About 5% of MS cases don't show up on an MRI (even with contrast). Having said that, MS is a disease that is both more obvious than ALS (vision problems, or, for my two brothers, severe impairment of one side of the body) and that is often (nearly always these days) treatable. Both of my brothers had very severe symptoms at their first attack. Both are on medication now (expensive, but covered by insurance). Both are (knock on wood!) nearly symptom-free at this point.Sure, MS might change to a more progressive form in the future, but it's been 5 years for one and 10 years for the other, and both are still doing just fine. Those who worry about MS should keep in mind that, these days, you'd rather have MS than most forms of cancer (MS is less life-threatening and more treatable), and MS is far less common than cancer.