Rosh Internal Medicine Practice Exam 2025 – Complete Prep Guide

Multiple sclerosis is characterized by the destruction of myelinated axons in the central nervous system (CNS). This autoimmune disorder results in the formation of plaques or lesions, primarily affecting the white matter where myelinated axons are densely located. In multiple sclerosis, the body's immune system mistakenly attacks the myelin sheath, which is the protective covering that surrounds nerve fibers. This damage disrupts the normal flow of electrical impulses along the nerve cells, leading to a wide range of neurological symptoms that can vary greatly among individuals.

The other conditions listed do not involve the destruction of myelinated axons in the CNS in the same way. Amyotrophic lateral sclerosis primarily affects motor neurons in the spinal cord and brain, leading to muscle weakness and atrophy without targeting myelin itself. Guillain-Barré syndrome is an autoimmune condition that affects the peripheral nervous system, leading to weakness and paralysis, but it does not involve the CNS and primarily impacts the nerve roots and peripheral nerves. Parkinson's disease is a neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra, largely affecting motor control, but does not specifically involve the destruction of myelin. Thus, multiple sclerosis is the condition that fits the description of my