Overview
Multiple sclerosis (MS) is a chronic autoimmune disease in which the immune system attacks the myelin sheath protecting nerve fibres in the brain and spinal cord, disrupting electrical signals. MS can cause a wide range of neurological symptoms. It follows a relapsing-remitting course in 85% of patients at onset. It is a leading cause of disability in young adults.
How common is it?
MS affects approximately 130,000 people in the UK — one of the highest prevalence rates in the world. It is more common in women (3:1 female to male ratio) and most commonly diagnosed between age 20 and 40.
Causes and risk factors
MS results from immune-mediated demyelination triggered by environmental exposures in genetically susceptible individuals. The precise autoantigen is not fully established.
Common risk factors
- Genetic susceptibility (HLA-DRB1*15:01 allele; highest risk but not deterministic)
- Epstein-Barr virus infection (strong and causal association — almost all MS patients have had EBV)
- Low vitamin D levels (inverse association)
- Smoking (increases risk and worsens progression)
- Latitude and UV light exposure (higher prevalence further from equator)
- Childhood obesity
- Female sex
Symptoms
- Optic neuritis: painful loss of vision in one eye (common first presentation)
- Limb weakness and fatigue
- Sensory disturbance: numbness, tingling, electric shock sensation on neck flexion (Lhermitte sign)
- Balance and coordination problems (ataxia)
- Bladder dysfunction: urgency, frequency, incomplete emptying
- Cognitive impairment and brain fog
- Depression and anxiety
- Sexual dysfunction
- Spasticity and muscle stiffness
- Fatigue — the most common and disabling symptom
When to see a doctor
Call emergency services (999 in the UK) for sudden weakness or numbness, new speech difficulty, sudden vision loss or major balance problems. These may be signs of a stroke, even in someone with multiple sclerosis. Do not wait 24 hours or drive yourself. Arrange assessment for other new or persistent symptoms, and contact your MS team about possible changes in an established condition.
Diagnosis
MRI of brain and spinal cord showing characteristic demyelinating lesions (dissemination in space and time). CSF analysis (oligoclonal bands). Visual evoked potentials. McDonald criteria (2017) guide diagnosis. Specialist neurology assessment essential.
Treatments
Disease-modifying therapies (DMTs)
A range of injectable (interferons, glatiramer acetate), oral (dimethyl fumarate, fingolimod, cladribine, ozanimod), and infusion (natalizumab, ocrelizumab, alemtuzumab) therapies reduce relapse rate and delay disability progression. Higher-efficacy treatments (ocrelizumab, alemtuzumab) are increasingly used earlier in disease.
Acute relapse management
High-dose intravenous or oral methylprednisolone (1g daily for 3 to 5 days) speeds recovery from relapses but does not alter long-term disability.
Symptom management
Baclofen or tizanidine for spasticity; oxybutynin or mirabegron for bladder urgency; amantadine, modafinil, or fampridine for fatigue; antidepressants for depression; cognitive rehabilitation for cognitive symptoms.
Autologous haematopoietic stem cell transplant (AHSCT)
High-dose chemotherapy followed by stem cell rescue to 'reboot' the immune system. Produces sustained freedom from disease activity in selected patients with aggressive early MS. NICE-approved for highly active RRMS in the UK.
Self-care and lifestyle
- Do not smoke — reduces relapse rate and slows progression
- Maintain vitamin D levels (supplement with 1,000 to 2,000 IU daily)
- Regular aerobic and resistance exercise improves fatigue, mobility, and cognition in MS
- Cooling strategies for heat-sensitive symptoms (Uhthoff phenomenon)
Prevention
No reliable prevention is established. Vitamin D sufficiency and avoidance of smoking from early life may reduce risk.
Sources for targeted updates
Updated: 11 September 2026. Sudden neurological symptoms must not wait 24 hours. This update covers the named sections; a full review of the remaining guide is pending.