-Evoked Potentials for Thoracic Spinal Decompression Surgery in Patients with Neurological Deficit

The application value of intraoperative neurophysiological monitoring in cervical spinal canal stenosis decompression surgery

BACKGROUND CONTEXT

Although intraoperative neurophysiological monitoring (IONM) has been widely recognized and used in spine surgery, its characteristics vary for different types of spinal disorders, necessitating the development of tailored monitoring strategies. Cervical spinal stenosis presents complex clinical symptoms and carries significant surgical risks, creating a critical need to clarify the monitoring features, alert patterns, and their relationship with outcomes in such surgeries. A comprehensive assessment and the development of a refined IONM monitoring plan throughout the perioperative period is an important direction for future research.

PURPOSE

This study aims to investigate the influencing factors of intraoperative neurophysiological monitoring (IONM) alarm events in patients with cervical spinal canal stenosis and to evaluate the predictive value of different IONM alarm patterns on neurological recovery following decompression surgery.

DESIGN

Retrospective study.

PATIENT SAMPLES

This analysis included 1,622 patients who underwent cervical spinal canal decompression surgery and had complete IONM monitoring data between February 2017 and December 2022.

OUTCOME MEASURES

The preoperative and postoperative neurological status of the patients was assessed using the modified Japanese Orthopaedic Association (mJOA) score. The primary IONM alarm indicators included somatosensory evoked potentials (SSEP) and transcranial motor evoked potentials (MEP), compared to the preoperative baseline.

METHODS

Logistic regression was employed to analyze the correlation between preoperative diagnostic risk factors and intraoperative alarm events. Additionally, a multifactorial interaction analysis was performed to determine the relationship between IONM changes and the reversibility of alarms with the six-month mJOA recovery rate.

RESULTS

Preoperative diagnoses of the ligamentum flavum hypertrophy and/or ossification of the posterior longitudinal ligament, combined with an mJOA score <12, were identified as high-risk factors for intraoperative alarms. The sensitivity of alarms in the high-risk group was 100%, with a positive predictive value of 90.6%; in the low-risk group, the sensitivity was 91.7%, with a positive predictive value of 40.74%. Variance analysis indicated that the mJOA improvement rate at six months was significantly lower in patients with irreversible IONM alarms compared to those with reversible alarms. Interaction analysis suggested that the reversibility of intraoperative alarm events was a principal predictor of postoperative outcomes, while risk factors for alarms had predictive value only in patients with irreversible alarms.

CONCLUSIONS

In patients with cervical spinal canal stenosis caused by disc degeneration, the presence of ligamentum flavum hypertrophy, ossification of the posterior longitudinal ligament, and preoperative mJOA scores <12 are significant high-risk factors for intraoperative alarms. The sensitivity and positive predictive value of intraoperative alarms in the high-risk group were significantly higher than those in the low-risk group. Moreover, patients with irreversible alarms exhibited poorer prognoses compared to those with reversible alarms, and preoperative alarm risk factors should not be considered independent predictors of patient outcomes.

Lower Extremity Somatosensory Evoked Potentials Predict Functional Outcomes in Complete Traumatic Cervical Spinal Cord Injury

BACKGROUND

Traumatic cervical spinal cord injury (tCSCI) is often a debilitating injury, making early prognosis important for medical and surgical planning. Currently, the best early predictors of prognosis are physical examination, imaging studies, and patient demographics. Despite these factors, patient outcomes continue to vary significantly. The purpose of this study was to evaluate the prognostic value of somatosensory evoked potentials (SSEPs) with functional outcomes in tCSCI patients.

METHODS

A retrospective study was conducted on prospectively collected data from 2 academic institutions. Patients 18 years and older who had tCSCI and underwent posterior cervical decompression and stabilization with intraoperative neuromonitoring were reviewed. The outcomes of interest were the American Spinal Injury Association (ASIA) Impairment Scale (AIS) grade and ASIA motor score at follow-up. Outcomes measures were assessed via student t-tests, chi-squared tests, and multivariable regression analysis.

RESULTS

A total of 79 patients were included. In complete injuries, detectable lower extremity SSEPs were associated with higher ASIA motor scores at follow-up (P = 0.002), greater increases in ASIA motor scores at follow-up (P = 0.009), and a greater likelihood of clinically important improvement in ASIA motor score (P = 0.024). Incomplete, AIS grade C injuries has higher rates of grade conversion (P = 0.019) and clinically important improvement in ASIA motor score (P = 0.010), compared to AIS grade A or B injuries.

CONCLUSIONS

The detection of lower extremity SSEP signals during initial surgical treatment of tCSCI is associated with greater improvement in ASIA motor scores postoperatively. The association is most applicable to patients with complete injury.

A Loading Dose of Dexmedetomidine With Constant Infusion Inhibits Intraoperative Neuromonitoring During Thoracic Spinal Decompression Surgery: A Randomized Prospective Study

Background: The effect of a bolus dose of dexmedetomidine on intraoperative neuromonitoring (IONM) parameters during spinal surgeries has been variably reported and remains a debated topic. Methods: A randomized, double-blinded, placebo-controlled study was performed to assess the effect of dexmedetomidine (1 μg/kg in 10 min) followed by a constant infusion rate on IONM during thoracic spinal decompression surgery (TSDS). A total of 165 patients were enrolled and randomized into three groups. One group received propofol- and remifentanil-based total intravenous anesthesia (TIVA) (T group), one group received TIVA combined with dexmedetomidine at a constant infusion rate (0.5 μg kg-1 h-1) (D1 group), and one group received TIVA combined with dexmedetomidine delivered in a loading dose (1 μg kg-1 in 10 min) followed by a constant infusion rate (0.5 μg kg-1 h-1) (D2 group). The IONM data recorded before test drug administration was defined as the baseline value. We aimed at comparing the parameters of IONM. Results: In the D2 group, within-group analysis showed suppressive effects on IONM parameters compared with baseline value after a bolus dose of dexmedetomidine. Furthermore, the D2 group also showed inhibitory effects on IONM recordings compared with both the D1 group and the T group, including a statistically significant decrease in SSEP amplitude and MEP amplitude, and an increase in SSEP latency. No significance was found in IONM parameters between the T group and the D1 group. Conclusion: Dexmedetomidine delivered in a loading dose can significantly inhibit IONM parameters in TSDS. Special attention should be paid to the timing of a bolus dose of dexmedetomidine under IONM. However, dexmedetomidine delivered at a constant speed does not exert inhibitory effects on IONM data.