Saturday, December 1, 2007

The Neurobiology of Multiple Sclerosis

Hauser, S.L. & Oksenberg, J.R. (October 5, 2006). The Neurobiology of Multiple Sclerosis: Genes, Inflammation, and Neurodegeneration, Neuron.

Multiple sclerosis (MS) is the most common cause of chronic neurological disability in adults. It is estimated to affect two million individuals worldwide. The diagnosis of MS has been aided by MRI technology which reveals multiple, asymmetrically-located white matter lesions throughout the CNS. The PNS, however, appears to be unaffected by the disease. The destruction of this insulating layer of myelin in the brain and spinal cord causes vital electrical signals to be sent more slowly and less efficiently.

Initial symptoms commonly include weakness or diminished dexterity in the limbs, sensory disturbance, monocular visual loss, double vision, and gait instability. As the disease progresses, bladder dysfunction, fatigue, and heat sensitivity are all likely to occur. Cognitive impairments include memory loss, impaired attention, problem-solving difficulties, slowed information processing, and difficulties in shifting between cognitive tasks. Depression is experienced by about 60% of patients during the course of the illness. Onset of symptoms may be either quick or slow depending on the individual.

The genetic component in MS is primarily suggested by aggregated family students and the high incidence of the disease in some ethnic populations (particularly those of northern European origin). Correlational data also suggest a role for environmental factors in MS, and common viruses are thought to be likely infectious agent culprits.

Numerous studies provide the rationale for a disease model driven by the loss of immune homeostasis and uncontrolled immune responses against structural CNS components. Therefore, treatments typically take aim at both inflammation and neurodegeneration. One class of drugs attempts to suppress the auto-immune response, while another aims to promote remyelination in surviving axons as well as more holistic repair. However, mixed therapeutic results in practice leave this an open problem for science to solve.

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