Multiple Sclerosis Introduction and Symptoms
Multiple Sclerosis (MS) is the most common disabling neurological disease of young adults. It most often appears when people are between 20 to 40 years old. However, it can also affect children and older people.
The course of MS is unpredictable. A small number of those with MS will have a mild course with little to no disability, while another smaller group will have a steadily worsening disease that leads to increased disability over time. Most people with MS, however, will have short periods of symptoms followed by long stretches of relative relief, with partial or full recovery. There is no way to predict, at the beginning, how an individual person’s disease will progress.
Researchers have spent decades trying to understand why some people get MS and others don't, and why some individuals with MS have symptoms that progress rapidly while others do not. How does the disease begin? Why is the course of MS so different from person to person? Is there anything we can do to prevent it? Can it be cured?
This article includes information about why MS develops, how it progresses, and what new therapies are being used to treat its symptoms and slow its progression. New treatments can reduce long-term disability for many people with MS. However, there are still no cures and no clear ways to prevent MS from developing.
What is Multiple Sclerosis?
Multiple sclerosis (MS) is a neuroinflammatory disease that affects myelin , a substance that makes up the membrane (called the myelin sheath) that wraps around nerve fibers (axons). Myelinated axons are commonly called white matter. Researchers have learned that MS also damages the nerve cell bodies, which are found in the brain’s gray matter, as well as the axons themselves in the brain, spinal cord, and optic nerve (the nerve that transmits visual information from the eye to the brain). As the disease progresses, the brain’s cortex shrinks (cortical atrophy).
The term multiple sclerosis refers to the distinctive areas of scar tissue (sclerosis or plaques) that are visible in the white matter of people who have MS. Plaques can be as small as a pinhead or as large as the size of a golf ball. Doctors can see these areas by examining the brain and spinal cord using a type of brain scan called magnetic resonance imaging (MRI).
While MS sometimes causes severe disability, it is only rarely fatal and most people with MS have a normal life expectancy.
What are plaques made of and why do they develop?
Plaques, or lesions, are the result of an inflammatory process in the brain that causes immune system cells to attack myelin. The myelin sheath helps to speed nerve impulses traveling within the nervous system. Axons are also damaged in MS, although not as extensively, or as early in the disease, as myelin.
Under normal circumstances, cells of the immune system travel in and out of the brain patrolling for infectious agents (viruses, for example) or unhealthy cells. This is called the "surveillance" function of the immune system.
Surveillance cells usually won't spring into action unless they recognize an infectious agent or unhealthy cells. When they do, they produce substances to stop the infectious agent. If they encounter unhealthy cells, they either kill them directly or clean out the dying area and produce substances that promote healing and repair among the cells that are left.
Researchers have observed that immune cells behave differently in the brains of people with MS. They become active and attack what appears to be healthy myelin. It is unclear what triggers this attack. MS is one of many autoimmune disorders, such as rheumatoid arthritis and lupus, in which the immune system mistakenly attacks a person’s healthy tissue as opposed to performing its normal role of attacking foreign invaders like viruses and bacteria. Whatever the reason, during these periods of immune system activity, most of the myelin within the affected area is damaged or destroyed. The axons also may be damaged. The symptoms of MS depend on the severity of the immune reaction as well as the location and extent of the plaques, which primarily appear in the brain stem, cerebellum, spinal cord, optic nerves, and the white matter of the brain around the brain ventricles (fluid-filled spaces inside of the brain).
What are the signs and symptoms of MS?
The symptoms of MS usually begin over one to several days, but in some forms, they may develop more slowly. They may be mild or severe and may go away quickly or last for months. Sometimes the initial symptoms of MS are overlooked because they disappear in a day or so and normal function returns. Because symptoms come and go in the majority of people with MS, the presence of symptoms is called an attack, or in medical terms, an exacerbation. Recovery from symptoms is referred to as remission, while a return of symptoms is called a relapse. This form of MS is therefore called relapsing-remitting MS, in contrast to a more slowly developing form called primary progressive MS. Progressive MS can also be a second stage of the illness that follows years of relapsing-remitting symptoms.
A diagnosis of MS is often delayed because MS shares symptoms with other neurological conditions and diseases.
The first symptoms of MS often include:
- vision problems such as blurred or double vision or optic neuritis, which causes pain in the eye and a rapid loss of vision
- weak, stiff muscles, often with painful muscle spasms
- tingling or numbness in the arms, legs, trunk of the body, or face
- clumsiness, particularly difficulty staying balanced when walking
- bladder control problems, either inability to control the bladder or urgency
- dizziness that doesn't go away
MS may also cause later symptoms such as:
- mental or physical fatigue which accompanies the above symptoms during an attack
- mood changes such as depression or euphoria
- changes in the ability to concentrate or to multitask effectively
- difficulty making decisions, planning, or prioritizing at work or in private life.
Some people with MS develop transverse myelitis, a condition caused by inflammation in the spinal cord. Transverse myelitis causes loss of spinal cord function over a period of time lasting from several hours to several weeks. It usually begins as a sudden onset of lower back pain, muscle weakness, or abnormal sensations in the toes and feet, and can rapidly progress to more severe symptoms, including paralysis. In most cases of transverse myelitis, people recover at least some function within the first 12 weeks after an attack begins. Transverse myelitis can also result from viral infections, arteriovenous malformations, or neuroinflammatory problems unrelated to MS. In such instances, there are no plaques in the brain that suggest previous MS attacks.
Neuro-myelitis optica is a disorder associated with transverse myelitis as well as optic nerve inflammation. Patients with this disorder usually have antibodies against a particular protein in their spinal cord, called the aquaporin channel. These patients respond differently to treatment than most people with MS.
Most individuals with MS have muscle weakness, often in their hands and legs. Muscle stiffness and spasms can also be a problem. These symptoms may be severe enough to affect walking or standing. In some cases, MS leads to partial or complete paralysis. Many people with MS find that weakness and fatigue are worse when they have a fever or when they are exposed to heat. MS exacerbations may occur following common infections.
Tingling and burning sensations are common, as well as the opposite, numbness and loss of sensation. Moving the neck from side to side or flexing it back and forth may cause "Lhermitte's sign," a characteristic sensation of MS that feels like a sharp spike of electricity coursing down the spine.
While it is rare for pain to be the first sign of MS, pain often occurs with optic neuritis and trigeminal neuralgia, a neurological disorder that affects one of the nerves that runs across the jaw, cheek, and face. Painful spasms of the limbs and sharp pain shooting down the legs or around the abdomen can also be symptoms of MS.
Most individuals with MS experience difficulties with coordination and balance at some time during the course of the disease. Some may have a continuous trembling of the head, limbs, and body, especially during movement, although such trembling is more common with other disorders such as Parkinson’s disease.
Fatigue is common, especially during exacerbations of MS. A person with MS may be tired all the time or may be easily fatigued from mental or physical exertion.
Urinary symptoms, including loss of bladder control and sudden attacks of urgency, are common as MS progresses. People with MS sometimes also develop constipation or sexual problems.
Depression is a common feature of MS. A small number of individuals with MS may develop more severe psychiatric disorders such as bipolar disorder and paranoia, or experience inappropriate episodes of high spirits, known as euphoria.
People with MS, especially those who have had the disease for a long time, can experience difficulty with thinking, learning, memory, and judgment. The first signs of what doctors call cognitive dysfunction may be subtle. The person may have problems finding the right word to say, or trouble remembering how to do routine tasks on the job or at home. Day-to-day decisions that once came easily may now be made more slowly and show poor judgment. Changes may be so small or happen so slowly that it takes a family member or friend to point them out.
How many people have MS?
No one knows exactly how many people have MS. Studies of the prevalence (the proportion of individuals in a population having a particular disease) of MS indicate that the rate of the disease has increased steadily during the twentieth century.
As with most autoimmune disorders, twice as many women are affected by MS as men. MS is more common in colder climates. People of Northern European descent appear to be at the highest risk for the disease, regardless of where they live. Native Americans of North and South America, as well as Asian American populations, have relatively low rates of MS.