Doctor's Notes on Neuropathy
Neuropathy means any diseases or malfunctions of the nerves. The four main types of neuropathy are Peripheral (nerves outside the brain and spinal cord), Cranial (the 12 cranial nerves), Autonomic (nerves of the involuntary nervous system) and Focal (neuropathy restricted to one area of the body).
General signs and symptoms of neuropathy for all four types of show a gradual loss of feeling, numbness, tingling and/or pain that may progress over time. For peripheral neuropathy, signs and symptoms can also include the inability to determine joint position of the extremities and/or extreme sensitivity to touch by the arms and legs. Cranial neuropathy can evolve one or more of the 12 cranial nerves; the general symptoms of neuropathy may localize mainly to the face and eyes; however, other cranial nerves may show similar symptoms. For autonomic neuropathy, because autonomic nerves control the function organs and glands, they usually produce many different symptoms and signs, depending upon what organs or glands are involved. Signs and symptoms may be one or more of the following: nausea, vomiting, incontinence, abdominal bloating, impotence, dizziness or fainting, constipation or diarrhea, heat intolerance, blurry vision, trembling, sweating and/or palpitations. Signs and symptoms of focal neuropathy may be any of the above signs or symptoms but usually affecting a localized body site like pain, numbness and/or tingling to the right big toe.
The main underlying cause any neuropathy is damage to one or more nerves. Damage to nerves can come from many different sources such as injuries, infections, vitamin deficiencies, toxins, autoimmune problems, diabetes, alcoholism, genetic or inherited disorders, drugs and/or medications, tumors and many others.
Regardless of the cause, neuropathy is associated with characteristic symptoms. Although some people with neuropathy may not have symptoms, certain symptoms are common. The degree to which an individual is affected by a particular neuropathy varies.
Damage to the sensory nerves is common in peripheral neuropathy. Symptoms often begin in the feet with a gradual onset of loss of feeling, numbness, tingling, or pain and progress toward the center of the body with time. The arms or legs may be involved. The inability to determine joint position may also occur, which can result in clumsiness or falls. Extreme sensitivity to touch can be another symptom of peripheral neuropathy. The sensation of numbness and tingling of the skin is medically known as paresthesia.
The loss of sensory input from the foot means that blisters and sores on the feet may develop rapidly and not be noticed. Because there is a reduced sensation of pain, these sores may become infected and the infection may spread to deeper tissues, including bone. In severe cases, amputation may be necessary.
When damage to the motor nerves (those that control movement) occurs, symptoms include weakness, loss of reflexes, loss of muscle mass, cramping, and/or loss of dexterity.
Autonomic neuropathy, or damage to the nerves that control the function of organs and glands, may manifest with a wide variety of symptoms, including:
- Nausea, vomiting, or abdominal bloating after meals
- Urinary symptoms, such as incontinence, difficulty beginning to urinate, or feeling that the bladder was not completely emptied
- Impotence (erectile dysfunction) in men
- Dizziness or fainting
- Constipation or diarrhea
- Blurred vision
- Heat intolerance or decreased ability to sweat
- Hypoglycemia unawareness: Low blood sugar levels (hypoglycemia) are associated with trembling, sweating, and palpitations. In people with autonomic neuropathy, these characteristic symptoms may not occur, making dangerously low blood sugar levels difficult to recognize.
Nerve damage may be caused by a number of different diseases, injuries, infections, and even vitamin deficiency states.
- Diabetes: Diabetes is the condition most commonly associated with neuropathy. The characteristic symptoms of peripheral neuropathy often seen in people with diabetes are sometimes referred to as diabetic neuropathy. The risk of having diabetic neuropathy rises with age and duration of diabetes. Neuropathy is most common in people who have had diabetes for decades and is generally more severe in those who have had difficulty controlling their diabetes, or those who are overweight or have elevated blood lipids and high blood pressure.
- Vitamin deficiencies: Deficiencies of the vitamins B12 and folate, as well as other B vitamins, can cause damage to the nerves.
- Autoimmune neuropathy: Autoimmune diseases such as rheumatoid arthritis, systemic lupus, and Guillain-Barre syndrome can cause neuropathies.
- Infection: Some infections, including HIV/AIDS, Lyme disease, leprosy, and syphilis, can damage nerves.
- Post-herpetic neuralgia: Post-herpetic neuralgia, a complication of shingles (varicella-zoster virus infection) is a form of neuropathy.
- Alcoholic neuropathy: Alcoholism is often associated with peripheral neuropathy. Although the exact reasons for the nerve damage are unclear, it probably arises from a combination of damage to the nerves by alcohol itself along with the poor nutrition and associated vitamin deficiencies that are common in alcoholics.
- Genetic or inherited disorders: Genetic or inherited disorders can affect the nerves and are responsible for some cases of neuropathy. Examples include Friedreich's ataxia and Charcot-Marie-Tooth disease.
- Amyloidosis: Amyloidosis is a condition in which abnormal protein fibers are deposited in tissues and organs. These protein deposits can lead to varying degrees of organ damage and may be a cause of neuropathy.
- Uremia: Uremia (a high concentration of waste products in the blood due to kidney failure) can lead to neuropathy.
- Toxins and poisons can damage nerves. Examples include gold compounds, lead, arsenic, mercury, some industrial solvents, nitrous oxide, and organophosphate pesticides.
- Drugs or medication: Certain drugs and medications can cause nerve damage. Examples include cancer therapy drugs such as vincristine (Oncovin, Vincasar), and antibiotics such as metronidazole (Flagyl), and isoniazid (Nydrazid, Laniazid).
- Trauma/Injury: Trauma or injury to nerves, including prolonged pressure on a nerve or group of nerves, is a common cause of neuropathy. Decreased blood flow (ischemia) to the nerves can also lead to long-term damage.
- Tumors: Benign or malignant tumors of the nerves or nearby structures may damage the nerves directly, by invading the nerves, or cause neuropathy due to pressure on the nerves.
- Idiopathic: Idiopathic neuropathy is neuropathy for which no cause has been established. The term idiopathic is used in medicine to denote the fact that no cause is known.
The perception of pain varies with each individual; terms such as stabbing, prickling, burning, tingling, and other descriptions have been used. Nerve pain is difficult to live with but in most individuals, it can be reduced. Nerve pain is also called neuropathic pain.
Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.