Functional electrical stimulation ( FES ) is a technique that uses low energy energy pulses to produce artificial body movements in individuals who have been paralyzed by injury to the central nervous system. More specifically, FES can be used to produce muscle contractions in limbs that are paralyzed to produce functions such as grasping, walking, bladder gargling and standing. This technology was originally used to develop neuroprostheses that were implemented to replace the function of permanent disturbance in individuals with spinal cord injury (SCI), head injury, stroke and other neurological disorders. In other words, the consumer will use the device whenever he wants to produce the desired function. FES is sometimes also referred to as neuromuscular electrical stimulation (NMES).
In recent years FES technology has been used to provide therapy to retrain voluntary motor functions such as grasping, reaching and walking. In this embodiment, FES is used as a short-term therapy, whose goal is the recovery of voluntary function and non-lifetime dependence on FES devices, hence the name functional electric stimulation therapy , FES Therapy FET or FEST ). In other words, FEST is used as a short-term intervention to help the central nervous system of consumers to relearn how to perform disrupted functions, rather than making consumers dependent on neuroprostheses for the rest of their lives.
Video Functional electrical stimulation
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Neurons are cells that are electrically active. In neurons, information is encoded and transmitted as a series of electrical impulses called action potentials, representing a brief change in the electrical potential of the cell about 80-90 mV. Neural signals are frequency modulated; ie the number of action potentials occurring in units of time is proportional to the intensity of the transmitted signal. The typical frequency action potential is between 4 and 12 Hz. Electrical stimulation can artificially generate this action potential by altering the electrical potential across the nerve cell membrane (this also includes the neural axons) by inducing an electrical charge around the outer cell membrane.
FES devices make use of this property to activate nerve cells electrically, which can then activate muscles or other nerves. However, special care must be taken in designing a safe FES device, since passing an electrical current through the network can cause adverse effects such as decreased stimulation or cell death. This may be due to thermal damage, electroporation of cell membranes, toxic products from electrochemical reactions on the electrode surface, or too much excretion of targeted neutrons or muscles. Usually FES is associated with neuronal and neuronal stimulation. In some applications, FES can be used to directly stimulate the muscles, if their peripheral nerves have been broken or damaged (ie, those with denatured muscles). However, most of the FES systems used today stimulate nerves or the point at which intersections occur between nerves and muscles. The stimulated nerve bundle includes the motor nerve (the efferent nerve - the nerve decreases from the central nervous system to the muscle) and the sensory nerve (the afferent nerve - rises the nerve from the sensory organs to the central nervous system).
Electric charge can stimulate motor and sensory nerves. In some applications, the nerves are stimulated to produce local muscle activity, that is, stimulation is aimed at producing direct muscle contraction. In other applications, stimulation is used to enable simple or complex reflexes. In other words, the afferent nerve is stimulated to generate reflexes, which is usually expressed as a coordinated contraction of one or more muscles in response to sensory nerve stimulation.
When the nerve is stimulated, that is, when sufficient electrical charge is given to the nerve cell, local depolarization of the cell wall occurs producing a spreading action potential to both ends of the axon. Typically, one "wave" of action potential will propagate along the axon toward the muscle (orthodromic propagation) and simultaneously, the "waves" of other action potentials will propagate toward the body cell in the central nervous system (antidromic propagation). While the direction of propagation in cases of antidromic stimulation and sensory nerve stimulation are the same, that is, toward the central nervous system, the final effect is very different. Antidromic stimulants have been regarded as irrelevant side effects of FES. However, in recent years the hypothesis has been presented indicating the potential role of antidromic stimulation in neurorehabilitation. Usually, FES deals with orthodromic stimulation and uses it to produce coordinated muscle contractions.
In cases where the sensory nerves are stimulated, the reflex arc is triggered by stimulation of sensory nerve axons at certain peripheral sites. One such reflex example is the reflex withdrawal flexor. Reflex withdrawal of the flexor occurs naturally when suddenly, the pain sensation applied to the sole of the foot. This results in flexion of the affected hip, knee and ankle, and the extension of the contralateral foot to gain legs from painful stimuli as quickly as possible. Sensory nerve stimulation can be used to produce desirable motor tasks, such as evoking reflex withdrawal flexors to facilitate walking on individuals after a stroke, or they may be used to alter reflexes or functions of the central nervous system. In the latter case, electrical stimulation is generally described by the term neuromodulation .
The nerves can be stimulated using surface (transcutaneous) or subcutaneous (percutaneous or implanted) electrodes. The surface electrode is placed on the surface of the skin above the nerve or muscle that needs to be "activated". They are non-invasive, easy to apply, and generally cheap. Until now the general belief in the FES field is that because of the impedance of skin-electrode contact, skin and impedance tissue, and current dispersion during stimulation, pulses of much higher intensity are needed to stimulate the nerve using surface stimulation electrodes compared with subcutaneous electrodes.
(This statement is true for all commercially available stimulators except the MyndMove stimulator, which has applied a new stimulation pulse that allows the stimulator to produce muscle contraction without causing discomfort during stimulation, which is a common problem with commercially available transcutaneous stimulation systems.)
A major limitation of transcutaneous electrical stimulation is that some nerves, such as those that conserve the hip flexor, are too deep to be stimulated using surface electrodes. This limitation can be partially solved by using an electrode array, which can use multiple electrical contacts to increase selectivity.
The subcutaneous electrode can be divided into percutaneous and implantation electrodes. The percutaneous electrode consists of a thin wire inserted through the skin and into the muscle tissue close to the targeted nerve. These electrodes usually remain in place for a short period of time and are only considered for short-term FES interventions. However, it should be mentioned that some groups, such as the Cleveland FES Center, have been able to use percutaneous electrodes safely with individual patients for months and years at a time. One disadvantage of using percutaneous electrodes is that they are susceptible to infection and special care must be taken to prevent such occurrences.
The other subcutaneous electrode class is the planted electrode. It is permanently grown in the consumer body and remains in the body for the rest of the consumer's life. Compared with surface stimulation electrodes, percutaneous implants and electrodes potentially have higher stimulation selectivities, which are characteristic of the desired FES system. To achieve higher selectivity while applying a lower amplitude of stimulation, it is recommended that both the cathode and the anode be around the stimulated nerve. The downside of the implanted electrodes is that they require invasive surgical procedures to be installed, and, as with any surgical intervention, there is the possibility of infection following implantation.
The typical stimulation protocol used in clinical FES involves electric pulse trains. Biphasic, balanced pulse filled is used because they increase the safety of electrical stimulation and minimize some of the side effects. Pulse duration, pulse amplitude and pulse frequency are key parameters set by FES devices. The FES device can be either a regulated current or voltage. The current FES system always sends the same charge to the network regardless of skin/network resistance. Therefore, the current FES system does not require frequent adjustment of stimulation intensity. Regulated voltage devices may require frequent intensity adjustment of stimuli as their charge changes as the skin/tissue resistance changes. The properties of pulse stimulation stimuli and how many channels are used during stimulation determine how complex and sophisticated FES-induced functions are. These systems can be as simple as FES systems to strengthen muscles or they can be complex like the FES system used to deliver simultaneously grabbing and grasping, or bipedal motion.
Note: This paragraph was developed in part using the material from. For more information about FES, please consult and other references provided in the paragraph.
Maps Functional electrical stimulation
History
FES was originally referred to as Functional Electrotherapy by Liberson, and it was not until 1967 that the term Functional Electric Stimulation was created by Moe and Post, and was used in a patent entitled, "Electrical stimulation of muscles deprived of nerve control with views giving muscle contraction and generating useful moments functionally ". Patent Offner describes the system used to treat footprints.
The first commercially available FES device handles foot decline by stimulating the peroneal nerve during walking. In this case, the switch, located at the tip of the user's shoe heel, will activate the stimulator imposed by the user.
General apps
Spinal cord injury
Injury to the spinal cord interferes with electrical signals between the brain and muscles, resulting in paralysis below the level of injury. Restoration of limb function and organ function setting is the main application of FES, although FES is also used for the treatment of pain, pressure, pain prevention, etc. Some examples of FES applications involve the use of Neuroprostheses that allow people with paraplegia to walk, stand up, restore handheld functioning of the hands to people with quadriplegia, or restore bowel and bladder function. FES high intensity of the quadriceps muscle allows patients with lower motor neuron lesions to increase their muscle mass, muscle fiber diameter, improve ultrastructural organization of contractile materials, increase force output during electrical stimulation and perform stand-up FES assisted exercise.
Walk in spinal cord injury
Kralj and his colleagues describe the technique for paraplegic gait using surface stimulation, which remains the most popular method used today. Electrodes are placed over the quadriceps muscles and peroneal nerves bilaterally. The user controls the neuroprosthesis with two buttons attached to the left and right handles of the walking frame, or on a stick or crutch. When neuroprosthesis is turned on, both of the quadriceps muscles are stimulated to provide standing posture. Electrodes are placed over the quadriceps muscles and peroneal nerves bilaterally. The user controls the neuroprosthesis with two buttons attached to the left and right handles of the walking frame, or on a stick or crutch. When neuroprosthesis is turned on, both of the quadriceps muscles are stimulated to provide standing posture. An alternative approach to the Kralj technique is the FES system for walking is developed using Compex Motion neuroprosthesis. Compex Motion neuroprosthesis for walking is an eight to sixteen channel surface FES system that is used to voluntarily restore walking on individual stroke injuries and spinal cord injuries. This system does not use peroneal nerve stimulation to activate movement. Instead, it activates all the relevant lower limb muscles in a sequence similar to that used by the brain to activate motion. Hybrid aids systems (HAS) and RGO neuroprosthes running are devices that also apply active and passive braces, respectively. Braces are introduced to provide additional stability during standing and walking. The main limitation of neuroprostheses for walking based on surface stimuli is that the hip flexors can not be directly stimulated. Therefore, hip flexion on walking must come from a voluntary effort, which is often absent in paraplegia, or from a flexor withdrawal reflex. Embedded systems have the advantage of being able to stimulate hip flexors, and therefore, to provide better muscle selectivity and better gait patterns. A hybrid system with exoskeleton has also been proposed to solve this problem. This technology has proven successful and promising, but at the moment this FES system is mostly used for training purposes and rarely as an alternative to wheelchair mobility.
Stroke and upper limb recovery
In the acute stage of stroke recovery, the use of cyclic electrical stimulation has been seen to increase the extensor isometric strength of the wrist. To increase the extensor strength of the wrist, there should be a degree of motor function in the wrist spared after stroke and have significant hemiplegia. Patients who will benefit from cyclic electrical stimulation of wrist extensors should be highly motivated to follow up with treatment, After 8 weeks of electrical stimulation, increased grip strength may be apparent. Many scales, which assess the upper extremity's defect rate after a stroke, use grip strength as a common good. Therefore, an increase in the extensor strength of the wrist will decrease the level of upper limb incapacity.
Patients with hemiplegia after stroke generally have shoulder pain and subluxation; both will interfere with the rehabilitation process. Functional electrical stimulation has been found to be effective for pain management and reduction of shoulder subluxation, as well as accelerating the rate and rate of motor recovery. Further, the benefits of FES are maintained over time; studies have shown that benefits are maintained for at least 24 months.
Drop leg
Dropping of the feet is a common symptom in hemiplegia, characterized by a lack of dorsiflexion during the gait swing phase, resulting in short, shuffling steps. It has been proven that FES can be used to effectively compensate for leg loss during the swing phase of gait. At a time before the phase escapes from gait, the stimulator provides a stimulus to the general peroneal nerve, resulting in muscle contraction responsible for dorsoflection. There are currently a number of drop-foot stimulators that use surface FES technology and are embedded. Foot drop stimulants have been successfully used with a variety of patient populations, such as stroke, spinal cord injury and multiple sclerosis.
The term "orthotic effect" can be used to describe an immediate improvement in the function observed when individuals switch on their FES devices compared to walking without assistance. This increase disappears once the person is shutting down their FES device. In contrast, "training" or "therapeutic effect" is used to describe long-term improvement or function recovery after a period using an existing device even when the device is turned off. Further complications for measuring orthotic effects and any long-term training or therapeutic effects are the presence of so-called "carry over effects". Liberson et al., 1961 was the first to observe that some stroke patients seem to benefit from temporary improvement in function and are able to harden their feet for up to an hour after electrical stimulation has been shut down. It has been hypothesized that this temporary increase in function may be associated with long-term training or therapeutic effects.
Stroke
Hemopharetic stroke patients, which are affected by denervation, muscle atrophy, and spasticity, usually experience abnormal walking patterns due to muscle weakness and inability to voluntarily contract certain ankle and hip muscles at appropriate walking phases. Liberson et al., (1961) was the first to pioneer FES in stroke patients. Recently, there have been a number of studies that have been done in this field. A systematic review conducted in 2012 on the use of FES in chronic stroke included seven randomized controlled trials with a total of 231 participants. This review found a small treatment effect to use FES for a 6 minute walking test.
Multiple sclerosis
FES has also been found useful for treating foot decline in people with multiple sclerosis. The first usage was reported in 1977 by Carnstam et al., Which found that it was possible to produce increased strength through the use of peroneal stimulation. More recent studies examined the use of FES compared with exercise groups and found that despite the orthotic effects for FES groups, no training effects in the run speed were found. Further qualitative analysis included all participants from the same study finding an increase in daily life activity and decreasing the number of falls for those using FES compared with exercise. A small, longitudinal observational study (n = 32) has found evidence for significant training effects through the use of FES. With NMES treatment there are measurable advantages in outpatient function.
However, larger observational studies (n = 187) support previous findings and found a significant increase in orthotic effects for walking speed.
Cerebral palsy
FES has been found to be useful for treating symptoms of cerebral palsy. A recent randomized controlled trial (n = 32) found significant orthotic and training effects for children with unilateral spastic cerebral palsy. Improvements are found in gastrocnemius flexibility, community mobility and balance skills. A recent comprehensive literature review of areas using electrical stimulation and FES to treat most children with disabilities includes studies on children with cerebral palsy. The reviewers summarize the evidence as a treatment that has the potential to increase a number of different areas including muscle mass and strength, spasticity, passive range of movement, upper limb function, walking speed, leg position and kinematic ankle. A further review concludes that adverse effects are rare and this technology is safe and well tolerated by this population.
National Institute for Health and Care Excellence Guidelines (NICE) UK)
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