P118. Establishing baseline motor and somatosensory evoked potentials (MEPs and SSEPs) prior to cervical spine surgery: Association with diagnosis, demographics, comorbidities, and patient-reported measures

Abstract

<h3>BACKGROUND CONTEXT</h3> During cervical spine procedures, motor evoked potentials (MEPs) and somatosensory evoked potentials (SSEPs) are the main modalities used for intraoperative neuromonitoring (IONM). Although MEPs and SSEPs monitoring have been recommended in cervical procedures, there is little research regarding risk factors for unmonitorable signals. <h3>PURPOSE</h3> To determine diagnosis, health history, demographic, and patient-reported symptom variables associated with attainability of monitorable baseline MEPs and SSEPs. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort review. <h3>PATIENT SAMPLE</h3> Records of adult patients who underwent elective surgery for cervical radiculopathy or myelopathy with IONM between January 2017 and December 2019 at a high-volume, single center were retrospectively reviewed. Patients with tumor or trauma were excluded. <h3>OUTCOME MEASURES</h3> Short Form-12 Physical (PCS-12), modified Japanese Orthopaedic Association (mJOA) survey, MEP and SSEP monitorability. <h3>METHODS</h3> Demographic data included age at time of procedure, sex, body mass index (BMI) and race. Health history data included 18 health conditions of the circulatory system, joints and other chronic disorders. Patient reported outcome measures (PROM) were derived from the SF-12 survey and the modified Japanese Orthopaedic Association (JOA) survey. All surveys and data were collected preoperatively. The baseline response of each muscle MEP and nerve SSEP was reported as monitorable or unmonitorable and documented in the electronic record during the procedure. Patients were separated into two cohorts based on the primary diagnosis of radiculopathy or myelopathy. Odds ratios were used to compare baseline monitorability of SSEPs and MEPs between cohorts, and within cohort comparisons utilized T-tests, Mann-Whitney U, and chi-squared tests, as appropriate, and logistic regression models. <h3>RESULTS</h3> Baseline MEPs were established in all myotomes in 93.5% of radiculopathic patients but just 87.6% of myelopathic patients, and for just lower extremity myotomes, baselines were established in 97.9% of radiculopathic patients but just 89.2% of myelopathic patients. Relative to radiculopathic patients, the odds ratios for unmonitorable baseline MEPs were significantly increased in myelopathic patients for all myotomes and lower extremity myotomes in particular (2.04 [1.52;2.78], and 2.68 [1.89, 3.82], p<0.001, respectively). For the myelopathic group, unmonitorable MEP signals were associated with age (p < 0.001), being male (p = 0.002) having high blood pressure (p < 0.001), peripheral vascular disease (p < 0.001), rheumatoid arthritis (p = 0.018), and type II diabetes (p < 0.001). For the radiculopathic group, unmonitorable MEP signals were only associated with gout (p < 0.001). For both groups, the majority of patients with unmonitorable lower extremity MEPs reported modest to moderate to major ambulatory dysfunction. Regarding SSEPs, the odds ratios for unmonitorable baselines were also increased in the myelopathic group relative the radiculopathic group (2.72 [1.86, 4.09], P<0.001), and for both groups, unmonitorable SSEPs were significantly associated with age, male sex, BMI, and type II diabetes (p values <0.005). <h3>CONCLUSIONS</h3> Baseline IONM signals are less likely to be established in myelopathic patients than radiculopathic patients. Age, male gender, and elevated BMI, and a history of a chronic circulatory or metabolic disorder such as high blood pressure, peripheral vascular disease, thyroid disorder, or type II diabetes were predictive of unmonitorable signals. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.