The symptoms of multiple sclerosis (MS) vary greatly from person to person. Symptoms can be mild or severe. They may appear briefly and then subside, or they may last for a long time. People also experience different combinations of symptoms. All MS symptoms are caused by inflammation leading to demyelination (destruction of the coating that insulates nerves) and the damage done to nerve fibers (axons).

Demyelination is the loss of myelin, the fatty covering that insulates the nerves in the brain and spinal cord. Wherever myelin is damaged, the message carried by the affected nerve becomes garbled or lost, altering the performance of some part of the body. Inflammation may also be associated with damage to the underlying nerve fibers (axons). It is thought that axon loss progresses as MS lesions age, resulting in irreversible damage. It is now believed that damage to nerve fibers begins before the patient even experiences the symptoms of MS.

The type of symptoms one experiences depends on where the demyelination occurs. Most people experience more than one symptom, but no one exhibits all of the possible symptoms. An individual's own symptoms can also vary from time to time. About 70 percent of patients experience complete or partial remission of symptoms, especially in the early stages of MS. Remissions occur when myelin is able to repair itself.

Here are some of the most common symptoms of multiple sclerosis:

About 15 percent of patients with MS report that their first symptom was a vision problem. In MS, the optic nerve, which connects the eye with the brain, can become inflamed and stripped of its protective insulation. This condition, known as optic neuritis, results in dimmed, grayed, or blurred vision, or even loss of vision in one eye. Sensitivity to light, "holes" in the visual field and distortion of color vision can occur. Other vision problems may be caused by nystagmus, or uncontrolled horizontal or vertical eye movements. All of these problems are usually temporary and normal vision returns within a few weeks. More than half of all patients experience optic neuritis at some point. Visual problems are less common in later stages of MS.

MS typically causes people to experience abnormal sensations that result from the loss of myelin. These altered sensations are known as paresthesias. They may include numbness in an arm or leg, tingling, itching, burning, "pins and needles," or an increase in sensitivity (hyperesthesia). Paresthesias occur spontaneously, and often involve only a patch of skin in a specific area, such as a hand, arm or leg. One kind of altered sensation is known as L'hermitte's sign,. an electrical shock-like sensation that occurs when the neck is flexed forward. The sensation travels down the spine and into the arms or legs. L'hermitte's sign is suggestive of MS, but a majority of patients don't experience this symptom. While it signifies that spinal cord damage has taken place in the neck region, it is not a conclusive indication of the disease.

L'hermitte's sign is a disturbing sensation, but it is not serious. While paresthesias are bothersome, they are considered more benign symptoms than major problems. Little can be done to alleviate numbness, but if a patient is especially annoyed by other abnormal sensations, medications can sometimes be prescribed to lessen the symptoms.

Fatigue is the most common symptom of MS, affecting 80 percent of patients. For many, it is the major disabling symptom. The fatigue experienced by patients with MS is unique and more severe than the ordinary tiredness experienced by other people. The fatigue of MS is both physical and mental, and can be overwhelming in both regards. Fatigue can make it difficult to concentrate. It slows the thinking process and makes one forgetful. It can even affect motivation. Other chronic symptoms of MS are made worse by fatigue. It can contribute to muscle pain and spasms. Because fatigue is "invisible" to everyone but the patient, it can be difficult for others to understand. MS fatigue generally increases with both physical exertion and exposure to heat and humidity. For many patients, fatigue is worse later in the day.

Weakness is different from fatigue. While the exhaustion of fatigue affects the whole person, weakness is more of a true loss of strength and control in the legs and sometimes in the arms. The legs may feel "heavy" and hard to move, especially at the end of a day or when stepping up onto a curb or a stair step. Weakness is often just temporary, but can last for an extended period. Weakness can contribute to problems with walking, for example. Weak foot and ankle muscles can cause "foot drop," a condition in which the toes drop before the heel when walking. Weak hip muscles can cause "hyperextension," requiring the leg to swing out so the foot can clear the ground when walking. Vision problems and several other symptoms, whether alone or in combination, can also make walking more difficult. Because many things can contribute to difficulty in walking, it is important to accurately identify the source of the difficulty. Once the underlying problem or problems are clear, medication, physical therapy, or other measures can be prescribed as needed. As with the other MS symptoms, weakness is caused by an interruption in the electrical impulses carried over the nerve pathways. Most patients will, at some point in the course of their disease, experience weakness in their extremities and have some difficulty with balance, walking or coordination as a result.

References

First published October 1, 1999
Last updated May 2, 2003
Copyright © 1999 Accordant Health Services, Inc. All Rights Reserved.

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