Ever considered there might be something wrong with sleeping horizontally?
How many people with ms have woken up in a somewhat worse state then before they went to bed?
How many people with ms experienced their first symptoms during the night and on waking up and trying to get out of bed?
It is so obvious to me at least that titling the bed so the head end is at least six inches / 15 cms higher than the foot end.
When you have grown tired of getting out of bed 4 or 5 times a night for a pee, consider tilting your bed to see what happens.
Try it and see.