While diagnostic criteria have been refined since the first formal criteria were developed in 1965, the diagnosis of MS has always relied on the definition of the disease as the development of new attacks of neurologic symptoms which are separated in time and location, or dissemination in time (DIT) and space (DIS). While there is no single specific test for MS, the diagnosis can be made by a combination or clinical history and examination findings, blood and CSF tests, rarely neurophysiological testing or histopathology, and especially MRI features, which are the most specific biomarker currently available for the diagnosis of MS. The diagnosis can now be made following the first clinical disease attack, or clinically-isolated syndrome (CIS), as long as other diseases which may resemble MS are excluded with multiple tests, brain and spinal cord MRI findings show CNS lesions which explain the clinical symptoms, and MRI findings also show further disease activity which satisfy the criteria for DIT and DIS.
As the unique ways in which children are affected by MS have been increasingly recognized, it has become clear that the most recent revisions to adult diagnostic criteria are significantly less sensitive and specific to the diagnosis of MS in the pediatric age group. This led to the publication of first consensus criteria for MS in children by the IPMSSG in 2007, which were most recently revised in 2013. These importantly also defined the most common other idiopathic demyelinating disease of childhood, including acute demyelinating encephalomyelitis (ADEM), neuromyelitis optica (NMO), acute transverse myelitis (ATM), and idiopathic optic neuritis (ON). While the most recent criteria for adult MS, the 2010 revised McDonald criteria, may be applied to most cases of pediatric MS, children with attacks including altered mental status, or otherwise meeting the definition of ADEM, would be considered as meeting criteria for diagnosis if they have subsequent disease-typical attacks with clinical and MRI features consistent with the 2010 McDonald criteria, and occur >3 months later.