CONDITIONS

Neuropathy

Neuropathy is the general term for pain or discomfort caused by damage to the nerves of the peripheral nervous system. Your peripheral nervous system is made up of the many nerves that bring signals from the brain and spinal cord to other — or peripheral — parts of the body, such as the hands and feet. Damage to those nerves can affect the way the body sends signals to muscles, joints, skin, and internal organs. This can cause pain, numbness, loss of sensation, and other symptoms.

4 Types of Neuropathy

• Peripheral neuropathy: Peripheral neuropathy is when the nerve problem affects the nerves outside of the brain and spinal cord. These nerves are part of the peripheral nervous system . Accordingly, peripheral neuropathy is neuropathy that affects the nerves of the extremities — the toes, feet, legs, fingers, hands, and arms. The term proximal neuropathy has been used to refer to nerve damage that specifically causes pain in the shoulders, thighs, hips, or buttocks.
• Cranial neuropathy:Cranial neuropathy occurs when any of the twelve cranial nerves (nerves that exit from the brain directly) are damaged. Two specific types of cranial neuropathy are optic neuropathy and auditory neuropathy. Optic neuropathy refers to damage or disease of the optic nerve that transmits visual signals from the retina of the eye to the brain. Auditory neuropathy involves the nerve that carries signals from the inner ear to the brain and is responsible for hearing.
• Autonomic neuropathy: Autonomic neuropathy is damage to the nerves of the involuntary nervous system. These nerves control the heart and circulation (including blood pressure), digestion, bowel and bladder function, the sexual response, and perspiration. Nerves in other organs may also be affected.
• Focal neuropathy:Focal neuropathy is neuropathy that is restricted to one nerve or group of nerves, or one area of the body.

Causes

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.

Symptoms

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 sugarlevels (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.

Diagnosis

All exams and tests performed depend on the clinical presentation of the symptoms of the patient with suspected neuropathy. The diagnosis of neuropathy and its cause involve a thorough medical history and physical examination to help your health care professional determine the cause and severity of neuropathy. A neurological examination, testing the reflexes and function of sensory and motor nerves, is an important component of the initial examination.

Although there are no blood tests that are specific for determining whether or not neuropathy is present, when neuropathy is suspected, blood tests are often used to check for the presence of diseases and conditions (for example, diabetes or vitamin deficiencies) that may be responsible for nerve damage.

Imaging studies such as X-rays, CT scans, and MRI scans may be performed to look for sources of pressure on or damage to nerves.

Specific tests of nerve function include:

• Electromyography(EMG) is a test that measures the function of the nerves. For this test, a very thin needle is inserted through the skin into the muscle. The needle contains an electrode that measures the electrical activity of the muscle.
• A nerve conduction velocity test(NCV) measures the speed at which signals travel through the nerves. This test is often done with the EMG. In the NCV test, patches containing surface electrodes are placed on the skin over nerves at various locations. Each patch gives off a very mild electrical impulse, which stimulates the nerve. The electrical activity of the nerves is measured and the speed of the electrical impulses between electrodes (reflecting the speed of the nerve signals) is calculated.
• In some cases, a nerve biopsymay be recommended. A biopsy is the surgical removal of a small piece of tissue for examination under a microscope. A pathologist, a physician specially trained in tissue diagnosis, examines the specimen and can help establish the cause of the neuropathy. The procedure is performed using a local anesthetic. The sural nerve (in the ankle), or the superficial radial nerve (wrist) are the sites most often used for biopsy.