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Clinically isolated syndrome and radiologically isolated syndrome

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2 min synopsisUK scopeSources checked 27 Aug 2026Clinical review pending
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Escalate

A first demyelinating-appearing syndrome may still be vascular, compressive, infectious or antibody mediated. Admit urgently for profound or bilateral visual loss, rapidly evolving paraplegia, respiratory weakness, a complete cord syndrome, sphincter retention, severe brainstem dysfunction, encephalopathy or systemic infection. Obtain urgent spinal imaging before attributing an acute cord syndrome to clinically isolated syndrome.

Synopsis

Distinguish a first clinical demyelinating event from incidental MRI appearances, quantify future multiple-sclerosis risk without deterministic counselling, and arrange specialist surveillance or treatment according to evolving criteria.

  • Clinically isolated syndrome is a first objective neurological episode caused by central inflammatory demyelination, lasting at least 24 hours, in a person not yet shown to meet full multiple-sclerosis criteria.
  • Typical clinically isolated syndromes are unilateral optic neuritis, partial transverse myelitis, a brainstem event or a cerebellar syndrome; vague dizziness, fatigue or paraesthesia without objective localisation is less specific.
  • Some first events already meet contemporary multiple-sclerosis criteria through MRI dissemination and cerebrospinal-fluid biomarkers, so clinically isolated syndrome is not a mandatory prolonged waiting stage.

Key red flags

Atypical severe event

Bilateral optic involvement, chiasmal disease, complete myelitis, longitudinally extensive cord signal or area-postrema symptoms suggest aquaporin-4 or MOG-associated disease and need urgent specialist assessment.

Investigation priorities

01
MRI brain with demyelination protocolFirst step

Assess lesion morphology, distribution, enhancement and evidence of dissemination.

Management branches

First clinical eventVerify objective demyelination

A first optic, cord, brainstem or cerebellar syndrome evolves over hours to days.

  1. Localise with a full neurological and ophthalmic examination, documenting duration, functional impact, previous subtle attacks and vascular, compressive, infectious or systemic clues.
  2. Arrange urgent imaging for severe cord or brainstem disease and specialist protocol brain and spinal MRI for a stable typical event, adding cerebrospinal fluid when it changes criteria.

Key medicines

Methylprednisolone for a clinical attackWhen a first demyelinating event is disabling, specialists may use the NICE multiple-sclerosis relapse regimen of 0.5 g orally daily for 5 days or selected intravenous therapy.
Disease-modifying therapy after CISUse only an agent and schedule licensed, NICE-approved and NHS-commissioned for the person's confirmed diagnosis and risk profile under an MS specialist.
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Sources and review status5 sources · checked 27 Aug 2026 · clinical review pending
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom