An employer is legally not entitled to know anything about your health issues or disabiltilies UNLESS it pertains to how a disability or health issue will effect your performance of the job duties that are outlined for you. It's a roll of the dice for you to tell them or not. It's a deep ethical bind you're in. If you want to be "up front" with them, you're definitely going to decrease the probablitily that you will get a job offer at all.
Let me ask you this. Do you think that a pharmacologist in Switzerland may have just now discovered a drug that will utterly cure your illness, and that my some miracle, the FDA approves it in just a month? Does your prognosis say that you WILL be rendered incapable of moving periodically or that you MAY be rendered incapable of moving? Is there ANY chance, under the sun, that your attendance rate would be on par with the rest of the company?
Think carefully about these things. Theoretically, one could KNOW that they were driving a car with bad brakes, get hired for a job and then get in an accident due to brake problems the next day and have to be hospitalized for a month. Do people disclose the state of their poorly running cars at an interview?
Marky