At present, there is no way to predict when or even if attacks of the disease will occur. Symptoms not only vary greatly from person to person but may also vary from time to time in the same person. The most typical pattern of MS is marked by periods of active disease or attacks, called exacerbations or relapses, followed by quiet periods called remissions.
Some people have few attacks and little if any disability over time. Others have what is called "relapsing-remitting" disease. This means they have exacerbations, which take place unpredictably, followed by periods of partial or total remission, which may last months, or even years. Still others experience a "primary-progressive" disease course with steadily worsening symptoms and no attacks or remissions. Thus, the disease ranges from very mild to intermittent to steadily progressive.
Dizziness is a common symptom of MS. Patients generally report a feeling of being off balance, or lightheaded, or in some cases having the sensation that they or their surroundings are spinning--this is called vertigo. These symptoms are due to lesions in the complex nervous pathways which coordinate visual, positional, and spatial input to the brain to produce and maintain equilibrium.
The symptoms of MS are varied. They are, in fact, a result of demyelination in the central nervous system, which leads to impaired electrical transmission of nerve impulses to muscles and other organs. The initial symptoms of MS are most often difficulty in walking, or abnormal sensations such as numbness or pins and needles. Optic neuritis (pain and loss of vision due to inflammation of the optic nerve), is another common presenting symptom. Somewhat less commonly, initial symptoms may include tremor, incoordination or slurred speech. At times, MS may have a sudden apoplectic-like onset of paralysis similar to a stroke. In rare cases, MS may begin as a decline in cognitive function.
Numbness of the face, body or extremities is one of the most common symptoms of MS, and is often the initial symptom experienced by a patient. The numbness may be mild, or may be so severe that it can interfere with the function of the affected part. For example, a patient with very numb feet may have difficulty walking; numb hands may preclude writing and dressing, or interfere with holding objects.
Fatigue is a common and often disabling symptom of MS. Estimates are that fatigue occurs in about 80% of MS patients. It may be the most prominent symptom in a patient who otherwise has minimal neurologic impairment, and can significantly interfere with the person's ability to work and function. Studies by MS researchers are beginning to delineate the characteristics of MS fatigue that differentiate it from fatigue experienced by persons without the disease. MS-related fatigue is more likely to be worsened by heat, comes on more easily, is generally more severe, and is more likely to interfere with daily responsibilities. It does not appear to be strongly correlated with depression or degree of physical impairment, and may occur first thing in the morning even if the patient has had a restful full night's sleep.
Muscle weakness is a common cause of gait difficulty. If both legs are affected, this is known as paraparesis; if only one leg is weak, it is a monoparesis. Patients may also have a foot drop which can cause them to stumble or trip. Weakness may often be compensated for by appropriate braces, canes, walkers, or other assistive devices.
Spasticity, an abnormal increase in resting muscle tone, is one of the most common symptoms of MS. The mechanisms whereby it arises are not fully understood, but loss of input from inhibitory nerve pathways is believed to be involved. Spasticity may be as mild as the feeling of stiffness or tightness of muscles, or may be so severe as to produce painful uncontrollable spasms of extremities, usually of the legs. Spasticity may also produce feelings of pain or tightness in and around joints and can also cause low back pain. In some patients whose legs are very weak, spasticity makes the legs more rigid, and actually helps them to stand, transfer or walk. Spasticity may be aggravated by extremes of temperature, humidity, or concurrent infections.
Visual symptoms are not uncommon in multiple sclerosis patients. They may be the result of inflammation of the optic nerve (optic neuritis), or lesions along the pathways that control eye movements and visual coordination. Optic neuritis may result in blurring or graying of vision, or monocular blindness. A scotoma or dark spot may occur in the center of the visual field. Optic neuritis is almost always self-limiting and patients generally make a good recovery. Recent studies suggest that treatment with IV methylprednisolone followed by a tapered course of oral steroids may be useful.
Nystagmus, or uncontrolled horizontal or vertical eye movements, is another common symptom. Nystagmus may be mild and only occur with extreme lateral gaze, or it may be severe enough to impair vision. Some drugs and special prisms have been reported to be successful in treating the visual deficits caused by nystagmus, and a related eye movement disorder, opsoclonus, which causes oscillopsia or 'jumping vision'.
Diplopia, or double vision, occurs when the pair of muscles that control a particular eye movement are not perfectly coordinated due to muscle weakness in one or both pairs. In this case, the images are not properly fused, and the patient perceives a false double image.