Should MS sufferers be allowed to drive buses?

Very delicate question and not meant to insult any Multiple Sclerosis sufferer. I was watching the news where a woman with MS who had trained previously as a bus driver could not find a job since being diagnosed with the disease. Although I believe they should not be discriminated against, surely for public safety there must be certain types of jobs that should be off bounds. This woman admitted somedays she could not move her legs and (having worked with MS sufferers) I know their limbs can go into uncontrolled spasms. What would happen if this occurred when the driver had to brake? Or if the foot went into spasm and pushed down on to the accelerator? Your views please.