Demyelinating Diseases Flashcards
(35 cards)
Demyelinating Disorders
Disorders characterized by loss of myelin around the axons
Types of Myelin Disorders
- Loss of myelination (demyelination) - damage to normal myelin
- Multiple sclerosis, Myelinolysis & Post-infectious/immune (ADEM, AHEM) - Improper formation of myelin (Dysmyelination) - defective myelin synthesis or turnover
Multiple Sclerosis
Autoimmune demyelinating disorder w/ episodes of disease activity that produce white matter lesions
MC demyelinating disease
“Relapsing & Remitting” course
Epidemiology, Etiology & RFs of MS
F:M = 2:1 (Young adults- 20-30 years) Unknown etiology - Smoking - Low Vit D (Farther away from equator) - Race (white) - EBV infection - Genes- HLA-DR Exacerbated by Inc body temp (hot baths, exercise)
Pathogenesis of MS
Autoimmune response directed against components of the myelin sheath
• Th1 and Th17 T cells react against myelin antigens and secrete cytokines –>
recruitment and activation of leucocytes –> demyelination
Both genetic and environmental factors are implicated
Gross morphology changes in MS
- Multifocal white matter lesion
Plaques
- Firmer than surrounding areas
- Well-circumscribes, slightly depressed, glassy appearing, gray-tan lesions
- Commonly adjacent to ventricles, in optic nerves, chiasm, brainstem, ascending & descending fiber tracts, etc.
Microscopic changes in MS
Active plaques
- Abundant macrophages & ongoing myelin breakdown
- Perivascular lymphocytic inflammation
Inactive plaques
- Little/no myelin left
- Prominent astrocytic proliferation & gliosis
CFs of MS
- Acute optic neuritis - painful unilateral vision loss w/ Marcus Gunn pupil
- Diplopia, ataxia, scanning speech, intention tremor, nystagmus/INO (b/l > u/l) (Brainstem / Cerebellar)
- Weakness & spasticity (Pyramidal tract)
- Electric-shock sensation, neurogenic bladder, paraparesis, sensory effects on truck & extremity - Spinal cord
Lab finding in MS
CSF
- Inc proteins (MBP- Myelin Basic Protein)
- Inc Immunoglobulins (IgG) (oligoclonal bands are diagnostic)
- Moderate pleocytosis
MS Treatment
B-interferon, Glatiramer & Natalizumab
- Slow relapses & progression
IV steroids
- Acute flares
Post-Infectious Demyelination
Immune-mediated demyelination ff infections
Etiology & Pathogenesis of Post Infectious Demyelination
- Viral infections or Vaccination
- Cross-reacting Ab –> Myelin damage
Patterns of Post- Infectious Demyelination
- Acute Disseminated Encephalomyelitis (ADEM)
2. Acute Hemorrhagic Encephalomyelitis (AHEM)
Acute Disseminated Encephalomyelitis (ADEM)
- Rapid progression (1-2wks after infection)
- Non-localizing symptoms (different from MS)
- Most recover completely
Acute Hemorrhagic Encephalomyelitis (AHEM)
- Mostly children & young adults
- Usually fatal (more devastating than ADEM)
Central Pontine Myelinolosis
Non-immune damage to oligodendrocytes in the pons
Etiology of Central Pontine Myelinolysis
After rapid Hyponatremia correction
- Renal or hepatic disease
- Severe vomiting & diarrhea
- CHF
- SIADH
CFS & Pathogenesis of Central Pontine Myelinolysis
Acute b/l paralysis
Unknown pathogenesis
Thiamine Deficiency Encephalopathy
“Wernicke Encephalopathy”
- Abrupt onset
RFs of Thiamine Deficiency
- Chronic alcoholism
- Gastric disorders
CFs of Thiamine deficiency
TRIAD of
- Encephalopathy & confusion
- Ocular palsies
- Ataxia
Treatment of Thiamine deficiency
Thiamine administration (early) - Delayed treatment can cause irreversible memory disturbances "Korsakoff's syndrome", no new memories & confabulations
Pathological features of Thiamine Deficiency
Foci of hemorrhage & necrosis in mamillary bodies, thalamus & peri-aqueductal gray matter
Neurological manifestation of Alcohol
- Peripheral neuropathy
- Cerebellar degeneration
- Seizures (withdrawal syndrome)
- Wernicke-Korsakoff syndrome - Thiamine deficiency
