Intraoperative Neuromonitoring Alerts That Reverse With Intervention

Abstract

Intervention-mediated recovery from adversely changed evoked potential recordings may provide evidence for improved outcomes during neurophysiological intraoperative monitoring. However, these reversible signal changes (RSCs) are ambiguous because the patient's neurologic status cannot be known either at signal decline or after intervention. This article describes methods to reduce this ambiguity. Randomized control trials are not always possible or ethical. Recent thought on grading evidence has acknowledged that guidelines first described by Sir Austin Bradford Hill may support evidence for causation. Causality guidelines identified RSCs most likely to be truly positive in three reported studies. Diagnostic statistics were revised accordingly. A range of revised positive predictive values and likelihood ratios was calculated in the three studies, using causality guidelines. The revised data were similar to those reported for other diagnostic tests used in medicine. The RSCs may be assessed using causality guidelines for more accurate reporting of diagnostic statistics while preserving information related to surgical intervention and recovery that is lost with end of surgery diagnostics or when RSCs are ignored. A method is described for including RSCs in diagnostic statistics. This approach will more readily permit assessment of the value of neurophysiological intraoperative monitoring in prediction and prevention of neurologic deficits.

Communication and collaboration in spine neuromonitoring: time to expect more, a lot more, from the neurophysiologists

“…Several evidential limitations persist, among them: few controlled trials, paradox or bias in the categorization of recovered signal loss in observational studies, unsettled motor evoked potential alert criteria, and the unknowable confounders within and disagreement among recent supersized retrospective data sets. 4,32,38,46,54 Notwithstanding these limitations, the reliability of any future IONM outcome trials is threatened when the neurophysiologist's role is diminished or neglected. As already described within the interventional cascade, the surgeon's decision to change the course of surgery after an alert crucially depends on the credibility of the interpreter/communicator.…”

“…This PPV may seem low until one realizes that in a low prevalence context (risk ≤ 1% in extradural spine surgery, for example) the PPV will look low even when the test is very accurate. 20,54 Among the reviewed Class I studies, no false-negative reports were made. However, a prediction analysis that looks at differences in outcomes (no injuries with negative testing, 30% risk of serious injury with positive testing) incompletely informs us about the role IONM might play in injury prevention.…”

Intraoperative Neurophysiologic Examination in Central Nervous System Tumor Surgery: Four-year Single-institution Experience

“…There were no false positive or false negative results in our study. False positive results can lead to harmful and unnecessary treatment with economic burden (20,21). False negative results have not been reported frequently in the literature.…”

Comparative Sensitivity of Intraoperative Motor Evoked Potential Monitoring in Predicting Postoperative Neurologic Deficits: Nondegenerative versus Degenerative Myelopathy

“…Studies have demonstrated high sensitivity and specificity for detecting neurologic deficit, 10 11 which may be due to lack of preoperative neurologic deficit and cord compression and the defined period of intraoperative time where the risk for neural injury is high in these cases. 12 IONM of MEPs can be focused during the time of maximal manipulation of neural elements, such as during osteotomy closure. Likewise, IONM of MEPs is associated with very high sensitivity and specificity for spinal cord tumor surgery.…”