Autoimmune CNS demyelinating disease with relapsing or progressive course.
Also known as: MS, multiple sclerosis, RRMS, SPMS, PPMS
Overview
Chronic autoimmune inflammatory demyelinating disease of the central nervous system, characterized by lesions disseminated in space (multiple CNS locations) and time (multiple episodes or accumulation over time). Phenotypes: relapsing-remitting (RRMS, ~85%), secondary progressive (SPMS, evolves from RRMS), primary progressive (PPMS, ~10-15%), and clinically isolated syndrome (CIS, first demyelinating event).
Epidemiology
Prevalence ~1 million in the US. Typical onset age 20-40. Female-to-male ratio ~3:1. Higher prevalence at higher latitudes (vitamin D, EBV link).
Try two board-style Multiple Sclerosis questions
Real questions from the FirstPassPA bank, with the full explanation. Pick an answer — no signup, no email.
Question 1NeurologyMedium
A 42-year-old female has had 2 attacks over 2 years: unilateral optic neuritis and transverse myelitis. MRI brain shows periventricular white matter lesions in a Dawson fingers pattern. CSF has oligoclonal bands. Anti-aquaporin-4 (anti-AQP4) antibody is negative. Which of the following is the most appropriate next step in management?
ALong-term oral prednisone
BEculizumab
COcrelizumab
DInfliximab
EIVIG infusions
Reveal answer & full explanation
Correct answer: C — Ocrelizumab
ALong-term oral prednisone
BEculizumab
COcrelizumab✓
DInfliximab
EIVIG infusions
Why Ocrelizumab is correct
This patient meets McDonald criteria (2017) for relapsing-remitting multiple sclerosis (RRMS): dissemination in space (periventricular, juxtacortical, infratentorial, or spinal cord lesions) plus dissemination in time (2 attacks over 2 years)
Dawson fingers are periventricular lesions perpendicular to the ventricles on sagittal MRI — present here
Negative anti-aquaporin-4 (anti-AQP4) makes neuromyelitis optica spectrum disorder (NMOSD) unlikely
TREAT-MS and DELIVER-MS trials support early high-efficacy therapy for young patients with active disease
Ocrelizumab (anti-CD20) is superior to interferon-beta-1a (IFN-beta-1a) (OPERA I/II trials) and is also FDA-approved for primary progressive multiple sclerosis (MS) (ORATORIO trial)
Why the others are wrong
Long-term oral prednisone — corticosteroids shorten an acute relapse but chronic oral steroids are not disease-modifying in MS: they do not lower relapse rate or slow disability accrual, and they add osteoporosis, hyperglycemia, and infection risk (right-concept-wrong-role)
IVIG infusions — intravenous immunoglobulin is used in antibody-mediated disorders such as Guillain-Barre syndrome and chronic inflammatory demyelinating polyneuropathy (CIDP); it is not an approved disease-modifying therapy for RRMS and has not shown consistent relapse or disability benefit (confused-with other autoimmune neurologic disease)
Eculizumab — used in NMOSD, not RRMS; this patient is anti-AQP4 negative, making NMOSD unlikely (confused-with NMOSD)
Infliximab — tempting as a potent biologic used across autoimmune disease, but TNF-alpha inhibitors can trigger or worsen central nervous system demyelination: TNF blockade increased relapses in an MS trial, and new or worsening demyelinating disease is a labeled warning, so they are avoided in MS rather than used to treat it (confused-with other autoimmune biologics)
Additional high-yield points
CRITICAL: First exclude NMOSD before starting MS drugs — interferons, natalizumab, and fingolimod can WORSEN NMOSD
Question 2NeurologyMedium
A 32-year-old woman presents with a 2-day history of right eye pain worsening with eye movement, followed by blurry central vision in the right eye. Visual acuity is 20/200 on the right. Fundoscopy is normal. MRI brain shows 3 periventricular T2 hyperintense lesions. Oligoclonal bands are present in cerebrospinal fluid (CSF). Which of the following is the most appropriate acute treatment?
AIntramuscular interferon beta-1a
BPlasma exchange therapy
CIntravenous methylprednisolone
DIntravenous immunoglobulin
EOral prednisone 1 mg/kg daily
Reveal answer & full explanation
Correct answer: C — Intravenous methylprednisolone
AIntramuscular interferon beta-1a
BPlasma exchange therapy
CIntravenous methylprednisolone✓
DIntravenous immunoglobulin
EOral prednisone 1 mg/kg daily
Why Intravenous methylprednisolone is correct
This presentation is optic neuritis — right eye pain worsening with eye movement, blurry central vision, and visual acuity 20/200 — the first demyelinating event likely representing multiple sclerosis (MS)
Periventricular lesions plus oligoclonal bands in cerebrospinal fluid (CSF) make MS highly likely: under the 2024 McDonald criteria, an optic nerve lesion documented by orbital MRI, OCT, or visual evoked potentials adds the second region for dissemination in space and the CSF bands substitute for dissemination in time (the 2017 criteria did not count the optic nerve, so this would have been a high-risk clinically isolated syndrome)
Acute treatment is IV methylprednisolone 1 g/day × 3–5 days, which speeds visual recovery (though it does not improve final visual acuity)
Why the others are wrong
Plasma exchange therapy — plasma exchange is reserved for a severe demyelinating attack that fails to improve after high-dose corticosteroids; it is not the initial treatment of a first episode of optic neuritis
Intramuscular interferon beta-1a — disease-modifying therapy (interferon beta, glatiramer, etc.) is started after acute treatment for relapsing-remitting MS, not as the acute intervention
Oral prednisone 1 mg/kg daily — this is the exact low-dose oral regimen that increased the rate of recurrent optic neuritis in the Optic Neuritis Treatment Trial, so it is not recommended as monotherapy
Intravenous immunoglobulin — IVIG is a first-line immunotherapy for Guillain-Barre syndrome and chronic inflammatory demyelinating polyneuropathy (CIDP), which makes it tempting for a central demyelinating attack, but trials in acute optic neuritis and MS relapse have not shown benefit; high-dose corticosteroid is first-line, and plasma exchange is the rescue for a severe attack that fails steroids
Additional high-yield points
Bioequivalent high-dose oral corticosteroid (roughly 1,250 mg of prednisone daily for 3 to 5 days) is an accepted alternative to IV methylprednisolone for an acute MS relapse; it is the 1 mg/kg oral dose that is harmful
That's 2. Get 7,700+ more.
Unlock the full FirstPassPA bank: 7,700+ board-style questions, flashcards, and an AI tutor that explains every answer. Your 7-day free trial includes everything, and there's no credit card required.
You've read your 2 free diagnosis previews. Create your free account to unlock the full Multiple Sclerosis outline — plus all 514 diagnoses, 7,700+ board-style questions, flashcards, and an AI tutor. Your 7-day free trial includes everything, and there's no credit card required.
Family history (HLA-DRB1*15:01 strongest genetic association)
Northern European ancestry
Pathophysiology
Autoreactive T cells (and B cells) cross a disrupted blood-brain barrier, attack myelin and oligodendrocytes, and produce demyelinating plaques in white matter (and increasingly recognized cortical lesions). Acute inflammation causes relapses; chronic neurodegeneration with axonal loss drives progressive disability. B cell roles (antibody, antigen presentation) explain efficacy of anti-CD20 therapies.
Clinical presentation
Symptoms
Optic neuritis: subacute monocular vision loss with pain on eye movement, dyschromatopsia (red desaturation), afferent pupillary defect
Internuclear ophthalmoplegia (INO): impaired adduction of the ipsilateral eye on horizontal gaze with nystagmus of the abducting eye — bilateral INO in a young patient is highly suggestive of MS
Sensory: paresthesias, numbness, Lhermitte sign (electric shock down spine with neck flexion)
Uhthoff phenomenon: symptom worsening with heat (exercise, hot shower, fever); heat causes conduction block in already-demyelinated axons, so it is a reversible pseudo-relapse with no new inflammation and needs no steroids
Migraine with white matter lesions — Headache history, lesions typically subcortical and asymptomatic; clinical correlation
Diagnostic workup
Diagnostic criteria
2024 McDonald criteria (Montalban et al., Lancet Neurol 2025), which replaced the 2017 revision: in a patient with a typical attack or progressive course and no better explanation, dissemination in space (DIS) = T2 lesions in ≥2 of 5 CNS regions (periventricular, cortical/juxtacortical, infratentorial, spinal cord, and now the optic nerve, shown by orbital MRI, OCT, or VEP). Lesions in ≥4 regions are sufficient on their own. With 2-3 regions, add one of: dissemination in time (simultaneous gadolinium-enhancing and non-enhancing lesions, a new lesion on follow-up MRI, or a second attack), positive CSF (≥2 CSF-specific oligoclonal bands or an elevated kappa free light chain index), or the MRI central vein sign in ≥6 lesions. Some radiologically isolated syndrome (RIS) and nonspecific-symptom cases now qualify with the same supportive evidence. The older 2017 criteria used 4 regions and required dissemination in time, with CSF oligoclonal bands as the only substitute.
Labs
CBC, BMP, LFTs, TSH, B12, RPR, HIV, vitamin D, ANA
Aquaporin-4 (AQP4) IgG — rules out NMOSD
MOG IgG — rules out MOGAD
Lyme serology if regional exposure
Imaging
MRI brain with and without gadolinium — periventricular, juxtacortical, infratentorial, and spinal cord lesions; ovoid lesions perpendicular to ventricles (Dawson fingers); enhancement indicates active inflammation (~6 weeks)
MRI cervical and thoracic spine — short-segment cord lesions (<2 vertebral segments — contrasts with NMOSD)
Acute relapse: IV methylprednisolone 1 g/day × 3-5 days (speeds recovery; does not change long-term disability); bioequivalent high-dose oral steroids are an alternative, but avoid low-dose oral prednisone alone for optic neuritis (Optic Neuritis Treatment Trial: more recurrences)
Plasma exchange (PLEX) for severe relapses unresponsive to steroids
Disease-modifying therapy (DMT) — start early for RRMS
Vitamin D supplementation (>1000 IU/day target serum 25-OH-D >30 ng/mL)
Vaccinations BEFORE starting immunosuppressive DMT (avoid live vaccines during therapy)
Smoking cessation
Physical therapy, occupational therapy, multidisciplinary MS care
Complications
Progressive disability accumulation (EDSS scale)
Cognitive impairment (~40-70% of patients)
Depression (high rates, increased suicide risk)
Bladder dysfunction with recurrent UTIs
Mobility loss, falls
PML (progressive multifocal leukoencephalopathy) — opportunistic JC virus infection in natalizumab- or other immunosuppressant-treated patients; risk rises with JCV antibody positivity, more than 2 years of natalizumab, and prior immunosuppressant use; unlike a relapse, deficits (often cognitive or behavioral) progress steadily over weeks and MRI shows a large confluent subcortical lesion without mass effect that usually does not enhance; confirm with CSF JCV PCR, stop natalizumab, and use plasma exchange to clear the drug
Increased infection risk with anti-CD20 and other immunosuppressive DMTs
Pseudo-relapse: symptom worsening from infection, heat, or stress without new inflammation
PANCE pearls
MS lesions are 'separated in time and space' — the diagnostic hallmark.
Bilateral INO in a young patient is MS until proven otherwise.
Long-segment (≥3 vertebrae) transverse myelitis suggests NMOSD, NOT MS — check AQP4-IgG.
Oligoclonal bands in CSF (unique from serum) support MS diagnosis and predict conversion from CIS.
Start DMT early — disability accrual is fastest in the first decade; high-efficacy first-line therapy is favored in many recent algorithms.
EBV is now considered a causal factor in MS (Bjornevik et al., Science 2022).
Pregnancy: relapse rate falls, most in the third trimester, then rebounds in the first ~3 months postpartum, with no long-term effect on disability. Plan DMT before conception: interferon beta and glatiramer have the most reassuring pregnancy data, while teriflunomide is teratogenic and needs accelerated elimination (cholestyramine) before conception.
References
AAN 2018 — Practice Guideline Recommendations Summary: Disease-Modifying Therapies for Adults With MS (Rae-Grant et al., Neurology 2018)
McDonald 2017 — Diagnosis of MS: 2017 Revisions of the McDonald Criteria (Thompson et al., Lancet Neurol 2018)
ECTRIMS 2018 — ECTRIMS/EAN Guideline on Pharmacological Treatment of People with MS (Montalban et al., Mult Scler 2018)
EBV-MS — Longitudinal Analysis Reveals High Prevalence of EBV Associated with MS (Bjornevik et al., Science 2022)
McDonald 2024 — Diagnosis of Multiple Sclerosis: 2024 Revisions of the McDonald Criteria (Montalban et al., Lancet Neurol 2025;24:850-865)
Practice Neurology questions on FirstPassPA
Turn this outline into retention. 7,700+ board-style questions with an AI tutor that explains every answer — free to start, no card required.
Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.