What is Multiple Sclerosis?

Borrowed from : The National MS Society

Multiple sclerosis (or MS) is a chronic, often disabling disease that attacks the central nervous system (CNS), which is made up of the brain, spinal cord, and optic nerves. Symptoms may be mild, such as numbness in the limbs, or severe, such as paralysis or loss of vision. The progress, severity, and specific symptoms of MS are unpredictable and vary from one person to another. Today, new treatments and advances in research are giving new hope to people affected by the disease.

MS is Thought to be an Autoimmune Disease

The body’s own defense system attacks myelin, the fatty substance that surrounds and protects the nerve fibers in the central nervous system. The nerve fibers themselves can also be damaged. The damaged myelin forms scar tissue (sclerosis), which gives the disease its name. When any part of the myelin sheath or nerve fiber is damaged or destroyed, nerve impulses traveling to and from the brain and spinal cord are distorted or interrupted, producing the variety of symptoms that can occur.

Most people with MS learn to cope with the disease and continue to lead satisfying, productive lives.

Four Disease Courses Have Been Identified in MS

Relapsing-Remitting MS (RRMS)

RRMS is the most common form of the disease. It is characterized by clearly defined acute attacks with full recovery (1a) or with residual deficit upon recovery (1b). Periods between disease relapses are characterized by a lack of disease progression. Approximately 85% of people with MS begin with a relapsing-remitting course.

Figure 1a
Figure 1a

Figure 1b
Figure 1b

Primary Progressive MS (PPMS)

PPMS is characterized by progression of disability from onset, without plateaus or remissions (2a) or with occasional plateaus and temporary minor improvements (2b). A person with PPMS, by definition, does not experience acute attacks. Of people with MS are diagnosed, only 10% have PPMS. In addition, the diagnostic criteria for PPMS are less secure than those for RRMS so that often the diagnosis is only made long after the onset of neurological symptoms and at a time when the person is already living with significant disability.

Figure 2a
Figure 2a

Figure 2b
Figure 2b

Secondary-Progressive MS (SPMS)

SPMS begins with an initial relapsing-remitting disease course, followed by progression of disability (3a) that may include occasional relapses and minor remissions and plateaus (3b). Typically, secondary-progressive disease is characterized by: less recovery following attacks, persistently worsening functioning during and between attacks, and/or fewer and fewer attacks (or none at all) accompanied by progressive disability. 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.

Figure 3a
Figure 3a

Figure 3b
figure 3b

Progressive-Relapsing MS (PRMS)

PRMS, which is the least common disease course, shows progression of disability from onset but with clear acute relapses, with (4a) or without (4b) full recovery. Approximately 5% of people with MS appear to have PRMS at diagnosis. Not infrequently a patient may be initially diagnosed as having PPMS and then will experience an acute attack, thereby establishing the diagnosis of PRMS.

Figure 4a
Figure 4a

Figure 4b
figure 4b

The Assessment of Disease Progression

Physicians evaluate disease progression in four ways:

  • Radiographically—by looking for new lesions, gadolinium-enhanced lesions, or an increased amount of disease on MRI
  • Electrophysiologically—by measuring changes in the sensory evoked potentials
  • Neurologically—by measuring changes in function on the neurologic examination
  • Functionally—by assessing the person’s physical and cognitive abilities