Which of the following is most descriptive of multiple sclerosis

A. Diease in which mylein sheath is gradually replaced by scar tissue
B. neuromuscular disorder caused by a deficiency of dopamine
C. Brain death due to cerebral hypoxia
D. Increased intracranial pressure that causes downward displacement(herniation) of the brain stem

thanks

A. Disease in which mylein sheath is gradually replaced by scar tissue

B is Parkinson's disease. C & D are mechanisms of injury in several conditions.

MS affects the ability of nerve cells in the brain and spinal cord to communicate with each other. Nerve cells communicate by sending electrical signals called action potentials down long fibers called axons, which are wrapped in an insulating substance called myelin. In MS, the body's own immune system attacks and damages the myelin. When myelin is lost, the axons can no longer effectively conduct signals. It scars the white matter of the brain and spinal cord. Your answer is A.