A 35-year-old woman presents with episodic neurological symptoms over 2 years: an episode of right optic neuritis that resolved over weeks, and now left arm tingling and weakness. Brain MRI shows periventricular T2/FLAIR hyperintense lesions perpendicular to the corpus callosum (Dawson's fingers). CSF shows oligoclonal bands in CSF not in serum. The McDonald 2017 criteria for diagnosis requires:

• A Two separate MRI scans 3 months apart showing new lesions
• B Positive VEP (visual evoked potential) in addition to MRI findings
• C At least three periventricular lesions on MRI alone
• D Dissemination in space (DIS) and dissemination in time (DIT) — both are satisfied here ✓

Explanation

The 2017 McDonald criteria for multiple sclerosis diagnosis require dissemination in space (DIS — lesions in ≥2 of 5 CNS regions: periventricular, cortical/juxtacortical, infratentorial, spinal cord, optic nerve) and dissemination in time (DIT — new T2 lesions, gadolinium-enhancing lesions, or CSF oligoclonal bands). In this patient, optic neuritis plus periventricular lesions with arm symptoms satisfies DIS, and the two clinical episodes plus CSF oligoclonal bands satisfies DIT.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.