- Seen in young adults (20–40 years, 3:1 female predilection) presenting with relapsing-remitting neurological episodes: optic neuritis (painful monocular vision loss), internuclear ophthalmoplegia (INO), transverse myelitis (Lhermitte sign), or sensory ataxia.
- Caused by chronic autoimmune inflammatory demyelinating disease of the central nervous system characterized by perivenular lymphocytic infiltration, breakdown of the blood-brain barrier, myelin destruction, and axonal transection separated in space and time (DIS and DIT).
Imaging Findings
- Brain & Spine MRI (Diagnostic Hallmark - 2017 McDonald Criteria):
- –Periventricular Ovoid Plaques ('Dawson Fingers'): Flame-shaped or fan-shaped T2/FLAIR hyperintense lesions oriented perpendicularly along the long axis of the medullary venules radiating outward from the lateral ventricular margins.
- –Corpus Callosum & Callososeptal Interface: Plaques lining the inferior callososeptal margin (classic early and highly specific MS sign).
- –Juxtacortical / Cortical Lesions: Plaques involving or directly abutting the cerebral cortex (involves subcortical U-fibers).
- –Infratentorial Plaques: Lesions in the pons, middle cerebellar peduncles, and medulla.
- –Spinal Cord Lesions: Multiple, short-segment (<2 vertebral segments in length), peripherally located lesions occupying <50% of cross-sectional cord area on axial T2WI, predominantly in the cervical cord.
- –DWI / ADC: Acute active demyelinating plaques can show transient peripheral diffusion restriction along the leading inflammatory edge, whereas chronic plaques show facilitated diffusion (elevated ADC).
- –**SWI / T2* GRE ('Central Vein Sign' & Paramagnetic Rim): High-resolution SWI demonstrates a tiny hypointense central venule ('central vein sign') running through the center of periventricular white matter plaques (distinguishing MS from small-vessel ischemic disease) and a hypointense iron-laden microglia paramagnetic rim** in chronic active 'smoldering' lesions.
- Active vs Inactive Plaques:
- –Active Demyelination: Solid, nodular, or classic open-ring (horseshoe) enhancement on post-contrast T1WI, with the non-enhancing gap facing the cerebral cortex/gray matter; restricted diffusion along the active advancing edge.
- –Chronic Inactive Plaques: T1 hypointense 'black holes' (permanent axonal destruction and matrix loss).
- –Dissemination in Space (DIS): ≥1 T2 lesion in at least 2 of 4 MS-typical CNS regions (periventricular, cortical/juxtacortical, infratentorial, spinal cord).
- –Dissemination in Time (DIT): Simultaneous presence of asymptomatic contrast-enhancing and non-enhancing lesions on any single MRI, OR a new T2/enhancing lesion on follow-up scan.
Differential Diagnosis
| Differential Diagnosis | Key Distinguishing Features |
|---|---|
Neuromyelitis Optica Spectrum Disorder (NMOSD) | Longitudinally Extensive Transverse Myelitis (LETM, ≥3 contiguous vertebral bodies) with central cord involvement (>50% cross-section); bilateral extensive optic neuritis involving chiasm; AQP4-IgG seropositive; periependymal lesions around 3rd/4th ventricles. |
Acute Disseminated Encephalomyelitis (ADEM) | Monophasic post-viral/post-vaccination acute encephalopathy in pediatric patients; large, fluffy, asymmetric, bilateral subcortical and deep gray matter lesions; synchronous enhancement (all lesions enhance or none enhance). |
Small Vessel Ischemic Disease (Microvascular / CADASIL) | Punctate subcortical white matter hyperintensities in elderly hypertensive patients; spares the corpus callosum and callososeptal interface; CADASIL specifically involves anterior temporal poles and external capsules. |
Neuro-Behçet / CNS Vasculitis | Brainstem/thalamic hyperintensities with associated systemic aphthous oral/genital ulcers, uveitis, and elevated inflammatory markers; vascular caliber irregularities on CTA/MRA. |
Important Points to Remember
- Diagnostic Pitfall: Mistaking a Tumefactive Demyelinating Lesion (TDL, >2 cm mass-like lesion with surrounding edema) for a high-grade glioma (GBM)! Crucial differentiating clue: TDL displays an open-ring (horseshoe) enhancement pattern with the non-enhancing opening pointing towards the cortex, whereas glioblastoma shows a closed, thick, nodular ring. Furthermore, TDL has relatively low perfusion (rCBV) and restricted diffusion restricted strictly to the leading peripheral rim.
- Crucial Review Areas:
- 1.Callososeptal interface on sagittal FLAIR (virtually pathognomonic for MS vs nonspecific microvascular ischemic lesions).
- 2.Optic nerves on coronal fat-suppressed T2 and contrast T1 for optic neuritis (hyperintensity and enhancement).
- 3.Cervical spinal cord on sagittal STIR and axial T2 (asymptomatic cord plaques contribute to Dissemination in Space).
- 4.Middle cerebellar peduncles and dorsal pons for infratentorial involvement.
- Case-Specific Radiologist Management:
- 1.Immediate Verbal Alert: Direct telephone notification to referring neurologist if an acute tumefactive lesion causing severe mass effect, or an acute cervical cord lesion threatening diaphragmatic/respiratory function, is identified.
- 2.Whole-Neuraxis Baseline Staging: If MS is suspected on brain MRI, complete staging with contrast-enhanced high-resolution Cervical and Thoracic Spine MRI to fulfill 2017 McDonald Criteria for Dissemination in Space and Time.
- 3.Avoid Unnecessary Biopsy for Tumefactive Plaques: If open-ring enhancement is demonstrated, advise neurosurgery against invasive biopsy or resection; trial high-dose IV methylprednisolone with follow-up MRI in 4–6 weeks.
- 4.Lumbar Puncture Correlation: Recommend CSF analysis for oligoclonal bands (OCBs) and elevated IgG index (positive in >90% of clinically definite MS; fulfills DIT under 2017 criteria even on a single scan).
- 5.Specialist Neuro-Immunology / MS MDT: Urgent referral to the dedicated Multiple Sclerosis Multidisciplinary Team for early initiation of Disease-Modifying Therapy (DMT: monoclonal antibodies like Ocrelizumab, Natalizumab, or Fingolimod) to prevent cumulative disability.