How MS Affects the Nerves and Causes Symptoms

Multiple sclerosis (MS) is a neurological condition that is most frequently diagnosed in young adults. It is believed to be an autoimmune disorder, where one’s own immune system becomes misdirected and causes damage to the body – in this case, the nerves of the central nervous system (CNS).

The CNS consists of the brain, optic nerves, and spinal cord. With MS, areas of the CNS become inflamed, damaging the protective covering (known as “myelin”) that surrounds and insulates the nerves (known as “axons”). In addition to the myelin, over time, the axons and nerve cells (neurons) within the CNS may also become damaged.

The damage to the protective covering and also to the nerves disrupts the smooth flow of nerve impulses. As a result, messages from the brain and spinal cord going to other parts of the body may be disrupted – causing the symptoms of MS. This disease affects everyone differently and can cause a variety of symptoms – including visual changes, numbness, bladder problems, fatigue, depression, mobility issues, and more.

For many, symptoms can flare-up and then subside over the course of days, months, or even years. These flare-ups are also referred to as relapses, exacerbations, or attacks. In the writing throughout this website, we will refer to these flare-ups as “relapses.”

While MS is not contagious, its causes are not yet fully understood and researchers continue to search for answers. Areas of inflammation and damage within the CNS are known as “lesions,” and these may be viewed through a magnetic resonance imaging (MRI) scan. The changes in size, number, and location of these lesions may determine the type and severity of symptoms. While individuals with relapsing forms of MS are believed to experience more inflammation than those with progressive forms of MS, lesions still occur for individuals with all forms of MS.

Types of MS

Multiple sclerosis (MS) affects each person differently. The most common types of MS are:

• Relapsing-Remitting MS (RRMS)
• Secondary-Progressive MS (SPMS)
• Primary-Progressive MS (PPMS)
• Progressive-Relapsing MS (PRMS)

Initially, most people with MS experience relapses. When someone experiences a relapse, he or she may be having new symptoms or an increase in existing symptoms. These usually persist for a short period of time (from a few days to a few months) and afterward an individual may remain symptom-free for periods of months or years. This type of MS, where an individual initially experiences relapses and remissions, is referred to as relapsing-remitting MS (RRMS). Approximately 80 to 85 percent of MS patients are initially diagnosed with this form of the disease.

Over time, RRMS may advance to secondary-progressive MS (SPMS). This form of MS does not have the dramatic variations in symptoms that RRMS does, but rather has a slow, steady progression – with or without relapses. If relapses do occur, they usually do not fully remit.

Individuals who are not initially diagnosed with RRMS may be experiencing a more steady progression of the disease from the onset. Approximately 10 percent of the MS population is diagnosed with primary-progressive MS (PPMS), where individuals experience a steady worsening of symptoms from the start, and do not have periodic relapses and remissions. Approximately 5 percent of patients are initially diagnosed with progressive-relapsing MS (PRMS). This type of MS steadily worsens from the onset, but relapses – with or without remissions – are also present.

For a full overview of MS – including details about who gets MS and possible causes – please visit the “MS Overview” of the “MS Information” section of MSAA’s website at mymsaa.org/ms-information/overview.