8 results on '"Chan, K. Ming"'
Search Results
2. Does experimental low back pain change posteroanterior lumbar spinal stiffness and trunk muscle activity? A randomized crossover study.
- Author
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Wong AY, Parent EC, Prasad N, Huang C, Chan KM, and Kawchuk GN
- Subjects
- Adolescent, Adult, Cross-Over Studies, Electromyography, Female, Humans, Low Back Pain etiology, Male, Middle Aged, Muscle Contraction physiology, Young Adult, Low Back Pain physiopathology, Lumbosacral Region physiopathology, Muscle, Skeletal physiopathology, Torso physiopathology
- Abstract
Background: While some patients with low back pain demonstrate increased spinal stiffness that decreases as pain subsides, this observation is inconsistent. Currently, the relation between spinal stiffness and low back pain remains unclear. This study aimed to investigate the effects of experimental low back pain on temporal changes in posteroanterior spinal stiffness and concurrent trunk muscle activity., Method: In separate sessions five days apart, nine asymptomatic participants received equal volume injections of hypertonic or isotonic saline in random order into the L3-L5 interspinous ligaments. Pain intensity, spinal stiffness (global and terminal stiffness) at the L3 level, and the surface electromyographic activity of six trunk muscles were measured before, immediately after, and 25-minute after injections. These outcome measures under different saline conditions were compared by generalized estimating equations., Findings: Compared to isotonic saline injections, hypertonic saline injections evoked significantly higher pain intensity (mean difference: 5.7/10), higher global (mean difference: 0.73N/mm) and terminal stiffness (mean difference: 0.58N/mm), and increased activity of four trunk muscles during indentation (P<0.05). Both spinal stiffness and trunk muscle activity returned to baseline levels as pain subsided., Interpretation: While previous clinical research reported inconsistent findings regarding the association between spinal stiffness and low back pain, our study revealed that experimental pain caused temporary increases in spinal stiffness and concurrent trunk muscle co-contraction during indentation, which helps explain the temporal relation between spinal stiffness and low back pain observed in some clinical studies. Our results substantiate the role of spinal stiffness assessments in monitoring back pain progression., (Copyright © 2016 Elsevier Ltd. All rights reserved.)
- Published
- 2016
- Full Text
- View/download PDF
3. Novel targeted sensory reinnervation technique to restore functional hand sensation after transhumeral amputation.
- Author
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Hebert JS, Olson JL, Morhart MJ, Dawson MR, Marasco PD, Kuiken TA, and Chan KM
- Subjects
- Adult, Amputation Stumps physiopathology, Electric Stimulation Therapy methods, Feedback, Physiological, Hand physiopathology, Humans, Male, Muscle Contraction, Robotics methods, Amputation Stumps innervation, Artificial Limbs, Electromyography methods, Hand innervation, Muscle, Skeletal innervation, Muscle, Skeletal physiopathology, Touch
- Abstract
We present a case study of a novel variation of the targeted sensory reinnervation technique that provides additional control over sensory restoration after transhumeral amputation. The use of intraoperative somatosensory evoked potentials on individual fascicles of the median and ulnar nerves allowed us to specifically target sensory fascicles to reroute to target cutaneous nerves at a distance away from anticipated motor sites in a transhumeral amputee. This resulted in restored hand maps of the median and ulnar nerve in discrete spatially separated areas. In addition, the subject was able to use native and reinnervated muscle sites to control a robotic arm while simultaneously sensing touch and force feedback from the robotic gripper in a physiologically correct manner. This proof of principle study is the first to demonstrate the ability to have simultaneous dual flow of information (motor and sensory) within the residual limb. In working towards clinical deployment of a sensory integrated prosthetic device, this surgical method addresses the important issue of restoring a usable access point to provide natural hand sensation after upper limb amputation.
- Published
- 2014
- Full Text
- View/download PDF
4. Electrical stimulation site influences the spatial distribution of motor units recruited in tibialis anterior.
- Author
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Okuma Y, Bergquist AJ, Hong M, Chan KM, and Collins DF
- Subjects
- Adult, Electromyography methods, Female, Humans, Male, Middle Aged, Peroneal Nerve physiology, Young Adult, Electric Stimulation methods, Muscle, Skeletal innervation, Recruitment, Neurophysiological physiology
- Abstract
Objective: To compare the spatial distribution of motor units recruited in tibialis anterior (TA) when electrical stimulation is applied over the TA muscle belly versus the common peroneal nerve trunk., Methods: Electromyography (EMG) was recorded from the surface and from fine wires in superficial and deep regions of TA. Separate M-wave recruitment curves were constructed for muscle belly and nerve trunk stimulation., Results: During muscle belly stimulation, significantly more current was required to generate M-waves that were 5% of the maximal M-wave (M max; M5%max), 50% M max (M 50%max) and 95% M max (M 95%max) at the deep versus the superficial recording site. In contrast, during nerve trunk stimulation, there were no differences in the current required to reach M5%max, M 50%max or M 95%max between deep and superficial recording sites. Surface EMG reflected activity in both superficial and deep muscle regions., Conclusions: Stimulation over the muscle belly recruited motor units from superficial to deep with increasing stimulation amplitude. Stimulation over the nerve trunk recruited superficial and deep motor units equally, regardless of stimulation amplitude., Significance: These results support the idea that where electrical stimulation is applied markedly affects how contractions are produced and have implications for the interpretation of surface EMG data., (Copyright © 2013 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.)
- Published
- 2013
- Full Text
- View/download PDF
5. Improving the accuracy of the multiple point stimulation technique.
- Author
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Porter CL, Alvarez A, Jones KE, Major LA, and Chan KM
- Subjects
- Adolescent, Adult, Biophysics, Female, Humans, Male, Time Factors, Young Adult, Action Potentials physiology, Electric Stimulation methods, Motor Neurons physiology, Muscle, Skeletal physiology
- Published
- 2009
- Full Text
- View/download PDF
6. Change in excitability of motor axons modifies statistical MUNE results.
- Author
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Major LA, Chan KM, Bostock H, and Jones KE
- Subjects
- Adult, Electric Stimulation methods, Electromyography methods, Female, Humans, Male, Probability, Reproducibility of Results, Time Factors, Young Adult, Action Potentials physiology, Axons physiology, Data Interpretation, Statistical, Motor Neurons physiology, Muscle, Skeletal physiology
- Abstract
Motor unit number estimation (MUNE) techniques--whether they reflect a true motor unit count or some related index--should not be confounded by changes in the neuromuscular system other than a decline in the number of functional motor units. In neurodegenerative conditions such as amyotrophic lateral sclerosis (ALS), there is evidence of changes in the excitability of motor axons. If changes in axon excitability confound a particular MUNE technique, this would influence the use of that technique in ALS patients. We hypothesized on the basis of computational models that changes in axon membrane excitability would change the outcome of a statistical MUNE test, even though the true number of motor units remained unchanged. To test the validity of the model predictions we induced changes in axon excitability of healthy control subjects by applying a polarizing current while simultaneously carrying out a statistical MUNE test. In a group of 7 subjects we found a significant difference in MUNE as a result of the change in axon excitability produced by the polarizing current (paired t-test, P < 0.05). We conclude that the statistical MUNE method is confounded by changes in axon excitability. Since increasing evidence shows that axon excitability is altered as part of the pathophysiological process underlying ALS, clinical researchers should be cautious when using statistical MUNE with this patient population.
- Published
- 2009
- Full Text
- View/download PDF
7. A new means of transcutaneous coupling for neural prostheses.
- Author
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Gan LS, Prochazka A, Bornes TD, Denington AA, and Chan KM
- Subjects
- Animals, Cats, Electric Stimulation Therapy methods, Equipment Design, Equipment Failure Analysis, Skin Physiological Phenomena, Electric Stimulation Therapy instrumentation, Electrodes, Muscle Contraction physiology, Muscle, Skeletal innervation, Muscle, Skeletal physiology, Peripheral Nerves physiology, Prostheses and Implants
- Abstract
Neural prostheses are electronic stimulators that activate nerves to restore sensory or motor functions. Implanted neural prostheses receive command signals and in some cases energy to recharge their batteries through the skin by telemetry. Here, we describe a new approach that eliminates the implanted stimulator. Stimulus pulse trains are passed between two surface electrodes placed on the skin. An insulated lead with conductive terminals at each end is implanted inside the body. One terminal is located under the cathodal surface electrode and the other is attached to a nerve targeted for stimulation. A fraction (10%-15%) of the current flowing between the surface electrodes is routed through the implanted lead. The nerve is stimulated when the amount of routed current is sufficient. The aims of this study were to establish some basic electrical properties of the system and test long-term stability in chronic implants. Stimulation of the nerve innervating the ankle flexors produced graded force over the full physiological range at amplitudes below threshold for evoking muscle contractions under the surface electrodes. Implants remained stable for over 8 mo. The findings provide the basis for a new family of neural prostheses.
- Published
- 2007
- Full Text
- View/download PDF
8. Transcranial direct current stimulation of the primary motor cortex affects cortical drive to human musculature as assessed by intermuscular coherence.
- Author
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Power HA, Norton JA, Porter CL, Doyle Z, Hui I, and Chan KM
- Subjects
- Adult, Electric Stimulation, Electromyography, Evoked Potentials, Motor, Female, Fingers, Humans, Transcranial Magnetic Stimulation, Wrist, Motor Cortex physiology, Muscle, Skeletal physiology
- Abstract
Intermuscular coherence analysis can be used to assess the common drive to muscles. Coherence in the beta-frequency band (15-35 Hz) is thought to arise from common cortical sources. Intermuscular coherence analysis is a potentially attractive tool for the investigation of motor cortical excitability changes because it is non-invasive and can be done relatively quickly. We carried out this study to test the hypothesis that intermuscular coherence analysis was able to detect cortical excitability changes in healthy subjects following transcranial direct current stimulation (tDCS). tDCS has been shown to increase (anodal stimulation) or decrease (cathodal stimulation) the size of the muscle potential evoked by TMS. We found that anodal tDCS caused an increase in motor evoked potential (MEP) size that was paralleled by an increase in beta-band intermuscular coherence. Similarly, the reduction in MEP size produced by cathodal tDCS was paralleled by a reduction in beta-band intermuscular coherence, while sham stimulation did not result in any change in either MEP amplitude or beta-band intermuscular coherence. The similar pattern of change observed for MEP and intermuscular coherence may indicate similar mechanisms of action, although this cannot be assumed without further investigation. These changes do suggest that at least some of the action of tDCS is on cortical networks, and that combined tDCS and intermuscular coherence analysis may be useful in the diagnosis of pathologies affecting motor cortical excitability.
- Published
- 2006
- Full Text
- View/download PDF
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