Criteria for Demonstrating Dissemination of CNS Lesions in Time on MRI Scan

The demonstration of dissemination in CNS lesions on MRI scans over time is one criteria for the diagnosis of multiple sclerosis.

Dissemination in time is said to be present if one of the following is identified on MRI.

Timing of MRI	MRI Finding
first scan < 3 months after onset, and second scan done >= 3 months after onset	new gadolinium-enhancing lesion
first scan < 3 months after onset, and second scan done >= 3 months after onset, and third scan done >=3 months after first scan (and after second)	new T2 or gadolinium-enhancing lesion
first scan done >=3 months after onset	gadolinium-enhancing lesion in a site not implicated in the original event
first scan done >=3 months after onset, and second scan done later (usually 3 months)	new T2 or gadolinium-enhancing lesion

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