Neuropathy and Diabetes

An individual who has diabetes is at risk of developing one of many different potentially deadly complications. Failure to take care of your diabetes can cause heart, lungs and kidney problems. It can also affect your feet and hands when nerve damage or neuropathy develops.

Terminology

In order to understand exactly what is going on in a case of neuropathy, it is important to understand some specific terms:[1]

  • Central nervous system  (CNS) – This is the main nerve system made up of the brain and spinal cord and is responsible for coordinating nervous system signals throughout the body
  • Peripheral nervous system – This system is made up of the nerves that run from the CNS throughout the body. In this category you find 3 different types of nerves: motor, sensory and automatic.[2] Each of them has an area of specialty. The motor nerves are in charge of voluntary muscle movements while the sensory nerves are in control of sensations. The automatic nerves are in charge of involuntary biological processes such as controling heart rate and blood pressure.
  • Spinal Cord – It is part of the CNS and connects the peripheral nervous system to the brain
  • Autonomic nervous system – Nerves controlling all of our most basic unconscious or automatic functions. Whether we are asleep or awake the automatic nervous system ensures automatic functions operate as they are supposed to do. These include vital activities like the heart beat, movements of the stomach and intestines, and breathing.

Neuropathy means “distressed nerves” and is the word used to describe a condition in which nerves are damaged.  Peripheral neuropathy indicates that one or more nerves outside of the brain or spinal cord are abnormal. This is a condition that approximately 60% to 75% of all diabetics experience.

Types of Neuropathy

There are several types of neuropathy. The ones listed below are the most common:

  • Distal symmetric polyneuropathy – This affects the feet and legs. It is the most common type of neuropathy.
  • Charcot foot or joint – This is also referred to as neuropathic arthropathy. It affects the feet.
  • Cranial neuropathy – This affects the nerves responsible for eye movement, sight, taste and hearing
  • Autonomic neuropathy[3] – Distress to the nerves of the heart, lungs, stomach, sex organs, bladder, intestines and blood vessels.
  • Compression neuropathy – This is the result of damage to a single nerve subjected to pressure

The Cause

The longer you have diabetes, the higher the potential for nerve damage. This occurs partly as a result of the different mechanisms of glucose transport found within the CNS. Instead of using insulin as a transport mode in the blood stream for getting glucose though the cell membrane, the cells of the CNS system simply let glucose enter through the cell’s membrane. In some cases, too much glucose can enter the nervous system cells leading to neuropathy.

The problem arising from too much glucose entering the nervous system cells is that there is an incomplete cell metabolism. The result is an overproduction of polyols or sugar alcohols and an excess quantity of free radicals. Both are responsible for cell damage. Possibly another contributing factor to neuropathy is the alteration of small blood vessels, which is a systemic problem in diabetes that is not properly managed.

Research indicates the following to be responsible involved in the process[4]:

  • Hyperglycemia-induced oxidative stress
  • Ischemia – not enough oxygen caused by poor circulation (another complication of diabetes)
  • Oxidized lipid–mediated nerve injury
  • Amplified mitochondrial oxidative stress in dyslipidemia
  • Possible co-regulation of lipid metabolism stress response, and axonal degeneration genes

These are scientific terms for describing cell metabolism that is working properly and thus nerve damage occurs.

Symptoms of Neuropathy

The indications of nerve damage vary according to the specific type. In the most common type of neuropathy called distal symmetric polyneuropathy, the first physical indications are a tingling sensation in either the hands and/or feet. Early signs include a feeling like an electric shock.[5] This progresses until the feet, legs or hands feel:

  • Sharp pains
  • A burning sensation
  • Stabbing sensations in one specific region of the foot or hand
  • Crawling skin
  • A very high sensitivity of touch – even the sensation of a bed sheet can result in pain
  • An overall “pins-and-needles” feeling[6]

In the instances of other types of neuropathy, there can be tingling and numbness (compression neuropathy), facial pain and/or paralysis (cranial neuropathy) and swelling and redness (Charcot foot or joint).

Medical examination

When you express concerns to a doctor over the sensations you feel in your feet, hands or elsewhere, the medical professional can test to see if they are caused by damaged nerves. The instrument of choice is a device called a “monofilament.” These instruments consist of calibrated, single-fiber nylon threads. They provide a specific amount of pressure to the skin and can detect abnormal levels of sensation.

The monofilament is a simple and affordable way of testing for neuropathy, particularly peripheral neuropathy. It is portable and very easy to use. A doctor can take it into the field or the test can be done in the office.

In addition to monofilament testing, your doctor can check your reflexes.  The doctor can test ankles and knees, elbow (both back and front) as well as your wrist. Slow reflexes may indicate nerve damage.

Whether the medical professional is using the monofilament or simply testing your reflexes, caution must be exercised when it comes to a diagnosis. Not all neurologic deficits in a diabetic patient are attributable to diabetes. Diabetics and non-diabetics can easily suffer from many other types of health problems that can manifest similar symptoms. This includes but is certainly not restricted to such serious diseases as multiple sclerosis.

Conclusion

One of the potential complications of diabetes is diabetic neuropathy. It can affect various parts of the body although it begins in the CNS. The most common type is distal symmetric polyneuropathy. Care needs to be taken to inform your doctor of any symptoms you experience and especially in the feet and hands.

References

[1] Marcovitch, H (2006). Black’s Medical Dictionary 41st edition. Lantham, Maryland: Scarecrow Press.

[2] American Diabetes Association (2009). Type 2 Diabetes. Your Healthy Living Guide. Alexandria, VA: ADA.

[3] Masharani, U (2008). Diabetes DeMYSTiFieD. New York: McGraw Hill.

[4] Pande , M; Hur, J; Hong,Y; Backus, C; Hayes, JM; Oh, SS; Kretzler, M; and Feldman, EL (2011).  “Transcriptional Profiling of Diabetic Neuropathy in the BKS db/db Mouse A Model of Type 2 Diabetes.” Diabetes, 60 (7): 1981-1989.

[5] Levin, ME; and Pfeiffer, MA (editors) (2009). The Uncomplicated Guide to Diabetes Complications, 3rd ed. Alexandria, VA: ADA.

[6] Stanley, K (2009). 50 Things You Need To Know About Diabetes. Alexandria, VA: ADA.

[7] This article was originally published July 12, 2012 and last revision and update of it was 9/10/2015.