Diabetes 21, Diabetic neuropathy
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Part of the cause of diabetic peripheral neuropathy is damage to the Schwann cells which form the myelin sheath around peripheral nerves. Schwann cell damage probably occurs for metabolic reasons and can lead to areas of demyelination. As part of the function of Schwann cells is to protect and nourish the nerve fibres there will be progressive fibre degeneration. In peripheral nerves the microvascular changes already described are likely to be an additional factor in the development of peripheral neuropathy. Ischaemia of peripheral nerves will lead to hypoxic damage as neurones are very sensitive to oxygen lack. Evidence for this comes from the fact that unmyelinated nerve fibres are affected as well as the myelinated fibres. Initially there will be shrinkage of axons followed by fragmentation. Neuropathy can lead to sensory and motor deficiency in the legs and often presents with tingling and numbness. Sensory neuropathy is the most common presentation resulting is reduced sensation and pain awareness from the feet. This can result in the patient being unaware of developing injuries to the feet. Bladder problems and impotence may also be caused by peripheral nerve defects.