Diabetic peripheral neuropathy (DPN) is a common and very disabling disorder for those living with diabetes.
By Shelley Diamond, BScPhm
Illustration by Martin Bregman
In fact, it will develop within 10 years of the onset of diabetes in 40-50% of people with type 1 or type 2 diabetes. Many with type 2 diabetes will have neuropathy at the time of diagnosis. Nerve damage most commonly results from reduced blood flow to the nerves as a result of damage to the blood vessels caused by hyperglycemia. Distal symmetrical polyneuropathy (DSP) is the most common manifestation, but many patterns of nerve injury can occur.
Pain, tingling and numbness are the symptoms most commonly associated with nerve damage, but other symptoms include erectile dysfunction and delayed gastric emptying. Most neuropathies are asymptomatic, however numbness and the inability to perceive pain or injury are dangerous and a common cause of foot ulceration. Minor foot injuries in people living with diabetes pose a greater risk in that they can become infected. With reduced blood flow, due to peripheral vascular disease, impaired healing can result in devastating consequences, such as ulcers and bone infection, which ultimately may lead to lower-extremity amputation. In Canada, adults with diabetes are almost 20 times more likely to be hospitalized with non-traumatic lower limb amputations than their counterparts without diabetes.
Screening your patients
The 2013 Canadian Diabetes Association Clinical Practice Guidelines recommend that people with type 2 diabetes be screened at diagnosis and then annually thereafter. Patients with type 1 diabetes should be screened five years after the postpubertal duration of diabetes and then annually thereafter.
When looking for signs of peripheral neuropathy, focus on patients with elevated blood glucose levels, elevated trigylerides, hypertension, high body mass index and those who smoke, since these are all risk factors of neuropathy.
For many years, healthcare professionals have been using the 10-g Semmes-Weinstein monofilament or the 128-Hz tuning fork to screen for neuropathy. The monofilament can be easily used in a pharmacy setting since it is rapid, easy to perform, inexpensive and not requiring special skills. It uses a soft nylon fiber to identify sensitivity to touch. The monofilament is applied to the dorsum of the great toe proximal to the nail bed using a smooth motion-touch. The filament should be bent for a full second, and then lifted from the skin. For more information on this technique, visit http://guidelines.diabetes.ca/Browse/Appendices/Appendix8.
Monofilament testing is useful, but limited by its accuracy. Many recommendations for testing sites and testing methods have resulted in different interpretations and less reproducible results.
Nerve conduction tests are the gold standard and provide greater accuracy, but they are expensive and time-consuming, and they require trained personnel, so they cannot be used routinely, especially in a pharmacy setting.
Recent advances in technology have provided an in-office nerve conduction testing device. NC-stat DPNCheck, manufactured by NeuroMetrix Inc. (Waltham, MA) and distributed by Superior Medical (http://www.superiormedical.com/), is a Health Canada-approved device measuring sural nerve conduction velocity and sensory nerve action potential amplitude. These parameters have been shown to be sensitive indicators of nerve degeneration in patients with diabetes and have been used to detect DPN. The DPNCheck offers a new point-of-care testing device that pharmacists can use in a clinic setting, or as part of a diabetes medication review. (Can Pharm J 2015;148:17-20).
Since underdiagnosis of neuropathy is a fundamental problem in the primary care of people with diabetes, your role in screening and helping patients reach their blood glucose targets is essential to prevent the devastating complications that can result from this condition. Consider adding this to your diabetes services now!