Peripheral Neuropathy is a medical condition in which there is damage to nerves in the peripheral nervous system. Peripheral neuropathy is often caused by damage or irritation to the conducting fibers of the nerves and / or damage to the insulating substance protecting the nerve. Peripheral neuropathy results in a thinning, patchy, or complete loss of their myelin sheath which results in partial or complete block of motor, sensory & autonomic communication from the brain.
There are more than 100 types of peripheral neuropathy with a variety of symptoms and prognosis. In general, peripheral neuropathies are classified according to the type of damage to the nerves. Distal peripheral neuropathy starts with damage to the end of a nerve farthest from the brain or spinal cord. Some forms of neuropathy involve damage to only one nerve and are called mono-neuropathies. Damage to several nerves is known as poly-neuropathy.
About 60 percent to 70 percent of people with diabetes have mild to severe damage to the nervous system. The symptoms of peripheral neuropathy can vary depending on whether motor, sensory, or autonomic nerves are damaged. Peripheral neuropathy is commonly known to affect one or all types of nerve simultaneously. The details of each nerve disorder include:
Sensory nerve damage
- Lack of sense of touch & vibration in hands & feet
- Failure to sense light & temperature
- Loss of reflexes & coordination such as walking pushing buttons
- Failure to sense injury such as cut or infection.
- Failure to detect pain (warning) of heart attack.
- Loss of pain sensation (problem in diabetes), contributing to the high rate of lower limb amputations among this population.
- Loss of sensory nerves can cause emotional stress, anxiety & quality of life
- Pain affects sleep and adds to the emotional stress
- Over sensing in the skin, so that people feel severe pain
- Sensory neuropathy may lead to changes in the skin, hair, as well as to joint and bone damage.
Motor nerve damage
- Muscle weakness. Other symptoms may include
- Painful cramps
- Muscle twitching visible under the skin), muscle atrophy (severe shrinkage of muscle size), and decreased reflexes.
- Debilitating motor skills (muscles for walking, talking hand control)
Autonomic nerve damage
- Affects function of the nearly every organ in the body
- Dysfunction of the parasympathetic and sympathetic nerves
- Inability to sweat normally (Sudomotor dysfunction), which may lead to heat intolerance
- Loss of bladder control
- Inability to regulate blood pressure (to expand or contract blood vessels).
- Sudden drop in blood pressure sitting to standing position (Orthostatic hypotension)
- Dizziness, light headed, or fainting (syncope)
- Irregular heartbeats (arrhythmia)
- Gastrointestinal symptoms (diarrhea, constipation)
- Difficulty swallowing
Peripheral neuropathy can be caused by a variety of factors. Since multiple nerves are affected by peripheral neuropathy, it is commonly referred to idiopathic neuropathy. This is because the specific cause of the neuropathy may not be identified. Some of the common causes of peripheral neuropathy include:
- Physical injury (trauma)
- Repetitive stress
- Frequently leads to entrapment neuropathies, a form of compression injury
- Repetitive, forceful activities that stress joints for prolonged periods
- Diseases or disorders that cause inflammation constricting nerve pathways
- Damage to muscle, tendons, ligaments, tendons that cause inflammation
- Metabolic and endocrine disorders (diabetes affects the ability to transform nutrients into energy & process waste products)
- High blood glucose levels (leading cause of peripheral neuropathy in the US)
- Overproduction of growth hormone (affects joints causing pain)
- Vasculitis (blood vessel inflammation constricts blood flow)
- Small vessel disease
- Autoimmune diseases (Immune system attacks the body’s own tissues)
- Sjogren’s syndrome, lupus, and rheumatoid arthritis
- Kidney dysfunction (high toxins can damage nerves)
- Cancers, tumors (compress nerve fibers)v
- Infections (viruses & bacteria)
- The human immunodeficiency virus (HIV)
- Exposure to toxins (including medication)
- Environmental or industrial toxins (exposure to lead, mercury & arsenic materials)
- Heavy alcohol consumption
In the case of diabetic autonomic neuropathy, the nerve damage typically progresses in an upward ascending pattern. The first evidence of nerve dysfunction occurs in the distal / peripheral region (feet) where the greatest distance exists from the brain. In the early (often asymptomatic) stages, the progression of the disease begins with microvascular dysfunction which can be detected using standard Sudomotor testing. The presence of microvascular dysfunction can lead to damage to the micro capillaries causing sudomotor (sweat) dysfunction. Sudomotor dysfunction is known as a form of autonomic dysfunction in which the autonomic nervous system fails to automatically stimulate a sweat response when needed.
Mild sudomotor dysfunction can cause damage to the sympathetic cholingergic fibers (C Fibers) which reduces nerve density over time. The damage to the nerves can progress causing pain or numbness (sensory nerves) in the feet with gradual progression upward. Peripheral diabetic neuropathy can progress to the hands, fingers ultimately to the heart (cardiac autonomic neuropathy).
Peripheral neuropathy may also cause foot deformities & blisters may exist in the numb areas because pressure & injury are often undetected by the patient. If the injury is not treated, infection & further damage can occur and spread to other areas. The infection may spread to the bone, and the foot may then have to be amputated. Many amputations are preventable if minor problems are caught and treated in time.