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Functional Electrical Stimulation (FES) - how does it aid the rehabilitation of spinal cord injury (SCI)?
By: Belinda Small - 05.07.07 (See writers details & Paralinks position on articles below.)
An great intervention used in the rehabilitation of a Spinal Cord Injury (SCI) is known as Functional Electrical Stimulation (FES).To understand FES we first need to comprehend what SCI is and the different classifications. Firstly it is damage to the spinal cord as a result of trauma (car accident) or disease (Spina bifida). Loss of sensation, function and reductions in mobility are outcomes of damage to the spinal cord. The site of the lesion along the spinal cord indicates the extent of paralysis. Lesions to the cervical spine (neck) are known as tetraplegia (quadriplegia), whilst lesions to the thoracic, lumbar and sacral regions are known as paraplegia. Quadriplegia means that there is loss of function of sensation in all four limbs, whilst paraplegics have reduced function or paralysis to the lower areas of the body. There are two distinct types of lesions in SCI; complete and incomplete. A complete lesion means that there is complete paralysis below the individualís lesion. An incomplete injury is when the spinal cord is only partially damaged. Depending on the location of the damage within the spinal cord can determine which parts of the body have reduced function or sensation. Over recent years there has been a gradual shift in incidence from complete to incomplete injuries. This could be attributed by better preventative measures and resuscitation methods.
The spinal cord contains Upper Motor Neurons (UMN) and Lower Motor Neurons (LMN). SCI can affect one or both of these neurons. UMNís are located within the spinal cord and carry messages to and from the brain to the spinal nerves along the spinal tract. The UMNís travel down the descending tracts of the spinal cord and send messages to begin muscle contraction. The LMNís are the spinal nerves that branch out from the spinal cord to other areas of the body. In SCI these signals canít pass the lesion and the muscles arenít able to be ďturned onĒ resulting in a reduction of sensation or function. FES can be used to turn on the muscles to help in atrophy (loss of muscle mass) by by-passing the lesion.
A great way of producing contractions in muscles that are paralysed is by means of FES. This is done by producing small pulses of electrical stimulation to nerves that supply the muscle. Advances in research into this area of rehabilitation with people affected by SCI has been of great importance in recent years. Applications of electrodes are either by surface stimulation, percutaneous fine wires or implanted electrodes. Implanted electrodes can be invasive but they have two advantages: they gain precise stimulation of the targeted muscle and they eliminate the turning on and off of electrodes. FES can only be effective in people with no significant lower motor neuron damage as direct excitation of the nerve and not just the muscle results in muscle activation.
Depending on the sites in which the electrodes are placed is significant to which muscles are affected and how they are contracted. FES in the upper extremity is seen to help improve hand grasp especially for those people with C5 and C6 tetraplegia. Lower extremity FES can be an implanted system that helps people with varying degrees of paraplegia and tetraplegia stand up, transfer and walk (with aid). Implantation of electrodes in the lumbar paraspinal muscles and lower extremities has seen to significantly improve trunk control. Stimulation of the sacral nerve roots helps to retain bladder control; it also has been seen to help in the reversal of erectile dysfunction.
Another common problem after SCI includes pressure ulcers. FES can significantly reduce the occurrence of this skin trouble by increasing the size of the glueteal muscles to give pressure relief of the sacral seating surface.
Scientists have discovered that different frequencies used in FES have distinctly different physiological effects. 50-100Hz is used in the control of muscle spasticity; 25-50Hz aids in efficient step-like knee and hip flexion and in frequencies lower than 15Hz only extensor movements are produced. The varying amounts of frequency help to control the movements in the patient most ideal for rehabilitation.
For people with incomplete SCI, complex electrical stimulation to achieve walking has been used. Muscle activation is sequenced by a computer. The computer sends a current to the stance limb that starts contraction of the quadriceps and gluteus muscles. The opposite leg receives a stimulus that creates hip flexion which is created from a reflex (withdrawal reflex) produced by the other leg. So who is eligible for this type of training? Studies suggest that it should only be used once the patient is able to stand with electrical stimulation for at least 3-5 minutes.
One study showed that a vast majority of participants in the study had demands for improvements in bowel, bladder and sexual function as well as demonstratable demand for walking improvements. Popularity for increased muscle size for cosmetic reasons was also a priority among this particular group. In the same study they revealed that only 2% of the participants had used the FES system for walking suggesting that it isnít sought of as an effective method in rehabilitation. However various other studies have found significant increases in muscular hypertrophy (size) and strength from the use of the FES system.
So what are the overall benefits of FES? In addition to the main purposes that FES has been used for, patients that have used the FES system have reported improved appearance of the legs, decreased spasms, increased blood flow, better skin quality, increased strength, enhanced trunk control, decreases in erectile dysfunction, increased bladder and bowel control, increased cardiovascular fitness, reduction in pressure ulcers, increased rates of bone turn over, restoration of respiratory function and improved locomotion.
NOTE: This paper is from Belinda Small. I am currently in my third year studying B. Exercise Science at the Australian Catholic University in Strathfield (NSW). This semester one of the subjects I am studying, Advanced Motor Control and Learning, requires me to write an article regarding any area of my choice involving motor learning and its relationship to the central nervous system. The topic I have chosen is on Spinal Cord Injury (SCI) and Functional Electrical Stimulation (FES) in a rehabilitation setting.
Our unit outline specifies that we seek to be published in an appropriate setting with a specific audience. I found Paralinks through internet surfing and thought this might be a good place to submit my article. I would greatly appreciate if you read over my article and consider posting it in your electronic magazine.
Yours sincerely; Belinda Small
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