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Pathology of Demyelinating Diseases Flashcards

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1
Q

What stain is used for myelin?

A

Luxol Fast Blue

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2
Q

Define Demyelination

A

loss of myelin sheath surrounding axons of nerves, with relative preservation of the axons. Can affect nerves of CNS and PNS

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3
Q

What causes demyelination?

A

damage to myelin sheath and the cells that produce the myelin

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4
Q

What is the functional importance of myelin?

A

crucial for proper nerve conduction

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5
Q

How is neuronal function affected by loss of myelin?

A

interruption of nerve transmission leading to neurological deficits

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6
Q

What is the most common demyelinating disorder?

A

Multiple Sclerosis

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7
Q

What is a vascular cause of demyelination?

A

Binswanger disease

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8
Q

What are autoimmune causes of demyelination?

A
  1. MS
  2. Acute Disseminated encephalomyelitis [ADEM]
  3. Guillain Barre Syndrome
  4. Chronic Inflammatory Demyelinating polyneuropathy
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9
Q

What is an infectious cause of demyelination?

A

Progressive Multifocal Leukoencephalopathy

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10
Q

What are metabolic causes of demyelination?

A
  1. CO poisoning
  2. Vitamin B12 deficiency
  3. Mercury poisoning
  4. Central pontine myelinolysis
  5. Hypoxia
  6. Radiation
  7. Alcohol
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11
Q

What clinical findings are suggestive of a primary demyleinating disorder?

A
  1. Diffuse/Multifocal neurological deficits
  2. Sudden/Subacute onset in young adults
  3. Onset after infection/vaccination
  4. Deficits that wax and wane
  5. Specific [unexplained optic neuritis, Ophalmoplegia]
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12
Q

What is neuromyelitis Optica?

A

A syndrome with synchronous bilateral optic neuritis and spinal cord demyelination

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13
Q

Describe the lesions seen in Neuromyelitis Optica

A
  1. Necrosis
  2. Inflammatory infiltrate
  3. Vascular deposition of immunoglobulin and complement
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14
Q

What would investigations of Neuromyelitis Optica reveal?

A
  1. Presence of a pathogenic antibody
  2. Areas of demyelination show loss of aquaporin 4
  3. WBC and Neutrophils in CSF
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15
Q

Epidemiology of Neuromyelitis Optica

A
  • More prevalent in women
  • poor recovery
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16
Q

What is Acute Disseminated Encephalomyelitis (ADEM)\?

A

Diffuse demyelinating disease that follows viral infection or immunization

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17
Q

What is the pathophysiology of Acute Disseminated Encephalomyelitis (ADEM)?

A

possibly an acute autoimmune reaction to myelin

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18
Q

Describe the clinical presentation of Acute Disseminated Encephalomyelitis (ADEM)

A
  1. Symptoms develop 1-2 weeks after viral infection or immunization
  2. Rapid clinical course, with most patients recovering completely
  3. Mortality is 20%
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19
Q

What is similar to Acute Disseminated Encephalomyelitis (ADEM)?

A
  • Lesions similar to those induced by immunization of animals with
    • Myelin components
    • Rabies vaccines prepared from brains of infected animals
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20
Q

What is the prognosis of Acute Necrotizing Hemorrhagic Encephalomyelitis?

A
  • Causes severe damage
  • usually fatal
  • Significant neurological deficits in survivors
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21
Q

Describe the histological appearance of ADEM and Acute Necrotizing Hemorrhagic Encephalomyelitis?

A

Hemorrhage and inflammation in lesion

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22
Q

Epidemiology of Acute Necrotizing Hemorrhagic Encephalomyelitis?

Study These Flashcards
A

In children and young adults, following a URTI

23
Q

What is associated with Central Pontine Myelinolysis?

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A

Severe electrolyte disturbance
Osmolar imbalance

24
Q

What is the clinical presentation of a patient with Central Pontine Myelinolysis?

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A
  • Rapid clinical presentation
  • Quadriplegia
  • Severe long-term deficits
  • Locked in syndrome

syndrome arises 2-6 days after rapid correction of hyponatremia

25
Describe the appearance of Central Pontine Myelinolysis?
Symmetric loss of myelin in the base of the pins and portions of the pontine tegmentum
26
Pathophysiology of Central Pontine Myelinolysis
damaged oligodendrocytes [due to rapid increase in osmolarity], with preserved neurons and axons. [no inflammation]
27
What's is the clinical term for Central Pontine Myelinolysis?
Osmotic demyelination syndrome
28
Progressive multifocal leukoencephalopathy (PML)
reactivation of JC virus in oligodendrocytes of immunocompromised patient [HIV1/2, etc.]
29
Describe the morphology of Subacute combined degeneration of spinal cord
Loss of myelin in posterior and lateral columns
30
Describe the clinical presentation of a patient with Subacute combines degeneration of Spinal cord
* Progressive sensory abnormalities * Ascending paresthesias * Weakness * Ataxia * Loss of sphincter control * Gait impairment * Megaloblastic anemia
31
What is the pathophysiology of Subacute combined degeneration of the spinal cord?
Vitamin B12 deficiency Accumulation of methylmalonyl CoA causes a decrease in myelin synthesis
32
What is the cause of tabes dorsals?
Trypanosoma pallidum [as a manifestation of tertiary syphilis]
33
Describe the morphology of Tabes dorsalis
Demyelination of dorsal column of spinal cord, with no inflammatory reaction and absence of Trypanosoma pallidum
34
Etiology of Hypoxic-ischemic demyelination
Severe small vessel disease: • Hypertension • Diabetes • Old age Global brain hypoxia: • Cardiac arrest • Asphyxia • Drug overdose
35
What structures are affected in Hypoxic-ischemic demyelination?
Globus pallidus + white matter
36
What is the presentation of Hypoxic-ischemic demyelination?
Acute: • Headache, Myalgia, Dizziness, Coma • Psychological impairment Chronic: • Delayed personality changes, Cognitive deficit, Dementia, Parkinsonism.
37
What is the morphology of Hypoxic-ischemic demyelination??
Acute: • Cherry red discoloration of white matter Chronic: • Necrosis of globus pallidus • Demyelination of white matter
38
How does hypoxia affect the brain?
ussually causes necrosis, but if it primarily affect the oligodendrocytes then we'd have demyelination
39
List the Peripheral Nervous System Demyelination Disorders
1. Acute Inflammatory Demyelinating Polyradiculoneuropathy 2. Chronic Inflammatory Demyelinating Polyradiculoneuropathy 3. Anti-Myelin Associated Glycoprotein (MAG) Neuropathy 4. POEMS Syndrome 5. Charcot Marie Tooth Disease
40
Describe the clinical presentation of a patient of GBS
Ascending Symmetric Weakness and paresthesias Weakness maximal at 3 to 4 weeks then resolves. Loss of deep tendon reflexes Sphincters spared
41
What is the most common cause of acquired inflammatory neuropathy?
GBS
42
What is the etiology of GBS?
Unknown etiology, but possibly autoimmune as it starts 5-21 days after infection, surgery and vaccination
43
What is the most common hereditary neuropathy?
Charcot marie tooth disease [Type 1 and Type X]
44
What is the pathophysiology of Chronic Inflammatory Demyelinating polyradiculoneuropathy?
T-cell mediated or humoral immunity
45
Anti-Myelin Associated Glycoprotein (MAG) Neuropathy
Associated with IgM monoclonal gammopathy against MAG (transmembrane glycoprotein)
46
What environmental factors are associated with MS?
Geographic variation role of low vitamin d level
47
What genetic factors are associated with MS?
Higher incidence in first degree relative and affected monozygotic twins Strong association with DR haplotype of MHC Association with IL-2 and IL-7 receptor genes Associations with genes encoding proteins involved in the immune response
48
What is MS?
autoimmune demyelinating disorder characterized by distinct episodes of neurologic deficits that are separated in time and are attributable to patchy white matter lesions that are separated in space
49
Describe the gross appearance of MS lesions
Multiple well circumscribed lesions with sharp border. lesions are firmer than surrounding white matter
50
Where would MS lesion be found?
adjacent to lateral ventricles Corpus callous Optic nerves and chiasm Brainstem fibers SC
51
What is the immune mechanism in MS?
TH1 secrete IFNγ, which activates macrophages TH17 promote recruitment of leukocytes activated leukocytes and their chemical products cause demyelination
52
What inflammatory cells are found in MS plaques?
Macrophages, T-Lymphocytes [CD4+, CD8+ [few]]
53
What is the microscopic morphology of MS lesions?
o Active plaque: § Myelin absent § Macrophages and lymphocytes § Centered on small veins § Axons relatively preserved o Inactive plaques § No inflammatory infiltrate § Loss of myelin § Reactive gliosis § Damage to axons
54
What findings are found in the CSF of a patient with MS?
Elevated protein Normal glucose Lymphocytes Macrophages Plasma cells Increased IgG Oligoclonal IgG bands on immunoelectrophoresis

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