maple

Canadian Medical Alliance for the Preservation of the Lower Extremity

Effects of Neuropathy


We defined neuropathy as a pathology within the nerve and discussed some of the many possible causes of neuropathy here.  On this page we discuss what effects neuropathy has on our bodies.  

What symptoms Occur with Neuropathy?

There are three main nerve groups affected by neuropathy.  First, neuropathy may affect the autonomic nerves, creating autonomic neuropathy.

 

 

 

 

 

 

 

 

Autonomic nerves control things you don’t think about. 

 

For example, your blood pressure, respiration, and heart
are controlled
by autonomic nerves.  And an autonomic
neuropathy may
result in high blood pressure (hypertension),
dizziness or
fainting and difficulty breathing.  Autonomic
neuropathy
may cause an abnormal or irregular heart rate.   

 

 

 

 

 

 

 

Our eyes' ability to adjust to dim light is controlled by
autonomic nerves, and neuropathic patients may have
difficulty focusing their eyes. 

 

They may have difficulty driving in the dark.

 

 

 

 

 

 

 

 

Autonomic nerves control how food moves through your

digestive system (Peristalsis) and how food is processed. 

 

So patients with autonomic neuropathy may experience

altered digestion, diarrhea or constipation, nausea,
altered apetite, or difficulty in swallowing. 

 

 

 

 

 

 

 

 

Urination is controlled by autonomic nerves and autonomic neuropathy may result in incontinence or an inability to empty the bladder. 

Sexual function is mediated by autonomic nerves and can be adversely affected by neuropathy. 

 

 

 

Perspiration is controlled by autonomic nerves as well, and

abnormalities in perspiration can be an result of neuropathy.  
 

One observable sign of neuropathy is excessive perspiration
with eating, something known as gustatory perspiration
It
is similar in appearance to the sweating seen when
someone
is eating spicy food, except in the neuropathic
patient, it is

seen when eating any meal. 

So keep an eye on the forehead of a diabetic when he is
eating and you may witness this phenomenon.  

 

 

In the lower extremities, patients with an autonomic neuropathy may exhibit excessive sweating, or extremely

dry skin (below left and right).  So if you have an autonomic neuropathy and dry skin, make certain to moisturize

appropriately.  

 

 

 

 

 

 

 

 

 

 

By altering moisture content, neuropathy can thus weaken

the skin, creating small cracks that make it more susceptible
to fungal infection,
bacterial infection--and ulceration. 

 

 

 

 

A diminished ability to perspire may also make someone less able to tolerate the heat.

 

 

 

 

Autonomic nerves also control blood flow, and thus, 

autonomic neuropathy can affect blood flow to the feet. 

The vessels may be open (patent), but the blood may be

shunted back to the heart prematurely

In the image to the right, we see the white, blanched skin

of the toes, indicating poor blood flow from the nerves

clamping down on the flow to the toes.

The toes may feel cold and uncomfortable.  Diminished
blood flow certainly inhibits the body's ability to repair

injury. 

 

 

 

 

 

 

 

 

 

In severe cases, as seen to the left, neuropathy can result in circulation so poor that the tips of the toes may even turn black and die--gangrene.

 

 

 

 

 

 

 

Neuropathy may affect the motor nerves—the nerves heading from the brain to the extremities (hands and feet).  In the foot, this may result in hammertoes, bunions, or an abnormal arch structure.  This may cause increased pressure under bony prominences, that predisposes a patient to ulceration. 

To the left we see tight tendons on the top of the foot caused from motor neuropathy.  Abnormal nerve signals sent to the muscles cause the toes to contract and twist in odd directions. 

As this progresses, ulcers could form on the top of the toe (below left) or on the tip of the toe (below).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

To the left we see a contracted large toe.  As the toe gets pulled upwards, it puts a retrograde force back
on the ball of the foot.  This has created a callus, and
is a potential site of a future ulcer.

This pressure site could be offloaded with an orthotic or a specialized shoe.  It could also be surgically corrected to realign the bones and prevent the mechanical forces that might cause the ulcer.  

 

 

 

 

 

 

Neuropathic contractures can be quite significant. 

Imagine the increase in pressure exerted on the
ball of
the foot when the patient to the right stands
up. 

Imagine how the toes fit in a regular shoe.  


Neuropathic-induced deformities can increase the
chances
of ulceration and infection.

 

 

 

 

 

 

 

 

 

Motor neuropathy can also change biomechanics -- the
movement function of the body.  An example can be
seen to the right, where the foot pronates, or rolls
inwards too much.  

This foot will be exposed to increased pressure and

friction forces, the physical forces creating ulcers.  

But abnormal mechanical function of the body like this
may also create issues higher up. 

 

 

When one foot pronates (rolls in) excessively,

the arch flattens and the leg and thigh rotate
inwards.

This may cause the pelvis, which sits on top of
the thigh bone to roll forward, down, and
become tilted (left).


 

 

 

 

 

 

The vertebrae (the bones of the spine) rest on the pelvis.  So a tilted pelvis could, in turn, cause the vertebrae to become misaligned. A previously straight spine (below left) may become crooked and misaligned (below right), a condition known as scoliosis. Such a deformity may compress nerves as they leave the spine, causing further nerve dysfunction.

 

 

Patients with motor neuropathy may also move

more clumsily and be more prone to falls. 

So severe is the motor neuropathy of the patient
to the right that he needs both an ankle brace and a

walker to get around. 

 

Neuropathy may also present as

sensory neuropathy—damage to
the nerves
coming from the
extremities towards the brain. 

 

Patients with sensory neuropathy

may experience a burning  or

“pins and needles” sensations,

abnormal electrical sensations,

or discomfort.

 

At times this can become very

uncomfortable and disabling. 

 

 

Sometimes there is just pain.  Constant, unrelenting pain.  Unassociated with any stimulus.  No injury.  No wound.  Just pain.

 

More commonly, and most importantly for patients with ulcerations on the foot, sensory neuropathy may experience a lack of sensation, or numbness. 

This, too can become profound.  Many doctors in the wound care field can relate stories of having found needles, pins, thumbtacks, and nails in the foot without the patient noticing. 

 

 

The author of this web page once found a jack (as with the children's
game
ball and jacks, right) inside a 36-year-old female patient's heel
bone.  The
patient couldn't feel having stepped on it; she only noticed
the problem
because of the smell of the infection that developed.  

 

 

 

And the author has had several patients pull their feet out of their shoes and leave a toe behind, without noticing anything amiss.

In many cases, amputations can be performed in the neuropathic patient, without the need for anesthesia, so profound is the neuropathy. 

 

As pain and temperature run up the same nerves, patients

with neuropathy commonly cannot feel the cold.  

The author of this web page has had several patients who

bragged about being tough enough that they were able to
walk barefoot across the snow to get the mail or take out
the trash. 

In reality, their feet were simply numb from the loss of nerve
function from neuropathy, and they were causing themselves
harm. 

 

 

 

 

 

 

 

 

 

The author of this web page had a patient who had already undergone the amputation of two toes, and was quite distraught when he developed a new ulcer on the bottom of his foot, thinking he might now lose a leg. 

It took over two months for us to get the ulcer healed. 

 

The patient was so happy, he rewarded himself by going fishing.  He stood in the river in waders, large boots that allow you to wade out into the water without getting your feet wet. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The waders kept the feet dry successfully. 

But even in the summer, the rivers of British Columbia run

cold, and the patient couldn't feel the thermal damage on

his toe.

The toe became infected with a resistant organism, and the

patient passed away from the infection that resulted from

this wound.  

 

 

 

 

 

 

 

 

 

 

At times the problem is just the opposite.  Sometimes neuropathic patients may also feel their feet are cold,

when they are not. 

Combine this with an inability to feel heat, and a greater fragility of tissues, and you have a problem.  

 

 

The author of this webpage

once saw a woman who
went into a hot tub with
her husband. 

 

She had neuropathy. 

He did not. 

She came out with enough
skin damage that she 
required substantial skin
grafts on her feet and legs. 

He emerged from the same hot tub without ill effect.  

 

Below we see a patient who, in the middle of summer, felt his feet were excessively cold.  He put his feet against
a heater.  He couldn't feel the damage.  

He presented with gangrene of the tips of his middle three toes of his left foot (below left).  When the black skin sloughed off (below right), bones were visible in two of the toes.   We removed the bones, and the patient recovered without issue.  But at no point did the patient take a single day off work.  It didn't hurt, so he refused to believe, it was a major issue.  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

To the near right we see an

x-ray of a normal ankle joint.  

 

The patient pictured to the

far right presented to the

author's office complaining

of instability in his ankle

while walking.  

He required a cane to help

support him, but he told 

me he knew it wasn't serious

because there was no pain.  

Even after the x-rays came

back and the patient he was

informed he had suffered a

devastating, limb-threatening

comminuted ankle fracture,

he was convinced it was

probably just a sprain.

 

 

 

 

 

Patients with sensory loss often find

walking more difficult, in that they

cannot feel the ground, another major
component
in instability. 

To the right is a patient who cannot
feel the
ground when he walks, and
this has given him an abnormal,

swaying gait. 

He works in construction, and he has
such poor
sensation that he falls 2-3
times per day at work, often just from
walking.

His co-workers have accused him of
being drunk.    

It's no longer safe for him to be on a

ladder.

It's better for him during the day when he can use his eyes to reorient his position.  At night, or when he is in a dark room, he can neither feel the ground nor use his eyes to reorient his body position, and he is particularly vulnerable to falling.  With the poorer circulation, poorer healing, and weaker bones of advancing age, the falls will become increasingly dangerous.

 

 

 

 

For many neuropathic patients, sensory loss simply

means they cannot feel when they've been on their

feet too much. 

 

They don't feel pain that the rest of us may feel, and

can't tell when the skin is becoming bruised, breaking

down and an ulcer is developing.  

 

 

 

 

 

Sensory loss is the single biggest factor in the development of ulcers, and without neuropathy, ulcers are very unlikely to develop.  But when we combine sensory loss with new bony prominences and abnormal gait from motor neuropathy and dry, less resilient skin from autonomic neuropathy and it's easy to see how foot ulcers develop.  We've devoted a page to neuropathic ulcerations here.  And we describe how the skin breaks down with neuropathy here.  

 

 

 

Further complicating matters, diabetics often develop

diabetic retinopathies (eye damage), too, which may
adversely affect their vision. 

 

So not only may they not be able to feel that something

is wrong with their feet, they often cannot see the
problems either. 

 

And with age, stiffness, arthritis, and weight gain,
they may not be able to bend to reach and care

for their feet either, even if they see a problem.

 

 

In Summary

So motor neuropathy can cause the toes to contract and the gait to become altered. 

 

Autonomic neuropathy can cause the skin to become dry and compromised, susceptible to trauma, ulcerations and infections.  It can also diminish blood flow to the feet, particularly the toes, making it difficult for the body to repair this damage. 

 

And sensory neuropathy can dull the sensations that should

warn the patient that any of this is happening.  This makes

the neuropathic patient more likely to ignore these harmful

processes, where as with the ability to feel pain, we would

listen to the warning signs of this damage.

  

 

 

 

“Just because you can't see the wound doesn't mean it isn't hurting.”
                          

-- Jodi Picoult, The Pact

"And I get down on my knees and pray, that they go away

And still it begins, needles and pins."

--"Needles and Pins"
   The Ramones

"Pain we obey"

 

             --Marcel Proust

Autonomic Neuropathy

Motor Neuropathy

Sensory Neuropathy

To return to the top of the page,
click on the maple leaf to the right.

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

Save a Life

Save a Limb

© 2023 by the Canadian Medical Alliance for the Preservation of the Lower Extremity.