Diagnostic Criteria for Multiple Sclerosis

Clinical Presentation and Diagnostic Features

The appearance of 2 new lesions over 2.5 years fulfills MS criteria for dissemination in time, as new T2 lesions appearing on follow-up MRI at least 3 months apart from initial imaging satisfy diagnostic requirements 1, 3
Four brain lesions demonstrate dissemination in space, meeting the threshold for multiple CNS lesions separated anatomically 2, 4
The patient's age (36 years) and sex (female) fit the classic MS demographic, as MS predominantly affects women in their 20s-40s 5
Lesion location, such as periventricular lesions perpendicular to the corpus callosum ("Dawson's fingers"), juxtacortical U-fibers, and infratentorial areas, supports MS diagnosis 5
Lesion characteristics, such as ovoid, ≥3 mm, well-demarcated, and may show gadolinium enhancement if active, are typical of MS 5
Spinal cord involvement, such as short-segment focal lesions (<2 vertebral segments) in lateral/dorsal columns, strongly supports MS 5

Obtain brain AND cervical/thoracic spine MRI with gadolinium to assess for additional lesions, enhancement patterns, and spinal cord involvement 5
Evaluate for dissemination in space by looking for lesions in ≥2 of 4 characteristic regions (periventricular, juxtacortical, infratentorial, spinal cord) 5
CSF analysis for oligoclonal bands and elevated IgG index can establish MS diagnosis if MRI criteria are not fully met 1, 4, 6

Multiple enhancing lesions in a young patient without known cancer makes metastases less likely, but approximately 20-40% of brain metastases present as multiple lesions 7, 8
Brain metastases typically show rim enhancement with extensive surrounding vasogenic edema on T2/FLAIR sequences 7
Requires systemic workup, including CT chest/abdomen or PET scan, to identify primary malignancy if imaging characteristics suggest metastases 8, 9