Oxford University Hospitals explains that the term motor neuron disease (MND) encompasses several different conditions, all of which involve premature degeneration of motor nerves (known as neurons or sometimes neurones).
When French Neurologist Jean-Martin Charcot, who is credited for being the first to detail descriptions about MND, looked at patients, he found that the most common feature of the condition was muscle wasting, the medical term for which is amyotrophy.
In addition to this, when looking at patients’ spinal cords, he found that many had scarring of the descending upper motor neuron pathways from the brain. The medical term for which is lateral sclerosis. As both of these processes were occurring simultaneously, Charcot coined the term amyotrophic lateral sclerosis (ALS).
Nearly 90 percent of patients with MND have the mixed ALS form of the disease, explaining why both of the terms are commonly used to mean the same thing.