The Singularity of Hawking’s ALS

Stephen Hawking’s life with ALS shows how much the disease varies, and how little we still know about it.
When Hawking came down with ALS in 1963, Cambridge University told him he had two years left to live.  More than fifty years later, the fate of a patient is the same.  We have developed only one drug for ALS, and that merely gives people three extra months.
Most people get ALS in old age and have a few years to live.  However, a small percentage of people, like Hawking, get ALS when they are young, and for some unknown reason these people can live ten years or more.  This makes some sense because young people are more resistant to disease in general, but Stephen Hawking has shocked the world by living to the age of 75.
The simple answer to Stephen Hawking’s survival is that he can still breathe and eat.  It is possible for someone to live without use of their arms and legs, but ALS gets really difficult when other more important muscles start to atrophy.  (The human heart is a special exception because it can beat without any communication from the brain.)  People with ALS usually die from suffocation or dehydration due to paralysis of the diaphragm or the swallowing muscles.  Stephen Hawking gets round-the-clock care, but he is known to have breathing difficulties, and he has been on a ventilator several times in recent years.
Why are the most important muscles in the body the last to break down?  It really comes down to the neurons that control these muscles.  For some unknown reason, the neurons that control voluntary muscles are more vulnerable to ALS than the neurons that control automatic bodily functions like digestion and bladder control.  It is possible that ALS causes some neurons to become overactive and poison themselves.  The only current treatment for ALS, Riluzole, is able to calm neurons down and make them live a little longer.
Other neurons are especially resistant to ALS.  Research has shown that the nerves going to the eyes are resistant to hyperactivity.  Stephen Hawking can still move his eyes, which is normal in the end stages of ALS.  He can still smile,  and he communicates via his electronic voice by twitching a muscle in his cheek.   Maybe his neurons are able to stay calm.
ALS is a highly variable disease.  We can describe several types of ALS, but not all cases fall into categories.  With his lifespan and incredible mind both untouched by ALS, Stephen Hawking’s case is like no other.