Relapsing-remitting MS (RRMS) is the most common form of MS, affecting about 85% (or more than 8 out of 10) people diagnosed with MS.
With RRMS, the patient experiences relapses (attacks, exacerbations, or flare-ups) during which there are increased symptoms and/or a worsening of neurologic function, followed by partial or complete recovery (or remission).
How is RRMS different from progressive forms of MS?
Much more common: RRMS is much more common than progressive courses of MS, which only affect 10% to 15% of patients. Patients with RRMS differ from those with progressive courses of MS in a number of ways.
Involves CNS inflammatory attacks: RRMS involves inflammatory attacks on myelin, the outer protective coating that surrounds nerve fibers in the CNS. During attacks, the activity of immune cells during inflammatory attacks can result in small areas of damage on neurons called lesions (or plaques). With progressive forms of MS (primary-progressive MS or PPMS, secondary-progressive MS or SPMS, and progressive-relapsing MS or PRMS), inflammatory attacks happen much less frequently.
Inflammatory attacks can cause lesions anywhere in the CNS, however patients with RRMS tend to have more brain lesions than spinal cord lesions. With PPMS, lesions are more common on the spinal cord and these lesions contain fewer inflammatory cells. With SPMS (to which most patients with RRMS eventually transition), the disease involves less inflammation and more loss of nerve fibers and brain atrophy. Like PPMS, PRMS has a progressive disease course from the beginning with steady gradual destruction and loss of nerve fibers with occasional relapses or inflammatory attacks.
Different rates of diagnosis by gender: RRMS tends to affect females 2 to 3 times as often as males, while in persons with PPMS, the numbers of males and females diagnosed are roughly equal.
Diagnosed earlier in life: RRMS tends to be diagnosed earlier in life than progressive disease courses, with most patients diagnosed in their 20s or 30s. PPMS is typically diagnosed 10 years later than RRMS. Within 25 years of initial diagnosis, approximately 90% of RRMS patients will have transitioned to SPMS.
Symptoms differ: RRMS tends to be associated with symptoms which include episodes of fatigue, numbness, vision problems, spasticity or stiffness of limbs, and bowel or bladder problems. By contrast, PPMS is associated more often with motor control difficulties and patients may have more difficulty walking or caring for themselves. Patients with PRMS and SPMS may have a steady but gradual worsening or progression of symptoms accompanied by attacks or relapses which involve sudden development of a new symptom or a worsening of an existing symptom.
How is RRMS diagnosed?
Diagnostic criteria (the evidence that must be present to make a diagnosis) for RRMS include evidence of two or more areas of damage to myelin in the CNS which has occurred at different points in time. Sometimes these diagnostic criteria are described as dissemination in space, referring to the two or more separate locations where demyelination happened, and dissemination in time, referring to the two or more occasions in time when damage has happened.
Additionally, it is necessary to rule out any other diseases or conditions that might have caused symptoms of CNS damage described above. Other causes of MS-like symptoms may include lupus, Sjögren’s syndrome, valculitis, Lyme disease, brain tumors, vitamin B12 deficiency, other demyelinating disease, and more.
Diagnosis of RRMS requires a careful medical history and neurologic exam. Tests useful in confirming the presence of CNS damage include magnetic resonance imaging (MRI), visual evoked potential (VEP) testing, and analysis of cerebrospinal fluid (CSF) which is taken using a lumbar puncture.
When an individual has experienced only a single episode or MS-like attack involving neurologic damage, that individual is said to have clinically-isolated syndrome (CIS). In an individual with CIS, it may take months or years for another episode to happen and a confirmed diagnosis of MS to be made. However, a person with CIS may never develop MS.