Diagnostic accuracy of motor evoked potentials to detect neurological deficit during idiopathic scoliosis correction: a systematic review.

OBJECTIVE The goal of this study was to evaluate the efficacy of intraoperative transcranial motor evoked potential (TcMEP) monitoring in predicting an impending neurological deficit during corrective spinal surgery for patients with idiopathic scoliosis (IS). METHODS The authors searched the PubMed and Web of Science database for relevant lists of retrieved reports and/or experiments published from January 1950 through October 2014 for studies on TcMEP monitoring use during IS surgery. The primary analysis of this review fit the operating characteristic into a hierarchical summary receiver operating characteristic curve model to determine the efficacy of intraoperative TcMEP-predicted change. RESULTS Twelve studies, with a total of 2102 patients with IS were included. Analysis found an observed incidence of neurological deficits of 1.38% (29/2102) in the sample population. Of the patients who sustained a neurological deficit, 82.8% (24/29) also had irreversible TcMEP change, whereas 17.2% (5/29) did not. The pooled analysis using the bivariate model showed TcMEP change with sensitivity (mean 91% [95% CI 34%-100%]) and specificity (mean 96% [95% CI 92-98%]). The diagnostic odds ratio indicated that it is 250 times more likely to observe significant TcMEP changes in patients who experience a new-onset motor deficit immediately after IS correction surgery (95% CI 11-5767). TcMEP monitoring showed high discriminant ability with an area under the curve of 0.98. CONCLUSIONS A patient with a new neurological deficit resulting from IS surgery was 250 times more likely to have changes in TcMEPs than a patient without new deficit. The authors' findings from 2102 operations in patients with IS show that TcMEP monitoring is a highly sensitive and specific test for detecting new spinal cord injuries in patients undergoing corrective spinal surgery for IS. They could not assess the value of TcMEP monitoring as a therapeutic adjunct owing to the limited data available and their study design.

Diagnostic accuracy of somatosensory evoked potential monitoring during scoliosis fusion.

The goal of this review was to ascertain the diagnostic accuracy of intraoperative somatosensory evoked potential (SSEP) changes to predict perioperative neurological outcome in patients undergoing spinal deformity surgery to correct adolescent idiopathic scoliosis (AIS). The authors searched PubMed/MEDLINE and World Science databases to retrieve reports and/or experiments from January 1950 through January 2014 for studies on SSEP use during AIS surgery. All motor and sensory deficits were noted in the neurological examination administered after the procedure which was used to determine the effectiveness of SSEP as an intraoperative monitoring technique. Fifteen studies identified a total of 4763 procedures on idiopathic patients. The observed incidence of neurological deficits was 1.11% (53/4763) of the sample population. Of the patients with new postoperative neurological deficits 75.5% (40/53) showed significant SSEP changes, and 24.5% (13/53) did not show significant change. Pooled analysis using the bivariate model showed SSEP change with pooled sensitivity (average 84%, 95% confidence interval 59-95%) and specificity (average 98%, 95% confidence interval 97-99%). The diagnostic odds ratio of a patient who had a new neurological deficit with SSEP changes was a diagnostic odds ratio of 340 (95% confidence interval 125-926). Overall, detection of SSEP changes had excellent discriminant ability with an area under the curve of 0.99. Our meta-analysis covering 4763 operations on idiopathic patients showed that it is a highly sensitive and specific test and that iatrogenic spinal cord injury resulting in new neurological deficits was 340 times more likely to have changes in SSEP compared to those without any new deficits.

Comparison of Subdermal Needle and Surface Adhesive Stimulating Electrodes for Somatosensory Evoked Potential Monitoring during Anterior Cervical Discectomy and Fusion.

INTRODUCTION: Needle stick injuries remain a physical and psychological burden to healthcare workers. Noninvasive surface adhesive stimulating electrodes used to generate somatosensory evoked potentials can help decrease this risk. METHODS: We performed a retrospective observational study of patients who underwent anterior cervical discectomy and fusion (ACDF) surgery to determine the utility and variability of using surface adhesive stimulating electrodes. Our analysis for utility compared alarm (significant changes) frequency, defined by established alarm criteria, between subdermal needle (Group I) and surface adhesive electrodes (Group II). We compared the variability by comparing the frequency of alarms based on establishing baselines during various stages of the procedure. RESULTS: Between Group I and Group II, no significant differences were found in demographic, age, number of levels decompressed and fused, and length of surgery variability. However, stimulation intensity was significantly higher in Group II. Significant differences in the mean frequency of alarm of cortical, subcortical, and Erb's somatosensory evoked potential (SSEP) responses for the upper extremities between the two groups were only observed for the upper left Erb's point amplitude (p = 0.03) at retraction and upper right cortical amplitude at incision (p = 0.02). The frequency of alarms of the amplitude of left ulnar cortical responses from SSEPs using surface adhesives when baselines were established at the beginning of the procedure, at the time of incision, and at placement of retractors were 13.83 % (±14.08%), 7.50 % (±7.56%) and 3.42 % (±3.48%), respectively. Comparatively, the frequencies of alarms of the amplitude of left ulnar cortical responses from SSEPs using needle electrodes were 18.07 % (±22.85%), 12.13 % (±17.30%) and 7.37 % (±11.82%), respectively. Similar results were observed from frequency for alarms from the right ulnar SSEPs. CONCLUSION: This study found little significant difference between the frequencies of alarm in patients who had SSEP responses obtained using surface adhesive electrodes when compared to needle electrodes. This lack of significant difference was observed even when alarms were established at various stages of the surgery before any major manipulation. For short procedures monitoring the upper extremities only, surface adhesive electrodes may provide a reliable alternative to invasive needle electrodes.

Is Two Really Better Than One? Examining the Superiority of Dual Modality Neurophysiological Monitoring During Carotid Endarterectomy: A Meta-Analysis.

BACKGROUND: Periprocedural stroke after carotid endarterectomy increases long-term mortality. Intraoperative monitoring with electroencephalography (EEG) and somatosensory-evoked potentials (SSEPs) helps predict perioperative stroke risk. However, the sensitivity of each technique when used independently still remains low. The aim of this study is to determine whether multimodal monitoring leads to an increase in sensitivity and diagnostic accuracy. METHODS: Relevant literature was obtained through a search of Embase, PubMed, and Web of Science databases and data were extracted. Data from the University of Pittsburgh Medical Center hospital records for the 2000-2012 period were included. Pooled estimates of sensitivity, specificity, and diagnostic odds ratio were obtained for single and multimodality neurophysiologic monitoring. A McNemar test was used to evaluate for any statistically significant differences in the sensitivities and false-positive rates. RESULTS: The diagnostic odds ratio of dual modality monitoring was found to be 17.4. The specificity of concurrent EEG and SSEP changes in predicting perioperative strokes was calculated to be 96.8% (95% confidence interval 94.1%-98.3%). The sensitivity of combined monitoring with a change in either modality designated as significant was 58.9% (95% confidence interval 41.2%-74.7%). Multimodality monitoring with a change in either EEG or SSEP as the alarm criteria was 1.32 times more sensitive than EEG alone and 1.26 times more sensitive than SSEP alone. CONCLUSIONS: The odds of having a change in either EEG or SSEP are 17 times more in patients with perioperative strokes. Dual modality monitoring is more sensitive at predicting perioperative deficits than EEG or SSEP used independently.