Table 3. Proposed McDonald criteria18 for the diagnosis of multiple sclerosis (MS)

* If the criteria are fulfilled and met, the diagnosis is MS. If the criteria are not completely met, the diagnosis is possible MS. If the criteria are fully explored and not met, the diagnosis is not MS.
† Symptoms lasting at least 24 hours would constitute an attack provided that the episode was not a pseudoattack such as due to fever or infection.
‡ Objective evidence of two lesions necessarily separated in space found on neurologic examination. A typical subclinical lesion detected by visual evoked potential testing (delayed response, well preserved waveform) can substitute for one clinical lesion.
§ MRI (a): Criteria for dissemination in space: three of the four following criteria need to be met:
1. ≥1 gadolinium (Gd)-enhancing lesion or ≥9 T2 lesions
2. ≥1 infratentorial MRI lesion
3. ≥1 juxtacortical lesion
4. ≥3 periventricular lesions
1 spinal cord lesion can substitute for 1 brain lesion
¶ CSF analysis demonstrates the presence of oligoclonal bands different from any such bands in the serum or an increased immunoglobulin G index.
∥ MRI (b): Criteria for dissemination in time:
1. If original MRI was performed <3 months after the clinical attack, a follow-up MRI (>3 months after event) is necessary. A new Gd-enhancing lesion on this follow-up MRI provides evidence of dissemination in time. Otherwise, another follow-up MRI (>3 months after first MRI) is necessary. A new Gd-enhancing or a new T2 lesion on this second follow-up MRI provides evidence of dissemination in time.
2. If the original MRI was performed ≥3 months after the clinical attack, a Gd-enhancing lesion (at a site not implicated by the clinical event) provides evidence of dissemination in time. Otherwise, a follow-up MRI is necessary (suggested to be 3 months after original MRI). A new Gd-enhancing or a new T2 lesion on this MRI provides evidence of dissemination in time.
Clinically definite MS*
    1: 2 Attacks + 2 lesions on examination
    2: 2 Attacks + 1 lesion on examination + [MRI (a)§ or 2 MRI lesions + abnormal CSF]
    3: 1 Attack + 2 lesions on examination + MRI (b)
    4: 1 Attack + 1 lesion on examination + [MRI (a)§ or 2 MRI lesions + abnormal CSF] + MRI (b)
    5: Progressive disease + abnormal CSF + MRI (b) +
        a) [≥9 T2 MRI lesions or ≥2 spinal cord lesions or 4–8 brain MRI lesions + 1 spinal cord lesion]
        OR
        b) Abnormal VEP + [≥4 brain MRI lesions or <4 MRI lesions + 1 spinal cord lesion]