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Peripheral Nerve Injuries

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Peripheral nerves are bundles of nerve fibers that exit the spinal cord individually or via two main plexuses known as the brachial plexus and the lumbosacral plexus. Peripheral nerve fibers transmit sensory and motor information between the body and the central nervous system (brain and spinal cord) through ventral and dorsal roots. Axons of motor neurons innervate muscles to produce both voluntary and involuntary movements. On the other hand, sensory axons make connections with sensory receptors in the skin to detect pain and sensation.
Stretch-related injuries, compression, and lacerations are among the three most common peripheral nerve injuries (Burnett). The severity and the amount of disruption to the internal structures of the nerve …show more content…

During this process the part of the axon distal to the site of injury begins to degenerate and break apart. The cell body increases in size, causing protein and RNA metabolism to increase assisting in the repair process. Myelin is altered into fat and phagocytized by macrophages. Since the nerve has loss of continuity the muscle will atrophy. In some severe cases, degeneration may extend proximal to the site of the lesion as well as distally. An influx of calcium into the axon is required for the sealing over process. Hours after the injury has occurred, the distal ends of the lacerated axon seal over and become inflamed with Schwan cells, fibroblasts and other growth factors allow for anterograde and retrograde axonal transport to continue for several days (Campbell). Additionally, as part of the degeneration process it has been seen that certain growth associated genes such as, growth associated protein-43 (GAP-43) mRNA, brain derived neurotropic factor (BDNF) and its receptor TrkB mRNA are elevated after injury to peripheral nervous tissue. The use of brief electrical stimulation has been shown to enhance and accelerate the expression of TrkB and BNDF thus, resulting in a positive effect on nerve regeneration (Al-majed and Geremia). Several mechanisms have been found to explain the role of electrical stimulation in promoting nerve regeneration. It is seen that electrical stimulation can employ its effects through elevating cAMP levels, expression of neurotrophic factors and regeneration-associated genes as well as having a direct impact on Schwann cells.

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