Multiple sclerosis (MS) is a chronic autoimmune disease in which a body’s immune cells mistakenly attack myelin — a protective sheath around nerve cells in the brain and spinal cord. While symptoms range widely in severity, MS sometimes progresses into a disabling disease, negatively affecting most parts of the body. Over two million people worldwide are believed to have MS. For those afflicted with the disease, MS comes in many forms and affects their health in different ways. Here is a guide to better understanding the nature of MS:

Your body and brain are in constant communication with one another to keep things running, like a general and an army. In both cases, the signal needs to be clear for the commands to be executed properly. When an individual has MS, his or her immune system is mistakenly attacking the central nervous system. MS damages the myelin sheath, which is the fatty protective substance around nerve cells. The myelin sheath ensures that neural messages are transmitted quickly and properly. Damage to the myelin causes a distortion in the crucial exchange between brain and body. This means the brain can no longer properly control the body, resulting in a litany of potentially serious symptoms.

There are four types of multiple sclerosis. Relapsing-remitting starts as a series of attacks followed by complete or partial remission. The symptoms will mysteriously lessen, only to return later after a period of stability. Primary-progressive is characterized by a gradual clinical decline in function, with no distinct remissions. Secondary-progressive begins with a relapsing-remitting course followed by a later primary-progressive course. Progressive-relapsing is a rare form of MS, in which the disease becomes progressively worse, with acute attacks flaring up along the way.

MS affects people in different ways, depending on the degree and location of the damage to the central nervous system. Symptoms may disappear completely, return after a few years or last an entire lifetime. The most common symptoms include: fatigue, numbness, bladder and bowel dysfunction, difficulty with motor control, vision problems, dizziness, sexual dysfunction and muscle spasms. Doctors use a battery of tests to diagnose the disease, including a look at your medical history, MRIs, a spinal tap and neurological exams. If an individual is experiencing any of the mentioned symptoms, the doctors will use these tests to determine if there has been any damage to the central nervous system.

The underlying cause of the disease is still unknown, and it’s not yet clear why some people have MS and others do not. It is now widely accepted that MS is an autoimmune disease, which means the immune system is functioning abnormally and attacking the central nervous system. However, whatever triggers the immune system to attack remains unclear, but experts tend to agree that it is a combination of genetic and environmental factors. A research study involving twins shows a 25 percent chance that identical twins will have MS, which suggests that there are factors outside of genetics contributing to the cause of MS. Researchers are now exploring different environmental factors that could contribute to this disease, and some hypotheses include vitamin D deficiency or exposure to industrial toxins.

There is no cure for MS, but there are a number of treatments available to help manage the symptoms and alter the course of the disease, such as anti-inflammation medicine. A handful of drugs can also help completely modify the course of the disease, delaying its progression and limiting the number of attacks. For most stages of the disease, a specialized support group of rehabilitative therapists can help maintain an individual’s overall health. These helpful practices include physical therapy, occupational and speech therapy and cognitive rehabilitation.