What is Peripheral Neuropathy?
Everything Your Doctor Doesn’t Have Time to Explain About Neuropathy
If you’re reading this, it’s likely you suspect you might be dealing with peripheral neuropathy. Or your doctor gave you a diagnosis, but you left your appointment still confused about what that really means.
Every case of peripheral neuropathy is pretty unique to its owner. Different causes, different distribution patterns, different impact types — all causing different symptoms in the body. At the same causing all kinds of confusion.
But why so varied? Because there are so many different things that can go wrong with your complicated nervous system.
Simple Explanation About Your Nerves
Before talking about the different types and kinds of peripheral neuropathy, a quick crash course about your peripheral nervous system and how it works is needed.
You’re likely more than aware that your nerves work by sending signals throughout your body, relaying information and signals from one area to another.
Motor nerves help your brain tell parts of your body when to move.
Sensory nerves relay information about things like pressure, pain, and vibration to the brain and spine.
Autonomic nerves control things that we don’t consciously control, like our heart rate and our digestive system.
Your nervous system is divided between the central nervous system — which is located in the brain and the spine — and your peripheral nervous system, which includes everything else that radiates outwards.
Closer to your central nervous system are the cell bodies, but the axon is the part to focus on here. The axons extend like branches all the way out from the nerve bodies in your central nervous system, to the tips of your fingers and toes.
Axons are covered by something called a myelin sheath, which is basically a protective coating of fats and proteins — it keeps your thicker nerve fibers protected and helps them conduct information faster.
Once a message or impulse has traveled down the axon branches, it must cross something called a synapse, which is essentially a gap between neurons. This is how a message gets to the next nerve, or to the body part to which it’s relaying its message.
Peripheral neuropathy, then, has a tendency to work in one of three different ways:
- Damaging the myelin sheath (demyelinating neuropathy)
- Damaging the axon itself (axonal neuropathy)
- Widening the space between nerves
Types of Nerve Damage
One of the very first considerations when peripheral neuropathy might be taking hold involves addressing what type of damage the neuropathy is inflicting.
Generally speaking, neuropathy tends to take its toll in one of two distinct ways.
Your nerve fibers — or axons — come in varying lengths. Some are smaller, some are medium-sized, and some are larger. It’s probably no shock that the larger ones have a tendency to be saddled with heavier informational loads. They also tend to be required to transmit information faster than their thinner counterparts.
Your larger nerve fibers are typically responsible for things like motor functions and the occasional bit of sensory relay. Being coated with a myelin sheath helps these larger fibers stay protected by insulating them from damage (very similar to the rubber coating on the outside of any electrical wire) while encouraging faster conductivity at the same time. When the myelin sheath is damaged, the nerve is not only put at risk for further damage, but it’s unable to transmit as fast as it normally should be.
Sometimes the myelin sheath is fully compromised and peripheral neuropathy is allowed to progress to the point where it starts eating away at the axon underneath. Other times, peripheral neuropathy attacks nerves that don’t have a myelin sheath to begin with.
In either case, the result is axonal neuropathy, wherein the axon is actually being directly damaged.
This is understandably worse than demyelinating neuropathy.
While demyelinating neuropathy is bad because it puts nerve endings at risk and makes them less effective at doing their jobs, axonal neuropathy can be worse in that it can cause nerves to do the wrong jobs altogether.
Positive Symptoms vs. Negative Symptoms (Really, They’re All Negative)
Damaged axons have a tendency to respond in one of two general ways, each one bringing with them a different set of symptoms.
Neuropathy causing positive symptoms will result in your nerves either overreacting wildly to normal stimulation or reacting to stimulation that isn’t actually there in the first place.
Neuropathy patients who can’t handle the agony that shoes and socks have become, or have trouble falling asleep due to phantom sensations keeping you up at night — you’re dealing with what is called positive symptoms.
Negative symptoms are how we describe what happens when your nerves don’t do their job well enough, or even at all. Slow conductivity or synaptic interruption can result in things like reduced sensation, numbness, or even a complete loss of feeling in parts of the body.
Nerve Damage Causes: Biological or Mechanical?
The cause is a huge part of solving the peripheral neuropathy puzzle. Though, not every case of peripheral neuropathy has a discernible cause. Now, don’t be alarmed. This doesn’t mean your doctor isn’t doing their job. It just means that, surprisingly enough, a lot of instances of peripheral neuropathy are defined as idiopathic in nature. This means that we simply don’t know what’s causing them.
Neuropathy is often caused by what we call a biological or pathological process. This basically means that something inside your body — whether caused by a foreign invader or not — has gone awry, resulting in damaged nerves.
Another very common type of biological process that causes neuropathy is known as an autoimmune response. This refers to an instance wherein your body actually attacks itself, destroying friendly cells with an immune system that would typically be used to target dangerous invaders and pathogens.
A biological process can be an infection or a virus. It might also be high blood glucose levels, toxicity from reduced kidney function, medications, environmental toxins. There are over 100 known causes of peripheral neuropathy, yet most of which cannot be identified by any sort of diagnostic testing.
Another category of causes for nerve damage is the mechanical process. This means that nerve damage was caused by way of some outside force. This might either be the movement of your very own body, or it could mean that your body has been impacted by something external.
Among the most common types of mechanically-induced neuropathy is carpal tunnel syndrome. You might already even be familiar with this term, having never realized that it’s actually a form of peripheral neuropathy. As you may well know, carpal tunnel syndrome is the result of repetitive motion causing a nerve in your wrist to become constricted, resulting in painful feedback. This is a perfect example of a mechanical cause.
Other examples of mechanical causes are things like injury, surgery, and other types of bodily trauma. Any number of traumatic experiences to the body can result in misalignment, compression, or other conditions that wind up damaging the peripheral nerves.
Neuropathy Distribution Type
Another one of the main ways that peripheral neuropathy is categorized is by its distribution pattern throughout your body.
This is to say: What kind of an area is your neuropathy impacting? Is it restrained in one place? Or is it occurring in multiple areas? Different distribution patterns get different names and help further categorize each type of peripheral neuropathy.
Mononeuropathy (Focal Neuropathy)
When nerve damage keeps itself mercifully contained to one single area in the body, we call it mononeuropathy or focal neuropathy. (“Focal” meaning it’s focused in one place.)
Most often, mononeuropathy is caused by a mechanical process. Typically repeated motions (especially ones that strain a part of the body), injuries, and other activities that can wind up causing nerves to become pinched or compressed. And when they do, you’ll feel it. Carpal tunnel syndrome is one of the most commonly-experienced types of focal compression mononeuropathy.
The good news here is that many times, focal neuropathy can be stopped in its tracks by simply changing the day-to-day behavior that brings it on.
Polyneuropathy (Generalized Neuropathy)
This one is probably why you’re reading this article right now. While mononeuropathy is common enough, it’s usually easy to treat and isn’t a chronic issue very often.
Polyneuropathy, on the other hand, can be more difficult to identify the source and more challenging to treat.
When polyneuropathy sets in, it means that multiple nerves are being damaged, and sometimes it happens all over the body at the same time. Typically, polyneuropathy takes hold first in the farthest parts of the body, where your nerve endings are the farthest away from the nerve bodies that help keep them healthy and functioning well, before spreading towards the more central areas.
It’s not quite as common as its counterparts and has an overwhelming tendency to be caused by a biological process, like inflammation or disease. When this type of neuropathy presents, it’s usually because the damage is actually originating near the central nervous system, where the nerve bodies are gathered.
Just between mononeuropathy and polyneuropathy sits multifocal neuropathy. This means there are several focused pockets of nerve damage, distributed throughout the body but in concentrated areas.