Table 1.

McDonald criteria for multiple sclerosis (MS).^[20]

Clinical presentation	Additional data needed for MS diagnosis
2 or more assaults; 2 or more lesions determined by objective medical evidence; or 1 lesion determined by objective medical evidence along with believable historical proof of a preceding attack.	None
2 or more attacks; objective clinical evidence of 1 lesion.	Dissemination in space, demonstrated by:  • ≥1 T2 lesion on MRI in at least 2 out of 4 MS-typical regions of the CNS (periventricular, juxtacortical, infratentorial, or spinal cord). OR  • Await a further clinical attack implicating a different CNS site.
1 attack; objective clinical evidence of 2 or more lesions.	Simultaneous occurrence of asymptomatic gadolinium-enhancing and non-enhancing lesions at any time serves as evidence of temporal dissemination.  OR • A new T2 and/or gadolinium-enhancing lesion or lesions on a subsequent MRI, regardless of when it first appeared in relation to a baseline scan.  • Hold off until a subsequent clinical attack.
1 attack; objective clinical evidence of 1 lesion (clinically isolated syndrome).	The spread in space and time is shown by:  • At least one T2 lesion in at least 2 of the 4 CNS areas that are characteristic for MS (periventricular, juxtacortical, infratentorial, or spinal cord)  OR • Watch for a subsequent clinical episode that involves a different CNS location. AND For timely distribution:  • The simultaneous existence of asymptomatic lesions that both enhance and do not enhance with gadolinium.  OR • A new T2 and/or gadolinium-enhancing lesion or lesions on a subsequent MRI, regardless of when it first appeared in relation to a baseline scan.  OR •delay till a subsequent clinical attack
Insidious neurologic progression suggestive of MS (PPMS).	One yr of illness onset (retrospectively or prospectively determined). PLUS 2 of the 3 aforementioned prerequisites There is evidence that the illness has spread across the brain based on one or more T2 + lesions in the MS-specific periventricular, juxtacortical, or infratentorial areas. There is proof of spatial spread in the spinal cord from 2 T2 + lesions in the cord. Positive CSF (indicators of oligoclonal bands include higher IgG index and/or isoelectric focusing).

CNS = central nervous system, CSF = cerebrospinal fluid, IgG = immunoglobulin g, MRI = magnetic resonance imaging, PPMS = primary progressive multiple sclerosis.