What is it?
Charcot-Marie-Tooth (CMT) is a genetic condition that causes damage to peripheral nerves. These nerves are responsible for passing on commands from the brain to the muscles and also information about sensations such as heat, pain, touch and balance.
Those with CMT therefore may find their muscles become slowly weaker over the years, particularly their feet and hands. Some also find that their sense of feeling becomes duller or numb in some areas.
In the UK around 25,000 people are thought to have CMT, making it the most common inherited neurological condition.
The nerves in your arms and legs (peripheral nerves) can be compared to electrical cables. The central wire is known as the axon and the plastic outer is the myelin sheath. Axons transmit the electrical signals to and from the brain and the myelin sheath acts as insulation, speeding up and nourishing the central axon.
What are the symptoms?
· Difficulty walking due to foot problems such as foot drop, high arches or flat feet
· Weakness in the hands, feet and forearms
· Loss of feeling in the feet, lower legs, hands and forearms
· Loss of fine control in the hands
· Weakness in the muscles of the hands
· Muscle tremor
· Hearing difficulties
What causes CMT?
· CMT is caused by a genetic mutation which affects the peripheral nerves, as of 2014 there are over 80 genes which have been found to cause different types of CMT
· Some forms of CMT affect the axon– making the signal to and from the brain weaker
· Other forms of CMT affect the myelin sheath– slowing down the signal
What are the main forms of CMT?
1. Demyelinating– affects the myelin sheath insulating and nourishing the nerve’s axon
2. Axonal– directly affects the axon
How is CMT diagnosed?
A neurologist will assess a number of areas in order to diagnose CMT. This will include family history, examination of muscle strength, reflexes, sensation and looking at your eyes and feet. Sometimes you will be offered a genetic test for the most common form of CMT. There are then two electro-diagnostic tests: nerve conduction tests and Electromyography (EMG) which help to distinguish between the different types of CMT.
Find out more at: www.cmt.org.uk/