Multiple sclerosis (MS) is one of the most common diseases of the central nervous system—including the brain, spinal cord, and optic nerves—which affects more than 2.3 million people worldwide. MS is an inflammatory demyelinating condition where an abnormal response by the immune system damages myelin, the fatty protein that insulates and protects nerve cells called axons. When myelin or axons are damaged, electrical nerve impulses transmitted to and from the brain and spinal cord are distorted or interrupted which may result in a variety of symptoms.
Most people are diagnosed with MS between the ages of 20 and 50, but MS can appear in young children and teens as well as much older adults. MS is significantly more common (at least 2–3 times) in women than men. Approximately 400,000 people are living with MS in the United States today—with 200 more people diagnosed every week. MS is not directly hereditary, although genetic susceptibility plays a part in its development, and MS is not contagious or infectious.
What is demyelination?
Whether you have been diagnosed with MS, are in the process of being diagnosed, or wonder what it takes to get diagnosed with multiple sclerosis, it is likely that you have heard of lesions. Lesions are hardened areas (scars) or plaques where myelin has been damaged. Multiple sclerosis literally means ‘many scars.’
The process of demyelination begins with inflammation. Think for a moment of a time when you accidentally cut a finger and may not have washed the wound immediately. The invaders of germs and bacteria are detected by the immune system which sends in a team of specialized white blood cells, called leukocytes, to fight and destroy the invaders. Perhaps the wound became red and inflamed while the battle was underway.
In multiple sclerosis, a breach in the blood-brain-barrier (BBB) allows specialized white blood cells, called T-cells and B-cells, to travel from the blood stream into the CNS. Once ‘killer’ T-cells mistake myelin for foreign invaders and go on the attack, they produce cytokines which destroy myelin and recruit macrophages to help destroy myelin and cut the nerve fibers. At the same time, regulatory T-cells enter the battle and release protective cytokines which ‘turn off’ the destructive white blood cells. Oligodendrocytes then furiously try to lay down new myelin before being destroyed themselves.
How do you know it is MS?
MS can be difficult to diagnose, since there are no definitive symptoms, physical findings or laboratory tests that can, by themselves, make the diagnosis. To establish a diagnosis of MS, doctors must: 1) find evidence of damage in at least two separate areas of the CNS, and 2) find evidence that the damage occurred at two separate points in time, at least one month apart, and 3) rule out all other possible diagnoses.
Inflammation and demyelination can be visualized with magnetic resonance imaging (MRI). An injection of gadolinium (a contrast agent) during MRI testing makes active lesions easier to detect. Active lesions may be called enhancing lesions on an MRI report. A different type of lesion, called a black hole, is believed to be evidence of axonal loss, meaning that the nerve fibers are ‘dead.’
Lesions do not always correlate with symptoms, nor do the number of lesions indicate level of disability. The appearance of lesions can change from week to week without any change in symptoms, and symptoms may come and go without any changes in lesions as seen by MRI. And, the presence of lesions does not always mean that a person has MS.
So why do we care so much about lesions in MS? Detecting lesions on an MRI scan helps to gather enough evidence for diagnosis. Monitoring disease activity through MRI also helps to determine whether current disease-modifying therapy (DMT) is working sufficiently or a change in treatments may be recommended.
Read more about how MS is diagnosed.
What are common disease courses for MS?
Most people with MS experience a relapsing form of the disease where there are acute episodes (attacks, exacerbations, relapses) or worsening neurologic function followed by partial or complete recovery of symptoms (remission). Progressive forms of the disease involve steady decline of neurologic function and increased disability. Some patients may experience aspects of both relapsing and progressive disease.
Read more about the different forms of MS.
How is MS treated?
Treatment for MS focuses on five areas: 1) treatment for acute relapses, 2) treatment for symptoms, 3) disease-modifying therapy, 4) rehabilitation to enhance or maintain physical function, and 5) psychosocial support. A well-rounded treatment approach for MS may include both pharmacological choices and non-pharmacological options, including complementary and alternative therapies.
Read more about treatment options for MS.