Acquired demyelinating diseases

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This is a brief video on non-hereditary demyleinating disorders.

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ADDITIONAL TAGS:
Acquired demyelinating diseases
Non-hereditary diseases in which normally-formed myelin degenerates as a result of insult on myelin or oligodendrocytes with preservation of the axons
Multiple sclerosis
Acute disseminated encephalo-
myelitis
Progressive multifocal leukoenceph-
alopathy
Leukoenceph-
alopathy associated
with AIDS
Central
pontine myelinolysis

Multiple sclerosis (MS)
Most common chronic CNS disorder in young adults (up to 1/1000)
Perivascular inflammation
Shows both acute and chronic lesions (polyphasic)
Acute: loss of oligodendrocytes; reactive astrocytes/macrophages
Chronic: fibrous astrocyte gliosis
Diagnosed with MRI and oligoclonal IgG bands in CSF (but not in serum)
RIGHT: abundant neutrophils and macrophages infiltrate where myelin is missing (top-left of image)
Distinct lesion edge
Multiple sclerosis
Acute disseminated encephalo-
myelitis
Progressive multifocal leukoenceph-
alopathy
Leukoenceph-
alopathy associated
with AIDS
Central
pontine myelinolysis

Acute disseminated encephalomyelitis (ADEM)
Resembles MS (sometimes called borderline form of MS)
Thought to follow viral infection (flu, MMR, herpes)
Perivenous inflammation
Loss of white matter to the vessels, histo shows macrophages
Monophasic lesions in white matter
Multiple sclerosis
Acute disseminated encephalo-
myelitis
Progressive multifocal leukoenceph-
alopathy
Leukoenceph-
alopathy associated
with AIDS
Central
pontine myelinolysis

Progressive multifocal leukoencephalopathy (PML)
Caused by the papovavirus JC virus
Most people have positive serology for JC (infected), with virus kept under control
Complication for immunocompromised patients (AIDS)
Early stage: multiple demyelination foci in white matter
Late stage: growing necrotic lesion involves cortex
Histo:
Macrophages engulfing myelin debris; not many other WBCs bc immunocompromised
Large, bizarre, transformed astrocytes
Enlarged oligodendroglial nuclei
Multiple sclerosis
Acute disseminated encephalo-
myelitis
Progressive multifocal leukoenceph-
alopathy
Leukoenceph-
alopathy associated
with AIDS
Central
pontine myelinolysis

Leukoencephalopathy associated with AIDS
Perivascular giant cells (multinucleated, with HIV antigens)
Release toxic cytokines that play role in pathogenesis
Causes AIDS dementia
Pallor of cerebral white matter (myelin degeneration not seen on histo)
Normal CT on left, AIDS brain on right
Multiple sclerosis
Acute disseminated encephalo-
myelitis
Progressive multifocal leukoenceph-
alopathy
Leukoenceph-
alopathy associated with AIDS
Central
pontine myelinolysis
LEFT:

RIGHT:
Public domain (government work)

Central pontine myelinolysis
Pathogenesis
Patients have chronic, severe hyponatremia (low Na)
Intracellular adaptations (cells pump out other osmoles) to compensate
Patients treated with saline to increase serum tonicity
Cells canâ€™t decompensate fast enough, causes shearing of the myelin cells
Predominantly iatrogenic
Demyelination is worse at base of pons (sometimes lateral geniculate bodies and internal/external capsules â†’ osmotic myelinolysis)
Multiple sclerosis
Acute disseminated encephalo-
myelitis
Progressive multifocal leukoenceph-
alopathy
Leukoenceph-
alopathy associated
with AIDS
Central
pontine myelinolysis
Pontine perivascular fibers hypointense to the rest of the pons