A 35-year-old woman has recurrent episodes of unilateral arm weakness lasting 20 minutes, with MRI showing a periventricular white matter lesion. CSF shows 3 oligoclonal bands not present in serum. Her visual evoked potential is delayed on the right. To confirm a diagnosis of multiple sclerosis (MS), the McDonald 2017 criteria require demonstration of:
- A Dissemination in space (DIS) and dissemination in time (DIT) based on clinical/MRI criteria ✓
- B Three or more gadolinium-enhancing lesions
- C At least 9 T2 lesions with one infratentorial lesion
- D Positive oligoclonal bands alone, regardless of clinical findings
Correct answer: A. Dissemination in space (DIS) and dissemination in time (DIT) based on clinical/MRI criteria
Explanation
The McDonald 2017 criteria require demonstration of dissemination in space (DIS: lesions in ≥2 of 4 typical CNS locations — periventricular, cortical/juxtacortical, infratentorial, spinal cord) AND dissemination in time (DIT: simultaneous enhancing and non-enhancing lesions on a single MRI, or new T2/Gd+ lesion on follow-up, or second clinical attack). Oligoclonal bands can substitute for DIT in patients with ≥1 clinical attack and DIS. Nine T2 lesions is not a standalone criterion. This patient's VEP and CSF OCBs contribute evidence.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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