About this Research Topic
Stroke remains the leading cause of adult disability and the second leading cause of death worldwide. Subsequent to a hemispheric stroke, many patients suffer a variety of disabling physical symptoms on the contralesional side of the body, including muscular weakness, impaired movement, and spasticity that together can be referred to as motor impairment. Currently, our understanding of the mechanisms underlying motor impairment is poor, and this is one reason why available treatments are limited. In general, motor impairment can be said to arise from changes in both neural and muscle properties, but the relative contribution of each is uncertain, and likely varies between patients. There is evidence that post-stroke weakness reflects reduced central neural drive to muscles as well as muscle atrophy. There are also reports of motor unit loss and remodeling (i.e., increased unit size, changes in contractile properties) of surviving motor units but their contribution to motor impairment is uncertain. Similarly, evidence indicates that motoneuron hyperexcitability and increased muscle stiffness contribute to post-stroke spasticity.
Different electromyographic (EMG) techniques have been developed to assess neural and muscular changes after stroke such as muscle atrophy, impaired muscle activation, motor unit loss, and altered motor unit control properties. Evaluation of spasticity involves mechanical measures and EMG-based techniques including the H-reflex and F wave to assess motoneuron excitability. The technique that uses EMG signals to control external devices have been successfully employed in patient populations to enhance motor function. More sophisticated and patient friendly EMG-controlled devices are being developed for rehabilitation uses.
With technical advances in electrode and amplifier design, EMG has broad applicability, from measurement of single muscle fiber action potentials and motor unit potentials, to whole muscle or muscle group activity. Single fiber EMG has been used to assess rearrangement of muscle fiber topography based on fiber density, jitter, and other measurements. Recording of single motor unit activity allows for the measurement of motor unit size and conduction velocity, as well as recruitment and firing rate properties, all of which may be altered after stroke. Surface EMG and high density surface EMG array evaluate overall muscle activity or activation patterns which provides information on movement coordination. In addition, advances in EMG signal processing provide new insights into understanding neuromuscular control after stroke.
We welcome researchers and clinicians to contribute original research articles or contemporary reviews to this Research Topic, which aims to improve our understanding of the mechanisms underlying motor impairment and it’s recovery following stroke, using EMG techniques. We encourage submission from individuals who use traditional or novel EMG methods to assess single fiber, motor unit, and whole muscle function in stroke survivors. The goal is to have a collection of papers that provides a broad overview of EMG techniques currently being used to understand motor impairment after stroke.
Areas of interests include but not limited to the following EMG-related topics:
• Advances in quantification of motor impairment
• Advances in quantification of motor recovery during rehabilitation
• EMG-controlled devices for stroke rehabilitation
• Novel EMG techniques and modelling
Keywords: Stroke, Electromyographic (EMG), Motor Unit, Motor Impairment, Rehabilitation
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