The MS Process and Symptoms

Multiple sclerosis (MS) is a disease 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 delayed and have trouble reaching their destination – causing the symptoms of MS. Although each person with MS experiences different types and severity of symptoms, the range of symptoms includes:

Illustration of MS damage to the myelin of a nerve cell
Illustration of MS damage to the myelin of a nerve cell
  • anxiety
  • balance issues
  • bladder dysfunction
  • bowel problems
  • cognitive changes
  • depression
  • dizziness/vertigo
  • fatigue
  • mobility and walking issues
  • numbness
  • pain
  • pseudobulbar affect (PBA)
  • sexual dysfunction
  • sleep issues
  • spasticity (stiffness)
  • speech difficulties
  • swallowing disorders
  • tremor
  • Uhthoff”s syndrome (when heat worsens visual symptoms)
  • visual disorders
  • weakness

Areas of inflammation and damage in the CNS are known as “lesions.” The changes in size, number, and location of these lesions may determine the type and severity of symptoms. Disease activity may also be evaluated from these changes in the size or number of lesions. Frequently, MS may be “clinically silent,” showing no increase in symptoms, yet continuing to show signs of disease activity within the CNS.

For individuals with relapsing forms of MS, early and continued treatment with a disease-modifying therapy (DMT) can often slow the “clinically silent” disease activity in the brain, reducing the size and number of active lesions. This is why most neurologists, as well as the American Academy of Neurology, recommend that individuals with relapsing forms of MS begin treatment as soon as possible after the diagnosis is established. However, treatment cannot be effective unless it is taken exactly as prescribed and without missing doses, so adherence is critical.

In addition to the lesions, areas of thick scar tissue may eventually form along the areas of permanently damaged myelin. These areas of scar tissue are referred to as “plaques.” The term “multiple sclerosis” originates from the discovery of these hardened plaques. Multiple refers to “many;” sclerosis refers to “scars.”

Lesions and plaques are viewed on a magnetic resonance imaging (MRI) scanner. This technology is used to help diagnose MS and evaluate its progress at various intervals. The MRI and other tools are described in the section titled, “Diagnosing MS and Evaluating Disease Activity,” beginning on page 10 of this booklet.


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