Diabetic peripheral neuropathy

"Please take off your socks" is one sentence all patients with diabetes need to (but rarely) hear. Diabetic neuropathy is common, occurring in 32% of type 2 diabetics, and it is a major contributor to lower limb amputation. Despite the ease and benefit of the foot exam in the diabetic patient, only the minority are examined regularly. It is easy to see how a physician in a busy practice might overlook the feet. Having a patient ready and barefoot on the examining table may be one way to remind us all about the feet, thus reducing a significant health care cost and cause of morbidity for the diabetic patient.

Diabetic neuropathy is a distal sensory polyneuropathy in which fibers are affected in a length-dependent way, thus first affecting the toes and the soles of the feet. Clues to diabetic neuropathy lie in the history and by simple examination of the feet. On history the patient may complain of burning pain, tingling, aching or numbness. Symptoms are often worse at night or awaken the patient from sleep. Physical examination begins with a general check for skin warmth or thinness, hair distribution (hair on the toes is a good sign), cracks or ulcers, pedal pulses, and neurologic exam, including vibration sensation, temperature sensation, or pressure sensation.

On physical exam there are three main ways to test for neuropathy: pressure, vibration, and pain/temperature sensation.

Although there are recent controversial claims that the duration of sensation of the tuning fork may be a sensitive predictor of early neuropathy, we prefer the use of the 5.07m monofilament pressure sensor to test for neuropathy in diabetic patients.

The use of the monofilament is a simple, portable, reliable method to identify early neuropathy. The filament is essentially a piece of firm nylon thread placed at a right angle on six sites of the sole of the foot and the toes. Pressure is applied to the filament until it buckles to form an arc. The test is normal if the pressure is felt, abnormal if the patient does not sense the filament. An abnormal monofilament test is associated both with a higher likelihood of ulceration and amputation.

The filament can be ordered in bulk quantities at a cost of pennies. They are light and fit easily in a shirt pocket. They come with a diagram to indicate areas on the foot that should be tested, and they are disposable.

The ever-increasing incidence of diabetes means that the burden of its morbidity, such as neuropathy, will increase as well. With a simple cost-effective and time-efficient tool like the monofilament, we have every reason to touch our patients' feet and help prevent the significant disability associated with foot ulcers and amputation.

In Practice
Date Posted: 8 August 2005