Your peripheral nervous system acts as the hardwiring of your body. Each nerve serves one of two essential functions. Afferent nerves bring sensory messages to the central system such as smell, touch, taste, or pain. Efferent nerves send motor function messages to the body, such as ‘make a fist’ or ‘stand up.’ Have you ever been sitting too long, and when you get up, you “can’t feel your legs”? On occasion, you might even stand or try to walk and your legs “give out” from under you. These transient episodes are the result of irritation or compression of a nerve resulting in temporary impairment of function.
However, there are other nerve related circumstances that are harbingers of problems that persist. These are usually resulting from the progression of chronic diseases and subsequent ongoing damage to the nervous system. One quite common disease resulting in neuropathy is the progression of diabetes. As longstanding elevated blood glucose gradually damages the peripheral nerves, commonly in the lower extremities, the ability to feel becomes compromised. Without the perception of pain, ulcers may occur, or small injuries may readily become infected. As circulation concurrently diminishes, these wounds may result in a need for amputation. Pins and needles sensation may give way to chronic pain or no sensation at all. Muscle weakness may also develop, contributing to balance and coordination issues. As multiple nerves are impacted, there are other system failures that may develop including vision, digestive and urogenital systems.
Multiple myeloma, multiple sclerosis and cancer are also diseases that can cause similar neurologic changes to occur. Chronic use of alcohol over time can also contribute to multiple health problems. Long term toxicity from alcohol has a possibility of causing chronic nerve damage as well with similar outcomes to diabetes. These nerve problems are progressive and unrelenting.
Injury is another widespread problem that may give rise to neurogenic pain. Damage to nerves from trauma may provide a source of chronic pain mediated directly from the nerve itself. An example of such trauma would be a herniated disc in the spine. As the disc extrudes, it can trap the nerve root and physically compress it. This acts as a source of constant pain until the nerve is decompressed. In addition to significant pain, this entrapment can also cause subsequent permanent muscle weakness to develop.
Infection is not a usual source of neurogenic pain, apart from shingles. This viral infection from childhood chicken pox will live and remain dormant in the spinal cord for decades. Later in life there may be some compromise to one’s resistance and the virus will break out. This presents as a painful, blistering red rash that follows the course of a nerve, commonly on the scalp, trunk, or extremity. As the inflammation occurs directly in the involved nerves, the pain can be severe and last for weeks to months. There are occasions that the pain does not resolve, causing persisting post-herpetic neuralgia. Fortunately, there is a readily available vaccine available from your doctor or pharmacy for shingles outbreak prevention.
The final example is the “phantom limb.” There are occasions where an amputated extremity continues to be perceived by the brain. This instance results from damage to the nerve at the site of the amputation which “misfires,” producing the perception of the persisting absent appendage.
Prevention and early treatments may be the best way to address the onset of neuropathic pain. When unsuccessful, there are alternative treatments that may be available including surgery, medications, and other interventional procedures. As with all health issues, your best resource for information should be
your primary care provider. Please consult your PCP should you have any issues, concerns or questions regarding your risks or treatments of neurogenic pain.
Bradford Croft, DO
East Flagstaff Family Medicine