Human Anatomy and Physiology
You pick up the telephone to call your friend. You dial a number which will, in effect, let the phone know where to send the signals. Except unknown to you, something has worn away the rubber which covers and protects the wires within your phone. Some signals cannot get through, and the ones that do are unclear. As a result your important information does not get conveyed to your friend. This is a circumstance similar to the process that occurs within the body of a person with Multiple Sclerosis. The name itself is revealing: multiple, more than one, and sclerosis, which refers to areas of sclerotic (scarred) tissue. Multiple sclerosis (MS) is a potentially debilitating disease in which your body's immune system eats away at the protective sheath that covers your nerves. MS is far more common in countries with temperate climates, including Europe, southern Canada, northern United States, New Zealand and southeastern Australia. The risk seems to increase with latitude and affects noticeably more women than men with the onset of clinical symptoms occurring between 15 and 50 years of age. It is the most common demyelization disease of the central nervous system. In the United States alone, there are at least 250,000 cases. Although the exact pathogenesis of the disease is unknown, it is believed that the clinical manifestations of multiple sclerosis are the result of an immune reaction consisting of the penetration of the blood-brain barrier (BBB), entrance into the CNS, and recognition of the myelin basic protein (MBP) and proteolipid (PLP) as foreign. The immune system's attack on these proteins induces the stripping of the protective coating of myelin and then eventual formation of plaques. These plaques or lesions can be found throughout the central nervous system, but are most prominently found in the white matter, optic nerve, brainstem, spinal cord, and cerebellum. The formation of these plaques causes the conduction of action potentials along the axon to be reduced, resulting in neurocognitive or neuromuscular impairment. Symptoms vary widely, depending on the amount of damage and which particular nerves are affected. People with severe cases of multiple sclerosis may lose the ability to walk or speak. It can be difficult to diagnose early in the course of the disease, because symptoms often come and go even disappearing for months. Signs and symptoms vary widely, they may include: • Numbness or weakness in one or more limbs, which typically occurs on one side of your body at a time or the bottom half of your body • Partial or complete loss of vision, usually in one eye at a time, often with pain during eye movement (optic neuritis) • Double vision or blurring of vision
• Tingling or pain in parts of your body
• Electric-shock sensations that occur with certain head movements • Tremor, lack of coordination or unsteady gait
Clinical symptoms of multiple sclerosis include: optic nerve dysfunction, internuclear ophthalmoplegia, upper motor neuron weakness, tremors, ataxia, sensory disturbances, and autonomic dysfunction. While the typical clinical course of multiple sclerosis is characterized by relapsing and progressive disability, there have been examples of subclinical cases of MS where the diagnosis is confirmed only by the presence of large confluent, demyelization plaques found only upon autopsy. Diagnosis is difficult, medical history and clinical examination must show at least two separate lesions that have occurred at more than one time. Because of the difficulty of diagnosis, the presence of MS is usually deemed to be definite, probable, or possible. A neurological examination can indicate lesions through the presence or absence of various signs and reflexes. A sign is an abnormality detected through...
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