Diabetic neuropathies

What is it?

Diabetic neuropathies are nerve disorders that may affect people with diabetes. They occur more often in people with persistently high blood sugar levels.

There are several different diabetic neuropathies. They include:

• Peripheral neuropathy. This is the most common type. It affects the longest nerves in the body. These nerves are part of the peripheral nervous system. This is the network of nerves that carry signals from your brain and spinal cord to the rest of your body and back. The most common symptoms of peripheral neuropathy are numbness or pain in the feet and lower legs.
• Autonomic neuropathy. This neuropathy damages collections of nerves that control your unconscious body functions. It may affect your digestion, circulation, and sexual function.
• Localized nerve failures (focal neuropathy). A nerve that controls a single muscle can lose its function. For example, focal neuropathy may cause problems with eye movement that result in double vision. Or it may cause drooping of one cheek.

Diabetic neuropathies occur in both type 1 and type 2 diabetes. They are most common in people whose blood glucose (blood sugar) levels are not well controlled.

Diabetic neuropathies can occur in people who have had diabetes for a short time. But they are most likely to affect those who have had the disease for more than a decade. It is also more common in people older than 40. People with diabetes who smoke are especially at risk.

Diabetic neuropathy results from several changes in the nerves. A persistently high concentration of blood sugar surrounding nerve cells definitely plays a role. The nerve cells must adjust their internal sugar content to be in balance with their surroundings. To do so, nerve cells make and store the sugar sorbitol. Sorbitol can gradually damage nerve cells.

Damage to blood vessels also contributes to diabetic neuropathy. When blood vessels that feed nerve cells are damaged, the nerves may not get enough oxygen and nourishment.

Symptoms

Most people who have had diabetes for 25 years have some form of neuropathy. Symptoms depend on the specific type of neuropathy.

• Peripheral neuropathy. This form of neuropathy causes symptoms in the limbs, especially the lower legs and feet. Symptoms can include
  • numbness
  • tingling
  • sharp or burning pain
  • hypersensitivity to touch
  • problems in balance or coordination.

If your feet are numb, you may not be aware when shoes don't fit properly. This can lead to the formation of a callus. These thickened skin areas can break down over time. They can change into an open sore (ulcer) that may become infected.

• Autonomic neuropathy. The symptoms of autonomic neuropathy vary. They depend on which of your automatic body functions have lost their normal nerve control. Any of the following problems can occur:
  • Incomplete bladder emptying. This can cause you to urinate more often. Urinary infections can be a problem. So can loss of bladder control.
  • Sexual function problems. Problems with erection, ejaculation, and sexual drive are common.
  • Stomach and bowel problems. Slow emptying of the stomach can cause nausea, vomiting, or bloating. The normal rhythmic squeezing of the small and large intestines can be slow or irregular, causing constipation or diarrhea. Swallowing may become difficult. Loss of control over bowel movements is possible.
  • Dizziness when standing. Normally, your heart gears up to pump a little faster and harder when you are standing up. Arteries help to keep your blood pressure steady by adjusting the squeeze of their muscular walls. Both your heart and arteries rely on nerve signals to know when to make these adjustments. These signals can fail in diabetes, causing your blood pressure to drop when you stand up. This is called orthostatic hypotension. The main symptom is lightheadedness with standing. You could faint if you don't sit or lie down when lightheadedness occurs.
• Focal neuropathy. The symptoms will vary, depending upon which nerve is affected. For example, you would have
  • double vision — if it is one of the nerves that controls movements of muscles attached to the eye
  • drooping of a cheek and inability to close an eye on the same side of the face (Bell's palsy) — if it is the facial nerve (cranial nerve number seven)
  • sudden weakness in the ankle (foot drop) — if it is the peroneal nerve (a branch of the sciatic nerve that controls foot movement).
• Radiculopathy. Damage to a nerve that begins in the spinal cord and tracks out between the vertebrae (the bones that surround and protect the spinal cord) is called radiculopathy. It can cause pain in any part of the body. When the damaged nerve is one that goes to an arm or leg, it can cause muscle weakness in the affected extremity.

Diagnosis

Your doctor usually can diagnose diabetic neuropathy based on your:

• medical history
• symptoms
• physical examination.

When necessary, more specialized testing may be done, such as:

• Nerve conduction studies check whether nerve impulses in the arms and legs are normal. Electromyography tests to see how well arm and leg muscles move in response to nerve signals. These two tests usually are done together. They involve a series of momentary minor electric shocks through small needles or pads on the skin.
• Ultrasound of the bladder performed right after you have passed urine is used to see if your bladder is functioning properly. Normally there should be very little urine in the bladder after using the bathroom.
• Gastric (stomach) emptying study tests how quickly food moves through your stomach. In this test, you eat food that contains a small amount of radioactive material. A series of pictures is taken by a machine that detects the radioactive signal. The inability to empty your stomach because damaged nerves can't tell the muscles to contract is called gastroparesis.
• Your doctor may also want to do endoscopy to make sure nothing else is causing the gastroparesis. In endoscopy, the doctor threads a flexible tube with a camera on the end through your mouth and advances it to look inside the stomach.
• Nerve biopsy involves taking a small sample of a nerve to be examined in a laboratory. This is rarely needed.

Expected duration

Peripheral and autonomic neuropathies are usually long-term problems. Focal neuropathy may last a few months, but may be chronic.

Prevention

Diabetic neuropathy is caused by abnormally high levels of blood glucose. Therefore, diabetics can help to prevent neuropathy by keeping blood sugar levels under good control.

In addition, avoiding smoking can help to prevent or delay neuropathies.

Treatment

Treatment of diabetic neuropathy focuses on

• tighter control of blood glucose
• pain relief
• a regular exercise program to burn glucose and build muscle strength
• avoiding smoking
• medications to treat autonomic problems and prevent bladder infections
• physical therapy
• meticulous care of the feet.

Healthy eating and regular exercise can keep blood sugar under control in some people with diabetes. For others, treatment with one or more medication or with insulin may be needed.

To relieve the pain of peripheral neuropathy, your doctor may first prescribe acetaminophen (Tylenol) or a nonsteroidal anti-inflammatory drug (NSAID), such as ibuprofen or naproxen.

There are many other medications available to reduce nerve pain. These include

• low doses of tricyclic antidepressant medications, such as:
  • • amitriptyline (Elavil)
    • nortriptyline (Aventyl, Pamelor)
    • desipramine (Norpramin)
• gabapentin (Neurontin)
• pregabalin (Lyrica)
• duloxetine (Cymbalta)
• venlafaxine (Effexor).

Your doctor may also recommend that you rub on a pain-relieving cream containing capsaicin or apply a lidocaine patch to the painful area. Other options include isosorbide dinitrate topical spray or transcutaneous electrical nerve stimulation (TENS) in which a patch of skin receives tiny electrical shocks intended to interrupt pain signals from the affected area.

If you have gastroparesis, eating small, frequent meals low in fat and fiber may help. Your doctor may prescribe metoclopramide (Reglan) to help the stomach empty.

There are many available treatments for constipation and diarrhea.

To help relieve constipation, drink plenty of fluids and exercise regularly. You also can take

• fiber
• stool bulking and softening agents, such as:
  • psyllium (Metamucil, Konsyl)
  • methylcellulose (Citrucel)
• stool lubricants, such as:
  • docusate sodium (Colace)
• enemas.

Use laxatives sparingly. Overuse may lead to dependence and make constipation worse.

For diarrhea, your doctor may prescribe

• fiber
• bulking agents (which help to change liquid stool into a soft solid stool)
• loperamide (Imodium).

If you have poor emptying of the urinary bladder, your doctor will help you minimize medicines that could contribute to the problem of incomplete bladder emptying. Catheters can be used to empty the bladder when neuropathy is severe. Bladder infections requiring antibiotics commonly occur in people with abnormal bladder function.

For erectile dysfunction (impotence), your doctor may prescribe

• sildenafil (Viagra)
• vardenafil (Levitra)
• tadalafil (Cialis)
• avanafil (Stendra).

Other possible treatments for erectile dysfunction include

• a vacuum cylinder with a hand pump
• injections into the penis of a drug that promotes erections
• a penile implant.

Dizziness when standing can be treated by drinking more fluids. Medicines that increase your body salt and water can also help.

For carpal tunnel syndrome, splints, an injection of a corticosteroid, or surgery may be recommended.

If peripheral neuropathy affects your feet, you should:

• wash your feet every day and make sure you dry between the toes.
• carefully check your feet for any cuts, sores, or swellings.
• wear soft, clean socks and well-fitting shoes.
• never go barefoot.
• cut your toenails straight across to avoid ingrown toenails.
• never try to remove calluses or warts yourself. Always show them to your doctor.

When to call a professional

See your doctor if you develop new or worsening symptoms of neuropathy.

Call your doctor whenever you have a cut or sore that isn't healing or looks like it is infected. It is extremely important to react promptly to injuries and infections, however minor.

Prognosis

In most cases of focal neuropathy, muscle weakness and/or pain subsides within a few months.

Peripheral neuropathies are persistent problems. The pain can last for years. Some people find that symptoms are easier to tolerate if the painful areas lose sensation and become numb. However, complete loss of feeling increases the risk of foot ulcers.

Additional info

National Institute of Diabetes and Digestive and Kidney Disorders
https://www.niddk.nih.gov/

American Diabetes Association
https://www.diabetes.org/