Diabetic neuropathy is a peripheral nerve disorder caused by diabetes. Also referred to as peripheral neuropathy or peripheral neuritis, neuropathy occurs when illness, injury, inflammation, medication, or other factors disrupt the ability of nerves outside the spinal cord to relay messages between the brain and muscles, skin, nerves, joints, or internal organs.
Neuropathy can affect:
- Sensory nerves, which control sensation
- Motor nerves, which control movement
- Autonomic nerves, which control involuntary or semi- involuntary body functions
- Any combination of these three main types of nerves
Researchers have identified more than 100 types of neuropathy. Symptoms, which may take days, weeks, or months to develop, depend on the type or types of nerves affected and on whether neuropathy affects a single nerve or group of nerves (mononeuropathy) or more than one nerve group (polyneuropathy).
Symptoms of Diabetic Neuropathy
The symptoms of diabetic neuropathy are often slight at first. In fact, some mild cases may go unnoticed for a long time.
Numbness, pain, or tingling in the feet, or legs may, after several years, lead to weakness in the muscles of the feet. Occasionally, diabetic neuropathy can flare up suddenly and affect specific nerves so that an affected individual will develop double vision or drooping eyelids, or weakness and atrophy of the thigh muscles.
Nerve damage caused by diabetes generally occurs over a period of years and may lead to problems with the digestive tract and sexual organs, which can cause indigestion, diarrhea or constipation, dizziness, bladder infections and impotence. The loss of sensation in the feet may increase the possibility for foot injuries to go unnoticed and develop into ulcers or lesions that become infected. Changes in the blood vessels of the retina known as diabetic retinopathy lead to vision changes and over time may lead to blindness.
The Body's Reaction to Neuropathy
Damage to sensory nerves can reduce or intensify sensation. This can prevent patients from realizing they've been injured or are experiencing pains warning of heart attack or other life-threatening emergency. Or, it can make even a gentle touch extremely painful. Nerves farthest from the brain and spinal cord are usually the first to malfunction. Pain and other symptoms often appear on both sides of the body, beginning in the feet and progressing toward the center of the body. Neuropathy that affects sensory nerves also causes nerve pain, burning, tingling, and numbness. Inability to determine joint position impairs coordination.
Cramping may indicate motor nerve damage, which reduces or destroys muscle control and can result in weakness and loss of muscle. Other symptoms of muscle involvement include:
- Breathing or swallowing problems
- Absence of fine motor skills needed for such tasks as tying shoes
When autonomic nerves are damaged, diminished ability to sweat or otherwise regulate body temperature can cause heat intolerance. Vision may blur, and falling blood pressure can cause fainting or dizziness. Other symptoms include:
- Abdominal bloating
- Feeling full after eating very little
- Nausea or vomiting after meals
- Unintentional weight loss
- Urinary hesitancy or incontinence
- A sense that the bladder doesn't fully empty
Symptoms of acute neuropathies begin suddenly and worsen rapidly. Damaged nerves heal slowly. Initial symptoms of chronic neuropathies are subtle. These conditions progress slowly and may remain unchanged for months or years. Symptoms may abate before they recur. Chronic neuropathies may worsen over time, but are rarely fatal.
Testing For Diabetic Neuropathy
The patient's history and symptoms and their suspected cause determine which diagnostic tests should be performed. Blood tests can detect diabetes, vitamin deficiencies, liver or kidney dysfunction, and other metabolic or immune system abnormalities that may be the source of symptoms. Cerebrospinal fluid may contain neuropathy-related abnormalities, and neurologic tests can reveal abnormalities in movement, sensation, and organ function.
Electromyography (EMG) involves inserting a needle electrode through skin and into muscle. The electrical activity detected when the patient flexes the muscle indicates how the muscle responds to nerve stimulation. Results are displayed on a fluorescent screen.
A patient who has an EMG will probably also have nerve conduction velocity testing. This procedure measures nerve damage by the speed at which an impulse travels along a nerve. Surface electrodes placed on the skin above the nerve emit mild electrical stimulation. Other electrodes record the resulting activity.
Nerve biopsy involves removing a small amount of tissue from the lower leg or elsewhere for laboratory examination. This invasive procedure can yield important information about the extent of nerve damage. Nerve biopsy is difficult to perform. It may cause neuropathic side effects, and many physicians believe neuropathy can be diagnosed without it.
Easier to perform that nerve biopsy, skin biopsy has fewer side effects than the more invasive procedure. Skin biopsy removes a thin section of skin, which is examined for damage to small nerve fibers.
Treatments for Diabetic Neuropathy
The goal of treating diabetic neuropathy is to relieve discomfort and prevent further tissue damage. The first step is to bring blood sugar levels under control by diet and medication. Another important part of treatment involves taking special care of the feet. Analgesics, low doses of antidepressants, and some anticonvulsant medications may be prescribed for relief of pain, burning, or tingling. Some patients may find that walking regularly, taking warm baths, or using elastic stockings may help relieve leg pain.
Prognosis for Diabetics with Neuropathy
The prognosis for diabetic neuropathy depends largely on how well the underlying condition of diabetes is handled. Treating diabetes may halt progression and improve symptoms of the neuropathy, but recovery is slow. The painful sensations of diabetic neuropathy may become severe enough to cause depression in some patients.
Research on Neuropathy
The NINDS conducts and supports research on diabetic neuropathy to increase understanding of the disorder and find ways to prevent and cure it. New medications are currently being examined to assess improvement or stabilization of neuropathic symptoms.