Which nervous system disorder is characterized by demyelination of neurons?

The disorder characterized by demyelination of neurons is Multiple Sclerosis. In this condition, the immune system mistakenly attacks the protective covering (myelin) of nerve fibers in the central nervous system, leading to disrupted communication between the brain and the rest of the body. This demyelination can result in a wide array of neurological symptoms, including problems with vision, muscle control, balance, feeling, and cognition.

Guillain-Barr Syndrome, while it does involve demyelination, primarily affects the peripheral nervous system and usually presents with weakness and sensory changes after an infection. In contrast, Parkinson's disease and Alzheimer's disease are neurodegenerative disorders that do not primarily cause demyelination. Parkinson's is associated more with the degeneration of dopamine-producing neurons, while Alzheimer's involves the buildup of plaques and tangles in the brain, leading to cognitive decline. Therefore, Multiple Sclerosis best fits the description of a disorder marked by demyelination of neurons.