Multiple sclerosis: an animated, cited guide

This page needs JavaScript for its animations. The outline and key answers are below, and every claim in the full version carries a numbered citation.

Not medical advice. MS Companion is an educational synthesis of published literature. It does not replace a clinician.

What is in it

What MS is Who gets it, the numbers, and where in the nervous system it strikes.
Myelin and demyelination How signals jump along a myelinated nerve fibre, and what a lesion does to them.
The immune attack T cells, B cells and the blood-brain barrier, step by step.
Genes and risk factors HLA-DRB1*15:01, Epstein-Barr virus, vitamin D, smoking and teenage obesity.
Relapse and remission over time Relapsing, secondary progressive and primary progressive MS on one timeline.
A relapse, week by week Onset, steroids and recovery, and how a pseudo-relapse differs.
Measuring disability: EDSS The 0 to 10 scale and what confirmed worsening means.
McDonald criteria calculator Dissemination in space and time, CSF, and the 2017 and 2024 rules.
The differential NMOSD, MOGAD and other conditions that look like MS.
How the drugs work Where each disease-modifying therapy acts.
The DMT ladder Escalation, early high-efficacy treatment and stopping in later life.
Safety and monitoring PML and the JCV index, infections, vaccines and rebound.
Toward a cure Remyelination, BTK inhibitors, stem-cell transplantation and EBV.
Symptoms and rehabilitation Fatigue, spasticity, bladder, walking, mood and cognition.
Living with MS Pregnancy, work, heat, exercise and planning.
Nursing care Assessment, giving the medicines, monitoring and teaching.
History and people From Carswell and Charcot to the 2024 criteria.
Flashcards, quiz and glossary Revision for students.
Sources Every reference behind the app.

Part 3 · Diagnosis

The differential

NMOSD, MOGAD, small-vessel disease, migraine and other conditions can look like MS. Watch MRI patterns morph from MS to NMOSD to MOGAD, then click red flags to see which mimics they point to.

MS is a diagnosis of exclusion: the criteria only apply when there is no better explanation ²¹⁸. Across studies, 5%–41% of MS diagnoses were wrong; the pooled figure was 15% ⁵¹². A 2008 consensus scored 79 red flags (36 major, 32 intermediate, 11 minor), and a 2023 consensus updated them ^315,442.

Three MRI patterns

Pattern

Schematic composite, not real scans. Lesion lengths follow the published definitions (MS cord lesions under two segments; LETM at least three contiguous segments); positions and shapes are illustrative.

Why the label matters Several MS drugs may make NMOSD worse. The international NMOSD panel noted observational data that interferon-β, natalizumab and fingolimod may worsen NMO ⁴⁹⁸. Early evidence In 5 AQP4-positive people first treated as MS with natalizumab, 9 relapses occurred on treatment, 4 people accumulated disability and 1 died ²⁴⁸. Relapses with rising AQP4 antibody titres on interferon beta-1a, and a catastrophic relapse after one natalizumab dose, have been reported; interferon-β, glatiramer acetate, fingolimod, natalizumab, alemtuzumab and dimethyl fumarate have all been linked to unexpected NMOSD exacerbations ^245,247,374.

Red flags

Click a red flag. The conditions it points to are flagged in the table below, and the box explains why.

Conditions × features

"—" means the sources used here give no distinguishing feature for that column, not that there is none. Rows marked with an underline jump the animation to that pattern. Routine syphilis or HIV testing: no source read for this guide gives consensus wording, so none is stated.

How misdiagnosis happens

Established

What people misdiagnosed with MS really had

110 patients at 4 US centres (Solomon 2016) ⁴⁴¹:

70% had received a disease-modifying therapy, 31% had unnecessary morbidity, and 33% had carried the wrong diagnosis for 10 years or more ⁴⁴¹.

Established

Referrals to two Los Angeles centres

17% and 19% of referrals already carrying an MS diagnosis were misdiagnosed (Kaisey 2019). Commonest true diagnoses: migraine 16%, RIS 9%, spondylopathy 7%, neuropathy 7%. About 110 patient-years of unnecessary DMT had been given ²²⁸.

Early evidence In 2024, 21% (73 of 347) of referrals for suspected MS in London had other disorders, most often migraine or functional neurological disorder with non-specific or vascular white-matter lesions ⁵⁴.

The three commonest errors

Treating symptoms atypical for demyelination as attacks.
Accepting attacks without objective evidence of a CNS lesion.
Over-relying on MRI spots in people with non-specific symptoms ⁴⁴¹.

Exam hookCord lesion over ≥3 vertebral segments (LETM), area postrema syndrome (intractable hiccups or vomiting), severe or bilateral optic neuritis, CSF cells >50/μL or no OCB: think NMOSD or MOGAD; their criteria rest on AQP4-IgG and MOG-IgG by cell-based assay. Interferon-β, natalizumab and fingolimod may worsen NMOSD. ^19,498

In plain wordsSeveral other conditions can leave spots on a scan that look like MS: migraine, ageing blood vessels, low vitamin B12, other immune diseases and infections. Some, like NMOSD, need different medicines, and some MS medicines can make them worse. That is why doctors look hard for clues that point elsewhere before they say "MS".