Multiple Sclerosis/Demyelinating Disease
Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system where the immune system attacks the myelin sheath—the protective coating around nerve fibers in the brain and spinal cord. This demyelination disrupts nerve signal transmission, causing a wide range of neurological symptoms that can vary greatly between individuals. MS is the most common demyelinating disease, affecting approximately 1 million people in the United States, with onset typically between ages 20-40 and affecting women about three times more often than men.
What is it?
Multiple sclerosis is characterized by the formation of demyelinating lesions or plaques scattered throughout the brain and spinal cord. These lesions represent areas where the immune system has attacked and damaged the myelin sheath, the fatty insulating material that wraps around nerve fibers and allows for rapid electrical signal transmission. When myelin is damaged, nerve signals are slowed, distorted, or blocked, leading to the diverse symptoms of MS. The term “multiple sclerosis” refers to the multiple scars (sclerosis) that form in the nervous system over time as damaged areas heal with scar tissue.
MS exists in several clinical forms: relapsing-remitting MS (RRMS), the most common type affecting about 85% of patients at diagnosis, involves distinct episodes of neurological symptoms (relapses) followed by periods of partial or complete recovery; secondary progressive MS (SPMS) develops in many RRMS patients after 10-20 years, characterized by gradual worsening without clear relapses; primary progressive MS (PPMS) affects about 10-15% of patients with gradual worsening from disease onset without relapses; and progressive-relapsing MS (PRMS), a rare form with steady progression from onset plus acute relapses. The exact cause of MS remains unknown, but it likely involves a combination of genetic susceptibility and environmental factors such as vitamin D deficiency, viral infections (particularly Epstein-Barr virus), smoking, and geographic location (higher prevalence farther from the equator).
Important to Know
MS symptoms vary widely depending on which areas of the nervous system are affected and can include vision problems (optic neuritis causing blurred or double vision, pain with eye movement), numbness or tingling in the limbs or face, weakness or difficulty with coordination and balance, fatigue (one of the most common and debilitating symptoms), bladder and bowel dysfunction, cognitive changes affecting memory and concentration, and heat sensitivity where symptoms worsen with increased body temperature. Diagnosis relies on demonstrating lesions “disseminated in space and time”—meaning multiple lesions in different parts of the nervous system that have occurred at different times. MRI is the primary diagnostic tool, showing characteristic white matter lesions particularly in periventricular regions, the corpus callosum, and the brainstem. Lumbar puncture may reveal oligoclonal bands in cerebrospinal fluid, supporting the diagnosis. Treatment has advanced significantly with multiple disease-modifying therapies (DMTs) available that can reduce relapse rates, slow disability progression, and decrease new lesion formation on MRI. These include injectable medications, oral therapies, and infusion treatments. Acute relapses are typically treated with high-dose corticosteroids. Symptomatic treatments address specific issues like spasticity, pain, fatigue, and bladder problems. With modern treatments, many people with MS can maintain good quality of life, though the disease course is highly variable and unpredictable.