Predicting intraoperative feasibility of combined TES-mMEP and cSSEP monitoring during scoliosis surgery based on preoperative neurophysiological assessment.

Abstract : BACKGROUND CONTEXT: Combined monitoring of muscle motor evoked potentials elicited by transcranial electric stimulation (TES-mMEP) and cortical somatosensory evoked potentials (cSSEPs) is safe and effective for spinal cord monitoring during scoliosis surgery. However, TES-mMEP/cSSEP is not always feasible. Predictors of feasibility would help to plan the monitoring strategy. PURPOSE: To identify predictors of the feasibility of TES-mMEP/cSSEP during scoliosis surgery. STUDY DESIGN/SETTING: Prospective cohort study in a clinical neurophysiology unit and pediatric orthopedic department of a French university hospital. PATIENT SAMPLE: A total of 103 children aged 2 to 19 years scheduled for scoliosis surgery. OUTCOME MEASURES: Feasibility rate of intraoperative TES-mMEP/cSSEP monitoring. METHODS: All patients underwent a preoperative neurological evaluation and preoperative mMEP and cSSEP recordings at both legs. For each factor associated with feasibility, we computed sensitivity, specificity, positive predictive value (PPV), and negative predictive value. A decision tree was designed. RESULTS: Presence of any of the following factors was associated with 100% feasibility, 100% specificity, and 100% PPV: idiopathic scoliosis, normal preoperative neurological findings, and normal preoperative mMEP and cSSEP recordings. Feasibility was 0% in the eight patients with no recordable mMEPs or cSSEPs during preoperative testing. A decision tree involving three screening steps can be used to identify patients in whom intraoperative TES-mMEP/cSSEP is feasible. CONCLUSIONS: Preoperative neurological and neurophysiological assessments are helpful for identifying patients who can be successfully monitored by TES-mMEP/cSSEP during scoliosis surgery.