Intraoperative neuromonitoring with MEPs and prediction of postoperative neurological deficits in patients undergoing surgery for cervical and cervicothoracic myelopathy

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>The use of intraoperative neurophysiological monitoring (IONM) in surgical decompression surgery for myelopathy may assist the surgeon in taking corrective measures to reduce or prevent permanent neurological deficits. We evaluated the efficacy of IONM in cervical and cervicothoracic spondylotic myelopathy (CSM) cases.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>The authors retrospectively reviewed 140 cases involving patients who underwent surgery for CSM utilizing IONM during 2011 at the University of California, San Francisco. Data on preoperative clinical variables, intraoperative changes in transcranial motor evoked potentials (MEPs), and postoperative new neurological deficits were collected. Associations between categorical variables were analyzed with the Fisher exact test.</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>Of the 140 patients, 16 (11%) had significant intraoperative decreases in MEPs. In 8 of these cases, the MEP signal did not return to baseline values by the end of the operation. There were 8 (6%) postoperative deficits, of which 6 were C-5 palsies and 2 were paraparesis. Six of the patients with postoperative deficits had demonstrated persistent MEP signal change on IONM. There was a significant association between persistent MEP changes and postoperative deficits (p &lt; 0.001). The sensitivity of intraoperative MEP monitoring was 75%, the specificity 98%, the positive predictive value 75%, and the negative predictive value 98%. Due to higher rates of false negatives, the sensitivity decreased to 60% in the subgroup of patients with vascular disease comorbidity. The sensitivity increased to 100% in elderly patients and in patients with preoperative motor deficits. The sensitivity and positive predictive value of deltoid and biceps MEP changes in predicting C-5 palsy were 67% and 67%, respectively.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>The authors found a correlation between decreased intraoperative MEPs and postoperative new neurological deficits in patients with CSM. Sensitivity varies based on patient comorbidities, age, and preoperative neurological function. Monitoring of MEPs is a useful adjunct for CSM cases, and the authors have developed a checklist to standardize their responses to intraoperative MEP changes.</jats:p></jats:sec>

Role of multimodal intraoperative neurophysiological monitoring during positioning of patient prior to cervical spine surgery

“…Monitoring TcMEPs is supposed to provide earlier detection of neurological injury and is associated with greater sensitivity (Hilibrand et al, 2004). Its superiority to SEPs has been reported in previous works (Clark et al, 2013), and that is compatible with the findings reported here, where TcMEPs showed greater sensitivity for identifying positioning related injuries. However, certain authors still recommend the use of both modalities (Costa et al, 2007;Sutter et al, 2007).…”

“…Certain studies point out that the combination of somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) in IONM is more effective than the use of only one of these methods for the detection of neurological injury during the surgical procedure (Pelosi et al, 2002;Costa et al, 2007;Sutter et al, 2007;Clark et al, 2013). However, neurological injury may not only appear during the surgical procedure itself, but can also occur during neck or arm positioning before surgery (Bose et al, 2004;Jahangiri et al, 2011).…”

“…Indeed, irreversible changes during IONM are predictive of severe adverse neurological outcomes (level of evidence class A) (Nuwer et al, 2012) which is why it is becoming more popular in cervical spine procedures because it seems to be producing better functional results (Li et al, 2012;Clark et al, 2013).…”

Central motor conduction studies in patients with spinal cord disorders: a review

“…The authors found that early surgical intervention for CSM could produce a beneficial effect on spinal cord functionality that can be detected by MEPs. Clark et al 22 also reported a correlation between decreased intraoperative MEPs and postoperative new neurological deficits in patients with CSM.…”

A controlled anterior sequential interbody dilation technique for correction of cervical kyphosis

“…42 To further mitigate the risk of neurological injury, we used intraoperative neuromonitoring; more specifically, we used transcranial motor evoked potentials. 8,22,35 The second concern with sequential interbody dilation and distraction is a theoretical increased risk for subsidence due to larger forces between the interface of the bony endplates and cage footplates as dilation is performed. The observed subsidence rates in this study fall within the lower range of previously reported rates following anterior cervical corpectomy and discectomy, even when utilizing a sensitive threshold of 2 mm of total subsidence.…”