Monofilaments and Diabetes

Peripheral neuropathy is a known complication of diabetes and many other diseases.

Diabetic peripheral neuropathy (DPN), which is the result of chronic hyperglycemia, causes permanent damage, at a microvascular level, to the nerves at the furthest points of the body, predominantly the feet, but also the fingers, hands and legs. Symptoms include numbness, burning, pain or pins-and-needles sensations, as well as muscle weakness. Up to 60% of diabetic patients develop some degree of DPN during their lifetime.

Uncontrolled DPN often leads to secondary disorders, including ulcerations, infections and amputations. In fact, it is estimated that between 4% and 7% of diabetics are likely to experience infection as the result of DPN during their lifetime. DPN can also be extremely painful, with few successful options for pain relief.

There is a significant latency period before the patient experiences symptoms of DPN. It is to the benefit of the diabetic patient to get an early diagnosis of DPN, in order to make changes necessary to limit permanent damage to the peripheral nerves.

There are a number of diagnostic tests available, most of them quite sophisticated and expensive. These include nerve conduction studies, velocity tests and electromyography. These tests involve the insertion of needles into the muscles and can be painful.

The simplest diagnostic test can be conducted in the physician’s office. It involves the use of a small nylon thread called a monofilament.

The Monofilament Test

The patient first removes their shoes and socks and reclines in the physician’s examination room. After the physician conducts an examination of the feet, looking for any evidence of injury or infection, the patient is asked to close their eyes. The physician sits at the feet and applies one end of the monofilament for one second, initially to the underside of the big toe. A slight pressure causes the monofilament to buckle, which denotes an application of 10g of force. The patient is asked if they can feel the touch of the monofilament. The application is made to the underside of the big toe, second, fourth and fifth metacarpals. It may also be made to several locations on the sole of the foot.

A tentative diagnosis of DPN can be made if the patient is unable to feel any individual application of the monofilament on either foot. Follow-up testing, using a tuning fork, applications of warm and cold or some of the more sophisticated testing previously mentioned can confirm the diagnosis.

This test can also be conducted on the fingers, hands or legs.

Advantages of the Test

The monofilament test is inexpensive, easily administered and can be performed during quarterly or annual checkups with the primary physician. This monitoring can be effective in monitoring the development of DPN and in emphasizing the need for better control of blood glucose levels.

Sources: DiabetesSymptoms.org and Indian Health Service, US Dept HHS