What is multiple sclerosis?

• A. Degenerative autoimmune disease affecting the peripheral nervous system
• B. Chronic autoimmune disease where the body's immune cells attack the myelin sheath in the CNS
• C. Acute infection of the CNS
• D. Autoimmune disease of the muscles

Answer: (B)

Multiple sclerosis is a chronic autoimmune disease of the central nervous system in which immune cells attack the myelin sheath around CNS nerve fibers. This demyelination slows or disrupts nerve conduction, producing a variety of neurologic symptoms that can appear in episodes and may become progressive over time. The key point is that the attack targets the CNS, not the peripheral nervous system, which is why it’s not a peripheral neuropathy. It’s not an acute infection, and it’s not a primary autoimmune disease of the muscles. Understanding MS hinges on recognizing the immune-mediated damage to CNS myelin and how that disruption of signaling leads to the diverse neurological signs seen in patients.