Multiple sclerosis (MS) is a life-long chronic disease diagnosed primarily in young adults. During an MS attack, inflammation occurs in areas of the white matter of the central nervous system (nerve fibers that are the site of MS lesions) in random patches called plaques. This process is followed by destruction of myelin, which insulates nerve cell fibers in the brain and spinal cord. Myelin facilitates the smooth, high-speed transmission of electrochemical messages between the brain, the spinal cord, and the rest of the body; when it is damaged, neurological transmission of messages may be slowed or blocked
completely, leading to diminished or lost function.
Symptoms of MS may be mild or severe and of long duration or short and appear in various combinations. The initial symptom of MS is often blurred or double vision, red-green color distortion, or even blindness in one eye. Most MS patients experience muscle weakness in their extremities and difficulty with coordination and balance. Most people with MS also exhibit paresthesias, transitory abnormal sensory feeling such as numbness or "pins and needles." Some may experience pain or loss of feeling. About half of people with MS experience cognitive impairments such as difficulties with concentration, attention, memory, and judgment. Such impairments are usually mild, rarely disabling, and intellectual and language abilities are generally spared. Heat may cause temporary worsening of many MS symptoms.
Physicians use a neurological examination and take a medical history when they suspect MS. Imaging technologies such as MRI, which provides an anatomical picture of lesions, and MRS (magnetic resonance spectroscopy), which yields information about the biochemistry of the brain. Physicians also may study patients' cerebrospinal fluid and an antibody called immunoglobulin G. No single test unequivocally detects MS. A number of other diseases produce symptoms similar to those seen in MS.
No one knows exactly how many people have MS. It is believed that, currently, there are
approximately 250,000 to 350,000 people in the United States with MS diagnosed by a
physician. This estimate suggests that approximately 200 new cases are diagnosed each
week. Estimates place the annual costs of MS in the
United States in excess of $2.5 billion.