Patient Factors Impacting Baseline MEPs in Patients Undergoing Cervical Spine Surgery for Myelopathy or Radiculopathy

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SpecialtyCare recently published research that evaluates patient factors that impact baseline motor evoked potentials (MEPs) in patients undergoing cervical spine surgery for myelopathy or radiculopathy.

The Research Abstract

This study evaluated monitorable MEPs attainability across demographic, health history, and patient-reported outcomes measures (PROM). This study included 2,532 adults who underwent elective surgery for cervical radiculopathy or myelopathy with intraoperative neuromonitoring (IONM) with motor evoked potentials (MEPs) between 2017 and 2019. 

Results of the Study 

Patients with some unmonitorable MEPs were significantly older males with higher incidences of high blood pressure, circulatory problems, peripheral vascular disease, rheumatoid arthritis, and type II diabetes. Some other data results showed:

Demographics, Health History, and PROMS

  • Patients with all monitorable MEPs reported significantly worse preoperative PROMs than patients with some MEPs that were unmonitorable
  • The mental component score and neck disability and pain index reported significantly worse in patients with all monitorable MEPs
  • Patients with all monitorable MEPs reported better physical components and LE mJOA scores
  • 58.7% of patients with some monitorable MEPs and 37.25 of patients with all monitorable MEPs reported LE dysfunction
  • Myelopathy remained a significant predictor of having any unmonitorable MEPs when controlling for patient demographics and comorbidities 
  • Other positive predictors included age, sex, peripheral vascular disease, type II diabetes, and high blood pressure 
  • Thyroid disease is inversely related to having any unmonitorable MEPs

Pattern of Baseline MEP Monitorability

  • Myelopathy patients were significantly more likely to have an unmonitorable MEP in any muscle
  • Myelopathic patients were more likely to have an unmonitorable MEP in at least one LE muscle or all LE muscles   
  • Monitorability was highest among myelopathy patients with normal mJOA-LE reported function and without a history of diabetes or hypertension
  • Myelopathy patients with abnormal mJOA-LE function and a history of diabetes or hypertension had the lowest rate of MEP monitorability


  • Compared to TIVA, a balanced IV and inhalational regimen significantly decreases the monitorability and amplitude of all muscle MEPs, increasing false negatives and decreasing sensitivity when gas is used
  • This effect is more pronounced on proximal muscle MEPs, such as the deltoid and biceps in the upper extremities or quadriceps and tibialis anterior in the lower extremities
  • TIVA is ideal for monitoring motor function with MEPs and critical for motoring nerve root function
  • Monitorability of IONM signals is associated with age, sex, and history of chronic circulatory or metabolic disorder
  • MEPs are less likely to be established in myelopathy patients compared to radiculopathy patients, particularly with self-reported LE dysfunction 

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