The peripheral nerves are a network of nerves that run from the brain and spinal cord (the central nervous system). They carry impulses to and from the rest of the body, such as the limbs and organs, and are responsible for the body's senses and movements.
A peripheral nerve is similar to an electrical cable, and is made up of two parts:
- The Axon – which transmits electrical information between your brain and limbs, similar to the wiring in an electrical cable
- The Myelin Sheath – which is wrapped around the axon to protect it and ensure the electrical signal isn't broken, similar to the insulation around electrical cable
In some types of CMT, faulty genes cause the myelin sheath to disintegrate. The axons become damaged without this protection, which affects the transmission of messages between the brain and the muscles and senses. This leads to muscle weakness and numbness.
In other types of CMT, the axons are directly affected and don't transmit electrical signals at the normal strength. This means muscles and senses are understimulated, leading to symptoms of muscle weakness and numbness.