Neurology

Multiple sclerosis

A chronic immune-mediated disease of the central nervous system causing neurological lesions and symptoms that are disseminated in space and time; diagnosis is specialist-led, relapses and progression must be distinguished, and disease-modifying therapy is selected according to disease activity.

In a nutshell

MS is an immune-mediated CNS demyelinating disease in which focal deficits are disseminated across pathways and time. Diagnose through a specialist using the current revised McDonald criteria, treat significant relapses with NICE high-dose corticosteroids, and use specialist disease-modifying therapy to reduce future inflammatory activity.

Classic presentation

A person under 50 develops a focal neurological deficit over more than 24 hours, such as painful monocular visual loss, diplopia, ascending sensory symptoms or limb weakness, then partially recovers; a previous episode may have affected a different CNS pathway.

Key points

Localise the symptom: optic nerve causes optic neuritis, spinal cord causes weakness or sensory and bladder symptoms, brainstem causes diplopia or internuclear ophthalmoplegia, and cerebellar pathways cause ataxia.
NICE NG220 uses the revised 2024 McDonald criteria; diagnosis combines history, examination, MRI and laboratory findings and must exclude mimics.
A relapse is new or worsening neurological dysfunction lasting beyond 24 hours without infection or another cause; heat or infection can temporarily worsen old symptoms without new inflammation.
NICE recommends high-dose oral methylprednisolone for a functionally important relapse after discussion with an MS-experienced clinician; steroids speed recovery but do not change long-term disease progression.
Disease-modifying therapy is specialist-selected according to phenotype and activity, safety, reproductive plans and current NICE and NHS England commissioning pathways.
Fatigue, spasticity, pain, bladder dysfunction, cognition, mood, mobility and sexual symptoms need multidisciplinary rehabilitation as well as medicines.
Sudden focal deficits are a stroke emergency; rapidly progressive weakness, a sensory level or new sphincter dysfunction require urgent exclusion of cord compression or another acute myelopathy.
Review the whole person at least annually, including progression, active disease, disability, medicines, pregnancy plans, driving, work, carers and social care.

First-line investigation

Specialist neurological assessment followed by MRI of the brain and relevant spinal cord regions, with targeted blood tests and CSF when needed to apply the revised criteria and exclude mimics.

Management

Recognise the emergency pattern

Use the stroke pathway for sudden focal symptoms; urgently assess rapidly progressive weakness, a sensory level, new bladder or bowel dysfunction, severe visual loss, infection or another acute myelopathy.^1,2

Confirm the diagnosis and phenotype

Take a focused history, examine for objective CNS signs, exclude mimics, arrange specialist MRI and targeted laboratory testing, and apply the current revised McDonald criteria rather than diagnosing from a scan alone.^1,3,2

Treat a significant relapse

After excluding infection and pseudo-relapse, discuss a functionally important relapse with an MS-experienced clinician for NICE-recommended high-dose oral methylprednisolone; use IV treatment only for the specified specialist or inpatient indications (see BNF).^4,8

Start specialist long-term care

Use current NICE technology appraisals and the NHS England June 2026 algorithm to select and monitor disease-modifying therapy, while providing exercise, rehabilitation and symptom-specific multidisciplinary care.^5,6,10

Protect pregnancy and treatment safety

Ask about pregnancy plans, contraception and breastfeeding, and coordinate any DMT change with the specialist MS team; do not stop treatment abruptly or omit infection and monitoring advice.^11,5,6

Review progression and function

Offer at least annual comprehensive review covering relapse activity, progression, disability, symptoms, bone health, mood, cognition, work, driving, carers, social care, palliative needs and who to contact if symptoms change.^7,4,2

Exam traps

Do not diagnose MS from vague fatigue, dizziness or a single incidental white-matter lesion; a compatible clinical pattern and specialist assessment matter.
Do not call infection-related worsening of old symptoms a relapse or give steroids reflexively; exclude pseudo-relapse first.
Steroids shorten relapse recovery but do not prevent future relapses or reverse established progression; DMT is the separate long-term strategy.
A sudden focal deficit is stroke until proven otherwise, not a routine MS relapse.
Do not treat all gradual disability accumulation as relapse; reassess for progression, active disease, treatment failure and alternative causes.
Do not start, stop or switch DMT outside the specialist pathway, and do not omit pregnancy, infection and monitoring considerations.

Illustrations

Demyelinated plaque and conduction blockDiagram of a myelinated axon conducting saltatorily compared with a demyelinated segment showing slowed or blocked conduction.PassFinals · original

Axial T2 brain MRI showing periventricular white-matter lesions in multiple sclerosisAxial brain MRI showing periventricular and juxtacortical white-matter lesions, illustrating characteristic lesion topography in multiple sclerosis.James Heilman, MD, Wikimedia Commons · CC-BY-SA-4.0

Relapsing-remitting and progressive disease activityDisease-course diagram showing episodic relapses with recovery and gradual disability accumulation, while distinguishing inflammatory activity from progression.PassFinals · original

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.