Former reality star and son of Ozzy Osbourne, Jack Osbourne's recent diagnosis of MS brings the disease to the forefront again. It affects the brain and spinal cord and can cause motor function problems, among many other things.

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Neurologist Dr. McGarvey says MS can affect the body in different ways. "If the area of the brain that controls sensation has a plaque that develops then a patient would have, say numbness, and if it occurs in the area that's involved in motor function then a patient could have weakness or difficulty with talking or moving."

Dr. McGarvey says there is a genetic component to being diagnosed, which mostly comes from studies on twins. "That show there is about a 25-percent concordance in monozygotic twins, which means identical twins, and it's 5 percent in dizygotic twins. But the majority of the causes that we believe now that are implicated in multiple sclerosis are more auto-immune or sometimes infection."

She says there are different way to treat the disease, including symptomatic treatments and therapy to lessen inflammation, but there is no cure.