Specialist nerve cells in the brain and spinal cord, called motor neurones, stop working and die prematurely.
The symptoms of MND begin gradually, typically appearing on one side of the body first.
In the earliest stages of the disease, MND can lead to a weakened grip, which can cause issues with picking up or holding objects.
There can be weakness in the shoulder, which makes it difficult to lift the arm above the head.
Post source: Daily Express