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S68 SFAP to MUAP: Temporal and spatial characteristics of MU
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Abstracts / Clinical Neurophysiology 128 (2017) e178–e303
pain-related evoked potentials (PREP) and nociceptive blink reflex (nBR) [4]. Borsook et al. (2007) reported increased fMRI activation of a single TN patient in the primary somatosensory cortex, insula, anterior cingulate, and thalamus to further support cortical involvement [28]. Structural changes of the cortical grey matter was also reported to further support a central origin of the disease.
Keywords: Trigeminal neuralgia, Neurophysiology, Central mechanism doi:10.1016/j.clinph.2017.07.076
S66 Pathophysiological implications and current evidence for the treatment of trigeminal neuralgia—Joanna Zakrzewska (University College London, Pain Clinic, London, United Kingdom) Aim: Appreciate how current understanding of the pathophysiology of trigeminal neuralgia has impacted on treatments. The ignition theory puts forward the hypothesis that some form of trauma to the trigeminal nerve at any level results in abnormal firing of neurons which result in episodic pain. It is likely that patients with trigeminal neuralgia have some form of abnormality of their sodium channels. Currently the most effective medications are sodium channel blockers whereas other drugs such as opioids whose mode of action is different are not effective. Current drugs act centrally and so result in significant side effects especially cognitive ones which often result in cessation of the medication. The episodic nature of the disorder also means patients can stop their medication for weeks or months and have no pain attacks. However if pain is poorly controlled or quality of life is significantly affected then surgical options can be utilised. It is postulated that pressure from a significant artery in the root entry zone leads to demyelination and consequently allows for ectopic impulses to be generated. Separating the vessel from the trigeminal nerve can lead to complete resolution of pain in 70% of cases for ten years. However some of the impulses may be generated at the Gasserian ganglion level and so destructive procedures at that level result in pain relief for an average of five years. These do however result in sensory changes. Keywords: Trigeminal neuralgia, Sodium channel blockers, Surgery doi:10.1016/j.clinph.2017.07.077
Symposium IX. – Motor unit with an electrophysiological microscope: from inside and from outside S67 Special phenomena in the motor unit during voluntary and electrical activation—Erik Stålberg (Uppsala Neuroscience, Clinical Neurophysiology, Uppsala, Sweden) Introduction: Different information is obtained about the motor unit (MU) from various EMG methods. Single Fiber EMG (SFEMG) explores individual muscle fibers and endplates, conventional EMG a larger part of the MU and Macro EMG represents the entire MU. Methods: The presentation will first discuss consequences for routine EMG of the temporal and spatial variation in the activation of MUs that may lead to misinterpretation of some EMG features. It will
also highlight some physiological parameters of conduction along a muscle fiber based on SFEMG. Results: The muscle fiber velocity shows a short-term facilitation by previous activity, which gives rise to variation in arrival time to the recording electrode, seen both at voluntary and electrical stimulation. During long term activity on the other hand, the velocity decreases, seen and heard as change in frequency spectrum of the EMG signals. A special phenomenon is the decrease in action potential amplitude in some myotonic disorders. A surface recorded amplitude drop at repetitive stimulation seen in these cases not sign of neuromuscular junction disturbance, but reflects amplitude changes of individual fiber action potentials. Amplitude of single fiber action potentials also varies in relationship to just previous activity, with lower amplitude for short intervals, also seen in conventional EMG. Different types of reflexes involving just one or a few neurons can be studied with SFEMG. Conclusion: Different single cell phenomena can be studied in situ in man, and many of these details can be seen in routine EMG, once we are aware of them. Keywords: Motor unit, Single fiber EMG, EMG doi:10.1016/j.clinph.2017.07.078
S68 SFAP to MUAP: Temporal and spatial characteristics of MU— _ _ Mehmet Baris Baslo (Istanbul University Istanbul Medical Faculty, Neurology, Istanbul, Turkey) Introduction: Motor unit action potential (MUAP) represents the summated activity of single fiber action potentials (SFAP) coming from individual muscle fibers those reside in the pick-up territory of recording needle. Calculated features of MUAP give reliable information concerning the architecture of motor unit under investigation but they also depend on the recording site and technique. Methods: In this presentation, features of SFAP will be discussed first as a measure of individual muscle fiber conductivity. Then, how MUAP features are changed by moving the needle near to tendon is questioned. Measuring the bioelectrical activity of motor unit across its territory by scanning EMG will be revisited. Results: SFAP represents the moving quadrupole in near field recordings. The faster the quardupole moves, the quicker the phases of SFAP change and lead to shorter ‘‘spike duration” in turn. The distribution of ‘‘spike duration” shows less central tendency in myopathic muscle, which can be related to increased variability among the muscle fibers. Furthermore, moving the recording site near to tendon exaggerates this conduction difference and leads to more spiky and temporally dispersed MUAP, a finding that is especially detected in simulation studies. Scanning the electrical activity of motor unit from side to side informs the examiner about the motor unit structure. New algorithms and methods were developed for extracting features from scanning EMG signals. Conclusion: The recorded activity of motor unit during voluntary drive changes by the placement of needle electrode. As it changes, it teaches us a lot! Keywords: Motor unit, Motor unit action potential, Recording site, Scanning EMG, EMG simulator doi:10.1016/j.clinph.2017.07.079
Abstracts / Clinical Neurophysiology 128 (2017) e178–e303
pain-related evoked potentials (PREP) and nociceptive blink reflex (nBR) [4]. Borsook et al. (2007) reported increased fMRI activation of a single TN patient in the primary somatosensory cortex, insula, anterior cingulate, and thalamus to further support cortical involvement [28]. Structural changes of the cortical grey matter was also reported to further support a central origin of the disease.
Keywords: Trigeminal neuralgia, Neurophysiology, Central mechanism doi:10.1016/j.clinph.2017.07.076
S66 Pathophysiological implications and current evidence for the treatment of trigeminal neuralgia—Joanna Zakrzewska (University College London, Pain Clinic, London, United Kingdom) Aim: Appreciate how current understanding of the pathophysiology of trigeminal neuralgia has impacted on treatments. The ignition theory puts forward the hypothesis that some form of trauma to the trigeminal nerve at any level results in abnormal firing of neurons which result in episodic pain. It is likely that patients with trigeminal neuralgia have some form of abnormality of their sodium channels. Currently the most effective medications are sodium channel blockers whereas other drugs such as opioids whose mode of action is different are not effective. Current drugs act centrally and so result in significant side effects especially cognitive ones which often result in cessation of the medication. The episodic nature of the disorder also means patients can stop their medication for weeks or months and have no pain attacks. However if pain is poorly controlled or quality of life is significantly affected then surgical options can be utilised. It is postulated that pressure from a significant artery in the root entry zone leads to demyelination and consequently allows for ectopic impulses to be generated. Separating the vessel from the trigeminal nerve can lead to complete resolution of pain in 70% of cases for ten years. However some of the impulses may be generated at the Gasserian ganglion level and so destructive procedures at that level result in pain relief for an average of five years. These do however result in sensory changes. Keywords: Trigeminal neuralgia, Sodium channel blockers, Surgery doi:10.1016/j.clinph.2017.07.077
Symposium IX. – Motor unit with an electrophysiological microscope: from inside and from outside S67 Special phenomena in the motor unit during voluntary and electrical activation—Erik Stålberg (Uppsala Neuroscience, Clinical Neurophysiology, Uppsala, Sweden) Introduction: Different information is obtained about the motor unit (MU) from various EMG methods. Single Fiber EMG (SFEMG) explores individual muscle fibers and endplates, conventional EMG a larger part of the MU and Macro EMG represents the entire MU. Methods: The presentation will first discuss consequences for routine EMG of the temporal and spatial variation in the activation of MUs that may lead to misinterpretation of some EMG features. It will
also highlight some physiological parameters of conduction along a muscle fiber based on SFEMG. Results: The muscle fiber velocity shows a short-term facilitation by previous activity, which gives rise to variation in arrival time to the recording electrode, seen both at voluntary and electrical stimulation. During long term activity on the other hand, the velocity decreases, seen and heard as change in frequency spectrum of the EMG signals. A special phenomenon is the decrease in action potential amplitude in some myotonic disorders. A surface recorded amplitude drop at repetitive stimulation seen in these cases not sign of neuromuscular junction disturbance, but reflects amplitude changes of individual fiber action potentials. Amplitude of single fiber action potentials also varies in relationship to just previous activity, with lower amplitude for short intervals, also seen in conventional EMG. Different types of reflexes involving just one or a few neurons can be studied with SFEMG. Conclusion: Different single cell phenomena can be studied in situ in man, and many of these details can be seen in routine EMG, once we are aware of them. Keywords: Motor unit, Single fiber EMG, EMG doi:10.1016/j.clinph.2017.07.078
S68 SFAP to MUAP: Temporal and spatial characteristics of MU— _ _ Mehmet Baris Baslo (Istanbul University Istanbul Medical Faculty, Neurology, Istanbul, Turkey) Introduction: Motor unit action potential (MUAP) represents the summated activity of single fiber action potentials (SFAP) coming from individual muscle fibers those reside in the pick-up territory of recording needle. Calculated features of MUAP give reliable information concerning the architecture of motor unit under investigation but they also depend on the recording site and technique. Methods: In this presentation, features of SFAP will be discussed first as a measure of individual muscle fiber conductivity. Then, how MUAP features are changed by moving the needle near to tendon is questioned. Measuring the bioelectrical activity of motor unit across its territory by scanning EMG will be revisited. Results: SFAP represents the moving quadrupole in near field recordings. The faster the quardupole moves, the quicker the phases of SFAP change and lead to shorter ‘‘spike duration” in turn. The distribution of ‘‘spike duration” shows less central tendency in myopathic muscle, which can be related to increased variability among the muscle fibers. Furthermore, moving the recording site near to tendon exaggerates this conduction difference and leads to more spiky and temporally dispersed MUAP, a finding that is especially detected in simulation studies. Scanning the electrical activity of motor unit from side to side informs the examiner about the motor unit structure. New algorithms and methods were developed for extracting features from scanning EMG signals. Conclusion: The recorded activity of motor unit during voluntary drive changes by the placement of needle electrode. As it changes, it teaches us a lot! Keywords: Motor unit, Motor unit action potential, Recording site, Scanning EMG, EMG simulator doi:10.1016/j.clinph.2017.07.079