Peripheral Neuropathy and the Insensate Foot: More Than Diabetes

In our February editorial, we wrote about articles that are published online ahead of print. In this month’s editorial, we want to call attention to one such important article that was published online in January 2019 and now appears in print in this issue: Plantar Ulcers and Neuropathic Arthropathies: Associated Diseases, Polyneuropathy Correlates, and Risk Covariates.1 Most clinicians attribute the insensate foot in persons with diabetes to neuropathy that develops approximately 10 to 15 years after the onset of abnormal serum glucose. Andrews et al1 challenge this belief. They assert that although diabetes mellitus is “one of the most common causes of peripheral neuropathy worldwide, it is not the cause of neuropathy in all patients with diabetes.”1,2 Further, the authors urge clinicians that “other causes should be actively excluded.”1,2 Dr Andrews and her colleagues from the Mayo Clinic retrospectively reviewed 69 patients who had neuropathy over a 3.5-year period. Of 61 adequately assessed patients, they identified 37 (61%) with diabetes, 22 (36%) with no associated disease (ie, chronic idiopathic axonal polyneuropathy), and two patients (3%) with hereditary sensory/autonomic neuropathy.1 Interestingly, the patients with diabetes had similar complications (neurotrophic ulcers, neuropathic arthropathies) to the patients who did not have diabetes. This led the authors to conclude that other factors were responsible for the neuropathy and its complications including older age, obesity, repetitive foot injury, and inadequate foot care. The authors are asking readers to look at peripheral polyarthropathy with new eyes. Other conditions associated with peripheral neuropathy include infections such as leprosy, syphilis, HIV, and hepatitis C virus. Neuropathy is also associated with alcohol abuse, arsenic poisoning, chemotherapy, and vitamin B12 deficiency. Any spinal cord defect (eg, spina bifida, cerebral palsy, paraplegia) can result in a distal neuropathy. Further, neuropathy is an adverse effect of nerve damage from intra-articular steroid injections. Clinicians should examine patients with neuropathy for chronic low-grade foot deformities as well as acute changes. Subacute or chronic changes often present insidiously, without patient awareness of pain or the resultant structural foot changes. Acute Charcot joint changes can be identified by a warm, swollen foot that may or may not have associated pain in a previously painless foot and a loss of protective sensation. An infrared thermometer3,4 may detect an 8° F to 15° F temperature increase over the other foot. Affected patients should cease weight bearing and further trauma with a wheelchair or bed rest until the application of a contact or irremovable cast. The consequences of delayed treatment include preventable lower-extremity amputation. Neuropathic ulcers are most often a result of repetitive trauma; they are associated with a smaller localized temperature increase of 4° F or more. Patient self-monitoring with noncontact infrared thermometers was studied in three randomized controlled studies.3,4 The studies enrolled 483 subjects with diabetes and high-risk feet; results demonstrated that daily patient self-monitoring with noncontact infrared thermometers significantly reduced foot ulcers when localized temperature increases were coupled with decreased ambulation. So what should we change based on this new information? First, early identification of peripheral neuropathy must include the general population and not only persons with diabetes.5,6 There are 60-second screening tests to identify high-risk feet,5 but feet frequently are not examined in routine care.6 The Andrews article1 heightens the need to screen all feet for chronic idiopathic axonal polyneuropathy and other causes of neuropathy. Further, clinicians must institute preventive foot care for all individuals with neuropathy.5,6 There is a 50% 5-year mortality associated with diabetes-related nontraumatic lower-limb amputations; this prognosis is worse than breast cancer in females, prostate cancer in males, or lymphoma in general!7 Early assessment and risk identification coupled with implementation of appropriate preventive foot care may save a limb—and ultimately save a life.FigureR. Gary Sibbald, MD, MEd, DSc (Hons), FRCPC (Med Derm), FAAD, MAPWCA, JMFigureElizabeth A. Ayello, PhD, RN, CWON, ETN, MAPWCA, FAAN

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