The late Stephen Hawking was an incredible human for a number of reasons, but not least for his deep perseverance despite the terminal diagnosis he was given as a young man.
“My expectations were reduced to zero when I was 21,” Hawking famously said. “Everything since then has been a bonus.” But how, exactly, did Hawking beat the odds when he was diagnosed with amyotrophic lateral sclerosis (ALS) in 1963?
As ALS is the most common form of motor neurone disease (MND), the terms are often used interchangeably, but this is not strictly accurate as there are other variants of MND.
In general, it is a progressive neurodegenerative disease that affects the nerve cells in the front of the brain and in the spinal cord. These cells are responsible for moving the muscles in your body. Over time, the death of these neurons leads to a loss of control of not only your limbs, but also your ability to swallow and even breathe. But as is usually the case, the disease is not quite that straightforward.
For a start, each variety of MND manifests in a slightly different way. For example, one rare subtype is known as progressive muscular atrophy (PMA), or Duchenne-Aran muscular atrophy, and primarily affects the motor neurons found in the spinal cord but not the brain.
Then there is primary lateral sclerosis (PLS), which again is not particularly common. In contrast to PMA, it generally tends to affect the motor neurons found in the brain, which degenerate and die, but not those in the spinal cord.
The most common form of motor neurone disease, however, is ALS, which is also known as Lou Gehrig’s disease after the famous baseball player who was diagnosed with it in 1939. In contrast to both PMA and PLS, this variant affects both the motor neurons found in the brain and in the spinal cord.
As if it wasn’t already convoluted enough, there is also growing evidence that the disease is not, as was previously thought, limited to just the motor neurons. It now seems that the damage to the cells can spread from the front of the brain and the spinal cord to other parts of the brain that don’t contain motor neurons. This can lead to the development of dementia-like symptoms.
Usually, when someone is diagnosed with ALS, they only have a few years left to live, as the damage spreads and the patient slowly loses movement in most parts of their body. When Hawking was diagnosed with the disease in 1963 at the age of 21, he was given two years to live. But against all odds, he managed to live into his 76th year of life. The reasons behind this are not fully understood.
There are two main ways in which people with ALS die. Either the muscles that control swallowing stop functioning, and they succumb to dehydration and/or malnutrition, or the diaphragm becomes paralyzed, and they stop breathing. The order and time in which these events occur are variable, so it's difficult to predict exactly what will happen.
What seems evident though is that for some reason that may never be clear, while most of Stephen Hawking's motor function slipped away, his disease did not progress to the stage of complete paralysis. This is likely just a quirk in the biology of the variety he had, meaning that Hawking was most certainly an outlier when it comes to ALS.
When discussing his mind – which clearly remained pin-sharp and active throughout his life – a similar picture emerges. While in some patients, as mentioned before, dementia-like symptoms can set in, for whatever reason this simply did not occur for Hawking, despite the slow progression of the disease across the rest of his body.
Doctors are still working furiously to uncover the causes of ALS, and all motor neurone diseases in general, but as ever it is tricky. With so much variation, things necessarily have to focus on small aspects, so we’re only getting there gradually. Once we understand exactly how it's caused, we can begin to figure out ways to target it, and hopefully, one day find a cure.