Charles S. Yanofsky, M.D.
Albert. W. Heck, M.D.
Jon L. Vickery, M.D.
Francis J. Janton, III, M.D.
MS is much more likely to cause disability than death but doesn't have to cause either. For most people the disease starts between the ages of twenty to forty and it is a little more common in women almost by 2:1 and affects whites more than other races. It is not at all an inherited disease, but a certain susceptibility runs in families with about a 1% incidence in first degree relatives (parents and sibs). We think there are inherited characteristics of the immune system making some people susceptible to the disease, but it is more common in brothers and sisters than parents and their children, and most ways it doesn't affect both identical twins. This means environmental factors, not heredity, are paramount. Another very interesting thing about MS is that it is much more common in temperate, basically colder climates than warmer ones, for example in New York vs. New Mexico and the incidence is at least ten times as high in some parts of England and Scandinavia than in low frequency areas of the world. When you move from a high to a low incidence region after the age of about 15 you carry high incidence with you. This suggests to some that the disease is caused by a virus, perhaps a virus spread indoors, prior to the age of 15.
For most people early disease is characterized by relapses and remissions. The inflammations in the nervous system correspond to attacks. What can be seen under a microscope or detected by an MRI scan is equivalent to an attack. Many times a large inflammation happens and a person will have no symptoms. At other times the inflamed area may be small but in a strategic or important area of the nervous system and symptoms will be severe.
About four fifths of patients have good recovery of function between attacks. This is called remission and most of the time they have little impairment even 10 years after diagnosis. The vast majority of these patients still function well and without significant disability after 20 years. Another way of saying this is that about 80-85 percent of all patients start out relapsing. By this we mean that these persons have actual attacks that can be documented. However roughly half of these patients will, as the years go on, stop having definable attacks of MS. These persons seem to be progressing but you can't pick out an attack or actual sub-acute worsening in their disease any more. They seem to slowly worsen even though they started out having attacks. This is called secondary progressive disease and roughly half of all relapsing patients eventually fall into this category as the years go on. This constitutes half of all patients and about half of them (a quarter of the total MS patients) e disabled after 10 years. About 1 in 10 patients starts with purely progressive disease. These are the most likely to lose function in their legs and to have the worst problem in the spinal cord. A very few patients seem to have progressive MS initially but then have a few discreet attacks. This is somewhat less than 5% of the total and is designated as Progressive-relapsing MS. These categories are of more than academic interest. We now have treatments that slow down the course of MS and they have only had demonstrated effect in specific subcategories of persons with the disease, but these treatments have not been proven to be beneficial in other categories. The most modern classification of MS then, includes four categories viz: Relapsing, Primary Progressive, Secondary Progressive, Progressive-relapsing.
A lot of people ask me what particular category they are in. They want to know whether they are still relapsing, having recognizable attacks, or if they have entered a progressive stage. More importantly some insurance companies will pay for medicines if a person falls in the relapsing category but not if they are progressive. This is a process that occurs gradually, almost imperceptibly, and it is very hard a lot of times to make this distinction. Sometimes a person will have one or more attacks within a few months, then the disease will become less active and they may not have another attack for 10 or even more years. Statistics that you may read (including the ones above) are unduly pessimistic because they are old, from the days where persons were diagnosed with more severe obvious disease, before the days of the MRI scan and other tests. People tend to see doctors and get diagnosed today with much more minor symptoms and at an earlier stage of their disease. In fact some people are seen and diagnosed today who may never have seen a doctor for the disease at all in years past. In other words MS can be extremely mild or benign. What will be in an individual person is hard to say. I find people are the most discouraged about this. They would rather be sure of what is going to happen to them even if we have only bad news. No one likes not knowing. After about five years so we can usually judge how bad the disease is going to be in an individual. But even then we have no way of prognosticating with certainty. To add to the confusion, there seem to be extremely mild forms of MS. Some persons have one attack of optic neuritis and only about a third of these will go on to have typical MS. Some patients have a bad inflammation of the spinal cord termed a transverse myelitis and only a small minority will have other symptoms of MS even when they are followed for a long time.
It is almost impossible to prognosticate early in the course of MS, to tell whether or not a person is likely to have severe disease. We can get a very rough idea though. We know that women constitute about 70% of patients. Young women who have either optic neuritis as their first attack (described above) or simple sensory or motor symptoms in just one small region of their body, are likely to fall into a good prognostic category. Persons who seem to be progressive at the outset or who have severe cerebellar (gross incoordination) or spinal cord motor signs at the outset tend not to fare well. This is only a very rough approximation. A lot of people do not follow these rules of thumb.
I have seen a number of patients with very severe disease early on and their prognosis appears to be terrible. Suddenly they may stop having attacks and make a good recovery. The best explanation for this is something in the person is exposed to that induces an immune attack on white matter or (this is conjectural) a virus exposure caused the disease. This is the same as finding an allergy in asthma that causes shortness of breath. The problem is trying to identify what is causing the reaction and it may be a different for each individual. The most likely substances are fats chemically similar to myelin but nothing is proved. We can say the multiple sclerosis rarely shortens a person's natural life span. It is not a fatal disease.