The underlying pathology of Multiple Sclerosis is:

• A. Parkinson's disease
• B. Amyotrophic lateral sclerosis
• C. Muscular Dystrophy
• D. Multiple Sclerosis

Answer: (D)

MS is an autoimmune disease in which the body's immune system attacks the myelin sheath that insulates nerve fibers in the brain and spinal cord. This leads to focal areas of demyelination, called plaques, with inflammation and later scar tissue (gliosis). When myelin is damaged, nerve impulses slow or block, producing the varied neurologic symptoms that come and go with relapses or progress over time. Oligodendrocytes—the cells that create CNS myelin—are damaged, and although axons can be initially spared, cumulative injury can impair conduction and function. This pattern—autoimmune demyelination in the central nervous system—is what sets MS apart from the other conditions listed, which affect different tissues (Parkinson’s with dopaminergic neuron loss in the CNS, ALS with motor neuron degeneration, and muscular dystrophy with muscle fiber defects).