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Foot Disorders | Neuropathy


What is Neuropathy?
Among the most common complications of diabetes is neuropathy. Unfortunately, even with your blood sugar in good control, neuropathy may occur. In fact, over time, this will occur in up to half of diabetics. Once diabetic neuropathy occurs, it almost always gets worse. Currently, there is no agreement on why it occurs, and there is no medical treatment to prevent it.

In diabetic peripheral neuropathy of the feet, usually you will have begun to notice sensory changes such as numbness or tingling in your toes. At first these symptoms will come and go, but then they will be constant. These unpleasant symptoms may interfere with your going to sleep, or cause you to awaken from your sleep. Over a period of time, these sensory disturbances may cause such a loss of sensibility that you will not feel how tight you shoes are or if you have a pebble in your shoe. Weakness of the foot muscles may also occur causing hammertoes or the arches of the feet to collapse.

Neuropathy is the leading cause of the ulcerations or holes that occur in the feet. Neuropathy is the leading cause of infections in the feet. Neuropathy is the leading cause of the loss of toes and, with advanced cases, amputation.
The purpose of this handout is to provide you with information that is a new source of optimism for patients with diabetes. By having an early measurement made of the sensibility in your feet, the earliest stages of neuropathy can be identified. In certain circumstances, it may be found that areas are present in your feet and ankles that cause compression of your nerves. These sites of pressure on your nerves can be treated with surgery in order to relieve the burning, tingling and pain and in many cases to restore sensation to your feet.

Why are Nerves in the Diabetic Compressed?
Nerves begin in the spinal cord and extend into the toes. Along this path, there are areas of anatomic narrowing. These exist in everyone and many are already known to you such as your “funny bone” at the elbow and the carpal tunnel in the wrist. There are similar tight places at the inside of your ankle, called the tarsal tunnel as well as one on the top of your foot.

The diabetic’s nerves are susceptible to compression because the nerves in a diabetic are swollen due to excess sugar in the nerves that draw in excess water. If a nerve swells in a place that is already tight, like the areas described above, then the nerve becomes pinched, or compressed, causing symptoms.

What are the Symptoms of Nerve Compression?
If your nerve gets pinched, it does not get enough oxygen. The nerve makes you aware of this lack of oxygen by sending you a warning message. You will feel buzzing, tingling or numbness in the areas that are supplied by that nerve.

In the foot, the posterior tibial nerve travels through a boney and fibrous tunnel on the inside of the ankle. This nerve supplies the entire bottom of the foot, including the heel. Compression of the posterior tibial nerve can result in numbness or tingling of the heel, the arch, the ball of the foot, and the bottom and tips of the toes. Continued compression of the nerve without treatment can further lead to muscle weakness, or atrophy, of the small muscles to the toes causing cock-up or hammertoes.

What is the Relationship between Neuropathy and Nerve Compression?
The most common form of nerve problem in the diabetic, diabetic neuropathy, is a change in sensation in a stocking and glove distribution. This means that the entire foot is affected, both the top and bottom, and all of the toes. The pattern of neuropathy is usually the same for both the left and right foot. In contrast, nerve compression usually is thought of as one nerve in one foot, and this suggests that with nerve compression, just part of one arm or of one leg would have the numbness pattern. This difference in the pattern of numbness associated with a nerve compression is one of the main reasons that doctors in the past have not considered that the symptoms of diabetic neuropathy are due to nerve compression.

The symptoms of diabetic neuropathy, of the sensorimotor polyneuropathy type, the most common type that we have been discussing thus far, are numbness and tingling, and weakness, and are essentially the same as those of nerve compression.

But what if there are more than one nerve compressed in the ankle and foot at the same time? Knowing that diabetes makes nerves susceptible to nerve compression and knowing that there are many areas of tightness that occur normally in everyone, it is possible that the diabetic could have more than one nerve compressed in each foot. It this were to be true, then multiple sites of nerve compression along the path of the nerves would give a stocking pattern to the symptoms of numbness and tingling.

Another way to think about the relationship of neuropathy and nerve compression is that diabetes creates the neuropathy according to some metabolic process. This neuropathy, then, creates the circumstances that allow nerve compression to occur. It is well known and accepted that nerve compression can cause the symptoms of numbness, tingling and muscle wasting of the muscles of the foot. It is possible, then, to think that the nerve compressions are superimposed upon the underlying neuropathy. This means that at some point in time, both neuropathy and nerve compression may exist together, but the symptoms may be due to the sites of compression.

What Type of Surgery can be Done?
The object of the surgery is to decompress, or loosen, the tight tunnels the pinched-off nerves are travelling through in the ankle and top of the foot. The surgery opens the tight area through which the nerve passes by dividing a ligament or fibrous band that crosses the nerve. This gives the nerve more room, allows blood to flow better in the nerve and permits the nerve to glide with movements of nearby joints and tendons.

How Does this Type of Surgery Help the Nerve?
Decompression of a peripheral nerve in a person with diabetes can alter the natural course or history of diabetic neuropathy by removing the tight areas along the length of the nerve that are the symptom-producing regions of friction.

The surgery to decompress the nerve does not change the basic, underlying (metabolic) neuropathy that made the nerve susceptible to compression in the first place. When the surgical decompression is done early in the course of nerve compression, restoration of blood flow to the nerve will stop the numbness and tingling. When decompression is done later in the course of nerve compression, and nerve fibers have begun to die, decompression of the nerve will permit the diabetic nerve to regenerate.

Of course, if one waits too long to decompress the nerve, recovery may not be possible. If you already have ulcerations on your feet, or have lost toes, then very little sensation may be recovered because the damage to the nerve has become irreversible.

Who is a Candidate for this Type of Surgery?
The ideal candidate for surgery to restore sensation and strength is the diabetic who is beginning to experience numbness and tingling in the feet and who may have noticed changes in the shape of the feet or toes. This patient should be examined in order to measure the degree of sensory and motor loss. The American Diabetes Association recommends Quantitative Sensory Testing every year. This painless test is performed by our certified sensory nerve test administrator in the office.

If the patient is seen sufficiently early in the course of nerve compression, it may be possible to relieve some of the pressure upon the nerve by wearing shoe inserts (orthotics) for the feet. Special instruction is given to the patient in terms of daily inspection of the foot for early signs of skin breakdown or infection. When the Quantitative Sensory Testing demonstrates sufficient sensory loss, special shoes may be required to protect the feet. There are some medications that can be given to relieve the discomfort of the neuropathy on a temporary basis. And of course, you must be sure that your blood sugar level is the best that it can be.

If the sensory loss progresses to the point where you have numbness and tingling throughout the day or it even wakes you up at night, then you may be a candidate for surgical decompression of your nerve. The ideal candidate does not wait until there is no feeling left or until there is already an ulceration present. The ideal candidate seeks surgical consultation while there is still time to reverse the damage to the nerves.

Where Is The Surgery Performed?
The procedure is performed by Dr. Ferragamo, on an out-patient (come-and-go) patient basis at Davis Surgery Center, 2120 Crowell Blvd., Davis, CA 9561 .

How Long Does the Surgery Take?

From the time you enter the operating room until the time you enter the recovery room is about two hours. You will stay in the recovery room for another hour. These times will vary for individual patients.

Do I have To Be Put To Sleep?
Most often, it is easier for you to have a general anesthetic in which you are truly put to sleep. It is also possible to have a spinal anesthesia, which just puts your legs to sleep. With a spinal anesthesia, you are usually made sleepy but do all of your own breathing. This is also known as “twilight medicine”. The best method for you will be determined in consultation with your own doctor and with the anesthesiologist.

Is the Surgery Painful?
No surgery is pain free but this surgery is not usually very painful. Partly, this is because you already have lost some of your sensation and partly it is because the surgery does not go into the joints. The surgery usually involves just cutting the skin and some ligaments and this usually is not too painful.

A long-acting local anesthetic will be put into your incisions so that when you awaken not only will there be very little pain but you may not feel your foot at all.

When the local anesthetic wears off, in about four hours, you will begin to feel your foot. If this becomes painful for you, you will have been given pain medication, which you may take for after the surgery if needed. You may have some increased pain as you begin to walk again.

When the nerves that have been “asleep” awaken, you may experience hot or cold or shooting pains in your toes. This is a good sign as it shows recovery, but it may still be uncomfortable for you. Medication can help these feelings too.

Do I Have to be Hospitalized?
Not in most cases. Most patients can have the surgery safely as an outpatient.

When Will I Have Quantitative Sensory Testing?
Quantitative sensory testing is the best way we have to measure the degree of function of the nerves of your toes and feet. This testing is done with a computer and does not hurt because there are no needles and no electric shocks. This is different from the exectrodiagnostic studies you may already have had.

The American Diabetes Association strongly suggests that every diabetic has quantitative sensory testing every year and so you may already have had your testing done. It must be done before surgery. So, if you have not already had it, it can be done within two weeks of your office consultation. The testing takes about an hour.

You will have testing done after surgery, too. Usually, it is done at about six to twelve weeks after surgery to document that neural regeneration is occurring. This will also document that the operated foot is improving and help us determine if you should proceed to have surgery on the opposite foot.

What are the Risks of this Surgery?
Although very rare, severe complications are possible. This is why your past medical history is so important to us in selecting the safest anesthesia for your surgery and in selecting the appropriate type of medical facility in which you should have your surgery.

With any surgery, there is always the risk of bleeding, infection, scar formation, the unpredictable nature of the healing process and failure of the procedure to achieve its desired goal.

Unique to the surgery you will have is the possibility of having a painful scar, of having apparent worsening of your symptoms as the diabetic nerve regenerates and delayed wound healing.

Overall, nerve decompression surgery is a valuable procedure in reversing the complications of diabetic neuropathy a is a new source of optimism is reversing potential complications of the feet in diabetics.

Copyright © 2007 Tracy Ferragamo, D.P.M., DavisPodiatryCenter.com


 

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