Disorders Of Myelin

Front 1

changes in nerve conduction due to demyelination

Back 1

higher amplitude and slower frequency
slower conduction velocity

Front 2

proteolipid protein (PLP), myelin basic protein (MBP), myelin-associated glycoprotein (MAG)

Back 2

CNS Myelin

Front 3

MAG, protein P0, no PLP

Back 3

PNS myelin

Front 4

made by oligodendrocytes, each of which forms 30-50 internodes

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CNS myelin

Front 5

made by Schwann cells, each of which forms one internode

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PNS myelin

Front 6

Conduction delay or block
Asynchrony of impulse transmission resulting in signal dispersion
Prolongation of refractory period
Failure These mechanisms results in negative symptoms or persistent neurologic deficits
of transmission of trains of impulses

Back 6

Consequences of demyelination

Front 7

the two categories of demyelination diseases

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Acquired disorders of myelin
Inherited metabolic diseases, also called leukodystrophies

Front 8

Multiple sclerosis and its variants
Acute disseminated encephalomyelitis (ADEM)
Acute hemorrhagic leukoencephalitis (AKA acute necrotizing hemorrhagic encephalomyelitis)
are types of:

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Immune-mediated aquired disorders

Front 9

Name the infectious agents associated with
Progressive multifocal leukoencephalopathy (PML)

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Polyomavirus (JC virus)

Front 10

Name the infectious agents associated with Subacute sclerosing panencephalitis (SSPE).

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measles

Front 11

Discuss the clinical context in which PML is usually encountered.

Back 11

Usually seen in immunocompromised patients

Front 12

Name the clinical state usually associated with central pontine myelinolysis (CPM).

Back 12

Usually due to rapid correction of chronic hyponatremia

Front 13

describe the role of vitamin B12 deficiency in the development of subacute combined degeneration of the spine cord.

Back 13

Cobalamin is an essential cofactor for methionine synthetase
Use to convert homocysteine  methionine
Methionine is the precursor of S-adenosyl-L-methionine (SAM)
SAM is the only methyl group donor in the nervous system.
Methylation is necessary to confer stability of the lamellar myelin.

Front 14

Decreased vascular density, especially in deep white matter in the brain, on MRI or CT; may be caused by demyelination, gliosis, or decreased perfusion.

Back 14

leukoaraiosis

Front 15

Describe the pathologic changes associated with small vessel disease causing dementia.

Back 15

Arteriolosclerosis induces small infarcts in the white matter.

Front 16

Inherited metabolic diseases
Usually spare subcortical U-fibers
Usually involve both CNS and PNS
Acquired demyelinating diseases typically involve only the CNS

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leukodystrophy

Front 17

autosomal recessive lysosomal storage disease; galactocerebrosidase deficiency.
Clinical syndrome of classic infantile form:
Normal neonatal development  onset at 3-6 months of irritability and with intensive crying; development ceases  violent tonic spasms to noise or bright light  deterioration of motor function with development of permanent opisthotonic posture (marked extension of head and body) with hypertonic flexion of extremities  myoclonus, optic atrophy; blindness  decerebrate posturing  death usually by 15 months

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Krabbe’s disease

Front 18

Galactocerebrosidase deficiency results in accumulation of
galactocerebroside in macrophages (globoid cells) which tend to cluster around blood vessels. Accumulation of psychosine, which is toxic to oligodendrocytes, results in demyelination which tends to spare subcortical U-fibers.

Back 18

Krabbe’s disease

Front 19

autosomal recessive lysosomal storage disease; arylsulfatase-A deficiency.

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Metachromatic leukodystrophy

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Late-infantile (< 2 years old) and intermediate forms tend to present with gait disorders and progressive loss of function; death in 5-10 years.
Juvenile form tends to present with behavioral and cognitive problems followed by gait disorder and progressive loss of function.
Adult form usually presents with psychosis and dementia.

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Metachromatic leukodystrophy

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X-linked; abnormality of very long chain fatty acid (VLCFA) metabolism

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Adrenal leukodystrophy

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seen in boys starting 5-9 years old with neurologic signs (behavioral disturbances, problems in school, progressive dementia, seizures, visual and hearing loss) preceding adrenal dysfunction (vomiting, diarrhea, hypotension).

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Adrenal leukodystrophy

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Rapidly progressive pyramidal, extrapyramidal, and cerebellar signs  vegetative state.
> 90% have abnormal adrenal function by ACTH stimulation testing.
Similar form with adolescent onset between 11-21 years old.

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Adrenal leukodystrophy

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preferential involvement of the more posterior white matter.

“Lorenzo’s oil” may help diminish severity of neurologic disability if given before the onset of symptoms

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Adrenal leukodystrophy

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characteristic inclusions in macrophages (linear structures). Inclusions may also be found in adrenal cortical cells, Schwann cells, and Leydig cells of testes.

Back 25

Adrenal leukodystrophy

Front 26

You can’t diagnose _____ from sections/slides from MS you have to look at the clinical symptoms

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ADEM

Front 27

Abrupt onset of neurological symptoms 2-30 days after and infection or vaccination.
Symptoms dependent on location of lesions – common: obtundation and depressed consciousness, unilateral or bilateral long tract signs, acute hemiparesis, ataxia. Meningismus may be seen. Seizures are more common in pediatric cases. May involved PNS.

Back 27

ADEM

Front 28

Hyperacute form of ADEM

Usually follows respiratory
Infection, e.g., Mycoplasma

Usually fatal

Necrosis of small vessels and
hemorrhage into surrounding
tissue

Back 28

Acute hemorrhagic leukoencephalitis