Demyelination of the myelin sheath throughout the brain stem, spinal cord, optic nerves and cerebrum causing destruction of the myelin sheath. What disease is this?

• A. Multiple sclerosis
• B. Amyotrophic lateral sclerosis
• C. Guillain-Barré syndrome
• D. Parkinson's disease

Answer: (A)

The main idea here is an autoimmune process that selectively attacks the myelin in the central nervous system, causing demyelination in multiple CNS regions. In multiple sclerosis, immune-mediated destruction targets the myelin sheaths around axons in the brain, spinal cord, optic nerves, and other CNS areas. This demyelination disrupts nerve conduction, leading to diverse neurologic symptoms such as visual disturbances from optic neuritis, weakness, numbness, gait and coordination problems, and other focal deficits depending on where lesions occur. The distribution—from brainstem and spinal cord to optic pathways and cerebrum—fits MS, which often presents in young adults with relapsing and remitting episodes and MRI shows multiple plaques of demyelination.

Other diseases involve different mechanisms or locations of pathology. Amyotrophic lateral sclerosis primarily affects motor neurons, leading to progressive muscle weakness without widespread CNS demyelination. Guillain-Barré syndrome targets the peripheral nerves and roots, causing ascending weakness and areflexia rather than CNS demyelination. Parkinson’s disease centers on degeneration of dopaminergic neurons in the substantia nigra with movement symptoms, not demyelination of CNS pathways.