The peripheral nervous system is involved in the communication and exchange of signals between the central nervous system (brain and spinal cord) and other parts of the body. The peripheral nervous system consists of three types of nerves, namely, sensory nerves, motor nerves, and autonomic nerves. Sensory nerves are responsible for carrying sensory information from different organs to the central nervous system; whereas, the motor nerves carry information from the central nervous system to the muscles. The autonomic nervous system is responsible for the involuntary actions of the body, such as respiration; gastrointestinal and cardiovascular (blood pressure, heart rate).(1)
How Common Is Peripheral Neuropathy or Is It A Rare Disease?
Peripheral neuropathy is due to damage or destruction of any of these nerves that disrupts the normal activity of the nerve and in the conduction of electrical impulses through and fro from the central nervous system to the muscles and vice versa. Peripheral neuropathy can either affect one, a combination of nerves types or all the nerves. Peripheral neuropathy is a very common condition and it affects approximately 25-30% of the Americans. It is all the more common in diabetics, affecting about 60-70% of all the patients of diabetes. Although neuropathy affects all age groups, older people are at an increased risk of developing neuropathy. It is also more common in men of Caucasian descent. There is also an increased risk in certain professions, such as those with repetitive tasks leading to the development of compression-related neuropathy.(1)
Causes Of Peripheral Neuropathy
Peripheral neuropathies are either hereditary or acquired, although acquired neuropathies are much more common than hereditary neuropathies. Acquired neuropathies can either be idiopathic (with no known cause) or be symptomatic (due to another condition/disorder). The various causes of acquired neuropathy include:
Physical trauma: It is the most common single nerve injury that can happen due to falls, accidents, sports, and medical procedures/conditions, which can lead to stretching, crushing, compressing or detaching of the nerve from the spinal cord. Broken or dislocated bone slipped disk, arthritis, repetitive or prolonged pressure on a nerve can all lead to nerve injury. Ulnar neuropathy and carpal tunnel syndrome are two examples of compressive neuropathy.(2)
Diabetes: It is the leading cause of polyneuropathy in the US. Approximately 60-70% of individuals with diabetes have mild to severe damage of sensory, motor or autonomic nerves causing numbness, tingling burning sensation, pain or weakness.(2)
Vascular and blood-related problems: Smoking, diabetes, arterial narrowing from high blood pressure or atherosclerosis and scarring or blood wall thickening from vasculitis can lead to patchy nerve damage causing mononeuropathy multiplex or multifocal mononeuropathy.(2)
Systemic autoimmune diseases including lupus, Sjogren’s syndrome, rheumatoid arthritis can lead to neuropathic pain. Hormonal imbalances also disturb normal metabolic processes causing tissue swelling that may compress peripheral nerves. Kidney and liver disorders lead to accumulation of toxins in the body that may damage nerve tissues. Nutritional/vitamin imbalance, alcoholism, and exposure to toxins lead to nerve damage. Vitamin B12 deficiency and vitamin B6 excess are well-known examples of vitamin imbalance neuropathy. The paraneoplastic syndrome can also lead to nerve damage. Chemotherapeutic agents along with radiation therapy may lead to polyneuropathy in about 30-40% patients. Infections (varicella-zoster virus, cytomegalovirus, herpes simplex, West Nile virus, Lyme disease, HIV lead to neuropathy. About 30% of patients with HIV can develop peripheral neuropathy and 20% develop distal neuropathic pain.(2)
Polyneuropathies related to genetics are rare. These can either be inherited or be sporadic or de novo (new mutation in an individual not passed down by the parents). There are genetic mutations that can cause only mild symptoms, which are noticed in early adulthood and lead to only mild impairment. While there are others that cause severe neuropathies and appear in infancy or childhood. Charcot Marie Tooth disease, also known as hereditary motor and sensory neuropathy, is the most common inherited neuropathic disorder. Small fiber neuropathies with pain itch and autonomic symptoms can also be genetic in nature.(2)
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