From The MS Information Sourcebook, produced by the National MS Society.
It is generally very difficult to predict the course of MS. The disorder varies greatly in each individual but most people with MS have a normal life expectancy. Nevertheless, a few patients with very severe disability may die prematurely of infectious complications (such as pneumonia) so that the overall life expectancy is only 95% of normal.
There are some guidelines that may be used to infer prognosis. Several studies have shown that people who have few attacks in the first several years after diagnosis, long intervals between attacks, complete recovery from attacks, attacks that are sensory in nature (i.e., numbness, tingling, visual loss), and nearly normal neurological examinations after 5 years tend to do better. People who have early symptoms of tremor, in-coordination, difficulty in walking, or who have frequent attacks with incomplete recoveries, early development of neurological abnormalities, or more lesions on MRI early on, tend to have a more progressive disease course.
People with MS Can Expect One of Four Courses of Disease
MS tends to take one of four clinical courses, each of which might be mild, moderate, or severe:
- A relapsing-remitting course (RRMS), characterized by partial or total recovery after attacks (also called exacerbations, relapses, or flares). This is the most common form of MS. Approximately 85% of people with MS initially begin with a relapsing-remitting course.
- A relapsing-remitting course that later becomes steadily progressive is called secondary-progressive MS (SPMS). Attacks and partial recoveries may continue to occur. According to some natural history studies, of the 85% who start with relapsing-remitting disease, more than 50% will develop SPMS within 10 years; 90% within 25 years. More recent natural history studies (perhaps because of the use of MRI to assist in the diagnosis) suggest a more benign outlook that these numbers suggest. Nevertheless, many patients with RRMS do develop SPMS ultimately.
- A progressive course from onset without any attacks is called primary-progressive MS (PPMS). The symptoms that occur along the way generally do not remit. Ten percent of people with MS are diagnosed with PPMS, although the diagnosis usually needs to be made after the fact-when the person has been living for a period of time with progressive disability but no acute attacks.
- A progressive course from the outset, with obvious, acute attacks along the way, is called progressive-relapsing MS (PRMS). This course is quite rare, occurring in only 5% of people with MS.
Researchers are currently trying to identify more precise indicators of the prognosis or predicted disease activity.