Which condition is characterized as a progressive terminal disease affecting motor neurons?

Amyotrophic lateral sclerosis (ALS) is characterized as a progressive terminal disease that specifically affects motor neurons. In this condition, the motor neurons in the brain and spinal cord degenerate and eventually die, leading to a decline in muscle function and strength. This neurodegeneration results in muscle wasting, difficulties with speaking and swallowing, and eventually paralysis, significantly impacting the person's quality of life.

In contrast, other listed conditions have different underlying mechanisms and effects. Multiple sclerosis involves the immune system attacking the protective covering of nerves, leading to various neurological symptoms, but it doesn't have the same direct impact on motor neurons as ALS does. Parkinson's disease primarily affects movement through the loss of dopamine-producing neurons, while Alzheimer's disease is related to cognitive decline and memory loss, not motor neuron degeneration. Each condition has its specific characteristics, but it is ALS that distinctly fits the criteria of a progressive terminal disease affecting motor neurons.