Scientists across the world have been working to develop spinal cord implants to aid in the recovery of paralyzed patients. Implants do not cause re-development of any neurological functions.
However, patients may be able to walk again with the use of these devices. When coupled with physical therapy, spinal cord implants allow patients to take their first steps since receiving a debilitating spinal cord injury. Studies conducted on the implants indicate approximately three out of five participants regained the ability to walk a short distance through repeated use of implanted devices in spinal cords.
Spinal cord implants effectively work to stimulate the spinal cord below the site of injury which increases the brain’s ability to regain control of neurological transmitters located in this region. The overall effectiveness of the implants is dependent upon the participant, as the implants only begin to function properly when the patient is commanding themselves to move forward. Still, for those whose mobility has been limited, these newest developments are heralding new possibilities.
When a spinal cord injury occurs, the signals transmitted from the brain to the spine are significantly weakened. Through this deterioration, the loss of motor function to the limbs takes place and leaves the affected individual paralyzed. Scientists working to develop a solution to these injuries found that the brain may still transmit signals to the damaged spinal region though the signals are not strong enough to regain control of the affected limbs. By developing a spinal cord implant, scientists were seeking an alternative method for producing a strong enough signal between the brain and the spine to promote the use of limb function once again.
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Spinal cord implants work by using epidural stimulation, meaning the implants provide an electrical stimulation to the spine mimicking the naturally occurring stimulation from the brain that takes place prior to injury. Once the electronical stimulation occurs, the spine enters an awakened state where it is more likely to receive and interpret the weakened signals transmitted from the brain. The implant itself is composed of 16 electrodes implanted below the site of injury in patients who have become paralyzed through various accidents. Along with the electrodes, doctors implant a battery device inside the abdominal wall of patients to work in connection with the epidural stimulator.
By placing the spinal cord implant below the site of injury, doctors were able to expand coverage over affected areas typically used to send sensorimotor signals from the brain to the legs. In connection with the abdominal battery, which is used to control the frequency and intensity of the stimulation, these implants helped simulate electrical activity in the muscles. Once this occurred, patients who had previously lost all motor control were able to feel the sensation of movement in their legs.
The results recorded in these initial trials indicate the spinal cord implants are only effective when used by some patients. The implants do not work inherently on their own—a patient, after receiving the implants, must work diligently in physical therapy to regain the ability to walk over a prolonged period. Of the four people monitored through a study conducted by Dr. Claudia Angeli and her team at the Kentucky Spinal Cord Injury Research Center, only two were able to walk unassisted after the spinal cord implants were positioned near the site of injury. These two patients had reportedly felt sensation in their limbs prior to receiving the implants, whereas the other two patients described a total loss of motor control following their accident.
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The two patients who gained the ability to walk unassisted had between 80 and 280 sessions of stimulation to the implants occurring over 15 and 85 weeks respectively. These stimulation sessions were accompanied by physical therapy to help the patients regain use of their muscles and to help the patients learn how to walk again. The remaining patients in the trial reported being able to sit and stand independently after receiving spinal cord implants, though they did not regain sensation in their legs and were unable to walk unassisted after repeated stimulation sessions.
Spinal cord implants appear to be more effective when used in some patients than in others, largely due to the patient’s ability to drive the movement of his or her legs. Dr. Kendall Lee of the Mayo Clinic has suggested this occurs because some patients are able to deliver specific stimulation parameters to the injured area whereas others are only capable of delivering random stimulation. Since the use of spinal cord implants in paralyzed patients is in the developmental stages, the devices require additional monitoring over a prolonged period with a larger focus group to determine the exact cause of this discrepancy.
One patient involved in the study overseen by Dr. Angeli suffered a spontaneous hip fracture after a weeklong trial with the spinal cord implants. The other three patients treated in this study saw mainly positive results as they developed the ability to stand, sit and walk short distances with and without assistance. According to Dr. Angeli, the balance between providing an appropriate amount of stimulation and providing too much stimulation has been hard to master throughout the process. If the patient is provided with too little stimulation, the motor functions remain dormant. If the patient is provided with too much stimulation, he or she experiences involuntary leg movements.
As of writing, patients involved in multiple trials across the world have not experienced severe side-effects after receiving spinal cord implants. Many patients report they have regained the use of their limbs through repeated physical therapy and stimulation sessions and have experienced an improved quality of life because of this development. Professor Gregoire Courtine of the EPFL research institute believes the spinal cord implants can be improved upon to provide a higher intensity level through the controlled stimulations. When this occurs, the patient is more likely to receive the appropriate neurotransmitters needed from the brain to control the function of the spinal cord. Low intensity stimulation, like that provided by the current spinal cord implants, does not replicate the naturally occurring electrical activity well enough to sustain continuous movement in the legs.
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