I read your question carefully and I understand your concern. In general after a new lesion in multiple sclerosis there is some improvement, mostly in the first month, but can be expected up to 6 months with physiotherapy. That doesn t mean that the disease won t have other relapses in the future, it is a chronic disease, it will progress, medication tries to slow it down but can t stop it. As for percentages it is difficult to speak about your brother in law case. That is because that description is not typical for MS, it is not a classical looking case. Usually it takes years before a patient is disabled to the degree you describe, not only 3 weeks. So either the diagnosis has been made very late, or he has had a lesion in a critical area which causes major disability like the spinal cord. So predictions should be made based on individual characteristics and his imaging information, can t generalize and give usual statistics. I hope to have been of help.