Demyelinating Disease and Multiple Sclerosis
Demyelination Basics
Mechanism
Demyelinating diseases impair saltatory conduction by damaging myelin, which slows or blocks signal transmission along affected pathways.
Clinical hallmark
Symptoms that come and go, affect different CNS regions over time, and localize to white matter are classic clues to multiple sclerosis.
Central vs peripheral demyelination
Central demyelination
- Multiple sclerosis is the prototype
- Brain, optic nerves, and spinal cord can be affected
Peripheral demyelination
- Guillain-Barré syndrome is a classic example
- Weakness with reduced reflexes and peripheral nerve involvement
Loss of myelin primarily impairs which physiologic property?
Myelin enables rapid saltatory conduction along axons.
Correct answer: Saltatory conduction
What is a typical pattern of multiple sclerosis over time?
Different neurologic deficits occur at different times and in different CNS locations.
Correct answer: dissemination in time and space
Clinical Presentation of MS
Common MS syndromes
| Syndrome | Typical clues |
|---|---|
| Optic neuritis | Painful monocular vision loss and color desaturation |
| Internuclear ophthalmoplegia | Impaired adduction with nystagmus of the abducting eye |
| Myelitis | Sensory level, weakness, bladder symptoms |
| Brainstem/cerebellar syndrome | Diplopia, ataxia, vertigo |
Painful monocular visual loss with decreased color vision is most consistent with:
Optic neuritis is a classic demyelinating presentation.
Correct answer: Optic neuritis
What eye movement abnormality is characteristic of internuclear ophthalmoplegia?
The affected eye cannot adduct appropriately during horizontal gaze.
Correct answer: impaired adduction
Diagnosis and Treatment Principles
Approach to suspected MS
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1
Step 1: Confirm a clinical syndrome compatible with demyelination.
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2
Step 2: Use MRI to look for dissemination in space and time.
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3
Step 3: Exclude mimics such as infection, nutritional deficiency, and vascular disease.
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Step 4: Treat relapses and consider disease-modifying therapy for long-term control.
Which imaging modality is most useful for evaluating MS lesions?
MRI is the primary imaging tool for detecting CNS demyelinating lesions.
Correct answer: MRI
Why are disease-modifying therapies used in MS?
They aim to lower inflammatory activity and cumulative disability.
Correct answer: to reduce relapses and slow disease progression