Four disease courses have been identified in MS (Lublin & Reingold, 1996).

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

Benign course

Natural history studies have demonstrated that a certain percentage of people with MS experience a benign course. However defining “benign MS” and determining the point at which a person can be classified as having a benign course, are the subject of some controversy.

Determining When the MS Disease Course is Benign

Natural history studies from Northern Ireland (McDonnell & Hawkins, 1998), Olmstead County, Minnesota (Pittock et al., 2004), South Wales (Hirst et al., 2008), and Gothenburg, Sweden (Andersen O. Natural course of MS: 50 years of follow-up. Multiple Sclerosis 2010; 16: S7–S392010), demonstrate conclusively that a certain percentage of people with MS experience a benign course, meaning no relapses and mild, stable disability over time. The estimate of 10% having benign disease after 20-30 years of illness seems realistic (Hutchinson, 2012).

The challenge lies in determining what the term “benign” really means, and how long into the disease course one has to wait in order to determine that the course is, in fact, benign. Natural history studies have relied heavily on the Expanded Disability Status Scale (EDSS) measure disease progression; however even within the studies cited here, there is variation in the score (<2 - <3) used to define benign MS. In addition, the EDSS places heavy emphasis on ambulation status, with little attention paid to other functions, including cognition (Balcer, 2001).

With increasing awareness of the potential for significant cognitive impairment in patients with CIS (Khalil et al., 2011) and in patients with little or no physical disability (Reuter et al., 2011; Amato et al., 2006), defining benign MS, and determining the patients for whom early and ongoing treatment with a disease-modifying agent is appropriate, are the subject of some debate: Hawkins, 2012 vs. Amato, 2012; Pittock et al., 2006 vs. Frohman et al., 2006