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Pathology 3 > alcohol and dymyelination > Flashcards

alcohol and dymyelination Flashcards

1
Q

alcohol metabolism

A

predominantly in the liver but also in the brain
3 major pathways
- alcohol dehydrogenase-aldehyde dehydrogenase
- microsomal ethanol oxidising system
- catalase

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2
Q

acute effects of alcohol

A

depressant
subcortical structures affected modulating cerebral activities
disordered cortical, motor, intellectual behaviour (including hippocampus - memory)
higher alcohol levels - cortical neurones then lower medullary centres depressed including respiratory centre - respiratory arrest

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3
Q

chronic affects of alcohol

A 
thiamine deficency 
- peripheral neuropathies 
- wernickle-korsakoff 
cerebral atrophy 
cerebellar degeneration 
optic neuropathy
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4
Q

primary CNS effects

A

alcohol related brain damage ARBD
direct alcohol toxicity
intoxication
chronic toxicity

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5
Q

secondary CNS effects

A

nutritional deficiencies - thiamine
malnourishment - central pontine myelinolysis
liver disease (hepatic encephalopathy)
increased risk of infection
increased incidence trauma
exacerbates hypertension, diabetes mellitus
interferes with metabolism and therapeutic action of various medications

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6
Q

other neurological effects of alcohol

A 
skeletal muscle (type 2 fibre atrophy) 
peripheral nerve (polyneuropathy)
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7
Q

major targets of alcohol in mature brains

A

supporting cells
glia - astrocytes, oligodendrocytes
and synaptic terminals

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8
Q

alcohol in developing brains

A

neurotoxic and teratogenic effects

impairs neuronal and glial function, disrupts neuronal survival, neuronal migration, glial cell differentiation

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9
Q

acute alcohol poisoning

A

ingestion of large quantities of alcohol can lead directly to death from cardiorespiratory paralysis
haemorrhage (thalamic, brainstem) due to systemic hypertension, altered cerebral arterial tone
acute neuronal necrosis (thalamus, seletcive cortex, cerebellum) due to neurotoxicity, hypoxic-ischaemic injury

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10
Q

acute alcohol intoxication/poisoning at autopsy

A

cerebral oedema at autopsy, +- haemorrhages

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11
Q

lethal levels of alcohol

A

> 450-500mg/dL potentiall lethal

1 glass wine blood level 20-30 mg/dL

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12
Q

fetal alcohol spectrum disorder

A

ethOH consumption in pregnancy can cause a variety of CMS abnormalities
ranges from gross morphological changes with intellectual delay (FAS) to more subtle cognitive and behavioral disorders (FAE - fetal alcohol effect), including ADHD spectrum and learning disorder
commonest toxin related malformation syndrome
probably more common cause of intellectual delay than down syndrome or fragile X syndrome

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13
Q

FASD and stage of exposure

A

early embryogenesis - miscarriage, affects survival and proliferation of progenitor cells = microcephaly
7-20 weeks GA - affects neuronal migration = reduces neuronal populations cortex, basal ganglia
3rd trimester - dissrupts the crucial late gestation brain growth spurt = apoptosis of brain cells throughout cerebrum, altered cerebellar development

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14
Q

microcephaly

A

most common abnormality
other changes include - hydrocephalus, agenesis of corpus callosum, structural abnormalities hippocampus, neuronal migration disorders, disproportionate frontal lobe size reduction

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15
Q

structural alcohol abnormalities of FAS

A 
small palebral fissures 
low nasal bridge 
flat midface 
underdeveloped jaw 
microcephaly 
epicanthal folds 
smooth philtrum
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16
Q

alcohol-related vitamin deficiencies

A
  • thiamine B1
  • niacin B3
  • pyridoxine B6
  • cobalamin B12
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17
Q

niacin deificency

A

pelagra
dementia, dermatitis (in sun exposed areas), diarhhoea, depression
peripheral neuropathy
treatment - nicotinic acid suppliment

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18
Q

thiamin deficiency

A

beri berii
poor nutritional intake
alcohol impairs absorption and utilisation of thiamine

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19
Q

with alcohol, thiamine deficiency in the brain leads to

A 
selective reduction in neurotransmitter levels 
selective neuronal loss 
white matter (myelin) degeneration 
microvascular damage predisposition to life threatening thalamic and brainstem haemorrhages
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20
Q

wernickle-korsakoff syndrome

A

thiamine deificiency
malnourished chronic alcoholics longstanding thiamin dificiency
excessive vomitng
malabsorbtion due to GIT disease
disseminated malignancy (esp. leukaemia and lymphoma)
acute - wernickle’
chronic - korsakoff psychosis pahses

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21
Q

wernicke syndrome

A

triad - confusion, ataxia, abnormal eye movements
affects mamillary bodies, walls of 3rd ventricle, anterior nucleus of thalamus, periaqueductal tissues of midbrain and floor of 4th ventricle
changes restricted to MB in less fulminant cases

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22
Q

acute wernicke encephalopathy

A

brain normal externally
vascular engorgement and haemorrhages in affected areas
micro changes depend on duration and severity

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23
Q

micro changes in wernicke encephalopathy

A

acute - rarefaction of neuropil and haemorrhage but preservation of neurons and axons
subacute - hyperplasia of capillary endothelial cells
chronic - loss of myelin in central portion of MB, gliosis, hemosiderin deposition

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24
Q

korsakoff psychosis

A

amnestic syndrome
usually secondary to wernicke encephalopathy
thought to be due to structural abnormalities in the dorsomedial nucleus of the thalamus
normal temporal sequence of established memory is disrupted patient beings to confabulate
high morbidity

25
Q

symptoms of korsakoff syndrome

A

severe irreversible loss of short term memory
inability to learn and later new information
confabulation
no clouding of conscousness
no general impairment of other cognitive function

26
Q

alcoholic dementia

A

more common in middle aged people
chronic alcoholics show neuropsychological impairment with imaging changes of atrophy
- spectrum from mild cognitive imapirment to dementia
- cerebral atrophy (periventricular, ventromedial) and ventricular enlargment at autopsy
- atrophy may be due to reduction in vlume of deep white matter rather than loss of gray matter

27
Q

reversibility of alcoholic dementia

A

some reversibility with abstinence, less marked with increased chronicity of drinking
changes +- due to nutrtional deficiencies rather than direct ressult of alcohol - particularly thiamine deficiency

28
Q

chronic toxicity - ARBD

A 
alcohol related brain dysfunctioon 
cerebral atrophy 
- 70g mean reduction in brain wieght 
white matter reduction 
neuronal looss - superior frontal lobe 
subcortical loss in the region of the hypothalamus 
cerebellar atrophy
29
Q

alcoholic cerebellar degeneration

A

about 1% of chronic alcohol exposure
truncal ataxia, unsteady gait, nystagmus
most common form of acquired ataxia in alcoholic patients
may be a sequel of wernicke syndrome
M > F
selectve atrophy of anteror portion of superior vermis of cerebellum

30
Q

alcoholic cerebellar degeneration microscopically

A

loss of purkinje cells, variable loss of granular cells and associated reactve proliferation of bergmann astrocytes and gliosis of molecular layer

31
Q

neuromuscular complications of alcohol

A

alcohol-related peripheral neuropathy

alcoholic myopathy

32
Q

alcohol related peripheral neuropathy

A

initially sensory, later also motor and autonomic
distal-predominant polyneuropathy
axonal degeneration +- demyelination
exacerbated by Vit B1 (thiamine), B3 (niacin), B6 (pyridoxine), or B12
alcohol also causes attenuation of small ntraepithelial nerve fibres

33
Q

alcoholic myopathy

A

most prevalent skeletal muscle disorder in western hemisphere
40-60% alcohol abusers
30% reduction in muscle mass, worse with duration and severity of alcohol exposure
pathology - selective type 2muscle fibre atrphy
occurs independant of nutritional state, vitamin defs

34
Q

demyelination

A

selective loss of the myelin sheath of a nerve fibre with preservation of the axon
excludes - disorders of myelin formation during development (leukodystrophies), loss of both axon and myelin sheath eg. infarction
results in coordination failure or slowing of conduction

35
Q

demyelination result in

A

coordination failure or slowing of conduction

36
Q

role of myelin

A

electrical insulator

  • reduce axon capacitance
  • increases resistance across axolemma
  • slatatory conduction
37
Q

disorders of myelin

A

demyelination

  • autoimmune, viral, toxin, drugs
  • abnormal myelin formation, leukodystrophies, dysmyelinating diseases
38
Q

primary causes of demylinating diseases

A

parimary - MS, acute disseminated encephalomyelitis, acute heamorrhagic leukoencephalopathy

39
Q

secondary causes of demylinating diseases

A

viral - progressive multifocal leukoencephalopathy (PML) (JC virus), HTLV-1 associated myelopathy
metabolic/nutritional - central pontine myelinolysis, marchiafava-bignami disease, mitochondral disease, subacute combined degeneration of the spinal cord (vit B12 deficiency
toxc - methotrexate, carbon monoxide, solvent abuse

40
Q

detecting demyelination

A

neuroimaging - MRI
visual evoked responses - demyelination slows conduction
macroscopic - white matter loses white appearance and becomes grey in colour
microscopic - luxol fast blue stain or immunohistochemistry for myelin proteins

41
Q

excluding infacrction in detecting demyelination

A

loss of myelin alone s not diagnostic - need to demonstrate preserved axons (slver sstain or IHC) to distinguish from other process eg. infarction

42
Q

multiple sclerosis

A

autoimmune, episodic, activity separated in time, lesions separated in space
commonest demylinating disease of the CNS
autpommune response against components of the myeline sheath

43
Q

appearance of MS

A

well circumscribed foci of demyelination (plaques) are distributed throughout the CNS
loss of apparently normal myelin sheaths with relative axonal sparing

44
Q

etiology of MS

A
  1. genetic factors
  2. environmental factors eg. highest prevalence at higher altitudes
  3. viruses - exposure to childhood voral infections may act as a trigger
  4. immunological factors - autoimmune disorder
45
Q

clinical features of MS

A

focal lesions in CNS eg. optic neurits
peak onset 20-40 years, very uncommon n childhood or > 60 years
F > M
chronic disease with variable and unpredictable course

46
Q

prognosis of MS

A

early years characterised by relapses followed by remission with recovery of function
later years often progressive deterioraton leading to irreversible disability
correlation between site of plaques and clinical signs and symptoms

47
Q

pathology of MS

A

weel circumscribed areas of gray discolouration withn the white matter (plaques)
usually numerous and scattered throughout CNS
most common sites - periventricular, deep cerebral white matter, interface between cortex and white matter and optic nerves and chiasm
variable in size 2-10mm in diameter
plaques also occur in grey matter but are difficult to detect macroscopically - best seen with IHC

48
Q

quality of plagues in MS

A

2-10mmoccur in grey matter but are difiicult to detect macroscopically

49
Q

CSF findings of MS

A

midly elevated protein
increased immunoglobulin levels, esp IgG
oligoclonal bands on protein electrophoresis
possible increased cell count (lymphocytosis
prossible breakdown products of myelin

50
Q

variants of MS

A 
classiic or chronic MS (charcot type) - relapses and remissions in early years aften followed by progressive disability in later years 
acute M (marburg type) - rapidly progressive disease which is fatal within months
51
Q

3 types of plaques

A

acute plaques
chronic (burnt out) plaques
shadow plaques

52
Q

acute plaques

A

extensive active dymylination
less well demarcated
macrophages containing phagocytosed myelin sheath debris
some indirect axonal damage at plaque margin (axonal swellings on APP immunohistochemistry)
lymphocytes and plasma cells
abundant reactive astrocytes

53
Q

post-viral autoimmune reactions to myelin

A

acute onset, monophasic

  1. acute disseminated encephalomyelitis ADEM
  2. acute necrotising haemorrhagic encephalomyelitis/leukoencephalitis AHL
54
Q

acute disseminated encephalomyelitis ADEM

A

rare monophasic self limiting disorder
onset 7-10days after non-specific URTI or other viral infectoin eg. measles, mumps, varicella or rubella
rarely follows immunisation (older vaccines which contained CNS antigens in their preparation)
immune mediated demyelination due to production of Ab which cross react with CNS myelin proteins
fatal up to 20%, rest compete recovery

55
Q

ADEM pathology

A

multifocal perivanous demyelination and inflammation scattered througout white matter
macro - oedema and vacular congestion n acute phase
micro - widespread cuffing of small blood vessels by lymphocytes and macrophages with a small perivascular region of oedema and demyelination

56
Q

acute haemorrhagic leukoencephalopathy AHL

A

very rare, young adults and children
petechial haemorrhages througout white matter
+- fibrinoid necrosis of small bllood vesselss with perivascular haemorrhages
perivascular demyelination +- axonal damage
rapidly progressve and usually fatal
hyperacute variant of ADEM

57
Q

central pontine myellinolysis

A

osmotic demyelination syndrome
symmetrical demyelinatng lesion in the centre of the pons
usually surrounding rim of preserved myelin
demyelination may extend through brainstem in a rostral or caudal direction
axons preserved (distinguishes from infarct)
due to metabolic derangement - specifically associated with rapid iatrogenic correction of hyponatreamia
monophasic disorder which is often fatal

58
Q

other causes of central pontine myelinolysis

A
  • thiamine deficiency

- alcohol with drawal

59
Q

prognosis of central pontine myelinolysis

A

mortality +- 30%
survivors often have severe motor dsabilities
extrapontine myelinolysis
- basal ganglia, thalamus, deep cortex, tips of cerebellar folia

Pathology 3 (11 decks)

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