What is the Course of MS?

Each case of MS displays one of several patterns of presentation and subsequent course. Most commonly, MS first manifests itself as a series of attacks followed by complete or partial remissions as symptoms mysteriously lessen, only to return later after a period of stability. This is called relapsing-remitting (RR) MS. Primary-progressive (PP) MS is characterized by a gradual clinical decline with no distinct remissions, although there may be temporary plateaus or minor relief from symptoms. Secondary-progressive (SP) MS begins with a relapsing-remitting course followed by a later primary-progressive course. Rarely, patients may have a progressive-relapsing (PR) course in which the disease takes a progressive path punctuated by acute attacks. PP, SP, and PR are sometimes lumped together and called chronic progressive MS. 

In addition, twenty percent of the MS population has a benign form of the disease in which symptoms show little or no progression after the initial attack; these patients remain fully functional. A few patients experience malignant MS, defined as a swift and relentless decline resulting in significant disability or even death shortly after disease onset. However, MS is very rarely fatal and most people with MS have a fairly normal life expectancy. 

Studies throughout the world are causing investigators to redefine the natural course of the disease. These studies use a technique called magnetic resonance imaging (MRI) to visualize the evolution of MS lesions in the white matter of the brain. Bright spots on a T2 MRI scan indicate the presence of lesions, but do not provide information about when they developed. 

Because investigators speculate that the breakdown of the blood/brain barrier is the first step in the development of MS lesions, it is important to distinguish new lesions from old. To do this, physicians give patients injections of gadolinium, a chemical contrast agent that normally does not cross the blood/brain barrier, before performing a scan. On this type of scan, called T1, the appearance of bright areas indicates periods of recent disease activity (when gadolinium is able to cross the barrier). The ability to estimate the age of lesions through MRI has allowed investigators to show that, in some patients, lesions occur frequently throughout the course of the disease even when no symptoms are present.