Tuesday, December 12, 2023

Artificial Prosthetic Nerve Innervation in the Alleviation of Phantom Limb Pain

Amputee patients have been at the forefront of prosthetic advancement for generations. Acting as the leading determinants of artificial limb efficacy throughout its scientific progression, these individuals have proven to reveal the most promising input in terms of developing prosthetics which most accurately mirror human limb capabilities. Subsequently, advancements in prosthetics have shown to not only improve quality of life through the simplification of day to day processes, but also through a potential ability to lessen the negative side effects associated with losing a limb, such as the phenomenon known as Phantom Limb Pain (PLP), where individuals experience uncomfortable sensations at the location of their vacant limb. 

In the scientific article, Robotic Leg Control with EMG Decoding in an Amputee with Nerve Transfers, Dr. Hargrove and his colleagues discovered that when utilizing electromyographic (EMG) signals in congruence with both native and surgically innervated muscles at the site of amputation, a knee amputee was able to successfully transition their leg movements on various terrains and when sitting down. This targeted muscle stimulation (TMS) which permitted these overall seamless movements has catalyzed the improvements of artificial limbs via neurological intervention. 

Similarly, the article, Brain (re)organisation following amputation: Implications for phantom limb pain, Dr. Tamar Makin underlines homunculus remapping of neurological somatotopic maps, in which amputee patients can experience a perceived sensation in their missing limb when a still present body part is physically stimulated. This is possible due to the overlapping representation of body parts within these map pathways, which detect stimulation even in a limb lost due to trauma or surgical amputation. These sensations can progress to feelings of discomfort and varying degrees of pain seen in PLP, leaving the patient with no means of assuaging this affliction. This article, however, also draws a potential solution through a connection to Dr. Hargrove's work, insinuating that by implementing a neurologically innervated prosthetic limb, the patient's neural plasticity – alongside manipulated nerve innervation - can develop the brain's awareness of a present limb, redirecting pain signals away from other bodily detection and alleviating PLP over time.

Overall, the cooperation of technological improvements in prosthesis development and the advancement of understanding brain mechanisms through the body's central and peripheral nervous system continue to make substantial progress in improving the lives of amputees based on individual cases. With these various realms of neurological study being explored, individuals have been given the freedom to choose how they wish to continue their lives post-amputation, whether that focuses on finding the most eloquent, advanced prosthetic or simply living everyday without incessent pain. 


References:

Hargrove, L. J., Simon, A. M., Young, A. J., Lipschutz, R. D., Finucane, S. B., Smith, D. G., & Kuiken, T. A. (2013). Robotic Leg Control with EMG Decoding in an Amputee with Nerve Transfers. New England Journal of Medicine, 369(13), 1237–1242. https://doi.org/10.1056/nejmoa1300126

Makin, T. R., & Flor, H. (2020). Brain (re)organisation following amputation: Implications for Phantom Limb Pain. NeuroImage, 218(1), 116943. https://doi.org/10.1016/j.neuroimage.2020.116943


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