Pearls & Oy-sters: Using Susceptibility-Based Imaging in Highly Active Late-Onset Multiple Sclerosis.

Central vein sign (CVS) and paramagnetic rim lesions (PRLs) are susceptibility-based imaging biomarkers recently integrated into the 2024 McDonald criteria for the diagnosis of multiple sclerosis (MS). These MRI signatures have moderate and high specificity, respectively, for the diagnosis of MS and can therefore be useful when evaluating atypical cases. We describe a 61-year-old woman with subacute onset ataxia and dysarthria and numerous simultaneously enhancing lesions involving the brain and spinal cord. CSF analysis showed lymphocytic pleocytosis (41 total nucleated cells [normal 0-5/μL], 98% lymphocytes) and an elevated protein of 89 (normal, 0-35 mg/dL) without hypoglycorrhachia. CSF kappa free light chains and IgG index were not elevated, and CSF-specific oligoclonal bands were absent. After a comprehensive investigation for alternative diagnoses, a brain biopsy revealed a demarcated macrophage-rich lesion with myelin loss and relative axonal preservation, CD3-predominant lymphocytic infiltrate, and rare CD20 positive B cells, consistent with active demyelination. A 7-tesla MRI subsequently demonstrated ≥12 CVS and ≥1 PRL, clarifying her diagnosis of relapsing late-onset MS. The implementation of susceptibility-based imaging biomarkers in the 2024 McDonald criteria may help circumvent the need for a brain biopsy in cases of atypical demyelinating disease, potentially facilitating earlier diagnosis and treatment.