Conway McLean, DPM, Journal columnist

Nerves are funny things. Obviously, they are responsible for many important functions. Want to pick up that cup of coffee and take a sip? Activate the nerve controlling the muscles in your arm which allow this to occur. Few of us think about all that is happening with this action, but it’s all possible because of the speedy transmission of signals through our nerves.

Nerves are delicate structures, relying on local tissues for support. Because of the electrically based process of signal transmission, physical stress to a nerve is going to cause problems, regardless of the nature of the impingement, be it a pinching of the nerve, stretching, or pressure to it. All will result in problems with propagation of whatever message the nerve is attempting to relay, along with the development of pain.

Let’s take for example the story of Will, a local fellow employed in a warehouse, moving heavy boxes and equipment. Although generally in good health, Will had begun to notice some tingling in all of his toes. Although not particularly painful initially, over the months, the sensations progressed in intensity, as well as its distribution. Typically, he was able to finish his workday without too much difficulty, but the unpleasant sensations were gradually worsening. It was at this point he was strongly encouraged by his wife to see a physician.

The initial assessment determined he was experiencing a form of diabetic neuropathy. Indeed, he had a family history of diabetes. Yet, upon testing his blood sugar levels, it was found to be quite normal. He was provided with a prescription for a pain reliever, gabapentin, a frequently prescribed medication originally approved for depression. The drug dulled the burning and tingling pain he was experiencing, but not much more. And it didn’t seem like much of a solution.

A specialist was consulted who questioned Will on the pattern of his pain, when it was better or worse, and how activity affected the discomfort. A characteristic of diabetic neuropathy is the effect of inactivity, whereby these uncomfortable sensations are more noticeable when non-weight bearing, as when lying in bed. Unlike orthopedic pain, which is often more noticeable when active, small fiber peripheral neuropathy is more symptomatic when inactive. And most evident when lying in bed, the sufferer trying to sleep.

One particularly misleading characteristic of nerves is the location of the symptoms when a nerve is injured in some fashion. As to the character of the pain from a nerve injury, they are rather distinctive, experienced as a burning sensation, or tingling, sometimes a shooting pain. But the individual with a nerve injury will usually feel the pain, whatever the type, in the area that the nerve was going to.

Returning to our friend Will, his research into neuropathy was not very inspirational, depressing actually. But a return to the specialist led to his performing a study on the health of his microscopically small skin nerves. When the results revealed a normal, healthy nerve count, the answer to his symptoms had to lie elsewhere.

The physician then recommended the application of a particular athletic strapping of his feet and ankles. This was an unexpected approach, but when the following days revealed an obvious and significant improvement in his symptoms, he was a believer. The taping of his ankles changed his biomechanics, the functioning of his feet and legs (as well as his hips and back). In basic terms, the tape kept his ankle from rolling excessively, which was stretching the nerve on the inside of his ankle.

The diagnosis for our protagonist’s condition was tarsal tunnel syndrome and, like its counterpart ‘carpal tunnel syndrome,’ it is classified as an entrapment neuropathy. Naturally, there are many causes for tarsal tunnel syndrome, from today’s example of a biomechanical one, to various tumors or masses developing within or around the tarsal tunnel. One of the more common structural reasons is a ganglionic cyst, which is an outgrowth of a tendon sheath or a joint capsule. These are benign growths but will cause problems if the cyst impacts some neighboring structure, like the nearby nerve, in this case.

Treatments vary, obviously depending on why they have nerve compression in this tunnel. Typically, it involves removing or resolving the pressure to the nerve. This may involve injections for a ganglion, or surgical removal in the case of some type of mass or tumor. In today’s example, because of the benefits of this sports taping, improving his biomechanics was clearly going to resolve Will’s symptoms. But this is often not a simple task.

This may require some type of stretching program, but most beneficial is the use of prescription, customized supports (foot orthoses) that were placed inside Will’s shoes. These functioned to keep his feet from rolling in too much, removing the physical stress from the nerve. But numerous additional therapies are helpful, especially therapeutic ‘cold’ lasers, particularly effective with no possibility for complications. Surgical options have been developed, with the standardized procedure involving a release of the fibrous bands forming the roof of the tunnel. And yet, a recent analysis of the results of this procedure, a tarsal tunnel release, were not very positive.

Tarsal tunnel syndrome is too often misdiagnosed, leaving the afflicted individual to suffer needlessly, often for years. Tingling in the toes or bottom of the foot may be some type of neuropathy, but there are many forms and variations on the theme. It’s important to know what type of nerve problem you have.

Seeing a specialist is more likely to lead to an accurate diagnosis when it’s a condition not obvious or not common. This is especially true with a relatively obscure pathology like tarsal tunnel. In Will’s case, as with so many medical conditions, finding out why he had the problem went a long way toward resolving it. And with the aid of his new foot supports, all he had to do for relief was put his shoes on.

EDITORS NOTE: Dr. Conway McLean is a podiatric physician now practicing foot and ankle medicine in the Upper Peninsula, having assumed the practice of Dr. Ken Tabor. McLean has lectured internationally on surgery and wound care, and is board certified in both, with a sub-specialty in foot orthotic therapy. Dr. McLean welcomes questions, comments and suggestions at drcmclean@penmed.com.