Diabetic Nerve Problems

Types of Diabetic Neuropathy

Distal symmetric polyneuropathy, also known as peripheral neuropathy, is classically described as having a “stocking-glove” distribution. That is, the loss of sensation begins in the feet and, over time, progresses up to the knees before including the fingers. The loss of sensation is symmetric and includes the inability to detect pain, vibration, pressure, and joint position. In addition to the infected ulcers described above, peripheral neuropathy can also eventually result in deformed Charcot joints of the foot, because the feet do not appropriately sense and respond to the contour of the surface on which they walk. More rare, diabetics can experience painful diabetic neuropathy, characterized by burning, shooting, light-ning-like pain in the legs.

A third type of diabetic nerve problem is diabetic autonomic neuropathy. The autonomic nervous system controls numerous bodily functions, such as circulation, respiration, digestion, and reproduction. Diabetic autonomic neuropathy, therefore, can manifest in many ways, including gastrointestinal and genitourinary dysfunction, rapid heartbeat, and lightheadedness on standing due to a drop in blood pressure. In addition to sensory and autonomic nerves, diabetes mellitus can also damage motor nerves, nerves that control muscle contraction. Diabetic motor neuropathy can be asymmetrical and may occur in locations such as the limbs and the muscles that control eye movements.

Clinical Aspects of Diabetic Neuropathy

Diabetic neuropathy may affect as many as 10 percent of diabetics, and its risk increases with poorer glucose control. The precise cause of diabetic nerve damage is not clear, although the high blood glucose levels and poor blood flow that are characteristics of diabetes mellitus are most likely involved. There are many other nondiabetic causes of neuropathies, and a physician must rule these out before diagnosing diabetic neuropathy. Nevertheless, the diagnosis must always be considered in a known diabetic patient, and all diabetics should receive routine neurological examinations.

Noninvasive diagnostic tests for diabetic neuropathy include the basic neurological examination that tests the motor function and sensation to pinprick, vibration, and temperature. Evidence of autonomic neuropathy is detected by monitoring changes in blood pressure and heart rate difference between sitting and standing. Definitive diagnosis requires further testing such as nerve conduction studies and [Page 515]nerve and skin biopsies. As with most other complications of diabetes, the best treatment for diabetic neuropathy is glycemic control, keeping the blood glucose level low through diet and/or treatment with oral diabetes medications or insulin. Reducing hyperglycemia decreases an individual's chance of getting diabetic neuropathy. Painful diabetic neuropathy can be treated symptomatically with tricyclic anti-depressants and antiseizure medications such as phenytoin, gabapentin, and carbamazepine.

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