Peripheral neuropathy: Full Explanation

Peripheral neuropathy is defined as a dysfunction of the nerves from the spinal cord to the arms or legs.

There are many different types of Peripheral neuropathy with different causes. One or more nerves may be affected.

You should first learn what are nerves and their function before we head to how neuropathy happens.

Types of Nerves and Their functions

Nerves are made up of multiple microscopic fibbers called neurons.

Their main function is to carry electric signal from one place to another. They run along the arms, legs and all over the body.

Let’s say for example you want to lift up your left arm, your brain will generate electrical signal which will travel via the spinal cord, then to the nerves of the left hand all the way to the muscles of the arm to tell them to lift up the arm. The whole process of course happens very fast before you even know it.

You have two types of neurons found inside the nerves:

1. Motor neurons: They carry electrical signal form the brain to the muscles and other organs (away from the brain)
2. Sensory neurons: Carry electrical signals from the organs to the brain for interpretation.

If you accidentally step on a sharp object, the pain receptors in the foot will detect that and convert it into electric signal which then is transported by sensory neurons to the spinal cord and brain.

Now in order for nerves to function effectively they must get enough blood supply and vitamins such as vitamin B6 and B1 among others.

Types of Peripheral Neuropathy

There are three main types of neuropathies grouped according to the number of nerves affected

1. Mononeuropathy: only one nerve is affected
2. Multiple mononeuropathy: single nerves from different places affected, for example sensory nerves of part of left arm and the other being on right leg (two separate palaces)
3. Polyneuropathy: Multiple nerves affected symmetrically both sides

The most common types of neuropathies are Polyneuropathy and Mononeuropathy.

Signs and Symptoms of Peripheral Neuropathy

If you have neuropathy, you may experience symptoms related to sensation and symptoms related to motor function.

For motor function, the muscles of the affected arm or leg become weak. There is loss of strength and difficult walking or lifting the affected arm or leg. Sometimes the muscles simple twitch without any significant movement.

If you have dysfunction of your sensory nerves, then you may experience the following symptoms:

• Tingling sensation
• Burning sensation
• Loss of sensation on the finger tips/toes or the affected area
• Pricking needles under the feet
• Feeling like there is an electric shock when moving suddenly
• Cramps

Causes

Peripheral neuropathy has many causes, some of them will be listed below

Common causes

• Diabetes Mellitus
• HIV infection
• Herpes Zoster
• Trauma (injury to the nerve)
• Nerve compression by in rheumatoid arthritis
• Carpal tunnel syndrome
• Certain drugs such as Those used to treat TB

Less common

• Guillain-Barre syndrome
• Tick bite
• Lead toxicity
• Alcohol abuse
• Vitamin B6 deficiency

Approach to diagnosis

Diagnosis of Peripheral neuropathy is done after history, physical examination and some tests. Blood tests are done to find the cause of Peripheral neuropathy if it is not obvious from trauma.

Having Diabetes mellitus for example is known to be risk factor for development of Polyneuropathy as a long term complication. Other giving signs are penetrating injuries of the limbs with significant bleeding, an injury may be caused by stab, car accident or gunshot wound.

An electromyography (EMG) may be performed for people with weak arm or leg to test nerve conduction in the muscles. A weak arm may be a sign of stroke and that should be ruled out as well.

Treatment of Peripheral Neuropathy

There are two main areas of focus when treating any king of peripheral neuropathy:

1. Treat the symptoms (supportive care)
2. Treat the cause

Supportive care

Supportive care involves curing the nerve pain.

Supplements with Vitamin B6 (pyridoxine) is given:

• Pyridoxine 25mg oral once daily is given to people who are on TB treatment such as Isoniazide.

For pain associated with neuropathy, one or more of the following drug doses may be used:

• Amitriptyline 25-50mg oral at night
• Carbamazepine 200mg oral twice a day
• Paracetamol (acetaminophen) 1g oral q6h
• Tramadol 50mg oral every 8 hours for severe pain only

Treatment of the cause

The next step after management of pain is treating the cause of neuropathy. It may be an infection with Varicella Virus that needs antivirals or an injury that needs surgery for repair. The most important thing is that once the cause is identified, it should be treated.