MS signs and symptoms vary greatly and can range from mild to severe. They can appear quickly and may disappear after a few days or weeks. In some cases they may only reappear years later. MS symptoms are triggered by the loss of myelin (a protective coating) on nerve fibers in the central nervous system — which encompasses the optic nerves, brain, and spinal cord — resulting in a lesion that may interfere with the transmission of nerve signals and therefore, depending on its location, cause the disease symptoms.
In patients with relapsing-remitting MS, disease symptoms usually improve after each relapse — a period referred to as remission in which partial or complete recovery from symptoms occurs. In patients with primary progressive MS, however, symptoms typically get worse over time without any obvious relapses or remissions periods. Effective treatments can help manage and to some extent prevent symptom progression.
Symptoms such as fatigue and spasticity can feel worse at night. Spasticity and stiffness, in particular, can get worse due to reduced movement (for example, as a person lies in bed) and due to tight muscles that make it harder to relax when trying to sleep.
Disease progression can vary significantly between people and according to the type of MS. People may experience periods where the disease symptoms are stable — these can last for years — but also periods of rapid symptom development (within hours or days). As a chronic, progressive disease, MS leads to increasing disability over time.
Currently there is no cure for MS, but research in the field over the past years has led to major advances in treatments and therapeutic strategies, especially in the areas of inflammation and myelin repair.