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91 Cards in this Set

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  • Back
how are axons damaged in demyelinating diseases?
they are relatively spared - myelin is the element prevalently affected
what part of the nervous system has more capacity for regenerating myelin?
CNS regeneration is more limited than the PNS
what is the commonest acquired myelin disease?
MS, by far
how common are inherited myelin diseases?
rare
what are inherited myelin diseases called?
leukodystrophies
what is the underlying problem in leukodystrophies?
inborn errors of metabolism
MULTIPLE SCLEROSIS
what is the incidence of MS in the US?
1 in 1000
what is the female to male ratio?
2 to 1
what ages can onset of MS occur, and what is most common?
most common onset in young adulthood, but can occur at any age
is PNS myelin, CNS myelin, or both affected?
CNS myelin only - essentially a disease of CNS white matter
can gray matter be involved?
yes - lesions can extend into gray matter, which is traversed by myelinated fibers
what type of immune response attacks myelin sheath components in MS?
cellular immune response
what particular cells appear to initiate this immune response?
CD4+ Th1 T cells
what were these cells mentioned to secrete?
macrophage-activating cytokines
what directly causes demyelination?
activated macrophages and their products
what is the lesion of MS called?
a plaque
what are sites of predilection for MS plaques (5)?
1) optic nerve/chiasm; 2) periventricular white matter of cerebrum; 3) brain stem; 4) cerebellum; 5) spinal cord
what types of plaques are there (3)?
1) active (acute); 2) inactive; 3) shadow plaque
what type of plaques have sharply defined borders?
active and inactive plaques - shadow plaques have poorly defined border
what type of plaques have an infiltrate?
active plaque only
what is the infiltrate composed of (2)?
1) lymphocytes (mainly CD4+, some CD8+); 2) macrophages
what type of plaques have decreased oligodendrocytes?
active and inactive plaques both have decreased oligodendrocytes
what type of plaques has active breakdown of myelin sheaths (demyelination)?
active plaques
are there lymphocytes and macrophages in inactive plaque?
no
what is the amount of myelin like in inactive plaque?
absent or severely depleted
what are axons like in inactive plaques?
substantially decreased
what are myelin sheaths like in shadow plaques?
abnormally thin myelin sheaths present, particularly at periphery
what is status of myelination interpreted as in shadow plaques?
either incomplete demyelination or as remyelination
what are frequent symptoms of MS (7)?
1) visual impairment; 2) weakness in extremity; 3) abnormal sensation in extremity; 4) dysarthria (slurring of speech); 5) ataxia; 6) vertigo; 7) urinary symptoms (frequency/urgency/incontinence)
what visual impairments are mentioned (4)?
1) diplopia; 2) blurring; 3) decreased acuity; 4) field defects
in what % of patients is optic neuritis the presenting feature?
15 to 20% of MS patients
in what % of MS patients does optic neuritis occur at some time during disease?
50%
is it always associated with MS?
no
what % of patients with an episode of ON go on to develop MS (range)?
10 to 50%
what fraction of patients with ON have normal ophthalmoscopic exam (optic disc appears normal) and what is this called?
two thirds - this is called retrobulbar neuritis
what does the optic disk look like in the other one third, and what is this called?
one third have optic disc swelling (mild and diffuse) - this is called papillitis
what other problem can be seen in the eyes of people with MS?
bilateral internuclear ophthalmoplegia (BINO)
what does BINO reflect a lesion in?
MLF (medial longitudinal fasciculus)
what happens on lateral gaze (2)?
1) abduction nystagmus; 2) adduction paresis
what is the course of disease like in multiple sclerosis?
variable
what is the usual course of MS like?
recurring attacks (relapses) individually developing over days to weeks, with gradual remission
what happens over time?
permanent neurologic damage tends to accumulate
what aspects of MS were said to vary widely (2)?
1) timing and nature of relapses; 2) cumulative pattern of residual deficit
what type of diagnosis is made in MS?
clinical
what is the criteria for diagnosis (how many of what, and in who)?
two or more necessarily separate CNS lesions in a patient who has at least two episodes of neurologic symptoms of the kind seen in MS
what is the classical diagnostic criterion?
multiplicity in time and space
what is the diagnostic laboratory test for MS?
there is none
what is usually found in the CSF in MS (2)?
1) increased mononuclear cells (<5 cells); 2) increased IgG with oligoclonal bands
what is not found in the CSF in MS, and makes diagnosis of MS unlikely if present?
PMN
what are oligoclonal bands?
a small number of discrete bands in gamma region on electrophoresis
what results of electrophoresis in the CSF and serum lend support to the clinical diagnosis of MS (2 conditions)?
OCB in the CSF in the absence of identical bands in the serum
in what certain location is IgG synthesized in MS that is abnormal?
within the CNS
what is necessary to exclude a systemic origin of the OCB?
paired serum sample (to show that the serum does not have the OCB)
in what % of MS patients is OCB eventually demonstrable?
eventually in 75-90% of patients
in what stage of MS may OCB be absent?
in the beginning (even though it will eventually demonstrate)
what pattern do increases in CSF IgG follow in MS?
variable - multiple determinations on same patient are often necessary to demonstrate IgG
what were a few patients with definite MS said to have, as far as CSF, Ig, and OCBs?
normal CSF immunoglobulins, but lack oligoclonal bands
in what other diseases may OCB be present (list)?
various CNS diseases - viral infections, spirochetal infections, cryptococcal meningitis, Guillian-Barre syndrome, meningeal carcinomatosis, GBM, Burkitt's lymphoma, others
what is the most sensitive means of detecting additional "silent" CNS lesions in MS?
MRI scan
what type of testing may detect slowed or abnormal conduction in visual, auditory, somatosensory, or motor pathways (providing evidence of a second lesion in a patient with a single clinically apparent lesion)?
evoked response testing
how much does the risk of MS increase in a first degree relative of someone with MS?
15 fold
CENTRAL PONTINE MYELINOLYSIS (CPM)
what is CPM characterized by (damage pattern and location)?
relatively symmetric demyelination in the center of the pons
what else does it occasionally involve?
the tegmentum
what is the main symptom of CPM?
rapidly evolving quadraplegia
what are the possible pathogenic factors of CPM (3)?
1) rapid correction of hyponatremia; 2) serum hyperosmolarity; 3) metabolic imbalance
what are predisposing conditions for CPM (3)?
1) alcoholism; 2) liver disease (especially following transplantation); 3) electrolyte/osmolar imbalance (various conditions)
what is the outcome of CPM like?
variable - may be fatal, but complete recovery is possible as well
GUILLAIN-BARRE SYNDROME (GBS)
what is another name for GBS?
acute inflammatory demyelinating polyradiculoneuropathy
what is GBS a disease of?
peripheral nervous system
how severe is it?
it can be life-threatening
what do 2/3 of cases follow?
an acute, influenza-like illness
what four organisms is there a significant epidemiologic association with?
1) C. jejuni; 2) CMV; 3) EBV; 4) M. pneumoniae
what is the pathogenic process behind GBS?
immunologic reaction
what areas are affected (2) by GBS, and what area is affected the most?
1) peripheral nerves; 2) craniospinal nerve roots; the area most severely affected is the cranial and spinal motor roots
what happens to these areas (2)?
1) inflammation; 2) demyelination
what is the main symptom of GBS, and how does it progress?
weakness beginning in the distal limbs and rapidly advancing to affect more proximal muscles
what is this phenomenon known as?
ascending paralysis
what is the main treatment for GBS?
supportive care (ventilation, respiratory care)
what else may be beneficial for GBS (2)?
1) plasmapheresis; 2) high-dose intravenous immunoglobulin (IV Ig)
what % have complete or near-complete recovery?
85%
what is one reason the recovery rate is so high?
the PNS has more capacity to regenerate myelin than the CNS
what causes death in GBR cases (3)?
1) respiratory paralysis; 2) autonomic instability/cardiac arrest; 3) complications of tracheotomy