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Demyelinating Diseases

demyelinating disease, p. 227

Terms

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Schwann cell
myelinates only ONE internode; loss -> segmental demyelination
secondary demyelinating disease
axonal injury is followed by loss of Schwann cells
central pontine myelinolysis
associated w/ RAPID correction of HYPONATREMIA -> rapidly evolving quadriplegia, CT lesions in basis pontis; symmetric demylination in pons
Progressive Multifocal Leukoencephalopathy
ill-defined extensive, multifocal lesions in cortical, cerebellar white matter; may involve entire lobe; lipid laden macros; fewer axons in center of lesions; inclusioned oligos at edges of lesions
spinal cord
second part of nervous system to get myelinated during development
multiple sclerosis
clinical features: optic neuritis (unilateral visual loss), brainstem (ataxia, nystagmus, CN signs), spinal cord (motor/sensory impairment of limbs, spasticity, incontinence); variable course over time
Krabbe's disease
clinical: onset b/t 3-6 months old; hyperirritability; exaggerated startle; stiffness, weakness; difficulty feeding; don't usually survive past 2 y.o.
leukodystrophies
disorders of dysmyelination; childhood onset; severe neurologic debilitation/motor incapacitation (earlier onset, more severe); symmetric degeneration or dysmyelination
shadow plaques
in MS, attempt at partial remyelination; thinned-out myelin sheaths at outer edges of plaque; ill-defined border
acute MS
aka Marburg form; in young people; fatal, fast course (months); no antecedent infection; large plaques, widespread myelin loss
neuromyelitis optica
aka Devic disease; bilateral optic neuritis; spinal cord involvement (gray matter); rapid, relentless progression in 20% of cases; lesions similar to MS plaques
Guillian-Barre Syndrome
Dx by: slowed nerve conduction velocity, clinical presentation, elevated CSF protein; treat w/ plasmapheresis, IVIG (eventual remyelination, recovery)
multiple sclerosis
distinct episodes of neurologic defects, separated in TIME, from white matter lesions separated in SPACE; HLA-DR2, 1st degree relatives -> greater risk
multiple sclerosis
autoimmune disorder; CD4+, CD8+ CMI, activate macrophages that attack myelin; also humoral immunity (elevated CSF Igs)
infantile, juvenile
forms of metachromatic leukodystrophy that are more severe; present w/ motor symptoms and progress to death w/in 5-10 years
Progressive Multifocal Leukoencephalopathy
viral encephalitis caused by reactivated virus; infects oligos (viral inclusions) and causes demyelination at gray-white matter interface; focal, progressive neurologic symptoms
Guillian-Barre Syndrome
macrophages activated by T cells -> strip myelin sheath from axon -> segmental demyelination widely distributed
Krabbe's disease
AR inheritance; failure of galactocerebrosidase, buildup of galactosylsphingosine (cytotoxic, injures oligos)
primary demyelinating disease
demyelination occurs by itself, without concurrent axonal loss
oligodendrocytes
myelinate internodes of SEVERAL axons; loss -> plaque in brain
Krabbe's disease
demyelination in CNS and PNS; aggregates of globoid cells (multinucleated giant cells) filled w/ cerebroside around vessels
multiple sclerosis
CSF: elevated protein, more IgGs, oligoclonal bands, more lymphos
central nervous system
last part of nervous system to get myelinated during development
adult
form of metachromatic leukodystrophy that has slower course; starts w/ cognitive/psych symptoms, followed by motor symptoms
multiple sclerosis
multiple, scattered, well-defined 'plaques' of gray discoloration in white matter (demyelination), esp. adjacent to lateral ventricles, optic nerves, optic chiasm, spinal cord, brainstem
secondary MS
initially relapsing-remitting, but eventually becomes progressive w/ each episode
metachromatic leukodystrophy
cortical demyelination, sparing of subcortical fibers; lipid-laden macrophages in white matter; vacuoles contain sulfatides, which dye funny
Guillian-Barre Syndrome
life threatening disease preceded by acute, flu-like illness (symptoms a few weeks later); offending organisms: C. jejuni, M. pneumoniae, CMV, EBV; secondary to immune response to infectious agent
primary MS
exacerbations with progression, little recovery from disease over time
active plaques
in MS, see inflammatory cells (esp. T cells) as perivascular cuffs, ongoing myelin breakdown w/ debris filled macrophages; preservation of axons, depletion of oligos; ill-defined
metachromatic leukodystrophy
AR inheritance; deficiency of arylsulfatase A, buildup of cerebroside sulfate
relapsing-remitting MS
episodes of focal neurologic deficits, followed by gradual remission; no clinical progression, no residual deficits; makes up 85% of MS
Guillian-Barre Syndrome
ascending paralysis (distal -> proximal); may progress to loss of respiratory muscle function; predominantly MOTOR loss, limited sensory involvement; axons intact/preserved, but poor conduction velocity
peripheral nerves
first part of nervous system to get myelinated during development
inactive plaques
in MS, little to no myelin, decreased oligos; less inflammatory infiltrate; astrocytic proliferation, gliosis; fewer axons; more well-defined

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