Diabetes is one of the most common causes of neuropathy and is associated with a wide range of clinical manifestations. Most patients with neuropathy have diabetic peripheral neuropathy (DPN) or autonomic neuropathies. These complications can often lead to pain, numbness, tingling, or other problems in the feet and hands. Since up to 50% of DPN cases may be asymptomatic, these patients are at risk of insensate injury to their feet, which can lead to foot ulcers or amputations. Autonomic neuropathies can lead to substantial morbidity and increased mortality, and negatively affect quality of life. For these reasons, early recognition and appropriate management of diabetic neuropathy is important.
“Recent research shows that risk factors for diabetic neuropathy are also those of myocardial infarction—obesity, increased waist circumference, hypertension, dyslipidemia, elevated triglycerides, and low HDL as well as inactivity and smoking,” says Aaron I. Vinik, MD, PhD, FCP, MACP. “People who take statins or fibric acid derivatives also appear to have a lower likelihood for the development of neuropathy.”
Exclude Other Neuropathic Conditions
Neuropathies occur in many forms, including carpal tunnel, tarsal tunnel, and lumbosacral entrapment, which can produce a similar symptom complex as DPN. Entrapment neuropathies, however, are managed very differently (eg, with splints, diuretics, and local injections). Before considering a treatment route, clinicians should distinguish the type of neuropathy. Symptoms specific to DPN include:
- All varieties of pain.
- Tingling, burning, or prickling sensations.
- Extreme sensitivity to touch, even light touch.
- Loss of balance and coordination.
These symptoms are often worse at night. Pain exacerbated by physical activity is typically not a symptom of diabetic neuropathy.
Ruling out other neuropathic conditions is particularly challenging when diabetic foot is present—there are many types of nerve entrapments (eg, medial plantar and lateral nerve entrapments). Foot deformities and muscle weakness can cause Morton’s neuroma; heel spurs and inflammation of the fascial lining may also occur. These conditions, among others, should not be confused with diabetic neuropathy.
Seek Out Diabetic Foot
More than 80% of amputations follow a foot ulcer or injury, emphasizing the need for early recognition of at-risk individuals. All patients with DPN should receive foot care education and consideration for podiatric referral. “A complete and comprehensive foot exam should occur for every patient seen in clinic the first time and yearly thereafter,” says Dr. Vinik (Table 1). “Feet should be examined for deformities or abnormalities because this can increase risks for foot ulcers and falling. One or more of the following can be used to assess sensory function: pinprick, temperature, vibration perception using a 128-Hz tuning fork, or pressure sensation using a 10-g monofilament pressure sensation at the distal halluces.”
Patients with DPN are at increased risk of falls and fractures. “Patients should undergo aggressive strength and balance training,” Dr. Vinik says. “Simply teaching patients to walk on an uneven surface (eg, with a foam mattress) has been shown to markedly reduce fall risk. Patients should also receive monofilaments so that they can test themselves daily at home. This induces a behavioral change, reinforcing the notion that patients should examine their feet regularly.”
Laser Doppler imaging assesses microvascular perfusion and blood flow. While not always necessary, Dr. Vinik recommends a clinical exam for palpation of visual dorsalis pedis and posterior tibial pulses. “This can provide invaluable clinical information on the status of the integrity of the perfusion to the lower extremity,” he says. “If you can’t feel them, an Ankle-Brachial Pressure Index is strongly recommended.”
Treat the Condition
Management of patients with DPN should begin with stabilizing and optimizing glycemic control (Table 2). In addition, some patients may require pharmacological treatment for painful symptoms. Following the treatment algorithm from the 2005 statement by the American Diabetes Association can be beneficial for more painful neuropathy cases. “Two drugs approved by the FDA specifically for neuropathy are pregabalin and duloxetine,” adds Dr. Vinik. “Both have been studied extensively and are effective in relieving pain. These medications, however, only manage symptoms and do not treat the underlying neurologic disorder. Ultimately, we need to better understand the underlying cause of the disease in order to prevent its development. Ideally, we want to achieve nerve regeneration—only then will we truly succeed in treating diabetic neuropathy.”
Aaron I. Vinik, MD, PhD, FCP, MACP, has indicated to Physician’s Weekly that he has or has had the following financial interest: Amgen, AstraZeneca, Athena, Boston Medical Technologies, Bristol-Myers Squibb, Eli Lilly, EMD Pharmaceuticals, Forest Laboratories, Fujisawa Healthcare, Genentech, GlaxoSmithKline, Guilford Pharmaceuticals, Knoll Pharmaceuticals, Medco, Merck, Mitsubishi Pharma America, NeurogesX, NEUROMetrix, Novartis, Paramount BioSciences, LLC, Pfizer, Recovexx, Regeneron Pharmaceuticals, Sankyo, Sanofi-Synthelabo, Sigma-Tau Pharmaceuticals, Synergy Biosciences, Takeda, TeraTechnologies, and Teva Pharmaceutical Industries.
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