J. Burgos

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.

P31-18 Spinal cord lesions during scoliosis surgery: our experience and neurophysiologic identification of the lesion level

Objective: In animal studies, it is shown that proximal (target-reaching) and distal (grasping) movements of the upper extremity are differently affected by spinal pyramidotomy. We analyzed the target-reaching movement in patients with cervical myelopathy, and examined if it is useful to evaluate symptoms, and to predict recovery after the decompression surgery. Methods: Twenty-eight pre-operative patients and 15 age-matched controls participated in the experiments. Some patients returned to the experiments, up to 1 year after the surgery. They performed targetreaching movements, cued by sound. Three-dimensional positions of the index finger were sampled by an electromagnetic motion tracking system. By analyzing the movement, reaction time, movement time and accuracy of touch position (TP) were obtained, as well as time for online correction (CT) induced by sudden target jump. The parameters were compared with scores of conventional tests; the JOA score, 10-second grip and release test, the manual muscle testing, and motor evoked potential induced by transcranial magnetic stimulation of the motor cortex. Results: All patients mainly claimed clumsiness in the hand movement pre-operatively, and showed significantly deteriorated scores in conventional tests. They also showed poor online adjustments of the reaching movement. It was reflected in long CT and variable TP, though the other parameters were not affected significantly. However, CT was not correlated with any score from conventional tests. After the surgery, CT immediately returned to the normal level, while the JOA score, which mainly evaluate hand functions, improved gradually during months. When including post-operative data, CT and JOA score were correlated, and recovery of the latter could be predicted better if including CT immediately after the surgery. Conclusions: The target-reaching movement is useful to evaluate deficits that cannot be detected by conventional tests. Post-operative JOA score suggests that recovery in hand functions partly depends on mechanisms for the reaching movement.

P31-21 Recording triggered EMG thresholds from axillary chest wall electrodes. A new refined technique for accuracy of upper thoracic pedicle screw placement

MEPs remained above 50% of baseline in all of 23 patients and no patients had postoperative vagus nerve deficits. Conclusions: Reliable facial and vagus nerve MEPs could be recorded throughout the procedure during skull base procedures. CB MEP monitoring can circumvent difficulties of standard EMG monitoring techniques, provide ongoing evaluation of facial and vagus nerve function and predict outcome with sufficiently useful accuracy.

234 Alignement Coplanaire (AC) : une nouvelle technique de correction tridimensionnelle de la scoliose. Résultats préliminaires en courbes type 1 de Lenke

Objectifs Presenter les resultats preliminaires de une nouvelle technique de correction de la scoliose, basee sur le realignement coplanaire des axes vertebraux. Methodes Vint cinq patients presentant une scoliose idiopathique de l’adolescent (Lenke type 1) furent traites par chirurgie posterieure, utilisant vis pediculaires) et reduction par Alignement Coplanaire(alignement dans le meme plan des pedicules. Description de l’AC :apres insertion des vis pediculaires, sont mis en place des prolongateurs rainures du cote de la convexite de tous les niveaux de la courbure puis est introduite une barre au travers de la rainure aux extremites des prolongateurs, creant un axe de rotation. Une seconde barre est introduite a cote de la premiere. La separation progressive de ces deux barres le long de la rainure des prolongateurs les amenera progressivement dans un seul plan, faisant coplanaires les axes anteroposterieurs des vertebres, et corrigeant la rotation et la translation. La separation des extremites des prolongateurs corrige la divergence posterieure des axes dans la zone de cyphose. Les courbes furent mesurees sur des teleradiographies du rachis debout en pre et en postoperatoire. La rotation vertebrale fut mesuree directement par scanner et RMN et indirectement sur les radiographies. Resultats Les courbes dorsales se corrigerent de 61 a 16° (73 %), les dorsolombaires de 39 a 12° (70 %). La rotation vertebrale au sommet de la courbe dorsale se corrigeait de 24 a 10° (56 %). La cyphose dorsale moyenne preoperatoire etait de 18° et se maintint egale en postoperatoire, pourtant, aucun patient ne presentait a la fin un modificateur sagittal de Lenke (-). La gibbosite dorsale passa de 30 a 11 mm en postoperatoire (65 %), sans qu’il fut necessaire de pratiquer aucune thoracoplastie. Il n’y eut pas de complications perioperatoires notables. Conclusion Dans cette serie, avec la technique d’AC une bonne reduction tridimensionnelle de la scoliose a ete obtenue. Les forces correctrices se distribuent entre tous les segments de la courbe et s’appliquent avant la mise ne place des barres de fixation definitives, les protegeant des efforts des manœuvres de reduction et facilitant leur insertion. On n’a pas observe de complications liees a la technique. L’AC pourrait permettre d’obtenir une correction planifiee en preoperatoire.

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.