Multiple sclerosis
Description
- Immune-mediated demyelination + axonal loss of the CNS, disseminated in space and time
- Peripheral nervous system is never involved - that is a defining negative
Phenotypes
| % | Features | |
|---|---|---|
| RRMS | ~85% at onset | Discrete relapses with full or partial recovery; no progression between |
| SPMS | Most RRMS eventually | Progressive disability accrual after an initial relapsing course, +/- superimposed relapses |
| PPMS | 10-15% | Progressive from onset; older (~40s), M=F, spinal cord predominant |
- Each classified as active/not active (relapse or new/enhancing MRI lesion) and progressing/not progressing - this drives PBS eligibility, not just description
- CIS - a first demyelinating episode not yet meeting criteria
- RIS - incidental MRI lesions, no clinical event; ~1/3 develop clinical MS within 5 years
- PIRA (progression independent of relapse activity) - disability accrues without relapses even in "RRMS"; the reason relapse-free is not disease-free
Common presentations
- Optic neuritis - subacute monocular loss, pain on eye movement, colour desaturation, RAPD, normal disc in 2/3 (retrobulbar)
- Transverse myelitis - partial, sensory level, bladder involvement; MS cord lesions are short, <2 vertebral segments, dorsolateral
- Brainstem - INO (bilateral INO in a young person = MS), diplopia, vertigo, trigeminal neuralgia
- Cerebellar - ataxia, intention tremor, scanning speech
- The classic triad of cerebellar + pyramidal + dorsal column signs in one patient
- Lhermitte sign - electric shock down the spine on neck flexion (dorsal column)
- Uhthoff phenomenon - transient worsening with heat/exercise. This is a pseudorelapse, not a relapse
6 more sections, plus exam facts
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