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CNS > Pathology of Demyelinating Diseases > Flashcards

Pathology of Demyelinating Diseases Flashcards

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?

A

In children and young adults, following a URTI

23
Q

What is associated with Central Pontine Myelinolysis?

A

Severe electrolyte disturbance
Osmolar imbalance

24
Q

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

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

syndrome arises 2-6 days after rapid correction of hyponatremia

25
Q

Describe the appearance of Central Pontine Myelinolysis?

A

Symmetric loss of myelin in the base of the pins and portions of the pontine tegmentum

26
Q

Pathophysiology of Central Pontine Myelinolysis

A

damaged oligodendrocytes [due to rapid increase in osmolarity], with preserved neurons and axons. [no inflammation]

27
Q

What’s is the clinical term for Central Pontine Myelinolysis?

A

Osmotic demyelination syndrome

28
Q

Progressive multifocal leukoencephalopathy (PML)

A

reactivation of JC virus in oligodendrocytes of immunocompromised patient [HIV1/2, etc.]

29
Q

Describe the morphology of Subacute combined degeneration of spinal cord

A

Loss of myelin in posterior and lateral columns

30
Q

Describe the clinical presentation of a patient with Subacute combines degeneration of Spinal cord

A
  • Progressive sensory abnormalities
  • Ascending paresthesias
  • Weakness
  • Ataxia
  • Loss of sphincter control
  • Gait impairment
  • Megaloblastic anemia
31
Q

What is the pathophysiology of Subacute combined degeneration of the spinal cord?

A

Vitamin B12 deficiency
Accumulation of methylmalonyl CoA causes a decrease in myelin synthesis

32
Q

What is the cause of tabes dorsals?

A

Trypanosoma pallidum [as a manifestation of tertiary syphilis]

33
Q

Describe the morphology of Tabes dorsalis

A

Demyelination of dorsal column of spinal cord, with no inflammatory reaction and absence of Trypanosoma pallidum

34
Q

Etiology of Hypoxic-ischemic demyelination

A

Severe small vessel disease:
• Hypertension
• Diabetes
• Old age

Global brain hypoxia:
• Cardiac arrest
• Asphyxia
• Drug overdose

35
Q

What structures are affected in Hypoxic-ischemic demyelination?

A

Globus pallidus + white matter

36
Q

What is the presentation of Hypoxic-ischemic demyelination?

A

Acute:
• Headache, Myalgia, Dizziness, Coma
• Psychological impairment

Chronic:
• Delayed personality changes, Cognitive deficit, Dementia, Parkinsonism.

37
Q

What is the morphology of Hypoxic-ischemic demyelination??

A

Acute:
• Cherry red discoloration of white matter

Chronic:
• Necrosis of globus pallidus
• Demyelination of white matter

38
Q

How does hypoxia affect the brain?

A

ussually causes necrosis, but if it primarily affect the oligodendrocytes then we’d have demyelination

39
Q

List the Peripheral Nervous System Demyelination Disorders

A
  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
Q

Describe the clinical presentation of a patient of GBS

A

Ascending Symmetric Weakness and paresthesias
Weakness maximal at 3 to 4 weeks then resolves.
Loss of deep tendon reflexes
Sphincters spared

41
Q

What is the most common cause of acquired inflammatory neuropathy?

A

GBS

42
Q

What is the etiology of GBS?

A

Unknown etiology, but possibly autoimmune as it starts 5-21 days after infection, surgery and vaccination

43
Q

What is the most common hereditary neuropathy?

A

Charcot marie tooth disease [Type 1 and Type X]

44
Q

What is the pathophysiology of Chronic Inflammatory Demyelinating polyradiculoneuropathy?

A

T-cell mediated or humoral immunity

45
Q

Anti-Myelin Associated Glycoprotein (MAG) Neuropathy

A

Associated with IgM monoclonal gammopathy against MAG (transmembrane glycoprotein)

46
Q

What environmental factors are associated with MS?

A

Geographic variation
role of low vitamin d level

47
Q

What genetic factors are associated with MS?

A

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
Q

What is MS?

A

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
Q

Describe the gross appearance of MS lesions

A

Multiple well circumscribed lesions with sharp border.
lesions are firmer than surrounding white matter

50
Q

Where would MS lesion be found?

A

adjacent to lateral ventricles
Corpus callous
Optic nerves and chiasm
Brainstem fibers
SC

51
Q

What is the immune mechanism in MS?

A

TH1 secrete IFNγ, which activates macrophages
TH17 promote recruitment of leukocytes

activated leukocytes and their chemical products cause demyelination

52
Q

What inflammatory cells are found in MS plaques?

A

Macrophages, T-Lymphocytes [CD4+, CD8+ [few]]

53
Q

What is the microscopic morphology of MS lesions?

A

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
Q

What findings are found in the CSF of a patient with MS?

A

Elevated protein
Normal glucose
Lymphocytes
Macrophages
Plasma cells
Increased IgG
Oligoclonal IgG bands on immunoelectrophoresis

CNS (10 decks)

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