A 28-year-old woman presents with a 3-month history of progressive visual blurring in the right eye and mild lower limb weakness. MRI brain shows multiple T2 hyperintense lesions. The structure marked **A** in the diagram demonstrates ovoid lesions perpendicular to the lateral ventricles with perivenular distribution. Which of the following clinical features would BEST support a diagnosis of multiple sclerosis in this patient based on the imaging pattern shown?

Explanation

## Why "Presence of oligoclonal bands in cerebrospinal fluid that are absent in serum, combined with dissemination in space and time on serial MRI" is right The imaging pattern marked **A** — ovoid periventricular T2 lesions perpendicular to the lateral ventricles (Dawson fingers) — is a hallmark of multiple sclerosis and represents perivenular demyelination along medullary veins at the callososeptal interface. According to McDonald 2017 Criteria (Harrison 21e Ch 444), diagnosis of MS requires DISSEMINATION IN SPACE (DIS — ≥1 T2 lesion in ≥2 typical regions including periventricular) AND DISSEMINATION IN TIME (DIT). CSF oligoclonal bands (≥2 bands present in CSF but absent in serum) are present in ~95% of MS patients and can substitute for DIT when combined with DIS. This combination directly fulfills diagnostic criteria for MS and is the most specific marker of CNS demyelination in this clinical context. ## Why each distractor is wrong - **"Longitudinally extensive transverse myelitis spanning ≥3 vertebral segments with central cord involvement"**: This finding is characteristic of neuromyelitis optica spectrum disorder (NMO-SD), NOT MS. MS spinal cord lesions are typically <2 vertebral segments, dorsolateral, and involve only partial cross-section. Longitudinally extensive transverse myelitis is a red flag for alternative diagnosis. - **"Acute presentation with optic neuritis and simultaneous bilateral internuclear ophthalmoplegia (INO)"**: While optic neuritis is a common presenting symptom of MS and bilateral INO in a young adult is highly suggestive of MS, this option describes acute clinical features rather than the diagnostic criteria anchored to the imaging pattern **A**. The question specifically asks what would "BEST support" diagnosis based on the imaging pattern shown — the answer must integrate the periventricular Dawson finger lesions with diagnostic confirmation. - **"Symmetric confluent white matter hyperintensities sparing the U-fibers with basal ganglia involvement"**: This describes the imaging pattern marked **B** in the diagram (confluent T2 hyperintensities sparing U-fibers), which is NOT the pattern shown at **A**. Additionally, basal ganglia involvement is atypical for MS and suggests alternative diagnoses such as ADEM or other demyelinating conditions. **High-Yield:** Dawson fingers (ovoid periventricular lesions perpendicular to ventricles) + oligoclonal bands in CSF + dissemination in space and time = MS diagnosis confirmed per McDonald 2017 Criteria. [cite: Harrison 21e Ch 444 — Multiple Sclerosis; McDonald 2017 Diagnostic Criteria]