L. Cabañes

ID 136 – Accidental spinal cord contusions during spine deformity surgeries

Introduction Accidental spinal cord contusions are a rare event during the surgical correction of spinal deformities Methods Multicenter (5 centers), observational, retrospective study. 691 patients with spinal deformities who underwent surgical correction. Intraoperative neurophysiologic monitoring of spinal cord function was performed with motor (MEPs) and somatosensory (SSEPs) evoked potentials. Results 23 patients suffered a spinal cord contusion, which become evident by a neurophysiologic event with a constant pattern. Ipsilateral MEPs were lost in the first place. Following that, contralateral MEPs were lost, and finally, SSEPs dropped. In the 19 cases with MEPs lost and preserved SSEPs, MEPs recovered during surgery. 4 of these patients presented a transient post-operative paresis with complete recovery, and the rest were asymptomatic. In the four cases which presented complete loss of MEPs and significant changes in the SSEPs, these changes did not recover, and the four patients presented some degree of post-operative paraparesis. Three of them were completely recovered after a few months. Conclusion Intraoperative accidental spinal cord contusions which produce a selective MEPs loss with intraoperative recovery have an excellent prognosis. When the contusions also produce changes on the SSEPs, they have a worst outcome, and produce transient neurologic sequelae.

O39: Intraoperative neurophysiological monitoring in patients with spinal cord injuries. Experimental study

Question: What is the agreement in spindle scoring within, between and among experts? How does spindle scoring by humans compare to automated spindle scoring algorithms? Methods: We crowd-sourced the collection of spindle scorings from 24 experts in a large and varied dataset of EEG (C3-M2) from 110 middle-aged sleeping subjects. Epochs were scored by an average of 5.3 unique experts. Two experts scored parts of the dataset multiple times. We developed a simple method to build a large gold standard by establishing group consensus among expert scorers. We tested the performance of six previously published automated spindle detectors against the gold standard and refined methods of performance analysis for event detection. Results: We found an interrater agreement (F1-score) of 61±6% (Cohen’s Kappa (κ): 0.52±0.07) averaged over 24 expert pairs and an intrarater agreement of 72±7% (κ: 0.66±0.07) averaged over two experts. We tested the performance of individual experts to a gold standard compiled from all the expert scorers and found average agreement of 75±6% (κ: 0.68) over the 24 experts. We recompiled the gold standard and excluded the single expert whose performance was being assessed, and found an average agreement of 67±7% (κ: 0.59). Overall, we found the performance of human experts to be significantly better than the automated sleep spindle detectors we tested (maximum F1-score of detectors: 52%). Conclusions: Sleep spindle characteristics between subjects are very diverse which makes the scoring task difficult. The low interrater reliability suggests using more than one expert when scoring a dataset.

P11.1 Neurophysiological intraoperative monitoring of the thoracic pedicle screw placement

Background: Diabetic neuropathy is not only the most common cause of neuropathy around the world but also it is the most important cause of morbidity and mortality among these patients. Aims: To clarifying value of different electrophysiological findings for detecting neuropathy in early stages of diabetes mellitus. Patients and method: Thirty patients with early stages of diabetes (duration <6 months, adult onset, 2 fasten blood sugar > 126 mg per deciliter) were analyzied with complete neurophysiological tests (motoric and sensory branches of four limbs plus EMG) with Toeenies model during year 2004 in 22 Bahman Mashhad Azad Medical University. Results: Sensory median distal latency was abnormal in 78% of patients whereas NCV of motoric branches of proneal and tibialis nerve was abnormal in 57% of them. Abnormality of sural nerve and EMG findings (positive sharp waves and fibrillation) was detectable in 10%. Radial sensoy nerve was intact in all of the patients. Conclusion: We belive that routine electrophysiological tests is Indicated in all newly diagnosed diabetic patients. The most sensitive test is distal latency of sensory median nerve. EMG had the least value.