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Kjell Olmarker - One of the best experts on this subject based on the ideXlab platform.
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New, clinically more relevant model for Nerve Root Injury in the rat.
Spine, 2013Co-Authors: Oscar Finskas, Asa Blixt, Yuki Fujioka, Kjell OlmarkerAbstract:Study design Exposure to nucleus pulposus and displacement of intraspinal nervous structures with assessment of spontaneous behavioral changes in rats. Objective To develop a controlled, experimental model for Nerve Root Injury. Summary of background data There are a number of experimental models presented for studies on radiculopathies. One frequently used model is based on exposure to nucleus pulposus and displacement of the dorsal Root ganglion (DRG). However, it is clinically more common that the Nerve Roots are displaced/compressed than the DRG. In this study, we developed a model for displacement of the Nerve Root by modifying the DRG model. Methods After removing the left L3-L4 facet joint, the underlying disc was punctured, and the L4 Nerve Root was displaced laterally by an injection needle (n = 10). In sham experiments, the same procedure was performed without disc puncture and displacement (n = 10). In 10 rats, the left L4-L5 facet joint was removed. The underlying disc was punctured and the L4 DRG was displaced medially by an injection needle. Assessment of spontaneous behavioral changes was performed on days 1, 3, 7, 14, and 21, postsurgery. Results There was a clear increase in duration of the behavior "unloading of the paw" after displacement of the DRG that was most pronounced on day 1 and then gradually declined. There was a similar pattern for this behavior induced by Nerve Root displacement, although the duration was higher than that for the DRG displacement. No apparent trends in behavioral changes were observed for the other behaviors studied. Conclusion Displacement of the Nerve Root induced more changes in the pain behavior than displacement of the DRG, but only for the behavior unloading of the paw. Because Nerve Root Injury is more common than DRG Injury, this model may be more clinically relevant than the DRG model. Level of evidence N/A.
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Indomethacin blocks the nucleus pulposus-induced effects on Nerve Root function. An experimental study in dogs with assessment of Nerve conduction and blood flow following experimental disc herniation.
European spine journal : official publication of the European Spine Society the European Spinal Deformity Society and the European Section of the Cerv, 2004Co-Authors: Itaru Arai, Koji Otani, Shinichi Kikuchi, Guang-ping Mao, Shinichi Konno, Kjell OlmarkerAbstract:Inflammatory mechanisms have been suggested to be involved in the basic pathophysiologic events leading to Nerve Root Injury after local application of nucleus pulposus. To assess if these nucleus pulposus-induced effects could be blocked by anti-inflammatory treatment, 41 dogs were exposed to either incision of the L6-7 disc to induce experimental disc herniation with (n=12) or without (n=14) indomethacin treatment per os (5 mg/kg per day), and no incision with (n=5) or without (n=10) indomethacin. Intraneural blood flow and Nerve conduction velocity were assessed after 7 days to evaluate the degree of Nerve Injury. Disc incision induced a reduction in Nerve Root and dorsal ganglion blood flow as well as Nerve function, similarly to previous studies. However, simultaneous treatment with indomethacin efficiently blocked the negative effects on both blood flow and Nerve conduction but had no effects per se. The present study thus indicates that inflammatory mechanisms may be of relevance in the pathophysiology of nucleus pulposus-induced Nerve Root Injury and thereby also for sciatica.
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Nucleus pulposus-induced Nerve Root Injury: effects of diclofenac and ketoprofen.
European spine journal : official publication of the European Spine Society the European Spinal Deformity Society and the European Section of the Cerv, 2001Co-Authors: Michael Cornefjord, Kjell Olmarker, Koji Otani, Björn RydevikAbstract:Main problem. Nucleus pulposus and/or chronic compression can induce spinal Nerve Root Injury. Inflammation has been proposed as having major importance in the pathophysiologic mechanisms involved in the induction of such injuries. Corticosteroids, potent anti-inflammatory drugs, have been demonstrated to reduce nucleus pulposus-induced spinal Nerve Root Injury. The aim of the present study was to assess the effects of two potent nonsteroidal anti-inflammatory drugs (NSAIDs), diclofenac and ketoprofen, in experimental nucleus pulposus-induced spinal Nerve Root Injury in a pig model. Methods. Eighteen pigs were included in the study. Autologous nucleus pulposus was harvested from a lumbar disc and applied locally around the first sacral Nerve Root after a partial laminectomy of the first and second sacral vertebrae. Six pigs were treated with daily intramuscular injections of diclofenac, 3 mg/kg body weight, for 7 days. Six other pigs were treated with daily intramuscular injections of ketoprofen, 4 mg/kg body weight, for 7 days. As controls, six pigs received injections with physiologic saline. After 7 days, the pigs were reanesthetized and the Nerve conduction velocity over the exposed Nerve Root area was determined. Results. The Nerve conduction velocity was significantly higher in pigs treated with diclofenac than in the saline-treated controls, (57±6 m/s vs 38±18 m/s, P
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selective inhibition of tumor necrosis factor α prevents nucleus pulposus induced thrombus formation intraneural edema and reduction of Nerve conduction velocity possible implications for future pharmacologic treatment strategies of sciatica
Spine, 2001Co-Authors: Kjell Olmarker, Björn RydevikAbstract:STUDY DESIGN The possibility to prevent nucleus pulposus-induced functional and structural Nerve Root Injury by selective tumor necrosis factor-alpha inhibition was assessed in an experimental model in the pig spine. OBJECTIVE The objective of the study was to evaluate the role of tumor necrosis factor-alpha in the mediation of nucleus pulposus-induced Nerve Injury by using selective inhibition. SUMMARY OF BACKGROUND DATA The cytokine tumor necrosis factor-alpha has been suggested to play a key role in the Nerve Root Injury induced by local application of nucleus pulposus. However, previous studies have not been able to distinguish the effects between tumor necrosis factor-alpha and other disc-related cytokines because of the use of nonspecific cytokine inhibition. METHODS Autologous nucleus pulposus was harvested from a lumbar disc and applied to the porcine sacrococcygeal cauda equina. The pigs were simultaneously treated with two selective tumor necrosis factor-alpha inhibitors (etanercept n = 8 and infliximab n = 5), a heparin analogue (enoxaparin n = 5) or saline for control (n = 5). After 7 days the Nerve conduction velocity over the application zone was determined and samples of the exposed Nerve Roots were collected for light microscopic evaluation. RESULTS The two tumor necrosis factor-alpha inhibitors prevented the reduction of Nerve conduction velocity and also seemed to limit the Nerve fiber Injury, the intracapillary thrombus formation, and the intraneural edema formation. However, treatment with enoxaparin did not seem to be different from control regarding reduction of Nerve conduction velocity or histologic changes. CONCLUSIONS The data clearly indicate that tumor necrosis factor-alpha is involved in the basic pathophysiologic events leading to Nerve Root structural and functional changes after local application of nucleus pulposus. The study therefore provides a basic scientific platform with potential clinical implications regarding the use of anti-tumor necrosis factor-alpha medication as treatment in patients with disc herniation and sciatica.
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Nucleus Pulposus-induced Nerve Root Injury: Relationship between Blood Flow and Motor Nerve Conduction Velocity
Neurosurgery, 1999Co-Authors: Koji Otani, Kjell Olmarker, Itaru Arai, Guang-ping Mao, Shinichi Konno, Shinichi KikuchiAbstract:OBJECTIVE: It is well known that nucleus pulposus induces Nerve Root Injury. The aim of this study was to assess the relationship between intraneural blood flow and motor Nerve conduction velocity (NCV) after incision of the adjacent disc. METHODS: A total of 65 dogs were used. A left hemilaminotomy was performed, the annulus fibrosus of the L6-L7 intervertebral disc was incised, and nucleus pulposus was gently pushed into the epidural space by saline solution injection. A left hemilaminotomy without disc incision was used as the sham operation. Seven dogs were used for incision and five dogs for sham treatment for each of the following time points: 1 day, 3 days, 1 week, 1 month, and 2 months of exposure. Five additional dogs were used to establish baseline data. Blood flow in the Nerve Root was measured in the left L7 Nerve Root with a tissue blood flowmeter, using an electrolytic hydrogen clearance method. Motor NCV over the exposed area of the Nerve Root was measured using a neurophysiological technique. RESULTS: There was a reduction in blood flow in the Nerve Root after disc incision that began after 1 day and was maximal after 1 week. This reduction had resolved by 1 month, however. The motor NCV showed a reduction pattern similar to that for blood flow in the Nerve Root, but reduction did not begin until 3 days after disc incision and was not fully resolved until 2 months. CONCLUSION: This study demonstrates that the reduction and recovery of motor NCV are related to, and preceded by, a reduction in blood flow in the Nerve Root. The data might provide important information regarding the basic pathophysiological mechanisms of nucleus pulposus-induced Nerve Root Injury.
Jeremy A. Lieberman - One of the best experts on this subject based on the ideXlab platform.
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increases in voltage may produce false negatives when using transcranial motor evoked potentials to detect an isolated Nerve Root Injury
Journal of Clinical Monitoring and Computing, 2010Co-Authors: Russ Lyon, Shane Burch, Anthony G Gibson, Jeremy A. LiebermanAbstract:Objective. Transcranial Motor Evoked Poten- tials (TcMEPs) are sometimes used during lumbar spine surgery in order to detect and prevent an intraoperative Nerve Root Injury. Typically, a fixed stimulus is applied, and one monitors for changes in response amplitude from several myotomes. Increased stimulating voltage may or may not alter the response after an acute Injury. Methods. We suture ligated the dominant Root innervating the tibialis anterior (TA) muscle in 7 experiments in swine monitored with TcMEPs. Injury to the Root was confirmed by an increase in threshold current needed to evoke an EMG response in the TA (from 0.32 ± 0.10 to 2.3 ± 0.9 mA, P < 0.01). We recorded TcMEPs at baseline, after Injury, and with incremental 25 V increases in stimulation up to 100 V. Results. After ligation, mean TcMEP amplitude in the TA decreased by 56% from baseline (P < 0.01). Adding voltage progressively restored mean amplitude to within 17% of baseline, but with wide variability in the response. In 1 experiment, there was no augmentation; 3 studies showed partial improvement toward baseline; and in 3 studies, the amplitude was augmented to levels above baseline. Conclusion. An acute Nerve Root Injury may be detected by TcMEP monitoring. However, if the stimulating voltage is increased after Injury, the response may or may not be affected. In complex spine procedures, adjustments to TcMEP stimulating parameters are often needed to maintain reproducible responses. However, if these changes are made during a period where Injury might occur, this could mask the changes and lead to a false-negative interpretation.
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Increases in voltage may produce false-negatives when using transcranial motor evoked potentials to detect an isolated Nerve Root Injury
Journal of clinical monitoring and computing, 2010Co-Authors: Russ Lyon, Shane Burch, Anthony G Gibson, Jeremy A. LiebermanAbstract:Objective. Transcranial Motor Evoked Poten- tials (TcMEPs) are sometimes used during lumbar spine surgery in order to detect and prevent an intraoperative Nerve Root Injury. Typically, a fixed stimulus is applied, and one monitors for changes in response amplitude from several myotomes. Increased stimulating voltage may or may not alter the response after an acute Injury. Methods. We suture ligated the dominant Root innervating the tibialis anterior (TA) muscle in 7 experiments in swine monitored with TcMEPs. Injury to the Root was confirmed by an increase in threshold current needed to evoke an EMG response in the TA (from 0.32 ± 0.10 to 2.3 ± 0.9 mA, P
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Mixed-muscle electrode placement (“jumping” muscles) may produce false-negative results when using transcranial motor evoked potentials to detect an isolated Nerve Root Injury in a porcine model
Journal of clinical monitoring and computing, 2009Co-Authors: Russ Lyon, Shane Burch, Jeremy A. LiebermanAbstract:Introduction Placing EMG electrode pairs that span several muscles is sometimes used to enhance the efficacy of electromyographic recordings. This technique, often referred to as “jumping,” has not been studied when using Motor Evoked Potentials (TcMEP) for detecting isolated spinal Nerve Root Injury during spine surgery.
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Monitoring of Nerve Root Injury using transcranial motor-evoked potentials in a pig model.
Spine, 2008Co-Authors: James M. Mok, Russ Lyon, Jeremy A. Lieberman, Jordan M. Cloyd, Shane BurchAbstract:STUDY DESIGN Animal experiment using transcranial motor-evoked potentials (tcMEPs) in a pig model. OBJECTIVE To validate measurement of tcMEPs from multiple myotomes in a pig model and determine the capacity to detect Injury to a single Nerve Root. SUMMARY OF BACKGROUND DATA The ability of intraoperative neuromonitoring methods to give information about a single Nerve Root remains poorly understood. Reports suggest that tcMEPs may be a reliable and accurate method to detect Nerve Root Injury. An animal model to study the sensitivity and specificity of this technique has yet to be validated. METHODS Transcranial stimulation was delivered through customized electrodes placed in burr holes over the motor cortex in 7 pigs. Spontaneous and evoked muscle potential activity was recorded in 5 myotomes (rectus femoris, vastus lateralis, vastus medialis, tibialis anterior, and gastrocnemius) bilaterally. After unilateral exposure of the L3-S1 Nerve Roots, sequential ligations were performed. The tcMEP responses from all myotomes were measured after ligation of each Nerve Root. RESULTS Robust MEP responses (range, 37-1165 mV) were achieved in all monitored myotomes. Significant decreases in tcMEP amplitudes occurred in specific myotomes after ligation of the corresponding Nerve Root. Consistent and substantial decreases were observed after L3 and L5 ligations in rectus femoris (48%) and tibialis anterior (67%), respectively. DISCUSSION Our results validate monitoring of tcMEPs in multiple myotomes to detect Nerve Root Injury in pigs. This model may be used for further study of the use of tcMEPs to detect predictors and risk factors of Nerve Root Injury during spinal surgery.
Isaac Goodrich - One of the best experts on this subject based on the ideXlab platform.
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efficacy of intraoperative monitoring of transcranial electrical stimulation induced motor evoked potentials and spontaneous electromyography activity to identify acute versus delayed onset c 5 Nerve Root palsy during cervical spine surgery
Journal of Neurosurgery, 2013Co-Authors: Vidya M Bhalodia, Daniel M Schwartz, Anthony K Sestokas, Gary M Bloomgarden, Thomas Arkins, Patrick Tomak, Judith Gorelick, Shirvinda Wijesekera, John Beiner, Isaac GoodrichAbstract:Object Deltoid muscle weakness due to C-5 Nerve Root Injury following cervical spine surgery is an uncommon but potentially debilitating complication. Symptoms can manifest upon emergence from anesthesia or days to weeks following surgery. There is conflicting evidence regarding the efficacy of spontaneous electromyography (spEMG) monitoring in detecting evolving C-5 Nerve Root compromise. By contrast, transcranial electrical stimulation–induced motor evoked potential (tceMEP) monitoring has been shown to be highly sensitive and specific in identifying impending C-5 Injury. In this study the authors sought to 1) determine the frequency of immediate versus delayed-onset C-5 Nerve Root Injury following cervical spine surgery, 2) identify risk factors associated with the development of C-5 palsies, and 3) determine whether tceMEP and spEMG neuromonitoring can help to identify acutely evolving C-5 Injury as well as predict delayed-onset deltoid muscle paresis. Methods The authors retrospectively reviewed the ...
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Efficacy of intraoperative monitoring of transcranial electrical stimulation–induced motor evoked potentials and spontaneous electromyography activity to identify acute-versus delayed-onset C-5 Nerve Root palsy during cervical spine surgery
Journal of neurosurgery. Spine, 2013Co-Authors: Vidya M Bhalodia, Daniel M Schwartz, Anthony K Sestokas, Gary M Bloomgarden, Thomas Arkins, Patrick Tomak, Judith Gorelick, Shirvinda Wijesekera, John Beiner, Isaac GoodrichAbstract:Object Deltoid muscle weakness due to C-5 Nerve Root Injury following cervical spine surgery is an uncommon but potentially debilitating complication. Symptoms can manifest upon emergence from anesthesia or days to weeks following surgery. There is conflicting evidence regarding the efficacy of spontaneous electromyography (spEMG) monitoring in detecting evolving C-5 Nerve Root compromise. By contrast, transcranial electrical stimulation–induced motor evoked potential (tceMEP) monitoring has been shown to be highly sensitive and specific in identifying impending C-5 Injury. In this study the authors sought to 1) determine the frequency of immediate versus delayed-onset C-5 Nerve Root Injury following cervical spine surgery, 2) identify risk factors associated with the development of C-5 palsies, and 3) determine whether tceMEP and spEMG neuromonitoring can help to identify acutely evolving C-5 Injury as well as predict delayed-onset deltoid muscle paresis. Methods The authors retrospectively reviewed the ...
Shane Burch - One of the best experts on this subject based on the ideXlab platform.
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increases in voltage may produce false negatives when using transcranial motor evoked potentials to detect an isolated Nerve Root Injury
Journal of Clinical Monitoring and Computing, 2010Co-Authors: Russ Lyon, Shane Burch, Anthony G Gibson, Jeremy A. LiebermanAbstract:Objective. Transcranial Motor Evoked Poten- tials (TcMEPs) are sometimes used during lumbar spine surgery in order to detect and prevent an intraoperative Nerve Root Injury. Typically, a fixed stimulus is applied, and one monitors for changes in response amplitude from several myotomes. Increased stimulating voltage may or may not alter the response after an acute Injury. Methods. We suture ligated the dominant Root innervating the tibialis anterior (TA) muscle in 7 experiments in swine monitored with TcMEPs. Injury to the Root was confirmed by an increase in threshold current needed to evoke an EMG response in the TA (from 0.32 ± 0.10 to 2.3 ± 0.9 mA, P < 0.01). We recorded TcMEPs at baseline, after Injury, and with incremental 25 V increases in stimulation up to 100 V. Results. After ligation, mean TcMEP amplitude in the TA decreased by 56% from baseline (P < 0.01). Adding voltage progressively restored mean amplitude to within 17% of baseline, but with wide variability in the response. In 1 experiment, there was no augmentation; 3 studies showed partial improvement toward baseline; and in 3 studies, the amplitude was augmented to levels above baseline. Conclusion. An acute Nerve Root Injury may be detected by TcMEP monitoring. However, if the stimulating voltage is increased after Injury, the response may or may not be affected. In complex spine procedures, adjustments to TcMEP stimulating parameters are often needed to maintain reproducible responses. However, if these changes are made during a period where Injury might occur, this could mask the changes and lead to a false-negative interpretation.
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Increases in voltage may produce false-negatives when using transcranial motor evoked potentials to detect an isolated Nerve Root Injury
Journal of clinical monitoring and computing, 2010Co-Authors: Russ Lyon, Shane Burch, Anthony G Gibson, Jeremy A. LiebermanAbstract:Objective. Transcranial Motor Evoked Poten- tials (TcMEPs) are sometimes used during lumbar spine surgery in order to detect and prevent an intraoperative Nerve Root Injury. Typically, a fixed stimulus is applied, and one monitors for changes in response amplitude from several myotomes. Increased stimulating voltage may or may not alter the response after an acute Injury. Methods. We suture ligated the dominant Root innervating the tibialis anterior (TA) muscle in 7 experiments in swine monitored with TcMEPs. Injury to the Root was confirmed by an increase in threshold current needed to evoke an EMG response in the TA (from 0.32 ± 0.10 to 2.3 ± 0.9 mA, P
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Mixed-muscle electrode placement (“jumping” muscles) may produce false-negative results when using transcranial motor evoked potentials to detect an isolated Nerve Root Injury in a porcine model
Journal of clinical monitoring and computing, 2009Co-Authors: Russ Lyon, Shane Burch, Jeremy A. LiebermanAbstract:Introduction Placing EMG electrode pairs that span several muscles is sometimes used to enhance the efficacy of electromyographic recordings. This technique, often referred to as “jumping,” has not been studied when using Motor Evoked Potentials (TcMEP) for detecting isolated spinal Nerve Root Injury during spine surgery.
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Monitoring of Nerve Root Injury using transcranial motor-evoked potentials in a pig model.
Spine, 2008Co-Authors: James M. Mok, Russ Lyon, Jeremy A. Lieberman, Jordan M. Cloyd, Shane BurchAbstract:STUDY DESIGN Animal experiment using transcranial motor-evoked potentials (tcMEPs) in a pig model. OBJECTIVE To validate measurement of tcMEPs from multiple myotomes in a pig model and determine the capacity to detect Injury to a single Nerve Root. SUMMARY OF BACKGROUND DATA The ability of intraoperative neuromonitoring methods to give information about a single Nerve Root remains poorly understood. Reports suggest that tcMEPs may be a reliable and accurate method to detect Nerve Root Injury. An animal model to study the sensitivity and specificity of this technique has yet to be validated. METHODS Transcranial stimulation was delivered through customized electrodes placed in burr holes over the motor cortex in 7 pigs. Spontaneous and evoked muscle potential activity was recorded in 5 myotomes (rectus femoris, vastus lateralis, vastus medialis, tibialis anterior, and gastrocnemius) bilaterally. After unilateral exposure of the L3-S1 Nerve Roots, sequential ligations were performed. The tcMEP responses from all myotomes were measured after ligation of each Nerve Root. RESULTS Robust MEP responses (range, 37-1165 mV) were achieved in all monitored myotomes. Significant decreases in tcMEP amplitudes occurred in specific myotomes after ligation of the corresponding Nerve Root. Consistent and substantial decreases were observed after L3 and L5 ligations in rectus femoris (48%) and tibialis anterior (67%), respectively. DISCUSSION Our results validate monitoring of tcMEPs in multiple myotomes to detect Nerve Root Injury in pigs. This model may be used for further study of the use of tcMEPs to detect predictors and risk factors of Nerve Root Injury during spinal surgery.
Russ Lyon - One of the best experts on this subject based on the ideXlab platform.
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increases in voltage may produce false negatives when using transcranial motor evoked potentials to detect an isolated Nerve Root Injury
Journal of Clinical Monitoring and Computing, 2010Co-Authors: Russ Lyon, Shane Burch, Anthony G Gibson, Jeremy A. LiebermanAbstract:Objective. Transcranial Motor Evoked Poten- tials (TcMEPs) are sometimes used during lumbar spine surgery in order to detect and prevent an intraoperative Nerve Root Injury. Typically, a fixed stimulus is applied, and one monitors for changes in response amplitude from several myotomes. Increased stimulating voltage may or may not alter the response after an acute Injury. Methods. We suture ligated the dominant Root innervating the tibialis anterior (TA) muscle in 7 experiments in swine monitored with TcMEPs. Injury to the Root was confirmed by an increase in threshold current needed to evoke an EMG response in the TA (from 0.32 ± 0.10 to 2.3 ± 0.9 mA, P < 0.01). We recorded TcMEPs at baseline, after Injury, and with incremental 25 V increases in stimulation up to 100 V. Results. After ligation, mean TcMEP amplitude in the TA decreased by 56% from baseline (P < 0.01). Adding voltage progressively restored mean amplitude to within 17% of baseline, but with wide variability in the response. In 1 experiment, there was no augmentation; 3 studies showed partial improvement toward baseline; and in 3 studies, the amplitude was augmented to levels above baseline. Conclusion. An acute Nerve Root Injury may be detected by TcMEP monitoring. However, if the stimulating voltage is increased after Injury, the response may or may not be affected. In complex spine procedures, adjustments to TcMEP stimulating parameters are often needed to maintain reproducible responses. However, if these changes are made during a period where Injury might occur, this could mask the changes and lead to a false-negative interpretation.
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Increases in voltage may produce false-negatives when using transcranial motor evoked potentials to detect an isolated Nerve Root Injury
Journal of clinical monitoring and computing, 2010Co-Authors: Russ Lyon, Shane Burch, Anthony G Gibson, Jeremy A. LiebermanAbstract:Objective. Transcranial Motor Evoked Poten- tials (TcMEPs) are sometimes used during lumbar spine surgery in order to detect and prevent an intraoperative Nerve Root Injury. Typically, a fixed stimulus is applied, and one monitors for changes in response amplitude from several myotomes. Increased stimulating voltage may or may not alter the response after an acute Injury. Methods. We suture ligated the dominant Root innervating the tibialis anterior (TA) muscle in 7 experiments in swine monitored with TcMEPs. Injury to the Root was confirmed by an increase in threshold current needed to evoke an EMG response in the TA (from 0.32 ± 0.10 to 2.3 ± 0.9 mA, P
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Mixed-muscle electrode placement (“jumping” muscles) may produce false-negative results when using transcranial motor evoked potentials to detect an isolated Nerve Root Injury in a porcine model
Journal of clinical monitoring and computing, 2009Co-Authors: Russ Lyon, Shane Burch, Jeremy A. LiebermanAbstract:Introduction Placing EMG electrode pairs that span several muscles is sometimes used to enhance the efficacy of electromyographic recordings. This technique, often referred to as “jumping,” has not been studied when using Motor Evoked Potentials (TcMEP) for detecting isolated spinal Nerve Root Injury during spine surgery.
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Monitoring of Nerve Root Injury using transcranial motor-evoked potentials in a pig model.
Spine, 2008Co-Authors: James M. Mok, Russ Lyon, Jeremy A. Lieberman, Jordan M. Cloyd, Shane BurchAbstract:STUDY DESIGN Animal experiment using transcranial motor-evoked potentials (tcMEPs) in a pig model. OBJECTIVE To validate measurement of tcMEPs from multiple myotomes in a pig model and determine the capacity to detect Injury to a single Nerve Root. SUMMARY OF BACKGROUND DATA The ability of intraoperative neuromonitoring methods to give information about a single Nerve Root remains poorly understood. Reports suggest that tcMEPs may be a reliable and accurate method to detect Nerve Root Injury. An animal model to study the sensitivity and specificity of this technique has yet to be validated. METHODS Transcranial stimulation was delivered through customized electrodes placed in burr holes over the motor cortex in 7 pigs. Spontaneous and evoked muscle potential activity was recorded in 5 myotomes (rectus femoris, vastus lateralis, vastus medialis, tibialis anterior, and gastrocnemius) bilaterally. After unilateral exposure of the L3-S1 Nerve Roots, sequential ligations were performed. The tcMEP responses from all myotomes were measured after ligation of each Nerve Root. RESULTS Robust MEP responses (range, 37-1165 mV) were achieved in all monitored myotomes. Significant decreases in tcMEP amplitudes occurred in specific myotomes after ligation of the corresponding Nerve Root. Consistent and substantial decreases were observed after L3 and L5 ligations in rectus femoris (48%) and tibialis anterior (67%), respectively. DISCUSSION Our results validate monitoring of tcMEPs in multiple myotomes to detect Nerve Root Injury in pigs. This model may be used for further study of the use of tcMEPs to detect predictors and risk factors of Nerve Root Injury during spinal surgery.