Health Matters: Pain - The body’s alarm system

Conway McLean, DPM, Journal columnist

Pain… it is a powerful word. Too many people complain of it, as well they should in the face of chronic conditions, like a degenerated knee joint or a chronic back problem. But acute pain is different, typically informing the individual some injury is occurring. That is important information.

Nerves have many vital functions in the human body, including that of informing the brain if there has been some trauma. Some of these fragile structures control muscles, telling you to bend your arm and your muscles acting appropriately. They also are important in stimulating some muscles we are voluntarily unable to manage or change, like your heart rate or intestinal movement. Nerves are the short term, immediate-effect control system for the body (while hormones are the long term control).

Many people suffer from a nerve problem making them unable to feel some painful stimuli. The term used to describe many of these conditions is peripheral neuropathy (PN). The name tells you about it: peripheral, as in away from your center; neuro which is related to nerves. The root ‘pathy’ means disease. Neuropathy is a common consequence of diabetes, although PN can be associated with many other underlying medical conditions.

Peripheral neuropathy affects some 20 million people in this country, especially people over the age of 55. As mentioned, it can involve various types of nerves, like those of the autonomic (think heart function), the motor nerves (the ability to pick up an object), and the sensory nerves (the sharp pain experienced when stepping on a tack). There are many and varied reasons one can develop PN, including physical trauma, repetitive injury, infection, metabolic problems, and exposure to toxins and some drugs.

Unfortunately, a good percentage of people, roughly a third, have no identifiable cause for their peripheral neuropathy. This is referred to as idiopathic, indicating the cause is unknown. Also common are acquired neuropathies, caused by environmental factors such as toxins, illness (such as diabetes) or infection (like Lyme’s disease or shingles). Alcoholism is a well-recognized origin for PN, as is chemotherapy. Hereditary neuropathies are found less frequently, the typical example being Charcot-Marie Tooth Disease.

You might imagine at this point this is an easy diagnosis to make, but nothing could be farther from the truth. According to studies, nearly 3/4th’s of those with neuropathy haven’t been diagnosed. Many with some type of PN don’t have obvious symptoms or signs, simply experiencing some mild numbness or occasional tingling, sensations easy to dismiss.

In contrast are the minority who have painful neuropathy, some experiencing a terrible burning, sometimes round the clock. Sleep can be a touchy subject for these individuals since the fiery sensations are more noticeable when lying in bed, with no other stimuli to distract the sufferer. Other sensations can include tingling or “pins and needles,” stabbing pains. Many complain of feeling like they are wearing a glove or their skin is thickened.

Structural deformities may result from this nerve condition. The toes are kept straight by a delicate balance of structures, primarily small muscles in the feet. These muscles, in turn, are controlled by nerves, coursing down the back and leg to the feet. When the nerves stop working, so do the muscles, leading to slowly progressive deformities. The prominent digit is more likely to experience recurrent pressure, often leading to thinning and weakening of the skin, a change which should be painful. But remember, these people don’t get those messages of pain from their toes or feet, and so, do nothing. How bad could it be if it doesn’t hurt?!

People with chronic neuropathy often lose their ability to sense temperature as well as pain. Consequently, they can burn themselves or develop open sores from prolonged pressure and be completely unaware some injury has taken place. And if they have an impaired immune system, as do those with diabetes, even minor skin trauma, a simple crack from dry skin, has led to infection and subsequently amputation.

Because of this loss of appropriate pain, diabetic foot specialists consider neuropathy “the first step on the stairway to amputation.” Without pain, a minor problem too often goes unnoticed and so, untreated. When eventually identified, the affected individual frequently takes no action because there is no pain. Hence, most diabetic amputations are preventable simply by educating them about neuropathy and its relation to pain from some form of skin trauma.

Diagnosing neuropathy is not difficult but rarely adequately performed. Most commonly, if anything at all is done to determine the presence of impaired nerve function, a small, thin piece of plastic (a monofilament) is used. Although these are known to be unreliable in making this diagnosis, they are better than nothing. The most precise, the most scientific, is a test examining the number of tiny skin nerves. The epidermal nerve fiber density test, developed by Johns Hopkins University, is the gold standard world-wide for making a definitive diagnosis, and provides a definitive count, a specific number, of functioning skin nerves.

The most common approach to treating neuropathy is oral medications which simply mask symptoms. Despite this being a chronic condition, many patients with diabetic peripheral neuropathy are treated with opioids, a class of pain reliever with high addictive potential. These are best used for acute pain, potentially depressing respiration if a mistake in dosage is made.

Many take an anti-inflammatory drug such as ibuprofen or naproxen (Alleve), although these too have potentially serious side effects. Various antidepressants have become popular of late for the treatment of chronic pain, most common examples being gabapentin (Neurontin) and pregabalin (Lyrica). Unfortunately, these help only a minority of people, relieving about half of their pain. Predictably, more than a third experience some complication from use of the drug.

Improving nerve health is a completely different approach to peripheral neuropathy. Some brand new forms of electric stimulation (very different from TENS units!) have been developed to aid nerve function, although large clinical trials have not yet been performed. Nutriceuticals are becoming more commonly recommended in modern medicine and this method of achieving better nerve health has few downsides.

The lifetime incidence of foot ulcers in people with diabetes is estimated to be as high as 25%, with some skin breakdown being the primary event preceding infection. The inability to feel certain pains correctly, what is referred to as “protective sensation,” is the most important factor allowing the development of an opening in the skin. Pain is a gift, but only seen as a gift when protective sensation is lost and damage occurs. If you are diabetic, or have peripheral neuropathy, learn about approved methods of diabetic foot care. It has the potential to save both life and limb.

Editor’s note: Dr. Conway McLean is a physician practicing foot and ankle medicine in the Upper Peninsula, with a move of his Marquette office to the downtown area. McLean has lectured internationally on wound care and surgery, being double board certified in surgery, and also in wound care. He has a sub-specialty in foot-ankle orthotics. Dr. McLean welcomes questions or comments atdrcmclean@outlook.com.


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