Association Between Motor-Evoked Potentials and Spinal Cord Damage Diagnosed With Magnetic Resonance Imaging After Thoracoabdominal and Descending Aortic Aneurysm Repair

The role of intraoperative extensor digitorum brevis muscle MEPs in spinal surgery

PURPOSE

Intraoperative muscle motor evoked potentials (m-MEPs) are widely used in spinal surgery with the aim of identifying a damage to spinal cord at a reversible stage. Generally, lower limb m-MEPs are recorded from abductor hallucis [AH] and the tibialis anterior [TA]. The purpose of this work is to study an unselected population by recording the m-MEPs from TA, AH and extensor digitorum brevis (EDB), with the aim of identifying the most adjustable and stable muscles responses intraoperatively.

METHODS

Transcranially electrically induced m-MEPs were intraoperative recorded in a total of 107 surgical procedures. m-MEPs were recorded by a needle electrode placed in the muscle from TA, AH and EDB muscles in the lower extremities.

RESULTS

Overall monitorability (i.e., at least 1 Lower Limb m-MEP recordable) was 100/107 (93.5%). In the remaining 100 surgeries in 3 cases, the only muscle that could be recorded at baseline was one AH, and in other 2 the EDB. Persistence (i.e., the recordability of m-MEP from baseline to the end of surgery) was 88.7% for TA, 89.8% for AH and 93.8% for EDB.

CONCLUSION

In our series, EDB m-MEPs have demonstrated a recordability superior to TA and a stability similar to AH. The explanations may be different and range from changes in the excitability of the cortical motor neuron to the different sensitivity to ischemia of the spinal motor neuron. EDB can be used alternatively or can be added to TA and AH as a target muscle of the lower limb in spinal surgery.

Paraplegia After Open Surgical Repair Versus Thoracic Endovascular Aortic Repair for Thoracic Aortic Disease: A Retrospective Analysis of Japanese Administrative Data

OBJECTIVES

To comparatively examine the risk of postoperative paraplegia between open surgical descending aortic repair and thoracic endovascular aortic repair (TEVAR) among patients with thoracic aortic disease.

DESIGN

Retrospective cohort study.

SETTING

Acute-care hospitals in Japan.

PARTICIPANTS

A total of 6,202 patients diagnosed with thoracic aortic disease.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The main outcome of this study was the incidence of postoperative paraplegia. Multiple logistic regression models, using inverse probability of treatment weighting and an instrumental variable (ratio of TEVAR use to open surgical repair and TEVAR uses), showed that the odds ratios of paraplegia for TEVAR (relative to open surgical descending aortic repair) were 0.81 (95% confidence interval: 0.42-1.59; p = 0.55) in the inverse probability of treatment-weighted model and 0.88 (0.42-1.86; p = 0.75) in the instrumental-variable model.

CONCLUSIONS

There were no statistical differences in the risk of paraplegia between open surgical repair and TEVAR in patients with thoracic aortic disease. Improved perioperative management for open surgical repair may have contributed to the similarly low incidence of paraplegia in these two surgery types.

Measuring CMAPs in addition to MEPs can distinguish peripheral ischemia from spinal cord ischemia during endovascular aortic repair

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MEP amplitude decreases occur frequently during endovascular aortic aneurysm repair.

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They are usually caused by peripheral ischemia due to femoral artery sheaths.

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Peripheral and central ischemia can be distinguished by measuring CMAP amplitudes.

Objective

Spinal cord injury is a devastating complication after endovascular thoracic and thoracoabdominal aneurysm repair (EVAR). Motor evoked potentials (MEPs) can be monitored to detect spinal cord injury, but may also be affected by peripheral ischemia caused by femoral artery sheaths. We aimed to determine the incidence of peripheral ischemia during EVAR, and whether central and peripheral ischemia can be distinguished using compound muscle action potentials (CMAPs).

Methods

We retrospectively analyzed all EVAR procedures between March 1st 2015 and January 1st 2020 during which MEPs were monitored. Peripheral ischemia was defined as both a reduction in MEP amplitudes reversed by removing the femoral sheaths and no clinical signs of immediate post-procedural paraparesis. All other MEP decreases were defined as central ischemia.

Results

A significant MEP decrease occurred in 14/27 (52%) of all procedures. Simultaneous CMAP amplitude reduction was observed in 7/8 (88%) of procedures where peripheral ischemia occurred, and never in procedures with central ischemia.

Conclusions

MEP reductions due to peripheral ischemia are common during EVAR. A MEP-reduction without a CMAP decrease indicates central ischemia.

Significance

CMAP measurements can help to distinguish central from peripheral ischemia, potentially reducing the chance of misinterpreting of MEP amplitude declines as centrally mediated, without affecting sensitivity.

Spinal Cord Infarction: A Single Center Experience and the Usefulness of Evoked Potential as an Early Diagnostic Tool

Background: Spinal cord infarction (SCI) is a rare disease and its early diagnosis is challenging. Here, we described the clinical features and imaging findings of SCI, and assessed the results of evoked potential (EP) studies to elucidate their diagnostic role in the early stage of SCI.

Methods: We retrospectively analyzed 14 patients who had spontaneous SCI. The demographic, neurological, and temporal profiles of the SCI patients were identified. We reviewed the imaging findings and assessed the changes in them over time. To review EP, central motor conduction time (CMCT) and somatosensory evoked potential (SEP) values were obtained. We also enrolled 15 patients with transverse myelitis (TM), and compared the clinical, radiological and electrophysiological features between SCI and TM patients.

Results: The ages of the SCI patients ranged from 54 to 73 years. Nine patients (64.3%) showed nadir deficits within 6 h. The most common type of clinical visit was via the emergency center. Nine patients (64.3%) presented with peri-onset focal pain. The median initial modified Rankin scale score was 3. For 9 patients (64.3%), initial T2 imaging findings were negative, but subsequent diffusion weighed imaging (DWI) showed diffusion restriction. Vertebral body infarction was observed in 5 patients (35.7%). EP data were available for 10 SCI patients. All 8 patients who had their CMCT measured showed abnormalities. Among them, motor evoked potentials were not evoked in 6 patients at all. SEP was measured in 10 patients, and 9 of them showed abnormalities; one of them showed no SEP response. For 5 patients, the EP studies were done prior to DWI, and all the patients showed definite abnormalities. The abnormalities in the EP findings of the SCI patients were more profound than those of the TM patients, even though the duration from the onset to the start of the study was much shorter for SCI patients.

Conclusion: SCI can be diagnosed based on typical clinical manifestations and appropriate imaging studies. Our study also indicates that immediate sensory and motor EP study can have an adjuvant diagnostic role in the hyperacute stage of SCI, and can improve the accuracy of diagnosis.

Utility of Motor Evoked Potential in Identification and Treatment of Suboptimal Positioning in Pediatric Craniovertebral Junction Abnormalities: A Case Report

Atlantoaxial dislocation (AAD) poses a significant challenge in terms of positioning and surgical fixation as there is increased risk of cord compression and ischemia. Intraoperative neuromonitoring (IONM) provides a useful tool to identify impending position-related dysfunction. Here we demonstrate the utility of using transcranial motor evoked potential (Tc-MEP) to identify and treat suboptimal positioning in a 13-year-old patient with AAD and Arnold-Chiari malformation.