Our nervous system is a marvelous biological machine that is tightly controlled by the brain and the spinal cord to act as a communication network between each part of the body. This occurs both at a conscious and subconscious levels. This complexity and its relationship with all body systems is a double-edged weapon, however, and it can become affected in a wide variety of conditions.
Our peripheral nervous system consists of the nerves that reach each individual receptor in our skin for sensation and each muscle fiber for motion. It starts in the spinal cord and then the nerves begin branching until they reach their destination. When signals reach the brain in sensation or come from it for motion, they come from a specific part of the brain in which the body is represented like a map, and this explains how we can move muscles or sense the location of pain without having to see it with our eyes.
What is peripheral neuropathy?
Peripheral neuropathy is a general term that means anything that can affect or damage, whether reversibly or irreversibly, the peripheral nervous system. It can affect any part of the nerve from where it exits the spinal cord to when it attaches to the muscle or receptor. It can be either affecting one nerve, also called mononeuropathy, or multiple nerves, also called polyneuropathy.
Diseases that affect a single nerve includes:
- Carpal tunnel syndrome: it affects the median nerve which supplies the hand.
- Cubital tunnel syndrome: where it affects the ulnar nerve.
- Piriformis syndrome: which causes sciatic nerve palsy, the nerve supplying the glutes and the back of the leg and thigh.
- Tarsal tunnel syndrome: tibial nerve supplying the foot and its muscles.
- Bell’s palsy: 7th cranial nerve damage following viral infection.
- Tumors: Some tumors can compress nerves, affecting their function and causing neuropathy.
On the other hand, multiple nerve affection (polyneuropathy) occurs in the following condition:
- Some hereditary disorders such as Hereditary Sensory Neuropathy
- Some diseases including inflammatory conditions like Guillain-Barre syndrome.
- Some vitamin deficiencies such as vitamin B12 deficiencies and folic acid deficiencies.
- Some metabolic diseases like diabetes mellitus and uremia from kidney failure
- Some infections, especially HIV and hepatitis C virus.
- Other conditions like paraneoplastic syndrome from tumors.
It is important to understand that the above causes, both local and systemic, do not affect the peripheral nerves equally. Some can damage nerves in a short period of time or “acutely”, and others take months or even years to cause significant or “chronic” damage. In the same sense, some affect the sensory nerves only, some affect motor only, and others affect both with varying degrees.