Multiple Sclerosis (MS)
Incidence
Approximately 1 in 1,000 people will develop MS. Most patients will develop their initial symptoms during young to middle adulthood but MS can present at virtually any age. MS is more common in females and often presents at a younger age than males. There is a higher incidence in individuals with a Northern European heritage, those who live in areas of higher latitude, and those who live in a more temperate climate rather than a tropical one. MS is very rare among African blacks, but occurs in African-Americans at a rate of approximately half that of white Americans. Race may also affect the clinical expression of MS, as evident in the Japanese and several other Asian populations who experience a form of MS that commonly involves the optic nerves and spinal cord rather than the brain.
Clinical Characteristics
Multiple Sclerosis (MS) is a progressive neurological disease that affects the central nervous system (brain and spinal cord). The outer covering of nerve cells (the myelin sheath) is specifically destroyed in MS, leading to weakness, sensation loss, and other neurological deficits. This disease most notably affects the brain, spinal cord, and the optic nerve by causing inflammation, swelling, and demyelination. The course of MS is highly variable and symptoms may be different for each individual. Initial symptoms of MS may include some or all of the following: numbness and tingling of hands or feet, weakness of one or both legs, loss of vision in one or both eyes, facial numbness, vertigo, double vision, problems with speech or language (dysarthria), jerkiness and incoordination (ataxia), or urinary frequency and urgency. L'Hermitte's symptom is also very common in MS and is characterized by a sensation resembling an electrical shock that occurs with forward flexion of the head. The sensation is most often felt on the front of the thighs but may occur down the spine or in the arms. Other common symptoms include pain, tremor, decrease in vision and color perception in one eye with eye pain, bladder difficulties including the inability to void, bowel difficulties (constipation, incontinence, rarely diarrhea), sexual dysfunction, and cognitive difficulty. Uveitis (inflammation in the eye) is also more common in MS. The underlying cause of MS is currently unknown. The two currently favored theories suspect MS to be either an autoimmune disorder or infectious disease. A variety of organisms, mostly viruses, have been proposed as the agent that causes MS but none have been proven. The current viewpoint suggests that the particular virus causing MS produces an autoimmune response in the body. Normally the immune system recognizes the virus as a foreign invader that is not supposed to be in the body. The current theory suggests that the antigen (protein that stimulates the immune system) on this virus is the same as a substance on the myelin sheath of the neurons. Therefore, the immune system binds the virus and destroys it, but also binds the myelin sheath and destroys it too. In addition to a potential viral trigger, the increased rate of MS in certain families points to a genetic component. No specific gene has yet been found, but studies have shown an increased risk for children when MS exists on both of the parents' sides of the family. Other factors, in addition to infection and genetic predisposition, associated with the onset of MS or recurrent episodes have been suggested as emotional and physical stress, trauma, surgery and anesthesia, diet, heavy metals, overexertion or fatigue, and heat, although none of these have been validated thus far. The effects of pregnancy on MS have been studied extensively and studies show that during pregnancy there is a decline in MS episodes and symptoms. Unfortunately, during the first three months after birth there seems to be an increase in MS episodes. Early diagnosis is crucial to treat MS effectively.
Precipitants
None
Provocation Tests
None
Diagnostic Procedures
There is no single test that confirms the diagnosis, but MS can be identified by the characteristic historical and physical findings. If a child is suspected to have MS, a variety of tests will be done to exclude other conditions and make the diagnosis of MS. A blood and cerebrospinal fluid test may be done to rule out infection and determine if the child has laboratory test results consistent with MS. An MRI (magnetic resonance image) of the brain can identify changes consistent with MS. An Evoked Potential test, which measures the time it takes for nerves to respond to stimulation, may also be done to confirm a pattern of central nervous system involvement that is seen in MS. Lastly, neurocognitive tests may be done to document associated cognitive deficits.