It’s a mouthful. Confused by what it even means? If you have a peripheral neuropathy diagnosis, you may want to better understand specifically what it says about your nerves.
The phrase peripheral neuropathy (or neuropathy for simplicity) is a type of damage to the nervous system. Specifically, it occurs when there is a problem with your peripheral nervous system, the network of nerves that carries information from your brain and spinal cord (central nervous system) to the rest of your body.
Peripheral neuropathy is not a lone disease, it is condition where nerves have been damaged due to an injury, inflammation, or other disorder.
Related: What is Peripheral Neuropathy?
In simplest terms — since there are over 100 types of neuropathies (1) — diagnosing peripheral neuropathy is generally a combination of the known factors.
Following are the factors that go into a peripheral neuropathy diagnosis and what they mean.
1. What Caused the Nerve Damage?
When the cause of nerve damage cannot be traced, it’s given the term idiopathic, which literally just means “unknown cause.” About a third of all cases are considered idiopathic.
When the cause can be traced, it is sometimes indicated in the peripheral neuropathy diagnosis. Examples of peripheral neuropathy diagnoses that include the cause are:
- Diabetic neuropathy
- Toxic neuropathy
- Alcoholic neuropathy
- Compression mononeuropathy
2. What Type of Nerve is Damaged?
The type of nerve affected is indicated in a peripheral neuropathy diagnosis. There may be one type of nerve fiber affected or a combination of nerve fibers.
There are three types of peripheral nerves that relay information between your brain and the rest of your body.
- Sensory nerves carry sensory information to the brain, like sight, smell, and sensation.
- Motor nerves connect the brain and spinal cord to muscles to stimulate movement.
- Autonomic nerves connect information with the brain and spinal cord to control involuntary function, like blood pressure, digestion, and heart rate.
Examples of diagnoses that state which nerve fibers are damaged include:
- Small fiber neuropathy (SFN): autonomic fibers and sensory fibers are mainly involved (5).
- Small fiber sensory neuropathy (SFSN): only the small sensory nerve fibers are involved (6).
- Sensorimotor polyneuropathy: affects both sensory and motor nerve fibers.
3. Which Nerves are Damaged?
Location of nerve damage and number of nerves damaged can vary widely case to case since it can affect any part of the body served by the peripheral nervous system.
A peripheral neuropathy diagnosis may reference the general location of damage. For example:
- Distal indicates the area farthest from the central body (feet)
- Symmetric indicates both sides of the body are affected
A peripheral neuropathy diagnosis will typically indicate the number of nerves affected (one, a few in limited locations, or many throughout the body).
Mononeuropathy is damage that occurs to a single nerve in the peripheral nervous system. It is most often caused by injury where long-term pressure on the nerve from misalignment in a joint, constriction, or swelling. Conditions affecting the whole body (systemic) can also cause damage to one nerve, but it is much less common (2).
Technically any single nerve can become damaged, but mononeuropathy is more common in nerves that are close to the skin, bone and joints where they can become compressed (3).
Examples of mononeuropathies are:
- Carpal tunnel syndrome
- Femoral neuropathy
- Radial nerve dysfunction
Multifocal neuropathy is damage to single nerves in more than one location. This type of neuropathy is more rare than the others and is generally attributed to autoimmune diseases, meaning your immune system mistakenly attacks your nerve cells as if they were invaders.
Motor nerves are usually affected in multifocal neuropathy. Those are the nerves that control your muscles, so damage causes symptoms like weakness, twitching, and cramping.
More commonly, people experience damage in multiple nerves throughout the body, called polyneuropathy (4). Infections, toxins, drugs, cancers, nutritional deficiencies, diabetes, autoimmune disorders, and other systemic disorders can cause many peripheral nerves to malfunction simultaneously.
Polyneuropathies are sometimes broken down into acute (where the condition comes on suddenly) and chronic (where the condition develops slowly over time).
4. What Part of the Neuron is Damaged?
To breakdown a diagnosis further, the type of nerve damage may be identified as well.
There are essentially two types of nerve damage that are typically identified in a peripheral neuropathy diagnosis.
- Demyelinating refers to damage to the protective myelin sheath around the axon and is usually a result of immune related, genetic, or inflammatory conditions (7).
- Axonal neuropathy refers to damage to the axon, the nerve fiber which carries electrical impulses. Axon damage occurs in a dying back pattern, starting at the point of damage (as in an injury) or at the furthest point away from the central body (the feet), and progress towards the central body (8).
Summary of a Peripheral Neuropathy Diagnosis
A peripheral neuropathy diagnosis is a combination of known factors involved with your condition and may include the location of damage, the type of nerve damaged, what part of the nerve is damaged, and/or what caused the damage.
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