Quick Answer
Demyelinating disorders are a 2 to 3 question topic per NEET PG paper across neurology and medicine. Lock these:
- MS epidemiology — young adult 20-40 years, women 3:1; temperate latitudes higher; India rising and under-diagnosed.
- Environmental risks — vitamin D deficiency, EBV, smoking, obesity; HLA-DRB1*15:01.
- MS clinical clues — optic neuritis, transverse myelitis, brainstem syndrome, Lhermitte sign, Uhthoff phenomenon.
- MS subtypes — RRMS ~85 percent (relapse-remit), SPMS (transitions), PPMS ~10-15 percent (gradual from onset), PRMS rare.
- McDonald 2017 criteria — DIS (2 of 4 CNS locations) + DIT (enhancing + non-enhancing OR new lesion OR CSF OCBs).
- NMO clue — LETM (spinal cord over 3 segments) + bilateral optic neuritis + area postrema syndrome + AQP4 antibody positive.
- MOG-AD — children, bilateral optic neuritis with disc swelling, ADEM-like; MOG antibody positive.
- Acute attack — high-dose IV methylprednisolone 1 g daily 3-5 days; plasma exchange if refractory.
- First-line DMT — interferon beta, glatiramer acetate, teriflunomide, dimethyl fumarate.
- Higher-efficacy DMT — natalizumab (check JCV), fingolimod, ocrelizumab (first PPMS drug), ofatumumab, cladribine, alemtuzumab.
- NMO treatment — rituximab, azathioprine, eculizumab (anti-C5), inebilizumab (anti-CD19), satralizumab (anti-IL-6R); AVOID interferon, natalizumab, fingolimod.
- India — interferon generics widely available; rituximab practical high-efficacy option; MSSI advocacy.
Multiple sclerosis and its differential diagnoses (NMO, MOG-AD, ADEM) require careful discrimination because treatment differs fundamentally — a mis-diagnosed NMO patient started on an MS drug can be actively harmed. NEET PG tests the McDonald 2017 criteria, the NMO vs MS distinction, the DMT ladder, and the Indian access landscape.
This deep dive walks through epidemiology → pathophysiology → clinical patterns → McDonald criteria → NMO and MOG-AD distinctions → DMT choice → symptomatic management → India context.
Epidemiology
- Young adult onset 20-40 years; women 3:1 (rising ratio over past decades)
- Temperate latitudes higher (north Europe, north America); lower in equatorial zones
- India — rising incidence and prevalence; under-diagnosed
- Environmental risk factors — low vitamin D, EBV infection (near-universal in MS, absent in non-MS controls; recent Karolinska cohort strongly supportive of causal role), smoking, childhood obesity
- Genetic — HLA-DRB1*15:01 the strongest single genetic risk; polygenic
Pathophysiology
- Autoimmune T-cell (Th1/Th17) driven inflammatory demyelination of the CNS with variable axonal loss and progressive neurodegeneration
- Plaques in the white matter — periventricular, juxtacortical/cortical, infratentorial (brainstem, cerebellum), spinal cord
- Blood-brain barrier disruption during active attack allows peripheral immune cells and antibodies into the CNS
- Later disease — chronic microglial activation, axonal degeneration, cortical grey matter demyelination, brain atrophy (progressive phenotype)
Clinical presentation
Relapses (attacks) — new neurological symptoms lasting over 24 hours, separated in time from previous attacks, in the absence of fever or infection. Common attack syndromes:
| Syndrome | Features |
|---|
| Optic neuritis | Unilateral painful vision loss over hours to days, colour desaturation especially for red, RAPD, central scotoma; retrobulbar (normal fundus) commonest in MS |
| Transverse myelitis | Sensory level, motor deficit, sphincter disturbance; short-segment in MS |
| Brainstem or cerebellar syndrome | Diplopia (INO — internuclear ophthalmoplegia classic), vertigo, ataxia, dysarthria |
| Sensory attacks | Numbness, paraesthesiae |
| Lhermitte sign | Electric shock down the spine on neck flexion (cervical cord plaque) |
| Uhthoff phenomenon | Transient worsening of symptoms with heat or exercise (temperature-sensitive conduction block) |
| Cognitive changes | Processing speed slowing, executive dysfunction; often earlier than appreciated |
| Fatigue | Very common; not proportional to exertion |
| Bladder / bowel / sexual dysfunction | Common in myelopathy |
| Trigeminal neuralgia | Bilateral or in young patient — think MS |
MS clinical subtypes
| Subtype | Course |
|---|
| Clinically isolated syndrome (CIS) | First demyelinating attack, not yet meeting DIT |
| Relapsing-remitting MS (RRMS) | ~85 percent at onset — discrete attacks with variable recovery |
| Secondary progressive MS (SPMS) | RRMS transitions to gradual progression without discrete attacks |
| Primary progressive MS (PPMS) | ~10-15 percent — gradual progression from onset; older onset; spinal cord dominant |
| Progressive-relapsing (PRMS) | Rare — progression from onset with superimposed relapses |
| Radiologically isolated syndrome (RIS) | Incidental MS-like MRI lesions in asymptomatic patient |
McDonald 2017 diagnostic criteria
MS is diagnosed when there is objective evidence of demyelinating CNS lesions disseminated in space AND disseminated in time, with reasonable exclusion of alternatives.
Dissemination in space (DIS)
- At least one T2 hyperintense lesion in 2 or more of the 4 typical CNS locations:
- Periventricular
- Juxtacortical or cortical (2017 revision — cortical lesions now count)
- Infratentorial (brainstem, cerebellum)
- Spinal cord
- Symptomatic MRI lesions now count toward DIS (previous versions excluded)
Dissemination in time (DIT)
- Simultaneous presence of a gadolinium-enhancing and a non-enhancing T2 lesion on a single MRI, OR
- A new T2 or new gadolinium-enhancing lesion on a follow-up MRI compared with baseline, OR
- CSF oligoclonal bands (2017 revision — OCBs can now substitute for DIT in a patient with typical CIS)
Additional 2017 revisions
- Evoked potentials no longer required
- No absolute contraindication to diagnosing MS on first attack if criteria met
Differential diagnosis of demyelinating disease
| Condition | Key clue | Test |
|---|
| NMO/NMOSD (Devic) | LETM (over 3 spinal segments), bilateral optic neuritis, area postrema syndrome | AQP4-IgG cell-based assay |
| MOG-AD | Children, bilateral optic neuritis with disc swelling, ADEM-like, relapsing | MOG antibody cell-based assay |
| ADEM | Post-infectious or post-vaccination, monophasic, encephalopathy, multifocal | Clinical + MRI large confluent lesions |
| CNS lupus | Systemic features, ANA, anti-dsDNA | ANA panel, complement |
| Neurosyphilis | Serology, CSF VDRL | VDRL, FTA-ABS |
| HIV | Serology, CD4 count | HIV serology, CSF PCR |
| B12 deficiency (SACD) | Peripheral neuropathy + posterior column + lateral column | Serum B12, MMA, homocysteine |
| Sarcoidosis | Systemic, hilar lymphadenopathy | ACE, CT chest, tissue biopsy |
| Leukodystrophy | Onset in childhood or family history | MRI symmetric, MRS, genetic |
| CADASIL | Migraine + strokes + dementia; anterior temporal T2 hyperintensity | NOTCH3 mutation |
| PML | Immunosuppressed (natalizumab, HIV) | JCV PCR CSF, MRI |
Acute relapse management
- High-dose IV methylprednisolone 1 g daily for 3-5 days — speeds recovery but does not change 6-month outcome
- Oral prednisolone alone (low-dose) — contraindicated for optic neuritis based on ONTT (increased recurrence)
- Plasma exchange (PLEX) — for steroid-refractory severe attacks (5-7 sessions)
- IVIG — alternative in refractory cases or pregnancy
Disease-modifying therapy (DMT)
Traditional ladder vs early highly effective therapy
- Traditional — start with a first-line moderate-efficacy DMT and escalate on breakthrough
- Modern (increasingly favoured) — start highly effective therapy early in patients with poor prognostic markers (high lesion load, early enhancement, brainstem or spinal involvement, poor recovery) because long-term disability accrues early
First-line moderate-efficacy DMT
| Drug | Route | Notes |
|---|
| Interferon beta-1a (Avonex) | IM weekly | Widely used in India (generic + biosimilar) |
| Interferon beta-1a (Rebif) | SC 3x weekly | |
| Interferon beta-1b (Betaferon) | SC alternate day | |
| Glatiramer acetate (Copaxone) | SC daily or 3x weekly | Safest in pregnancy |
| Teriflunomide (Aubagio) | Oral daily | Long half-life, teratogenic — washout required |
| Dimethyl fumarate (Tecfidera) | Oral BID | Flushing; lymphopenia risk (PML risk in prolonged low CD4) |
Higher-efficacy DMT
| Drug | Route | Notes |
|---|
| Natalizumab (Tysabri) | IV monthly | Alpha-4 integrin inhibitor; very effective; check JCV antibody — JCV-positive on prolonged natalizumab risks progressive multifocal leukoencephalopathy (PML) |
| Fingolimod (Gilenya) | Oral daily | S1P receptor modulator; first-dose bradycardia (6-hour observation), macular oedema; VZV serology required |
| Ocrelizumab (Ocrevus) | IV 6-monthly | Anti-CD20; first drug approved for PPMS in addition to RRMS; HBV reactivation risk; infection risk |
| Ofatumumab (Kesimpta) | SC monthly | Anti-CD20; self-administered |
| Cladribine (Mavenclad) | Oral pulses | Short courses, long-term B/T cell depletion |
| Alemtuzumab (Lemtrada) | IV pulses year 1 + year 2 | Highly effective; autoimmune complications years later (thyroid, ITP, glomerulonephritis); now second-line |
| Ublituximab (Briumvi) | IV monthly | Newer anti-CD20; shorter infusion |
Newer S1P modulators (fewer cardiac and macular effects)
- Ozanimod (Zeposia)
- Ponesimod (Ponvory)
Pre-DMT screening (all patients)
- HBV, HCV, HIV, VZV serology
- Latent TB screening (India-relevant)
- JCV antibody before natalizumab
- ECG + macular exam before fingolimod
- Baseline CBC, LFT, TFT
DMT and pregnancy
- Glatiramer acetate — safest to continue in pregnancy if needed
- Interferon beta — acceptable
- Natalizumab — may be continued in high-activity disease under specialist care
- Fingolimod, dimethyl fumarate, teriflunomide, cladribine — stop before conception (teriflunomide requires cholestyramine washout)
- Ocrelizumab, ofatumumab — stop before conception; B-cell depletion effect on fetus
- Post-partum rebound — high risk of relapse; plan DMT resumption early
Symptomatic management
| Symptom | Management |
|---|
| Spasticity | Baclofen, tizanidine, gabapentin, botulinum toxin (focal), intrathecal baclofen (severe) |
| Fatigue | Amantadine, modafinil; exercise; heat avoidance |
| Bladder — urgency, frequency | Anticholinergics (oxybutynin, solifenacin); mirabegron; intermittent self-catheterisation for retention |
| Bowel | Bulk laxatives, dietary fibre |
| Sexual dysfunction | Sildenafil, tadalafil; counselling |
| Depression | SSRI; cognitive behavioural therapy |
| Walking speed | Dalfampridine (potassium channel blocker); physiotherapy |
| Neuropathic pain | Gabapentin, pregabalin, amitriptyline, duloxetine, carbamazepine (for trigeminal neuralgia) |
| Cognitive | Cognitive rehabilitation; treat depression |
| Uhthoff / heat sensitivity | Cooling vests, avoidance |
Neuromyelitis optica spectrum disorder (NMOSD)
Pathophysiology
- Autoimmune astrocytopathy — IgG against aquaporin-4 (AQP4) water channels on astrocyte foot processes
- Complement-mediated astrocyte injury with secondary demyelination and neuronal loss
- Antibody-negative NMO (~20-25 percent) may be MOG antibody-positive or truly seronegative
Clinical clues (contrast with MS)
| Feature | NMO | MS |
|---|
| Optic neuritis | Often bilateral simultaneous, severe, poor recovery, chiasmal | Unilateral, milder, good recovery |
| Myelitis | LETM — over 3 vertebral segments on MRI | Short-segment |
| Brain MRI | Usually normal or non-MS pattern | Multi-focal periventricular, juxtacortical |
| Area postrema syndrome | Intractable hiccups and vomiting | Not typical |
| CSF | High protein, neutrophilic pleocytosis (attack) | Mononuclear pleocytosis, OCBs |
| OCBs | Uncommon | Common (over 90 percent RRMS) |
| Antibody | AQP4-IgG positive | Negative |
Diagnostic criteria (IPND 2015)
- AQP4-antibody positive — at least one core clinical characteristic — makes NMOSD
- AQP4-antibody negative or unavailable — more stringent MRI criteria plus at least 2 core criteria
Treatment (fundamentally different from MS)
- Acute attack — high-dose IV methylprednisolone; plasma exchange for severe or refractory
- Maintenance immunosuppression:
- Rituximab — B-cell depletion; widely used off-label (highly effective; India-affordable as biosimilar)
- Azathioprine — with steroid taper
- Mycophenolate mofetil
- Eculizumab (Soliris) — anti-C5 complement inhibitor; NMO-approved; meningococcal vaccination required
- Inebilizumab (Uplizna) — anti-CD19; NMO-approved
- Satralizumab (Enspryng) — anti-IL-6R; NMO-approved
- AVOID — interferon-beta, natalizumab, fingolimod (may worsen NMO)
MOG antibody-associated disease (MOG-AD)
- Separate demyelinating entity; MOG antibody against myelin oligodendrocyte glycoprotein
- Presentations:
- ADEM in children (post-infectious multifocal syndrome)
- Optic neuritis (often bilateral, prominent disc swelling — papillitis)
- Transverse myelitis (may be LETM)
- Cortical encephalitis
- Course — monophasic in half; relapsing in half — need immunosuppression
- Treatment — high-dose IV methylprednisolone for acute attack; steroid-sparing immunosuppression for relapsing disease (mycophenolate, azathioprine, IVIG, rituximab)
- Test MOG antibody cell-based assay in optic neuritis (especially bilateral), ADEM, and paediatric demyelination
Acute disseminated encephalomyelitis (ADEM)
- Post-infectious (viral, mycoplasma) or post-vaccination monophasic multifocal demyelinating disorder
- Children most commonly (though can occur in adults)
- Presentation — encephalopathy (mandatory for diagnosis), multifocal neurological deficits (motor, sensory, cranial nerves, ataxia), fever, headache; onset days to weeks after preceding illness
- MRI — large confluent T2 hyperintense lesions in white matter, basal ganglia, thalamus, brainstem; may enhance
- CSF — pleocytosis, elevated protein; OCBs usually absent (contrast with MS)
- Treatment — high-dose IV methylprednisolone 3-5 days; IVIG or plasma exchange for refractory; usually monophasic — recurrence should raise suspicion of MS or MOG-AD
India-specific context
- MS prevalence in India — rising; historically low but under-diagnosed due to limited MRI and antibody testing access
- DMT access — interferon beta-1a and beta-1b widely available through Indian generics and biosimilars at fraction of imported price; teriflunomide and dimethyl fumarate generics available; higher-efficacy agents (natalizumab, fingolimod, ocrelizumab) accessible at tertiary centres with substantial out-of-pocket even after PMJAY
- Rituximab — widely used off-label for both MS and NMO in India; biosimilar very affordable — often the practical high-efficacy first-line
- Diagnostic infrastructure — MRI ubiquitous; AQP4 and MOG antibody cell-based assays at NIMHANS, AIIMS, SGPGI, PGIMER and commercial reference labs
- Multiple Sclerosis Society of India (MSSI) — advocacy, financial aid, physiotherapy access, patient education
- Ayushman Bharat PM-JAY — coverage state-variable; state schemes (Arogyasri, Karunya, etc.) provide additional support
- Endemic infection screening essential — TB, HBV, HCV, HIV — before immunosuppression
NEET PG MCQ traps
- MS peak — young adult 20-40 years, women 3:1.
- HLA-DRB1*15:01 — strongest MS genetic risk.
- Vitamin D, EBV, smoking, obesity — environmental risk factors.
- Lhermitte sign — electric shock down spine on neck flexion (cervical cord plaque).
- Uhthoff phenomenon — transient worsening with heat.
- RRMS ~85 percent at onset; PPMS ~10-15 percent (older, spinal cord).
- McDonald 2017 DIS — 2 of 4 CNS locations.
- McDonald 2017 DIT — enhancing + non-enhancing OR new lesion on follow-up OR CSF OCBs.
- Optic neuritis in MS — unilateral, retrobulbar (normal fundus), central scotoma, RAPD.
- INO (internuclear ophthalmoplegia) — young adult with MS classic; MLF lesion.
- NMO clue — LETM (spinal cord over 3 segments); bilateral optic neuritis; area postrema.
- AQP4 antibody — NMOSD.
- MOG antibody — MOG-AD (bilateral ON with disc swelling, ADEM-like, children).
- ADEM — post-infectious, monophasic, encephalopathy; OCBs usually absent.
- Acute relapse — high-dose IV methylprednisolone 1 g × 3-5 days.
- AVOID oral prednisolone alone for ON — ONTT increased recurrence.
- Natalizumab + JCV positive — PML risk.
- Fingolimod — first-dose bradycardia, macular oedema; VZV serology needed.
- Ocrelizumab — first drug approved for PPMS; anti-CD20.
- Alemtuzumab — autoimmune complications years later (thyroid, ITP, GN).
- NMO — avoid interferon, natalizumab, fingolimod — may worsen.
- NMO treatment — rituximab, eculizumab (anti-C5), inebilizumab (anti-CD19), satralizumab (anti-IL-6R).
- Eculizumab — meningococcal vaccination required (complement inhibition).
- Glatiramer acetate — safest DMT in pregnancy.
- Rituximab — widely used off-label for both MS and NMO in India (biosimilar affordable).
- Optic Neuritis Treatment Trial (ONTT) — over 2 lesions on baseline MRI → over 80 percent 10-year MS conversion.
- Trigeminal neuralgia in young patient — think MS.
- CSF OCBs — over 90 percent RRMS; uncommon in NMO.
- Pre-DMT TB screening — mandatory in Indian setting.
- Post-partum rebound — high MS relapse risk; plan DMT resumption early.
Recent updates and Indian context
- McDonald 2017 revisions — OCBs substitute for DIT; cortical lesions count; symptomatic MRI lesions count
- AQP4-IgG cell-based assay — sensitivity greater than 75 percent; specificity greater than 99 percent
- MOG antibody disease — increasingly recognised distinct entity; cell-based assay now standard
- Ocrelizumab (2017) — first drug approved for PPMS
- Ofatumumab (2020) — subcutaneous anti-CD20; self-administered
- Ublituximab (2022) — shorter-infusion anti-CD20
- Ozanimod (2020) and ponesimod (2021) — newer S1P modulators with better cardiac safety
- Eculizumab, inebilizumab, satralizumab — NMO-approved biologics (2019-2020)
- EBV causal role — Karolinska longitudinal cohort (2022) strongly supports EBV as necessary trigger for MS
- India MS Society (MSSI) — expanding chapters and advocacy
- PMJAY — variable state coverage; NCG paediatric neurology and neuro-oncology networks include MS in some centres
Frequently asked questions
How does the McDonald 2017 criteria diagnose multiple sclerosis?
The McDonald 2017 criteria diagnose multiple sclerosis when there is objective evidence of demyelinating CNS lesions disseminated in space AND disseminated in time, with reasonable exclusion of alternative diagnoses. Dissemination in space (DIS) is satisfied by at least one T2 hyperintense lesion in 2 or more of the 4 typical MS-CNS locations — periventricular (touching the ventricles), juxtacortical or cortical (touching the grey-white junction), infratentorial (brainstem, cerebellum), and spinal cord. Dissemination in time (DIT) is satisfied by simultaneous presence of a gadolinium-enhancing and a non-enhancing T2 lesion on a single MRI, OR a new T2 or new enhancing lesion on a follow-up MRI compared with a baseline. A major 2017 revision is that CSF oligoclonal bands (OCBs) can now substitute for DIT in a patient with a typical clinically isolated syndrome — meaning MS can be diagnosed on the first clinical event when the MRI shows DIS and the CSF shows OCBs, without waiting for a second clinical attack or a follow-up MRI. This shortens the diagnostic interval, which matters because early disease-modifying therapy improves long-term disability. Cortical lesions and symptomatic MRI lesions now count toward DIS (previous versions excluded them). Evoked potentials are no longer required. The differential of a first demyelinating event includes NMO/NMOSD (test aquaporin-4 antibody), MOG antibody-associated disease (test MOG antibody, especially in children or with bilateral optic neuritis or ADEM-like presentation), CNS lupus, neurosyphilis, HIV, B12 deficiency subacute combined degeneration, sarcoidosis, and leukodystrophy — a wrong diagnosis of MS in one of these leads to wrong DMT and can harm the patient.
Why is it critical to distinguish NMO from MS before starting disease-modifying therapy?
Distinguishing NMO/NMOSD (Devic disease) from MS before starting DMT is critical because several MS-effective drugs — particularly natalizumab, fingolimod, and interferon-beta — either do not work or actively worsen NMO. NMO is an autoimmune astrocytopathy driven by IgG antibodies against aquaporin-4 water channels expressed on astrocyte foot processes, and clinical clues that raise NMO suspicion include longitudinally extensive transverse myelitis (LETM — a spinal cord lesion spanning 3 or more contiguous vertebral segments on MRI, in contrast to MS which typically causes short segmental lesions), bilateral simultaneous or severe optic neuritis (MS optic neuritis is usually unilateral and milder), area postrema syndrome (intractable hiccups and vomiting from a dorsal medulla lesion), brainstem syndromes, and diencephalic or symptomatic cerebral syndromes. The 2015 International Panel for NMO Diagnosis (IPND) criteria stratify diagnosis — AQP4-antibody positive plus at least one core clinical characteristic makes NMOSD, and AQP4-antibody negative or unavailable requires more stringent MRI and multiple core criteria. Treatment differs fundamentally — acute NMO attacks respond to high-dose IV methylprednisolone but often need plasma exchange for severe or steroid-refractory attacks; maintenance immunosuppression uses B-cell depletion with rituximab, azathioprine, mycophenolate, or the newer NMO-approved biologics eculizumab (anti-C5 complement inhibitor), inebilizumab (anti-CD19), and satralizumab (anti-IL-6R); interferon-beta and natalizumab and fingolimod can worsen NMO relapse rate and are contraindicated. MOG antibody-associated disease is a separate demyelinating entity (test MOG antibody in relapsing optic neuritis, ADEM-like presentation, transverse myelitis in children) with a different treatment approach — usually steroids for acute attacks and steroid-sparing immunosuppression (mycophenolate, azathioprine, IVIG, rituximab) for relapsing disease.
How do you choose a disease-modifying therapy in relapsing-remitting MS?
Disease-modifying therapy in relapsing-remitting MS is chosen by matching disease activity, patient preference, comorbidity, safety monitoring, and cost. The traditional ladder started with lower-efficacy, safer first-line agents and escalated to higher-efficacy drugs on breakthrough disease; a modern alternative is early highly-effective therapy for patients with poor prognostic features (high lesion load at baseline, early gadolinium enhancement, brainstem or spinal cord involvement, poor recovery from first attack) because long-term disability is largely accrued in the first 5-10 years. First-line moderate-efficacy options — interferon beta-1a (weekly IM, subcutaneous three times a week) or interferon beta-1b (subcutaneous alternate day), glatiramer acetate (daily or 3-times-weekly subcutaneous), teriflunomide (daily oral), dimethyl fumarate (twice-daily oral). Higher-efficacy options — natalizumab (monthly IV alpha-4 integrin inhibitor — very effective but check JC virus antibody status because JCV-positive patients on prolonged natalizumab develop progressive multifocal leukoencephalopathy, PML), fingolimod (daily oral S1P receptor modulator — first-dose bradycardia and macular oedema; requires first-dose observation), ocrelizumab (6-monthly IV anti-CD20 — the first drug approved for primary progressive MS in addition to relapsing MS; hepatitis B reactivation and infection risk), ofatumumab (monthly subcutaneous anti-CD20), cladribine (short oral pulses — long-term B and T cell depletion), alemtuzumab (highly effective but autoimmune complications years later — thyroid disease, ITP, glomerulonephritis; now second-line). Newer S1P modulators — ozanimod, ponesimod — have fewer cardiac and macular effects than fingolimod. Ublituximab is a newer anti-CD20 with shorter infusion time. For patients wanting family planning, glatiramer acetate is the safest to continue during pregnancy; interferon beta acceptable; natalizumab may be continued in high-activity disease; dimethyl fumarate and fingolimod stopped before conception. Monitor MRI every 6-12 months for silent disease activity even in asymptomatic patients — new lesions are a signal to escalate.
What is the classic presentation of optic neuritis and how does it differ between MS, NMO and MOG-AD?
Optic neuritis is inflammation of the optic nerve presenting as subacute (over hours to days) monocular vision loss with periorbital pain worsened by eye movement, colour desaturation especially for red, and a relative afferent pupillary defect (RAPD or Marcus Gunn pupil) demonstrated by the swinging flashlight test. Central scotoma is the classic visual field defect. Fundoscopy is normal in retrobulbar optic neuritis (the inflamed segment is behind the disc, so the disc looks normal) — the disc is swollen only in anterior (papillitis) forms. Uhthoff phenomenon — transient worsening of vision with heat or exercise — is characteristic. In classical MS optic neuritis, vision loss is usually unilateral and moderate, recovery is good over weeks to months, MRI orbits shows a short segment of enhancement of the optic nerve, and OCT shows retinal nerve fibre layer thinning after recovery. In NMO/NMOSD (AQP4 positive), optic neuritis is often bilateral (simultaneous or rapidly sequential) and severe with poor recovery, and can cause chiasmal involvement — always test AQP4 antibody in severe or bilateral optic neuritis. In MOG antibody disease (MOG-AD), optic neuritis is often bilateral, severe, may have prominent disc swelling on fundoscopy, and typically recovers better than NMO but has a relapsing course requiring immunosuppression. Investigation for isolated optic neuritis includes MRI brain and orbits with contrast (predicts risk of conversion to MS — over 2 lesions on baseline MRI raises 10-year MS risk to over 80 percent in the Optic Neuritis Treatment Trial), AQP4 antibody (cell-based assay), MOG antibody (cell-based assay), CSF for OCBs if MRI is suggestive of MS. Acute treatment is high-dose IV methylprednisolone (1 g daily for 3-5 days) which speeds recovery but does not change 6-month outcome; oral prednisolone alone is contraindicated for optic neuritis based on ONTT because it increased recurrence.
How is disease-modifying therapy access managed in India and what are the affordable options?
India has a large and under-diagnosed MS burden, but access to disease-modifying therapy is uneven and dominated by cost. Interferon beta-1a and beta-1b are the most widely available first-line DMTs in India through generic and biosimilar manufacturers, priced far below imported products, and are frequently the first-line choice in resource-limited settings. Glatiramer acetate biosimilars are available at Indian tertiary centres. Oral first-line agents — teriflunomide and dimethyl fumarate — are available at moderate cost through generic manufacturing. Higher-efficacy agents including natalizumab, fingolimod, ocrelizumab, and cladribine are available at major tertiary neurology centres but with substantial out-of-pocket cost even after PMJAY coverage; rituximab (widely used off-label for both MS and NMO in India because of cost) is available very affordably as biosimilar and is often the practical first-line high-efficacy agent for patients who cannot afford ocrelizumab. Diagnostic infrastructure — MRI is available across all tertiary centres and most district hospitals; AQP4 antibody and MOG antibody cell-based assays are available at reference laboratories (NIMHANS, AIIMS, SGPGI, and commercial reference labs). Ayushman Bharat PM-JAY coverage for MS is variable state-by-state; state schemes like Arogyasri in Telangana and Karunya in Kerala provide additional support. The Multiple Sclerosis Society of India (MSSI) supports patients with advocacy, financial aid, physiotherapy access, and awareness. Rehabilitation — physiotherapy, occupational therapy, spasticity management with baclofen and botulinum toxin, bladder management, cognitive rehabilitation — is delivered at neurology tertiary centres and MSSI chapters. Vaccination and infection screening (HBV, HCV, HIV, TB, JCV before natalizumab) are essential parts of DMT initiation in the Indian setting given endemic TB and HBV.
This content is for educational purposes for NEET PG exam preparation. It is not a substitute for professional medical advice, diagnosis, or treatment. Clinical information has been reviewed by qualified medical professionals.
Written by: NEETPGAI Editorial Team
Reviewed by: Pending SME Review
Last reviewed: July 2026
