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Pathology- Multiple Sclerosis (MS)
This guide summarizes key information on Multiple Sclerosis to aid understanding and effective study.
I. Definition & Epidemiology:
This guide summarizes key information on Multiple Sclerosis to aid understanding and effective study.
I. Definition & Epidemiology:
- Definition: MS is a relapsing-remitting, demyelinating disease of the Central Nervous System (CNS). Neurological disturbances affect different CNS areas at different times. Think intermittent attacks in different locations.
- Epidemiology:
- Peak onset: 20-30 years old.
- Slightly more common in females.
- Significant geographical variation: higher incidence at higher latitudes (farther from the equator), near absence near the equator. This hints at environmental factors.
- Aetiology (Cause): Unknown. Leading hypothesis: immune-mediated demyelination triggered by a childhood infection in genetically susceptible individuals. Think infection + genetics = trigger.
- Pathogenesis (Mechanism):
- Demyelination episodes cause acute neurological deficits (symptoms) developing over days and lasting weeks.
- Early stages: Complete recovery is typical.
- Progression: Slower recovery, residual deficits, axonal death, and permanent disability due to extensive axonal loss. Think initial recovery, then progressive damage.
- Optic Nerve: Blurred vision, loss of color vision.
- Cerebellum: Vertigo, incoordination.
- Brainstem: Eye movement disorders.
- Spinal Cord: Patchy numbness/tingling, progressing to paraplegia (paralysis of lower limbs), incontinence, and sexual dysfunction.
- Macroscopy (Gross Examination): Well-circumscribed grey plaques in CNS white matter. Common locations: optic nerves, periventricular white matter, brainstem, cervical spinal cord. Think visible lesions in specific areas.
- Histopathology (Microscopic Examination):
- Active plaques: Inflammatory infiltrate, myelin sheath destruction.
- Established plaques: Complete myelin loss, reduced oligodendrocytes (myelin-producing cells), relatively normal or slightly reduced axon numbers (initially).
- Most patients experience progressive disease.
- Significant complications due to disability: pneumonia, urinary tract infections, pressure sores. Think disability leads to secondary complications.
- Relapsing-remitting: Periods of attacks followed by periods of remission (partial or complete recovery).
- Demyelination: Damage to the myelin sheath surrounding nerve fibers, impairing signal transmission.
- Geographical variation: Strong evidence for environmental influence.
- Progressive axonal loss: The ultimate cause of permanent disability.
- Location-specific symptoms: The location of the demyelination dictates the presenting symptoms.
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