To Paul, and others in this thread, I am so very sorry to read your stories. It is a reminder of how unpredictable life can be but it is amazing how resourceful human beings are in overcoming some of the things which are thrown at us.
I went through life thinking I would be invincible - I'd always been quite a serious athlete when younger and carried on running every day well into middle age, never having smoked and I barely drink. Our bodies have a habit of betraying us and it is so unfair at times. My problems are very mild compared to others in this thread. A couple of years ago I pretty much lost the use of my lower arms and hands - I couldn't do anything for myself, I couldn't wash my hair, tie my shoelaces, go shopping, or open my handbag or purse. I saw the neurologist and rheumatologist and it turned out that I had arthritis in my joints in my hands and also the bones in my neck had collapsed compressing the nerves to my hands and arms causing numbness in my fingers. Sometimes at night I lose the feeling in my entire left side. Holding a plate of food is fun and I get through crockery at an alarming rate. Some days opening bottles/jars, dialling a phone number, and filling a kettle will defeat me. Aside from that, legs are unaffected and I can still go for a run most days - however as I age that will change.
Although I improved (providing I don't exceed my limitations or else I'm back to square one) since then I have not been able to type (I can write, but no more than a sentence or two and it is pretty illegible), but I get by very well with voice activation software (Dragon Naturally Speaking) without which I could not manage. I was told I would likely have to give up my profession but of course you can't do that when it's your living. After a few months of rest I bought an Olympus OMD and that was a turning point. Micro 4/3 cameras are so small and light and they have amazing functionality - they have enabled me to carry on doing my job (providing I do not take more than two or three assignments per week) so I do think that could be an option for anyone with reduced mobility. The other good thing about these cameras is that they have excellent in body stabilisation so if you are quite shaky, like me, they smooth things out nicely. They have all of the lenses necessary to all kinds of photography. I am all for scaling down equipment size and weight.