In his lecture on Targeted Muscle Reinnervation (TMR), Dr. Gregory A Dumanian explained amputees can have their nerves, which are still functioning even after the loss of the limb, and reattach them into larger muscle groups. This is exercised as when a limb is lost, the nerves that are associated with that limb are still functioning and receiving neuronal signals. Because these signals have nowhere to go, the ends of the neurons swell up and cause severe pain to the individual. The expression of these signals account for the phantom limb sensation. The phantom limb sensation are the feelings that an individual experiences in regards to a limb or organ that is not physically part of the body. Fortunately, Dr. Dumanian was able to use TMR to prevent the pains by reinnervating them into muscles, such as the pectoral muscle in the chest. In doing so, patients were able to regain full sensory and mobile abilities when a prosthetic limb was attached in place of the amputated limb. Upon attachment of the prosthetic limb, patients were able to regain their mobility. What is astonishing is that when moving their limb, they were not doing anything special. They simply reported that they imagined their arm moving, and due to TMR, the prosthetic was functioning as though it were the original arm.
As seen with Melissa Loomis from Ohio, who lost her arm when she tried to separate her pets from fighting with a raccoon. The arm that was given to her was advanced high technology. “It designed to integrate with the body and use the brain’s natural neurotransmissions for control.” (Moncrieffe). As seen with the TMR in Dr. Dumanian’s presentation, the stimulation cap processed the electric signals directly from the nerves to the prosthetic. This is what reactivated the pathways that originally were there with her original arm. As these pathways are reawakened, there is minimal, if not any, learning involved with the prosthetic as it is all based on what is there with muscle memory and the nerves telling the prosthetic the action it needs to perform. What is even more interesting here is how Mike McLoughlin, a chief engineer of Research and Exploratory Development Department at APL managed to bring back the sense of touch to Loomis. This involved placement of 100 sensors in the arm to send feedback through the reinnervated nerves, thus allowing Loomis to experience her sense of touch.
In creation of this prosthetic, the main focus for McLoughlin was to ensure to the patient that they were controlling the prosthetic, and not the other way around. Loomis describes how natural it was for her to just motion her making a fist and having witness the prosthetic to the same was amazing. With this innovation, McLoughlin wishes to further ease the process of adding a prosthetic limb to the body through noninvasive techniques. The sole purpose of the prosthetic to begin with it is to bring back mobility and sensory abilities to those who have lost them. Future aims also include cost reductions for patients to afford such high tech prosthetics.
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