Revised diagnostic criteria of multiple sclerosis.

Multiple sclerosis (MS) is a chronic demyelinating disease of the central nervous system (CNS) of presumed autoimmune etiology, characterized by localized areas of inflammation, demyelination, axonal loss and gliosis in the brain and spinal cord. Although the clinical presentation and course of the disease are highly variable, several disease types can be recognized, including relapsing-remitting-(RR), primary-progressive-(PP), secondary-progressive-(SP), progressive-relapsing-(PR) MS and clinically-isolated syndrome (CIS). There is no single clinical feature or diagnostic test that is sufficient to diagnose MS, and the diagnosis is mainly a clinical one. Over the years, several sets of criteria have been proposed for the diagnosis of MS, based on the principles of dissemination in space (DIS) and dissemination in time (DIT) of CNS lesions, and the exclusion of other diseases with similar characteristics. With each revision, new diagnostic criteria modified disease definitions and diagnostic thresholds, while aiming at maintaining sensitivity and improving specificity. According to the older Schumacher and Poser criteria, MS can be diagnosed clinically by demonstrating 2 separate attacks (fulfilling DIT criteria) involving at least 2 different areas of the CNS (fulfilling DIS criteria). The 2001 McDonald criteria and their 2005 revision incorporated defined magnetic resonance imaging (MRI) criteria for DIS and DIT that provided guidance on how to diagnose MS after CIS. The most recent 2010 McDonald criteria simplify requirements for DIS and DIT and may allow for an earlier diagnosis of MS from a single baseline brain MRI if there are both silent gadolinium-enhancing and nonenhancing lesions. Despite these important advances in the diagnosis of MS, some questions still remain regarding the application and the implications of the new criteria in the daily clinical practice and in clinical trials. Most importantly, thorough clinical evaluation and judgment along with careful differential diagnosis still remain the basics in the diagnosis of MS.