Why Do Nerves in A Diabetic PATIENT Become Compressed?

Nerves begin in the spinal cord and extend into the toes. Along this path, there are areas of anatomic narrowing. These are “tunnels” your nerve has to pass through. 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 a tunnel on the top of your foot, and one on the outside of the knee, called the fibular tunnel.

In a diabetic patient, nerves are susceptible to compression because they 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.

In the foot, the posterior tibial nerve travels through a 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 hammertoes and other conditions.

What is the Relationship between Neuropathy and Nerve Compression?

The most common form of nerve problem, 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, usually starting in the toes and working its way up the foot and leg. The pattern of neuropathy is usually the same for both the left and right foot.

In contrast, nerve compression usually is thought of as affecting just 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 are numbness and tingling, weakness, and loss of balance, and are essentially the same as those of nerve compression.

But what if there is more than one nerve being 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 someone 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 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 traveling through in the foot, ankle, and leg. 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 into 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.

There are 3 areas in the foot and leg that are susceptible to compression.

  1. The tibial nerve as it travels through the tarsal tunnel, where the flexor retinaculum and deep fascia of the abductor hallucis muscle belly constrict the nerve.
  2. The deep peroneal nerve on the dorsum of the foot where the nerve is susceptible to compression from the overlying short extensor tendon to the great toe.
  3. The common peroneal nerve just below and to the side of the knee, where the deep fascia of the peroneal muscles compress the nerve against the head of the fibula bone.

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.

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Who is a Candidate for this Type of Surgery?

The ideal candidate for surgery to restore sensation and strength is someone with diabetes who is beginning to experience numbness and tingling in the feet, who may have noticed changes in the shape of the feet or toes, or may have begun to experience problems with balance or falling. This patient should be examined in order to measure the degree of sensory and motor loss.

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 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. Do not wait until there is no feeling left or until there is already an ulceration present. Seek surgical consultation while there is still time to reverse the damage to the nerves.

For more information on Neuropathy Treatment in the Scottsdale area, call L. David Richer DPM today at 480-629-5903!