Wednesday, September 26, 2018 1:00 PM – 2:00 PM Navigation and Intraoperative Monitoring: 44. A novel MRI-based classification of spinal cord shape and CSF presence at the curve apex to assess risk of intraoperative neuromonitoring data loss with thoracic spinal deformity correction

Abstract

BACKGROUND CONTEXT Intraoperative loss of neuromonitoring data can be detrimental for both the patient and the surgeon. We propose a classification system to identify spinal cords at risk for data loss with thoracic deformity correction based on the preop axial MRI images at the curve apex. PURPOSE To test the hypothesis that the architecture of the spinal cord and amount of CSF on MRI at the thoracic apex can identify patients at risk for intraoperative loss of neuromonitoring data during spinal deformity correction. STUDY DESIGN/SETTING Review of thoracic deformity patients undergoing surgical correction at a single large academic center. PATIENT SAMPLE Thoracic deformity patients undergoing surgical correction. OUTCOME MEASURES Occurrence of intraoperative loss of trans-cranial neuromonitoring data. METHODS We reviewed 128 consecutive patients undergoing surgical correction of a thoracic deformity with pedicle screw/rod constructs. On preop MRI axial imaging at the apical concavity, three types of spinal cord/CSF architecture were defined. Type 1: circular cord with visible CSF between the cord and the apical concave pedicle. Type 2: circular cord but no visible CSF between it and the concave pedicle. Type 3: cord deformed against the apical concave pedicle, with no intervening CSF. RESULTS Of the 128 pts: 81 (63%) had Type 1; 32 (25%) Type 2; and 12 (11.7%) Type 3 spinal cords. Lower extremity transcranial motor-evoked potentials (TcMEPs) and/or somatosensory evoked potentials (SSEPs) were lost intraoperatively in 21 (16%) cases, with full recovery of data in 20 of those. On regression analysis, a Type 1 spinal cord was protective against intraoperative data loss (odds ratio = 0.17, p=.0003). A Type 2 spinal cord had no association with data loss (OR=0.66, p=.49). Type 3 spinal cord had significantly higher odds of intraoperative data loss (OR=28.3, p CONCLUSIONS This MRI-based spinal cord risk classification scheme identifies patients at risk of losing monitoring data during surgery. Patients with the spinal cord deformed against the apical concave pedicle (Type 3) have 28 times greater odds of losing monitoring data during surgery versus Type 1 (normal cord with adequate CSF) and Type 2 (normal cord without CSF between cord and concave pedicle). FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.