RRMS and PPMS - A Comparison, Part I

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Few people know about Primary Progressive MS (PPMS) because so few people have it. I am going to talk today about Primary Progressive MS (PPMS) and compare this type of MS with Relapsing/Remitting MS (RRMS), the most common type.

This article is presented in two parts.

Part I is an introduction presenting a "big picture" of the difference between the little-known PPMS and the common, well-known RRMS. Part II is more descriptive, including treatment and research.

I am not doctor, but I feel compelled to discuss this topic after a young woman who was diagnosed with PPMS asked, "Why doesn't anyone ever talk about PPMS?" I'm here to tell you that more people are talking about it and acting on it now.

There is more MS information available today than ever before, but most of that information is about RRMS. The vast majority of people with MS have the RRMS type. Because there is not as much information or activity about PPMS and the other MS types, people living with them sometimes feel simply left out in the cold.

The following table represents a comparison of MS types by their occurrence. Percentages are approximate. The types may evolve from one to another, are diagnosed in regions where labels have not yet been standardized, or may not be diagnosed at all.

Metrics of MS types by occurrence within MS population

Just as we do not know why we get MS, little or nothing is known about why we develop one type or another. Why do some people with Relapsing Remitting MS never move on to Secondary Progressive? Why do some people experience benign periods? Also, other conditions may mimic MS so they are often difficult to distinguish and make diagnosis more difficult.

MS is usually diagnosed for people between 20 - 50 years old, although we know it ranges from young babies to very old people. PPMS, however, is not usually identified in patients until their late 30s or 40s.

Life expectancy for someone with MS has improved over the last 80 years.   In 1936, only 8 percent of people with MS were expected to live 20 years beyond diagnosis. Today anyone with MS is expected to live about as long as a non-affected person; statistics say perhaps just 5-7 years less.


MS diagnosis often takes months or even years following unexplained events such as numbness or interrupted vision.

Diagnosis is still a long process, however, consisting of several steps done over time. These steps usually include the following:

  • Neurological history, episodesor attacks
  • Primary MRI, or a series of spinal MRIs
  • Evoked potentials tests indicating a slowing in nerve conduction speeds
  • A spinal tap showing oligoclonal banding in the spinal fluid
  • Eliminate similar conditions

Leading to an RRMS diagnosis, I had several episodes, each different, each treated by a different doctor. There was no one to identify the pattern as MS, until I was lucky enough to find the right neurologist who confirmed my diagnosis. This story is not unique to me; rather, it is similar to 85% of people diagnosed with MS.

I was diagnosed in 1989, just a few years after Dr. Ian McDonald published the first version of his MS diagnosis criteria.   The sum of my tests along with the MRI identified my episodes as indicative of MS. His criteria has helped to standardize MS diagnoses.

The same steps with different results lead to PPMS when a spinal MRI identifies incidental white-matter abnormalities. It helps exclude compression of the spinal cord while eliminating other conditions on the route to a definite MS diagnosis. There is an especially higher incidence of delayed visual evoked potentials.

PPMS is unique because there are no periods of relapse and recovery preceding the progression. When PPMS is suspected, neurologists prefer to delay diagnosis for at least a year or two to ensure there is no relapse.

Disease Course

There is no certain predictability for an MS disease course because each case is individual. In all types, stress worsens the symptoms, but there is still no predictable outcome.

Relapsing/Remitting MS is characterized by periods when a symptom appears or reappears for at least 24 hours, called attacks, exacerbations, or flares. These relapses are followed by periods of complete or partial recovery that may last days, weeks, months, or even years before symptoms return.

Years, or perhaps even decades later, symptoms worsen and progress in a manner without clear periods of relapsing or recovering symptoms, moving RRMS into the Secondary Progressive (SPMS) phase. The disease-modifying drugs in common use today tend to delay that evolution so it is unclear if fewer people with RRMS will develop SPMS.

Primary Progressive MS is characterized by steady onset, usually beginning with walking. Motor dysfunctions steadily worsen as the MSer develops increasing disability without any inflammatory attacks. There are few lesions in the brain, but there is spinal cord and neurological damage.

PPMS experiences less unpredictability because there is more steady progression than in any other type. No one group, of course, can predict with certainty the degree of disability to be attained, but it is likely to be worse faster than other types.

Location of Lesions

Lesions show up in different areas indicating types of MS. The location of abnormalities and lesions differs in each MS type.

RRMS is generally active in the brain, and lesions show up in a brain MRI.

PPMS begins in the spinal cord rather than the brain. There are fewer and smaller cerebral MRI abnormalities; that is, fewer lesions show on the brain MRI over time, but the PPMS patient probably experiences greater disability.

Hopefully, this article begins to clarify the Primary Progressive MS. Next, in Part II, I will continue the comparison between RRMS and PPMS including descriptions of prognosis, treatment and research.

If you get a diagnosis, get on a therapy, keep a good attitude and keep your sense of humor. ~ Teri Garr