How MS is tested on Step 1

Lesions disseminated in space and time.

Optic neuritisPainful monocular vision loss, color desaturation,RAPDINOMLF lesion; adducting eye fails, abducting eye showsnystagmusLhermitte signElectric shock down the spine on neck flexion;cervical cordSpinal cordWeakness, spasticity, hyperreflexia, bladder urgencyCerebellumAtaxia, intention tremor, scanning speech
MS symptoms. Bilateral INO in a young adult strongly suggests MS.

Diagnosis

Imaging and CSF support the clinical picture.

TestFindingMeaning
MRI (T2/FLAIR)Ovoid white matter plaques perpendicular to the ventricles ("Dawson fingers")Lesions in typical locations; enhancing lesions are active
CSFOligoclonal IgG bands, raised IgG index; mild lymphocytesIntrathecal antibody production
Evoked potentialsSlowed conductionSilent demyelination
PathologyPlaques with myelin loss, preserved axons early, gliosisOligodendrocytes are lost

Diagnosis requires lesions disseminated in space and in time (McDonald criteria); CSF bands can stand in for time.

Disease courses and look-alikes

Most patients start with relapses and remissions.

  • Relapsing-remitting: most common course; attacks followed by partial or full recovery.
  • Secondary progressive: steady worsening after an initial relapsing course.
  • Primary progressive: gradual decline from onset; ocrelizumab is approved.
Multiple sclerosisT-cell and B-cell demyelinationShort spinal cord lesionsBrain plaques commonOligoclonal bands usually presentInterferon-β and other DMTsNeuromyelitis opticaAntibodies to aquaporin-4 (astrocytes)Long cord lesions (≥ 3 segments)Severe optic neuritis, often bilateralOligoclonal bands often absentSome MS drugs worsen itvs
MS vs NMO. Peripheral demyelination (Guillain-Barré syndrome) causes areflexia instead of hyperreflexia.

Treatment

Treat relapses, prevent new ones, and manage symptoms.

DrugMechanismKey risk
IV methylprednisoloneCorticosteroidShortens relapses; no long-term benefit
Interferon-βImmunomodulationFlu-like symptoms, depression, liver enzymes
Glatiramer acetateMyelin basic protein decoyInjection-site reactions
NatalizumabAnti-α4 integrin; blocks leukocyte entry to CNSPML (JC virus)
OcrelizumabAnti-CD20 (B cells)Infusion reactions, infections
FingolimodS1P receptor modulator; traps lymphocytes in nodesBradycardia, macular edema
BaclofenGABA-B agonistTreats spasticity

Plasma exchange is used for severe relapses that do not respond to steroids.

Worked example

Spot separate episodes.

functions Worked example — eye pain in a young woman

A 28-year-old woman has 3 days of pain on moving the right eye and blurred vision. A year earlier, an episode of leg numbness resolved over weeks. MRI shows several periventricular white matter lesions. What is the diagnosis and what would CSF show?

  1. Painful monocular vision loss is optic neuritis.
  2. An earlier, separate episode in a different location shows dissemination in time and space.
  3. Periventricular plaques are typical of MS.
  4. CSF commonly shows oligoclonal IgG bands from antibody production within the CNS.

Answer. Relapsing-remitting multiple sclerosis; CSF oligoclonal bands. Treat the relapse with IV corticosteroids.