What Is Motor Neurone Disease?

Motor neurone disease (MND) is a group of conditions in which the nerve cells that control movement gradually stop working. In much of the world, including the United States, the most common form is known as ALS (amyotrophic lateral sclerosis), or Lou Gehrig's disease. The names point at the same underlying problem: the slow failure of the body's motor neurones.

What the disease does

Your muscles do not decide to move on their own. They wait for instructions, carried from the brain down the spinal cord by specialised nerve cells called motor neurones. In MND, these neurones degenerate and die. The messages stop getting through, and muscles that no longer receive signals begin to weaken, stiffen and waste away.

Crucially, MND usually attacks only the motor system. In most people the senses, the bladder and bowel, and the intellect are largely unaffected. This is the particular cruelty of the disease and, in Hawking's case, the source of one of the most striking facts about him: his body failed progressively while his mind remained entirely intact. He continued to do original theoretical physics long after he had lost almost all voluntary movement.

Symptoms and progression

MND often begins subtly, and its first signs depend on which muscles are affected earliest. Common early symptoms include weakness in the hands or legs, a weakening grip, slurred speech, difficulty swallowing, muscle cramps and twitches, and unexplained stumbling or fatigue. Over time the weakness spreads. As the muscles involved in speaking, swallowing and breathing become affected, communication and breathing grow difficult, which is ultimately what makes the disease life-threatening.

The disease does not follow a single path. It varies enormously between individuals in where it starts, how fast it moves, and which functions it takes first.

Who it affects, and the prognosis

MND is considered a relatively rare disease. In the United Kingdom, around 5,000 adults are living with it at any one time. It can affect adults of any age but is most often diagnosed in people over fifty. There is, as yet, no cure. Treatments can ease symptoms and modestly slow progression, and good care and communication technology can preserve quality of life and independence, but they cannot stop the disease.

The prognosis is hard: most people live between two and five years from the onset of symptoms. That figure is exactly what makes Hawking's story so extraordinary.

Why Hawking's survival was so exceptional

Hawking was diagnosed in 1963, at the age of twenty-one, and told he might have two years. He lived for fifty-five more. Survival of that length is almost without parallel and is not fully understood. The likeliest explanation is that he had a rare, very slowly progressing form of the disease, possibly linked to its unusually early onset; juvenile-onset cases sometimes follow a far slower course. World-class medical care, the resources to fund it, and his own refusal to be defeated all played their part, but the fundamental reason remains a genuine medical curiosity.

His case did an enormous amount of good simply by being visible. For millions of people, Stephen Hawking was the face of motor neurone disease, and proof that a diagnosis is not the same as an ending. He became a patron of the MND Association in 2008 and used his fame to raise awareness and funds throughout his life.

If you would like to help fund research and care, see how to support MND research.

Explore further: symptoms and diagnosis, the types of MND, living with the disease, supporting someone with MND, and other notable people affected.