In April, 2001, an international panel in association with the NMSS of America recommended revised diagnostic criteria for multiple sclerosis. These new criteria have become known as the McDonald criteria after their lead author. They make use of advances in MRI imaging techniques and are intended to replace the Poser Criteria and the older Schumacher Criteria. The new revised criteria are as follows:
 

Clinical Presentation	Additional Data Needed
2 or more attacks (relapses) 2 or more objective clinical lesions	None; clinical evidence will suffice (additional evidence desirable but must be consistent with MS)
2 or more attacks 1 objective clinical lesion	Dissemination in space, demonstrated by:  MRI or a positive CSF and 2 or more MRI lesions consistent with MS or further clinical attack involving different site
1 attack 2 or more objective clinical lesions	Dissemination in time, demonstrated by: MRI or second clinical attack
1 attack 1 objective clinical lesion (monosymptomatic presentation)	Dissemination in space by demonstrated by: MRI or positive CSF and 2 or more MRI lesions consistent with MS and Dissemination in time demonstrated by: MRI or second clinical attack
Insidious neurological progression suggestive of MS (primary progressive MS)	Positive CSF and Dissemination in space demonstrated by: MRI evidence of 9 or more T2 brain lesions or 2 or more spinal cord lesions or 4-8 brain and 1 spinal cord lesion or positive VEP with 4-8 MRI lesions or positive VEP with <4 brain lesions plus 1 spinal cord lesion and Dissemination in time demonstrated by: MRI or continued progression for 1 year

What Is An Attack?

• Neurological disturbance of kind seen in MS
• Subjective report or objective observation
• 24 hours duration, minimum
• Excludes pseudoattacks, single paroxysmal episodes

• 30 days between onset of event 1 and onset of event 2

• Magnetic resonance imaging (MRI) Three out of four:
• 1 Gd-enhancing or 9 T2 hyperintense lesions if no Gd-enhancing lesion
• 1 or more infratentorial lesions
• 1 or more juxtacortical lesions
• 3 or more periventricular lesions
(1 spinal cord lesion = 1 brain lesion)
 
• Cerebrospinal fluid (CSF)
• Oligoclonal IgG bands in CSF (and not serum)
• or elevated IgG index
• Evoked potentials (EP)
• Delayed but well-preserved wave form

• A Gd-enhancing lesion demonstrated in a scan done at least 3 months following onset of clinical attack at a site different from attack,

or
• In absence of Gd-enhancing lesions at 3 month scan, follow-up scan after an additional 3 months showing Gd-lesion or new T2 lesion.

Diagnostic Criteria links:
International Panel Revises Diagnostic Criteria For MS
Recommended diagnostic criteria for multiple sclerosis

MS Glossary
All About Multiple Sclerosis