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W4 Multi-channel surface EMG
S26
Workshops / Clinical Neurophysiology 117 (2006) S25–S31
ing functional connectivity among different brain areas, such as diffusion tensor imaging. doi:10.1016/j.clinph.2006.07.069
W3 Intraoperative monitoring: Spinal cord M.R. Nuwer 1, V. Deletis 2 1
UCLA, Department of Neurology, USA St. Luke’s-Roosevelt, R 11C-08, Newman Institute for Neurology and Neurosurgery, USA
2
Surgery at and around the spinal cord places the cord at risk from ischemic, thermal or mechanical injury. The most feared injuries cause motor loss, e.g., paraplegia. Somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) are used for spinal cord intraoperative monitoring (IOM). SEPs are easiest to monitor and were first to gain widespread acceptance. SEP IOM reduced postoperative paraplegia by more than 60%. In the SEP technique, spinal cord pyramidal tract integrity is inferred from SEP posterior column monitoring. Correlations were good, yet some discrepancies occurred between posterior column function and motor outcome. SEPs during myelotomy for spinal cord tumors did not predict motor deficits well. In contrast, MEPs monitor pyramidal tracks directly. Transcranial or direct electrical cortical stimulation produces corticospinal (pyramidal) D and I waves recordable directly from the spinal cord. Limb muscle MEPs can and should be monitored too. These techniques more confidently warn surgeons, and predict and prevent intraoperative injury to the spinal motor pathway. Combining D wave spinal recording with muscle MEPs is a reliable technique. D wave without muscle MEPs has shown false positive changes when assessed in scoliosis surgery, possibly due to recording electrode movement during spinal column distraction. Many users now combine SEP and types of MEP, tailored to the particular patient’s condition, surgery and anesthesia regimen. Further development of IOM techniques could map dorsal and lateral columns of the exposed spinal cord, new tools better to prevent intraoperative spinal injury. doi:10.1016/j.clinph.2006.07.070
W4 Multi-channel surface EMG M. Zwarts, D. Stegeman Radboud University Medical Centre, Netherlands The development of multichannel surface EMG electrodes (up to 128 channels) has revolutionized surface EMG applications. In this workshop, the spatial aspect of the motor unit action potential (MUP) is emphasized in relation to the results of high-density, multichannel sEMG measurements. Using a two-dimensional grid, it becomes
possible to display the SEMG activity in a spatio-temporal way. For all SEMG measurements, especially for multichannel SEMG, we recommend to record and store the signals of the individual electrodes in the array or grid referenced to a remote reference electrode (thus in a monopolar fashion). This approach enables a versatile and purpose-dependent (re-)selection, both with respect to the desired montages (e.g., bipolar, Laplacian) and to the way in which the EMG activity is displayed (e.g., column, row, two dimensional map of amplitude or spectral content). At low force levels, it is possible to extract single MUPs using the spatio-temporal information. This results in a unique pattern of the amplitude distribution of the motor unit over the skin (fingerprint). In this way, endplate zone, depth, size, position, conduction velocity, and firing pattern of a MU can be estimated. Emerging possibilities provided by MUP size and fingerprint measurements in neuromuscular disease and motor control are discussed. We conclude that multichannel sEMG adds unique, and sometimes indispensable, spatial information to the present knowledge of motor units. doi:10.1016/j.clinph.2006.07.071
W5 TMS: Intracortical inhibition R. Chen Toronto Western Research Institute, University of Toronto, Division of Neurology, Canada Cortical activity depends on the balance between excitatory and inhibitory influences. Transcranial magnetic stimulation can be used to test different excitatory and inhibitory systems in the human motor cortex. Cortical inhibition that originates within the motor cortex includes short-interval intracortical inhibition (SICI), which is likely related to GABA-A transmission. SICI is a complex phenomenon and may represent the net effect of different inhibitory and excitatory circuits. The other forms cortico-cortical inhibitions are long-interval intracortical inhibition (LICI) and the silent period, which are likely related to GABA-B transmission. The motor cortex may also be inhibited by stimulation of other areas. Stimulation of the opposite motor cortex induces interhemispheric inhibition (IHI) that may be measured with the ipsilateral silent period or by a paired stimulation method. IHI at short (10 ms, IHI10) and long (40 ms, IHI40) interstimulus intervals are likely mediated by different mechanisms. Cerebellar stimulation also inhibits the motor cortex through transmission in the cerebellothalamocortical pathway. Stimulation of peripheral nerves inhibit the motor cortex and the effect of median nerve stimulation has been termed short and long latency afferent inhibition (SAI and LAI) depending on the time between nerve stimulation and TMS. These different cortical inhibitory circuits interact in a complex manner. For example, SICI is inhibited by LICI, IHI10 and cerebellar stimulation, but not by LAI.
Workshops / Clinical Neurophysiology 117 (2006) S25–S31
ing functional connectivity among different brain areas, such as diffusion tensor imaging. doi:10.1016/j.clinph.2006.07.069
W3 Intraoperative monitoring: Spinal cord M.R. Nuwer 1, V. Deletis 2 1
UCLA, Department of Neurology, USA St. Luke’s-Roosevelt, R 11C-08, Newman Institute for Neurology and Neurosurgery, USA
2
Surgery at and around the spinal cord places the cord at risk from ischemic, thermal or mechanical injury. The most feared injuries cause motor loss, e.g., paraplegia. Somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) are used for spinal cord intraoperative monitoring (IOM). SEPs are easiest to monitor and were first to gain widespread acceptance. SEP IOM reduced postoperative paraplegia by more than 60%. In the SEP technique, spinal cord pyramidal tract integrity is inferred from SEP posterior column monitoring. Correlations were good, yet some discrepancies occurred between posterior column function and motor outcome. SEPs during myelotomy for spinal cord tumors did not predict motor deficits well. In contrast, MEPs monitor pyramidal tracks directly. Transcranial or direct electrical cortical stimulation produces corticospinal (pyramidal) D and I waves recordable directly from the spinal cord. Limb muscle MEPs can and should be monitored too. These techniques more confidently warn surgeons, and predict and prevent intraoperative injury to the spinal motor pathway. Combining D wave spinal recording with muscle MEPs is a reliable technique. D wave without muscle MEPs has shown false positive changes when assessed in scoliosis surgery, possibly due to recording electrode movement during spinal column distraction. Many users now combine SEP and types of MEP, tailored to the particular patient’s condition, surgery and anesthesia regimen. Further development of IOM techniques could map dorsal and lateral columns of the exposed spinal cord, new tools better to prevent intraoperative spinal injury. doi:10.1016/j.clinph.2006.07.070
W4 Multi-channel surface EMG M. Zwarts, D. Stegeman Radboud University Medical Centre, Netherlands The development of multichannel surface EMG electrodes (up to 128 channels) has revolutionized surface EMG applications. In this workshop, the spatial aspect of the motor unit action potential (MUP) is emphasized in relation to the results of high-density, multichannel sEMG measurements. Using a two-dimensional grid, it becomes
possible to display the SEMG activity in a spatio-temporal way. For all SEMG measurements, especially for multichannel SEMG, we recommend to record and store the signals of the individual electrodes in the array or grid referenced to a remote reference electrode (thus in a monopolar fashion). This approach enables a versatile and purpose-dependent (re-)selection, both with respect to the desired montages (e.g., bipolar, Laplacian) and to the way in which the EMG activity is displayed (e.g., column, row, two dimensional map of amplitude or spectral content). At low force levels, it is possible to extract single MUPs using the spatio-temporal information. This results in a unique pattern of the amplitude distribution of the motor unit over the skin (fingerprint). In this way, endplate zone, depth, size, position, conduction velocity, and firing pattern of a MU can be estimated. Emerging possibilities provided by MUP size and fingerprint measurements in neuromuscular disease and motor control are discussed. We conclude that multichannel sEMG adds unique, and sometimes indispensable, spatial information to the present knowledge of motor units. doi:10.1016/j.clinph.2006.07.071
W5 TMS: Intracortical inhibition R. Chen Toronto Western Research Institute, University of Toronto, Division of Neurology, Canada Cortical activity depends on the balance between excitatory and inhibitory influences. Transcranial magnetic stimulation can be used to test different excitatory and inhibitory systems in the human motor cortex. Cortical inhibition that originates within the motor cortex includes short-interval intracortical inhibition (SICI), which is likely related to GABA-A transmission. SICI is a complex phenomenon and may represent the net effect of different inhibitory and excitatory circuits. The other forms cortico-cortical inhibitions are long-interval intracortical inhibition (LICI) and the silent period, which are likely related to GABA-B transmission. The motor cortex may also be inhibited by stimulation of other areas. Stimulation of the opposite motor cortex induces interhemispheric inhibition (IHI) that may be measured with the ipsilateral silent period or by a paired stimulation method. IHI at short (10 ms, IHI10) and long (40 ms, IHI40) interstimulus intervals are likely mediated by different mechanisms. Cerebellar stimulation also inhibits the motor cortex through transmission in the cerebellothalamocortical pathway. Stimulation of peripheral nerves inhibit the motor cortex and the effect of median nerve stimulation has been termed short and long latency afferent inhibition (SAI and LAI) depending on the time between nerve stimulation and TMS. These different cortical inhibitory circuits interact in a complex manner. For example, SICI is inhibited by LICI, IHI10 and cerebellar stimulation, but not by LAI.