Are your hands and feet burning? Feeling like pins and needles? This could be Small Fiber Neuropathy (SFN)

Do you sometimes feel a burning sensation in your hands or feet, a tingling sensation, or a prickly pain? Do you feel unbearable pain even when the bedsheet hits your leg? Even if you think these things are just random things, there may be a medical reason behind this. Today we are going to talk about a condition called Small Fiber Neuropathy (SFN), which causes these symptoms. Although this is a bit of a long name, let's understand it simply.

What is Small Fiber Neuropathy (SFN)?

Simply put, Small Fiber Neuropathy (SFN) is a condition of the peripheral nervous system. Okay, that sounds a bit complicated, doesn't it? Let's break it down.

Imagine that our body is covered in a network of nerves, like an electrical wiring system. It has very fine, tiny nerve fibers, no thicker than a hair. These are the ones that carry sensations like heat, cold, and pain that our skin feels to the brain. SFN is when those tiny nerve fibers become damaged for some reason.

When these nerves are damaged, they don't work properly. They start sending the wrong signals to the brain. That's why you feel burning, prickling, or tingling pain in your arms and legs for no reason.

This condition affects not only the nerves in the skin, but also other delicate nerves that control vital functions in our body (for example, blood pressure, heart rate). SFN is not life-threatening, but it can sometimes be a symptom of another serious condition.

What are the main symptoms of this?

The symptoms of SFN can vary from person to person. But the most common symptom, especially in the early stages, is pain in the hands and feet. This pain sometimes comes and goes, sometimes it is constant. It can also get worse over time.

Let's see what the main symptoms are.

Why does Small Fiber Neuropathy (SFN) occur?

This is a very important question. In about half of people with SFN, no cause can be found . Doctors call this condition ``Idiopathic Small Fiber Neuropathy.'' That means "SFN of unknown cause."

However, there are several factors that could account for the remaining half.

Due to other medical conditions

Often, SFN is a side effect of another disease.

• Diabetes: The main and most common cause of SFN is diabetes. Uncontrolled blood sugar levels over a long period of time can damage these delicate nerves.
• Impaired glucose intolerance: This is a precursor to diabetes. Here too, nerves can be damaged.
• Immune system disorders:Diseases like Celiac disease, Sjögren's syndrome, and Sarcoidosis can cause the body's own immune system to attack these nerves.
• Infections: Infections such as Hepatitis C or HIV can also cause SFN.
• Vitamin B deficiency: Vitamin B12 deficiency in particular can damage nerves.
• Alcohol use disorder
• Thyroid disease
• Metabolic syndrome

Inherited disorders

Sometimes this condition can also be caused by genetic factors. This means that someone in your family has it and you can get it too. `Fabry disease` and `Familial amyloidosis` are some such examples.

Due to some drugs and toxins

These nerves can also be damaged as a side effect of some of the medications we take.

• Some chemotherapy drugs for cancer
• Some antibiotics (e.g. metronidazole, nitrofurantoin)
• Drugs like `tumor necrosis factor inhibitors`

What are the complications of this?

There are two main complications caused by SFN.

1. Loss of pain sensation: One of the main risks of this is loss of pain sensation. Imagine you are touching a hot pot on the stove, but if you don't feel the heat, you could burn your hand. The chances of such accidents happening are high. Therefore, it is important for someone with SFN to regularly check their limbs for any injuries.

2. Falls: Dizziness, difficulty walking, and loss of balance increase the risk of falls.

How does a doctor find this?

Once you've described your symptoms, your doctor will examine you and ask you questions. There is no single test to confirm SFN, so you may need to have several tests.

• Skin biopsy: This is the most important test to diagnose this disease. Here, a very small piece of skin (about 3 millimeters) is taken and examined under a microscope to see how dense the fine nerve fibers are.
• Quantitative sudomotor axon reflex test (QSART): This tests how the nerves involved in sweating are working.
• Electromyography (EMG) and Nerve conduction studies: These tests usually look at the function of large nerve fibers. These tests are often normal in SFN. However, they are helpful in ruling out other neurological conditions.
• Blood tests: Blood tests are done to look for underlying causes, such as diabetes, vitamin deficiencies, and thyroid problems.
• Genetic tests: This test can be done if there is a suspicion of a hereditary cause.

What are the treatments?

Doctors focus on two main goals during treatment.

1. Treat the underlying cause: This is the most important thing. If it is due to diabetes, then the diabetes is well controlled. If it is a vitamin deficiency, then the necessary vitamins are given. When the cause is properly treated, the damage to the nerves can be stopped or reduced.

2. Controlling pain and other symptoms: There are special medications to control nerve pain.

Some of the main types of drugs used are listed below.

When should I see a doctor?

If you have already been diagnosed with SFN by a doctor, see your doctor again if you notice the following changes:

• What if the pain in my feet now spreads to my hands?
• If the frequency or severity of the pain increases.
• If new symptoms appear, such as dizziness or difficulty walking.

When you see your doctor, you can ask the following questions.

• "Why am I having these symptoms?"
• "Will these symptoms get worse?"
• "What are the best treatments I can have?"
• "Will I have this condition forever?"