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ID 119 – Short-latency somatosensory evoked potentials to median and tibial stimulation recorded by intracerebral electrodes
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Abstracts / Clinical Neurophysiology 127 (2016) e18–e132
ID 119 – Short-latency somatosensory evoked potentials to median and tibial stimulation recorded by intracerebral electrodes—S. Pro, N. Specchio, E. Rebessi, C.E. Marras, L. Fusco, F. Vigevano, M. Valeriani (Department of Neuroscience, Ospedale Pediatrico Bambino Gesù, Rome, Italy)
ID 137 – Spinal cord tolerance to antero-posterior and lateral compression: Experimental study—L. Cabañes a, G. de Blas b, MaMar Moreno a, C. Correa a, L.M. a, C. Barrios b, J. Burgos b (a Clinical Neurophysiology, Hospital Ramón y Cajal, Madrid, Spain, b Orthopedic Surgery, Hospital Ramón y Cajal, Madrid, Spain)
Objective: Preoperative evaluation, by means of intracerebral electrodes, in patients presenting with symptomatic drug resistant epilepsy, provides an opportunity to explore the S1 area in depth. Methods: We studied 7 pediatric patients with drug resistant epilepsy. Intracerebral electrodes were implanted in frontal, temporal and parietal lobes at different sites, depending on seizure types. SEPs were recorded to median and tibial nerve stimulation from the intracerebral electrode contacts referred to the earlobe ipsilateral to the stimulation. The analysis was addressed to the electrode contacts where an inversion of SEP component polarity was observed. Results: A part from the median nerve N20 origin from the anterior bank of the postcentral gyrus, in 3 patients having electrode contacts close to medial surface of the parietal lobe, an inversion of polarity of the tibial nerve P40 component was observed. Conclusion: This is the first study demonstrating the origin of the tibial nerve P40 component from the medial surface of the S1 area by using intracerebral SEP recording.
Summary: The aim of this study is to establish, by means of neurophysiologic monitoring, the tolerance of the spinal cord to compression. Material and methods: Spinal cord was exposed through a large laminectomy in 13 domestic pigs. Progressive compression of the spinal cord was performed with a precise compression device with a pair of parallel blades that were set up antero-posteriorly or to both sides of the spinal cord, and then sequentially approximated to cause a progressive cord compression. Spinal cord to spinal cord evoked potential (EP), D-wave recordings and somatosensory epidural evoked potential (SSEP) were obtained for each approach of the sticks. Results: For progressive compression, changes on the evoked potentials were observed after a mean displacement of the sticks of 1.5 ± 1 mm for the motor EP, 1.5 ± 0.7 mm for the cord to cord EP, and 2.5 ± 1.3 for the SSEP when provoking an antero-posterior compression; and 2.9 ± 1.1 mm, 2.7 ± 1 mm, and 4.1 ± 1.3 respectively when performing the lateral compression. Conclusion: The spinal cord is more sensitive to antero-posterior compression that to lateral compression. In both cases, cord to cord EP and D-wave are the first neurophysiologic parameters to detect the injury, whereas the SSEPs are less sensitive to compression.
doi:10.1016/j.clinph.2015.11.342
doi:10.1016/j.clinph.2015.11.344
ID 136 – Accidental spinal cord contusions during spine deformity surgeries—MaMar Moreno a, L. Cabañes a, G. de Blas a, L.M. Antón b, V. García b, J. Burgos b (a Clinical Neurophysiology, Hospital Ramón y Cajal, Madrid, Spain, b Orthopedic Surgery, Hospital Ramón y Cajal, Madrid, Spain) 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. doi:10.1016/j.clinph.2015.11.343
ID 143 – Motor mapping using high-frequency cortical stimulation & EMG pickup—T. Darcey a,b, E. Kobylarz a, K. Bujarski a, V. Thadani a, B. Jobst a, P. Krauss a, D. Roberts a,b (a Department of Neurology, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA, b Section of Neurosurgery, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA) Introduction: We describe a cortical and subcortical mapping method for use in the OR under local or general anesthesia, as well as at the bedside in patients with implanted electrodes. The method distinguishes primary, supplementary and subcortical motor elements based on EMG responses, and does not require patient cooperation. Methods: Trains of constant-current, pulses are applied via a handheld probe and/or subdural electrodes. Triggered EMG from multiple contralateral face, arm and leg are used to register motor responses. In the OR, the handheld probe is used to identify and spare cortical and subcortical motor elements, while steady-state triggered EMG via subdural electrodes is used for monitoring during resections. Results: The method is simple and convenient to implement with typical intraoperative monitoring equipment, and standard disposable sterile probes and electrodes. We describe our experience with over 100 cases with significant pre-operative risk of motor function disruption. Resections were limited when MEP signal loss was observed and by the detection of low threshold MEPs in the resection margins. This led to maximal resections with minimal residual tumor, while preserving motor function. In the small number of cases with MEP signal loss at closing, the majority had transient deficits with full recovery. doi:10.1016/j.clinph.2015.11.345
Abstracts / Clinical Neurophysiology 127 (2016) e18–e132
ID 119 – Short-latency somatosensory evoked potentials to median and tibial stimulation recorded by intracerebral electrodes—S. Pro, N. Specchio, E. Rebessi, C.E. Marras, L. Fusco, F. Vigevano, M. Valeriani (Department of Neuroscience, Ospedale Pediatrico Bambino Gesù, Rome, Italy)
ID 137 – Spinal cord tolerance to antero-posterior and lateral compression: Experimental study—L. Cabañes a, G. de Blas b, MaMar Moreno a, C. Correa a, L.M. a, C. Barrios b, J. Burgos b (a Clinical Neurophysiology, Hospital Ramón y Cajal, Madrid, Spain, b Orthopedic Surgery, Hospital Ramón y Cajal, Madrid, Spain)
Objective: Preoperative evaluation, by means of intracerebral electrodes, in patients presenting with symptomatic drug resistant epilepsy, provides an opportunity to explore the S1 area in depth. Methods: We studied 7 pediatric patients with drug resistant epilepsy. Intracerebral electrodes were implanted in frontal, temporal and parietal lobes at different sites, depending on seizure types. SEPs were recorded to median and tibial nerve stimulation from the intracerebral electrode contacts referred to the earlobe ipsilateral to the stimulation. The analysis was addressed to the electrode contacts where an inversion of SEP component polarity was observed. Results: A part from the median nerve N20 origin from the anterior bank of the postcentral gyrus, in 3 patients having electrode contacts close to medial surface of the parietal lobe, an inversion of polarity of the tibial nerve P40 component was observed. Conclusion: This is the first study demonstrating the origin of the tibial nerve P40 component from the medial surface of the S1 area by using intracerebral SEP recording.
Summary: The aim of this study is to establish, by means of neurophysiologic monitoring, the tolerance of the spinal cord to compression. Material and methods: Spinal cord was exposed through a large laminectomy in 13 domestic pigs. Progressive compression of the spinal cord was performed with a precise compression device with a pair of parallel blades that were set up antero-posteriorly or to both sides of the spinal cord, and then sequentially approximated to cause a progressive cord compression. Spinal cord to spinal cord evoked potential (EP), D-wave recordings and somatosensory epidural evoked potential (SSEP) were obtained for each approach of the sticks. Results: For progressive compression, changes on the evoked potentials were observed after a mean displacement of the sticks of 1.5 ± 1 mm for the motor EP, 1.5 ± 0.7 mm for the cord to cord EP, and 2.5 ± 1.3 for the SSEP when provoking an antero-posterior compression; and 2.9 ± 1.1 mm, 2.7 ± 1 mm, and 4.1 ± 1.3 respectively when performing the lateral compression. Conclusion: The spinal cord is more sensitive to antero-posterior compression that to lateral compression. In both cases, cord to cord EP and D-wave are the first neurophysiologic parameters to detect the injury, whereas the SSEPs are less sensitive to compression.
doi:10.1016/j.clinph.2015.11.342
doi:10.1016/j.clinph.2015.11.344
ID 136 – Accidental spinal cord contusions during spine deformity surgeries—MaMar Moreno a, L. Cabañes a, G. de Blas a, L.M. Antón b, V. García b, J. Burgos b (a Clinical Neurophysiology, Hospital Ramón y Cajal, Madrid, Spain, b Orthopedic Surgery, Hospital Ramón y Cajal, Madrid, Spain) 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. doi:10.1016/j.clinph.2015.11.343
ID 143 – Motor mapping using high-frequency cortical stimulation & EMG pickup—T. Darcey a,b, E. Kobylarz a, K. Bujarski a, V. Thadani a, B. Jobst a, P. Krauss a, D. Roberts a,b (a Department of Neurology, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA, b Section of Neurosurgery, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA) Introduction: We describe a cortical and subcortical mapping method for use in the OR under local or general anesthesia, as well as at the bedside in patients with implanted electrodes. The method distinguishes primary, supplementary and subcortical motor elements based on EMG responses, and does not require patient cooperation. Methods: Trains of constant-current, pulses are applied via a handheld probe and/or subdural electrodes. Triggered EMG from multiple contralateral face, arm and leg are used to register motor responses. In the OR, the handheld probe is used to identify and spare cortical and subcortical motor elements, while steady-state triggered EMG via subdural electrodes is used for monitoring during resections. Results: The method is simple and convenient to implement with typical intraoperative monitoring equipment, and standard disposable sterile probes and electrodes. We describe our experience with over 100 cases with significant pre-operative risk of motor function disruption. Resections were limited when MEP signal loss was observed and by the detection of low threshold MEPs in the resection margins. This led to maximal resections with minimal residual tumor, while preserving motor function. In the small number of cases with MEP signal loss at closing, the majority had transient deficits with full recovery. doi:10.1016/j.clinph.2015.11.345