Multiple Sclerosis — Symptoms, Causes & Treatment | MyMedicPlus

Multiple sclerosis (MS) is a chronic, immune-mediated inflammatory disease of the central nervous system (CNS) causing demyelination (destruction of the myelin sheath surrounding nerve axons) and progressive axonal damage, leading to the accumulation of neurological disability over time. It affects 2.8 million people worldwide and is the most common non-traumatic cause of neurological disability in young adults. The disease follows three main clinical phenotypes: relapsing-remitting MS (RRMS — accounting for 85% of cases at diagnosis, characterised by discrete episodes of neurological dysfunction called relapses or exacerbations with full or partial recovery between them); primary progressive MS (PPMS — approximately 10–15% at diagnosis, characterised by steadily worsening neurological function from disease onset without distinct relapses); and secondary progressive MS (SPMS — develops in a majority of RRMS patients after 20–25 years, characterised by a gradual accumulation of disability with or without superimposed relapses). MS is 3 times more common in women than in men, with peak onset between 20–40 years. Though not directly fatal in most cases, MS causes significant disability and has a profound impact on quality of life, independence, and mental health.

MS results from immune-mediated destruction of myelin by autoreactive CD4+ T helper cells (particularly Th1 and Th17 cells) and B lymphocytes that breach the blood-brain barrier and attack oligodendrocytes (myelin-producing cells) and myelin itself in the CNS. This causes demyelinated plaques (lesions), impairs saltatory nerve conduction, and ultimately leads to axonal degeneration and irreversible disability. Risk factors: female sex (3:1 female-to-male ratio — sex hormones influence immune function and disease course); latitude above 40 degrees (UV-B deprivation leads to vitamin D deficiency — a key environmental modifier of MS risk); HLA-DRB1*15:01 genetic variant (the most strongly associated genetic risk locus, present in 60% of MS patients vs 30% of controls); Epstein-Barr virus (EBV) infection — landmark studies including the US military cohort (Bjornevik et al., Science 2022) demonstrated a 32-fold increased MS risk after EBV infection, providing strong evidence for EBV as a necessary trigger; cigarette smoking (doubles MS risk and accelerates progression); childhood obesity (50% increased risk); low vitamin D levels in childhood and adolescence; and prior infectious mononucleosis. Genetic risk: first-degree relatives of MS patients have a 20–40-fold higher risk than the general population; monozygotic twin concordance is 25–30%, confirming that environmental factors are essential alongside genetic susceptibility.

MS symptoms are highly diverse, reflecting the anatomical distribution of demyelinating lesions throughout the CNS. Common presentations: optic neuritis (painful loss of vision in one eye, typically in a young woman — often the first presenting feature; accompanied by pain on eye movement and reduced colour saturation; recovers partially or fully over weeks to months); limb weakness (usually asymmetric, worse in legs; upper motor neuron pattern — spasticity, brisk reflexes, upgoing plantar response — Babinski sign); sensory symptoms (numbness, tingling, burning, or electric sensations — particularly in the hands, feet, and trunk; Lhermitte's sign — electric shock sensation down the spine on neck flexion — indicates cervical spinal cord involvement); cerebellar symptoms (intention tremor, dysarthria, ataxia, nystagmus — Charcot's triad historically: nystagmus + dysarthria + intention tremor); gait disturbance (spastic gait, ataxic gait, or foot drop); bladder dysfunction (urgency, frequency, nocturia, hesitancy — present in 75%); bowel dysfunction (constipation, urgency); sexual dysfunction; fatigue (the most prevalent and disabling symptom — affects 80–90% of MS patients; not related to physical disability level, worsened by heat — Uhthoff's phenomenon); cognitive impairment (processing speed, working memory, attention — affects 45–70%; can occur early and independently of physical disability); and depression (comorbid in 50% of MS patients — both from the disease itself and psychosocial impact). Uhthoff's phenomenon: temporary worsening of established MS symptoms with increased body temperature (hot bath, fever, exercise) — not a true relapse.

The 2017 McDonald Criteria require demonstration of dissemination in space (DIS — lesions in at least 2 of the 4 characteristic CNS locations: periventricular, juxtacortical, infratentorial, spinal cord) and dissemination in time (DIT — presence of gadolinium-enhancing and non-enhancing lesions simultaneously, or new lesions on follow-up MRI), established by MRI, clinical assessment, or cerebrospinal fluid (CSF) analysis. Brain and spinal cord MRI with gadolinium contrast: is the cornerstone investigation — reveals T2/FLAIR hyperintense white matter lesions characteristic of MS (periventricular lesions — 'Dawson's fingers' perpendicular to ventricles; juxtacortical; infratentorial; spinal cord); gadolinium-enhancing lesions indicate active inflammatory breakdown of the blood-brain barrier; T1 hypointense 'black holes' indicate chronic axonal loss. Cerebrospinal fluid (CSF) analysis (lumbar puncture): oligoclonal bands (IgG bands present in CSF but not in paired serum) are present in 85–90% of MS patients — supports diagnosis when MRI criteria are not fully met. Visual evoked potentials (VEPs): prolonged P100 latency confirms subclinical optic neuritis or past demyelination not captured on MRI. Blood tests: exclude mimics — B12 deficiency, HIV, neurosyphilis, ANA/ANCAs (vasculitis), NMO-IgG/AQP4 antibodies (neuromyelitis optica spectrum disorder — NMOSD — an important MS mimic requiring different treatment), and MOG-IgG antibodies (MOGAD).

Disease-modifying therapies (DMTs) are the cornerstone of RRMS management — reducing annualised relapse rate, slowing MRI lesion accumulation, and reducing long-term disability progression. Moderate-efficacy DMTs (platform therapies): interferon-beta (IFN-beta 1a and 1b — injectable), glatiramer acetate (injectable), dimethyl fumarate (Tecfidera — oral), teriflunomide (Aubagio — oral) — reduce relapse rate by 30–50%; appropriate for lower-risk RRMS. High-efficacy DMTs: natalizumab (Tysabri — monthly IV infusion; anti-VLA4 monoclonal antibody; reduces relapse rate by 68%; risk of PML — progressive multifocal leukoencephalopathy — from JC virus reactivation in seropositive patients; requires JCV serology monitoring); ocrelizumab (Ocrevus — IV infusion every 6 months; anti-CD20 monoclonal antibody depleting B lymphocytes; reduces relapse rate by 46–47% vs interferon; the first and only DMT approved for both RRMS and PPMS); ofatumumab (Kesimpta — subcutaneous anti-CD20, self-administered monthly); alemtuzumab (Lemtrada — administered in 2 courses separated by 12 months; highly effective but requires careful monitoring for secondary autoimmunity); cladribine (Mavenclad — oral; given in 2 short courses over 2 years). For PPMS: ocrelizumab slows disability progression and reduces MRI lesion accumulation — the only treatment with proven PPMS efficacy. Relapse treatment: IV methylprednisolone 1g daily for 3–5 days (shortens relapse duration by approximately 1 week but does not change long-term disability accumulation). Symptomatic therapy: fatigue (fampridine to improve walking speed; amantadine; graded exercise); spasticity (baclofen 10–80 mg/day oral, or intrathecal baclofen pump for severe spasticity; physiotherapy; cannabinoids — nabiximols/Sativex mouth spray, NICE-approved for MS spasticity); bladder dysfunction (oxybutynin, solifenacin for urgency; intermittent self-catheterisation for retention; mirabegron); neuropathic pain (gabapentin 300–3600 mg/day, pregabalin, amitriptyline); depression (SSRI, CBT, exercise).

Progressive disability is the primary long-term complication — wheelchair dependence occurs in approximately 50% of RRMS patients within 15–25 years without effective DMT; modern high-efficacy DMTs have substantially reduced this risk. Depression (comorbid in 50% of MS patients) significantly impairs quality of life and is independently associated with worse disability outcomes — mental health screening and active treatment are essential. Cognitive impairment (MS-associated cognitive dysfunction, particularly in information processing speed, working memory, and episodic memory) affects 45–70% and can occur independently of physical disability; it significantly impairs employment, relationships, and quality of life. Urinary tract infections from neurogenic bladder dysfunction are a major and recurring source of morbidity — and a common trigger of pseudo-relapses (Uhthoff's phenomenon) and true relapses. Dysphagia and aspiration pneumonia in advanced MS cause significant morbidity and mortality. JC virus-related progressive multifocal leukoencephalopathy (PML) is a rare but potentially fatal or severely disabling complication of natalizumab treatment in JCV-seropositive patients (risk up to 1 in 100 with high antibody index and prolonged treatment) — managed by monitoring antibody index and switching therapies. Secondary autoimmune conditions (thyroid disease, immune thrombocytopenia, nephropathy) are a well-recognised complication of alemtuzumab therapy.

No definitive primary prevention exists, but modifiable risk reduction is achievable. Maintain adequate vitamin D levels throughout life — target 25-OH vitamin D levels above 100 nmol/L; supplementation with 1,000–2,000 IU/day is safe and recommended (higher doses under medical supervision in documented deficiency). Never smoke — smoking doubles MS risk and accelerates transition to secondary progressive MS; smoking cessation at any stage in the disease slows progression. Healthy childhood bodyweight reduces MS risk. After diagnosis, early initiation of high-efficacy DMT ('treat to target' strategy) rather than the traditional escalation approach is increasingly recommended by NICE and the MS Society — studies show that earlier high-efficacy treatment results in significantly less long-term disability accumulation. Regular monitoring: neurological review every 3–6 months; annual brain and spinal cord MRI to detect new or enlarging lesions or gadolinium-enhancing activity (treat to target for MRI inactivity); annual EDSS (Expanded Disability Status Scale) assessment; Symbol Digit Modalities Test (SDMT) for cognitive monitoring. Multidisciplinary support: physiotherapy (maintaining gait and strength), occupational therapy (energy conservation, adaptive aids), neuropsychology (cognitive rehabilitation), specialist MS nursing (medication management, crisis support), bladder/bowel nursing, and psychology (CBT for depression and adjustment). Avoid overheating (Uhthoff's phenomenon — cooling vests and cooling strategies for heat-sensitive individuals).

Attend Emergency Department immediately for: sudden severe vision loss in one eye with pain on eye movement — acute optic neuritis requiring urgent ophthalmology review and consideration of IV methylprednisolone; sudden loss of ability to walk, bilateral leg weakness, or loss of bladder or bowel control — spinal cord relapse or transverse myelitis; very high fever with deterioration of MS symptoms — pseudo-relapse from infection (Uhthoff's phenomenon — symptoms worsen with body temperature rise; fever must be treated urgently); severe confusion or altered consciousness — unusual in MS and requires exclusion of other causes. Contact your neurologist or MS nurse urgently for: new neurological symptoms lasting more than 24 hours — may be a relapse requiring treatment with IV methylprednisolone 1g daily for 3-5 days (shortens relapse duration but does not change long-term disability trajectory); symptoms developing within 2 weeks of contrast MRI showing new gadolinium-enhancing lesions; worsening disability even between relapses — may indicate a change in MS course requiring DMT switch. Seek emergency care if starting natalizumab and developing: new or worsening confusion, vision problems, or motor symptoms — possible PML (progressive multifocal leukoencephalopathy) — requires urgent MRI and specialist review.