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Pathology

Peripheral Neuropathy

Peripheral Neuropathy is one of the most common forms of disease within the Peripheral Nervous System. Damage or malfunction in peripheral nerves generates not only acute and chronic pain, but also changes in sensory pathways. In response to such nerve damage, restorative processes, including Inflammation and other proinflammatory processes, create hyperexcitability within the sensory neurons, called peripheral sensitization. These peripheral nerve fibers are then able to associate with nociceptive fibers and are then able to elicit pain. This sensitization pathway is not functioning during either normal tissue operation or lack of inflammation unless the sensory neurons are been permanently damaged. The pain that stems from Peripheral Neuropathy stems from NMDA receptors and the release of the neurotransmitter glutamate from sensory neurons in the brain. Release of glutamate and coupled neurotransmitters that connect neurokinin receptors causes release of magnesium and calcium ions while simultaneously activating NMDA receptors. This causes postsynaptic cells to send a painful signal to the brain. Upon interaction with Calcium, the NMDA receptors become more sensitive and the neuronal threshold is lowered. Mononeuropathy is a subset under the broad context of Peripheral Neuropathy and occurs only when a single nerve outside of the Central Nervous System is affected. The most common forms of mononeuropathy are when physical stress is placed on a particular nerve, known more specifically as compression neuropathy. One of the most common forms of mononeuropathy is carpal tunnel syndrome. Common symptoms of carpal tunnel syndrome include pain and numbness in the thumb, index and middle finger. One of the major causes of carpal tunnel syndrome is demyelination of axons through mechanical stress. A lack of myelin can prevent nervous transmission and eventually, development of an endoneural edema. This culminates in the degeneration of axons and release of pro inflammatory molecules, causing pain and redness. Other subsets of peripheral neuropathy include polyneuropathy which causes pain in similar areas on both sides of the body, diabetic neuropathy or nerve damage associated with diabetes mellitus, and autonomic neuropathy which consists of peripheral nerve damage that directly affects the autonomic nervous system.