Written by Stephen A. Wilson
From his column To Your Health
Peripheral neuropathy (PN) is a complex disease process about which books are written and entire careers focused. It can be frustrating, infuriating, painful, and even disabling.
PN describes a variety of symptoms arising from damage to nerves located outside the brain or spinal cord. Common symptoms include abnormal sensation—pain, tingling, burning, numbness, vibration, temperature, sharp throbbing or jabbing, and hyperesthesia (increased sensitivity to touch and other stimuli), and weakness. Symptoms often starting in the hands or feet and move up the limb. There may be a sensation of wearing stockings, socks, or gloves; imbalance or decreased coordination can occur that may result in falling.
Typically, symptoms related to abnormal sensations and weakness occur and are the focus; however, PN may occasionally affect digestion, urination, circulation, heat intolerance, and sweating (too much or too little).
PN can affect a single nerve (mononeuropathy, of which carpal tunnel syndrome is an example), two or more nerves in different places (multiple mononeuropathy), or many nerves (polyneuropathy). Most people with PN have polyneuropathy.
Common causes of PN include diabetes mellitus, nerve damage (injury or compression), alcohol use, vitamin deficiencies (especially B6, B12, E, thiamine, folate), toxins or medications; 25-to-45% of PN is idiopathic, from an unknown cause. Other less likely causes include thyroid disease, cancers, chronic liver or kidney disease, infection (e.g., HIV, syphilis, or leprosy), gout, significant obesity, thyroid disease, amyloid, sarcoid, vasculitis, or celiac. In rare cases, the cause may be related to copper deficiency or arsenic poisoning.
There are some toxins like gold, lead, mercury, thallium, glue and other solvents that can cause PN. Cancer chemotherapy drugs can also be culprits. Other drugs that have been connected to PN include amiodarone, chloroquine, lithium, procainamide, hydralazine, statin, tumor necrosis factor alpha inhibitors, phenytoin (Dilantin), and others. Most of the time these drugs are safe, but occasionally, especially at prolonged or high doses, some people get PN.
When looking for causes, since there are many, a physician will start with a detailed history and physical exam, and lab tests. Depending on the results, other testing, like imaging, nerve function, and nerve or skin biopsies, may be necessary.
In medicine an uncommon presentation of a common illness is more likely than a common presentation of an uncommon illness. In PN, an odd presentation of diabetes, vitamin, alcohol, trauma, or medication-related PN is more likely than a classic presentation of something rarer. So, expect your doctor to start an evaluation with the more common causes. Keep in mind the cause of PN often remains unclear or unknown. Treating the symptoms is the key.
Treatment includes: improving the state of chronic diseases like diabetes mellitus, gout, or obesity; replacing missing vitamins; removing offending agents such as alcohol, medications, or toxins; relieving compression (e.g., via surgery, splints, or injections for carpal tunnel syndrome); or physical therapy for weakness. Medications may also be used.
Oral medicines that can help decrease or alleviate neuropathic pain include gabapentinoids, such as gabapentin (Neurontin), pregabalin (Lyrica) and antidepressants, like amitriptyline, nortriptyline, venlafaxine, duloxetine (Cymbalta), or bupropion (Wellbutrin). Sometimes the topical medications lidocaine and capsaicin are added to support oral therapy. Occasionally and selectively opioids are used when other therapies have failed. They are not used routinely because of limited effectiveness. Also, dose escalation over time is often needed, but can paradoxically start to make pain worse, or result in long-term safety concerns (constipation, falls, drug-drug interaction, overdose), and the potential for abuse or addiction.
Depending on the cause or duration of the illness, the degree of return to normal and alleviation of PN symptoms varies. Often, the goal is to improve symptoms, decrease pain, and improve function and quality of life. It is better to address symptoms sooner than later, so see your doctor if you have any concerns.
As I close, I’d like to step away from my role as a physician and share news from my alma mater. Dr. Colleen Derr was recently elected as the 15th president of Eastern Nazarene College. I invite you to learn more about her by visiting https://enc.edu/.
Dr. Stephen A. Wilson, MD, MPH, FAAFP, is Chair of Family Medicine at Boston University Chobanian and Avedisian School of Medicine, Chief of Family Medicine for Boston Medical Center, President of Boston University Medical Group - Family Physicians, Inc., and a member of the ENC Board of Trustees.