A chronic neurodegenerative disease characterized by random demyelination of motor and sensory neurons. Scar tissue forms where myelin is missing, creating lesions that block the neuron from transmitting electrical impulses. Cumulatively, this process results in hardening and stiffening of nerve structures where demyelination has taken place, giving rise to the name sclerosis, which means “hardening.” The myelin sheath is a protective covering that surrounds the neuron’s axon, or tail, sheltering the nerve signals it transmits from interference. Researchers do not know what causes demyelination; it appears to be an interaction of genetic, autoimmune, and environmental factors. Multiple sclerosis is significantly more common in people with family members who have multiple sclerosis or who live in temperate parts of the United States and Europe. Multiple sclerosis most commonly emerges in early adulthood (between the late 20s and early 40s) but can appear at any age.
Impaired motor function sometimes can appear at first to be Parkinson’s disease when multiple sclerosis is manifested in middle age, although symptoms do not fit the classic Parkinson’s profile. It is rare for such confusion to persist after a careful neurologic evaluation. As in Parkinson’s disease, there is no conclusive diagnostic test as yet for multiple sclerosis. Imaging studies such as MAGNETIC RESONANCE IMAGING (MRI) and COMPUTED tomography (ct) scan certain studies of the cerebrospinal fluid (the fluid surrounding the brain), and some neurophysiologic studies such as visual evoked potentials often can detect the fingerprints of demyelination and the lesions that form there, helping to confirm the diagnosis of multiple sclerosis, and rule out other neurodegen-erative diseases.
The symptoms and course of multiple sclerosis are unpredictable. Most people experience symptom-free periods (remission) that can last years, and others experience complete debilitation within a short period. Depending on the nerves that are involved, multiple sclerosis can impair motor skills and mobility, speech, vision, and sensory perceptions. Symptoms often are bilateral (affecting both sides of the body). Steroid medications that relieve inflammation relieve symptoms in some people. Motor function impairments do not respond to levodopa or other anti-parkin-son’s MEDICATIONS.
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