maple
Canadian Medical Alliance for the Preservation of the Lower Extremity
The majority of the neuropathic ulcers described
on this website arise from neuropathy. So it's
important to understand a little about this topic.
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On this page we discuss what neuropathy is and
some of the conditions that may cause it.
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We discuss the clinical effects of neuropathy in
greater detail here, but let's start with some
definitions.
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What is Neuropathy?
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Simply put, the word "neuropathy" describes
a disorder in the nerves that causes abnormal
nerve function.
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Many people assume neuropathy refers specifically to the loss of sensation. And certainly, this is the major issue with how neuropathic ulcerations form, because when we can't feel pain, we cannot feel when excessive pressure, friction and damage starts to cause pathology.
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But neuropathy affects other nerves in the body as well. Motor nerves, the nerves that send signals to our muscles to move us, may be affected by neuropathy. And autonomic nerves, the nerves that control the things in our body we don't think about, like heart rate and blood pressure, are affected too. We discuss this in more detail here.
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How many Diabetics Will Get Peripheral Neuropathy (altered sensation in the feet)?
60-70%. So about 2 in 3.
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Dyck PJ, Davies JL, Wilson DM, Service FJ, Melton LJ 3rd, O'Brien PC. Risk factors for severity of diabetic polyneuropathy: intensive longitudinal assessment of the Rochester Diabetic Neuropathy Study cohort. Diabetes Care. 1999
Sep;22(9):1479-86. PubMed PMID: 10480512.
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Yet over 90% of people with diabetic peripheral neuropathy are unaware they have it.
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Bongaerts BW, Rathmann W, Heier M, Kowall B, Herder C, Stöckl D, Meisinger C, Ziegler D. Older subjects with diabetes and prediabetes are frequently unaware of having distal sensorimotor polyneuropathy: the KORA F4 study. Diabetes Care. 2013
May;36(5):1141-6. doi: 10.2337/dc12-0744. Epub 2012 Dec 28. PubMed PMID: 23275355; PubMed Central PMCID: PMC3631873.
What are the Causes of Neuropathy?
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There are dozens of possible causes of neuropathy. And they may tend to cause varying types of symptoms involving both sensory, motor, and autonomic nerves.
Diabetes is far and away the most common cause
of neuropathy. In fact, diabetes is more common
than all other causes of neuropathy combined.
Diabetes is so common as a cause of neuropathy
that it often erroneously assumed that any
individual with neuropathy must have diabetes.
The effect of diabetic neuropathy on the foot can
be seen in a variety of nerves. It can affect the
autonomic nerves, leading to dry skin and altered
circulation. It can affect motor nerves, leading to
deformities in the foot. And it can affect the
sensory nerves, leading to ulcers (holes in the
skin). The combination of these effects may lead
to infections, amputations and even premature
death. For more on diabetes, click here.
Alcoholic toxicity is another condition that can
lead to significant levels of neuropathic dysfunction,
and it can mimic diabetic neuropathy in that it can
results in the loss of sensation and ulceration.
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Autoimmune and connective tissue diseases are a broad category of overlapping diseases that may also cause neuropathy. Rheumatoid arthritis (RA, seen below left), lupus, Sjogren’s syndrome, multiple sclerosis (MS), Necrotizing Vasculitis, Chronic Inflammatory Demyelinating Polyneuropathy, and Guillain–Barré Syndrome (below right) are the most common examples.
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The two classic examples of an Infection causing neuropathy are leprosy (Hansen's disease) and syphilis. In fact, before the advent of antibiotics that can treat these conditions, and before the advent of insulin and other medications that helped diabetics live longer, leprosy and syphilis were the most common cause of neuropathic ulcerations. We still see leprosy in India, Brazil, Indonesia and parts of Africa, where antibiotic therapy can be expensive and hard to come by. But other than for immigrants, leprosy is largely a thing of the past in Canada and the first world. Today the most common infections causing neuropathy are Lyme disease, Shingles, HIV, Epstein Barr, Diphtheria, and Hepatitis C.
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Vitamin deficiencies involving vitamins B-1, B-6, B-12, folate, vitamin E, and niacin may be the second most common cause of neuropathy. However, vitamin deficiencies don't typically create the level of pathology such as ulcerations that many of these other conditions do.
Genetic conditions like Charot-Marie-Tooth
(CMT) disease can cause neuropathy. An
example of the motor CMT neuropathy,
characterized by high arches and contracted
toes is seen to the right.
Less common examples of genetic disorders
that can cause neuropathy are porphyria and
Refsum's disease.
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Spinal abnormalities such as trauma,
malformations and compressions and
disc disease can lead to significant
neuropathy commonly seen in the
lower extremity.
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This may result in chronic pain, a chronic
absence of pain, muscle wasting, weakness
and dysfunction.
Neoplasms (tumors), both malignant
and benign can exert pressure on nerves,
causing neuropathy. One example is seen
to the right.
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Repetitive motion injuries like carpal
tunnel disease and tarsal tunnel disease in
the foot can irritate nerves, creating
neuropathy. In the hand this may result in
tingling to burning pain, weakness and
dysfunction. In the foot this may lead to
similar symptoms and make it difficult to
walk.
Medications for things like chemotherapy
and HIV infections can be toxic to nerves
and result in damage that may result in
numbness, pins and needles sensations,
burning and weakness.
Chronic disease of the liver and kidney
can also cause neuropathy. In fact, the
treatment for severe kidney disease,
dialysis, can be a cause of neuropathy
in and of itself.
The manifestations of renal disease exhibited
in the foot has become a specialty of the author
of this web page. An example is seen to the
right.
Miscellaneous causes of neuropathy include
a tight cast, particularly the peroneal nerve,
amyloidosis, hypothyroidism, and exposure to
heavy metals and chemicals.
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There are literally dozens of causes of neuropathy.
Yet it has to be pointed out that some 20% of
sensory neuropathy cases are idiopathic—with no
known cause. So there are either more potential
causes of neuropathy than we know, or we are not
very good at identifying and differentiating these
conditions.
Because diabetes accounts for more cases of
neuropathy and wounds than all other causes
combined, we have a page devoted to diabetes.
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To learn more about the effects of neuropathy, click here.
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Scanning electron micrograph of cultured human neuron (nerve cell).
Photo credit: Mark Ellisman and Thomas Deerinck, National Center for Microscopy and Imaging Research, UC San Diego
"When pain is over, the remembrance of it often becomes a pleasure."
--Jane Austen, Persuasion
Above: The collapse of this foot in stance is a result of the loss of function of the motor nerve to the posterior tibial muscle, which supports the arch and pushes off in gait. This is a result of Guillain–Barré disease.
Above: The classic appearance of a foot with rheumatoid arthritis, with misaligned toes drifting laterally (away from the midline of the body) and the prominent rheumatoid nodule (the lump on the bottom of the foot). When accompanied by sensory loss, these nodules may ulcerate.
Above: The typical high arch and contracted digits seen with the motor neuropathy of Charcot-Marie Tooth Disease. This can lead to a jarring gait, and pressure spots in the ball of the foot and in the tips of the toes.
Above: A rare neoplasm known as mycosis fungoides, a lymphoma of the skin. These can create issues with the sensory nerves and may ulcerate. In this case, the neoplasm was fatal.
This page written by Dr. S A Schumacher
Podiatric Surgeon
Surrey, British Columbia Canada
All clinical photographs owned and provided
by Dr. S A Schumacher. They may be reproduced
for educational purposes with attribution to:
Dr. S A Schumacher, Surrey, BC Canada
To return to the top of the page,
click on the maple leaf to the right.
Above: The foot of a diabetic with neuropathy.
Above: Three ulcers seen in the patient with neuropathic foot
of this dialysis patient with chronic, end-stage renal disease.
These lesions all healed, and the patient was able to walk with
custom-made shoes.
