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Neurology > Demyelination and Dementia > Flashcards

Demyelination and Dementia Flashcards

1
Q

what is demyelination

A

preferential damage to the myelin sheath with relative preservation of axons

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2
Q

what is the role of myelination

A

Locally confining neuronal depolarisation
Protecting axons
Forming nodes of Ranvier (precipitate rapid saltatory conduction)

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3
Q

what cell myelinates

A

oligodendrocytes

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4
Q

what does myelin damage cause

A

disrupts neuronal conduction

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5
Q

what are the acute causes of demyelination

A
  • MS
  • acute disseminates encephalomyelitis
  • acute haemorrhagic leukoencephalitis
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6
Q

what are the secondary causes of demyelination

A 
viral 
-progressive mulitofcal leukoencephalopathy
metabolic insults 
-central pontine myelinosis
toxic
-CO, organic solvents, cyanide
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7
Q

what is the epidemology of MS

A

1/1000
F:M 2:1
peak incidence 20-30yrs
association with latitude

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8
Q

what is MS

A

auto immune demyelinating disorder characterised by distinct episodes of neurological deficits, separated in time and which correspond to spatially separated foci of neurological injury

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9
Q

what is needed for a clinical diagnosis of MS

A 
Two distinct neurological defects occurring at different times
A neurological defect implicating one neuro‐anatomical site, and a  MRI appreciated defect at another neuro‐anatomical site
Multiple distinct  (usually white matter) CNS lesions on MRI

Also supportive
Visual evoked potentials (evidence of slowed conduction)
IgG oligoclonal bands in CSF

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10
Q

what is seen on MRI in MS

A

areas of hyperintensity - plaques

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11
Q

what are the clinical features of MS

A

presentation typically with a focal neurological deficit

  • optic neuritis (unilateral vision loss painful)
  • spinal cord lesions (motor/ sensory deficit in trunk and limbs , spasticity, bladder dysfunction)
  • brain stem lesions (CN nerve signs, ataxia, nystagmus, internuclear ophthalmoplegia)

acute/ insidious onset
relapsing and remitting / progressive

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12
Q

what type of matter does MS principally affect

A 
white matter (axons)
cut surface of brain shows plaques, surface (grey) is normal
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13
Q

what do MS plaques look like

A

well circumscribed, well demarcated, irregular shaped, glassy
non anatomical and non symmetrical distribution

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14
Q

where in CNS typically gets plaques in MS

A 
adjacent to lateral ventricles
corpus callosum 
optic nerves and chiasm 
brainstem 
ascending and descending tracts 
cerebellum 
spinal cord
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15
Q

what is the histology of an active MS plaque

A

perivascular inflammatory cells
recruitment of microglia
ongoing demyelination

are yellow/ brown with ill defined edge

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16
Q

what is the histology of inactive plaques

A

gliosis
little remaining myelinating axons
oligodendrocytes and axons both reduced in numbers

grey/ brown well demarcated lesions, typically around lateral ventricles

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17
Q

what are shadow plaques in MS

A

reflects a degree of myelination

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18
Q

what are the risk factors for MS

A

lattitude
vit D deficiency
viral trigger? (EBV)
genetics- familial, HLA DRB1

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19
Q

what is the immune pathogenesis of MS

A

t cells

  • TH1 cells – IFN‐g activating macrophages
  • TH17 cells – recruiting and activating damaging leukocytes
  • lymphocytic infiltration

humeral factors
-oligoclonal IgG bands on CSF

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20
Q

why is MS classed as an immune mediated disease

A

Lymphocytic infiltration in histology
Oligoclonal IgG bands in CSF
Genetic linkage to HLA DRB1

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21
Q

what are the degenerative diseases of the cerebral cortex

A

alzheimers disease
pick disease
CJD (prion disease)

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22
Q

what are the main degenerative diseases of the basal ganglia and brain stem

A

parkinsons, huntingtons

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23
Q

what is a degenerative diseases of the spinocerebellar

A

spinocerebellar ataxias

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24
Q

what are the degenerative diseases of the motor neurones

A

MND

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25
Q

what is the pathology of degenerative diseases

A

simple neuronal atrophy and subsequent gliosis

26
Q

what is dementia

A

an acquired and persistent generalised disturbance of higher mental functions in an otherwise fully alert person

27
Q

where do neurodegenerative diseases typically affect

A

functionally related neuronal groups

28
Q

is dementia part of the normal ageing process

A

no

29
Q

what are the primary dementias

A

alzheimers
lewy body
picks disease (fronto-temporal dementia)
huntingtons

30
Q

what are the secondary dementias

A

other disorders that give rise to dementia:

  • multi infarct (vascular)
  • infection (HIV/syphilis)
  • trauma
  • metabolic
drugs and toxins (alcohol)
vit B12 def 
paraneoplastic syndromes 
intracranial SOL 
chronic hydrocephalus
31
Q

what are the most common subtypes of dementia

A

alzheimers
vascular
lewey body
frontotemporal (picks)

32
Q

what is the epidemiology of alzheimers

A 
F:M 2;1
1% in 60-65
40%+ in >85s
1% familial (amyloid precursor proteins presenilin 1 &2)
increased incidence in trisomy 21
33
Q

what happens to symptoms of alzheimers when onset later

A

is more severe

34
Q

what is the presentation of alzherimers

A

insidious impairment of higher intellectual function with alterations in mood and behaviour

35
Q

what are the late features of alzheimers

A

progressive disorientation, memory loss, aphasia = indicates severe cortical dysfunction

profound disability, muteness and immobility

36
Q

what causes death in alzheimers

A

secondary cause e,g, bronchopneumonia

37
Q

what is the pathology of alzheimers

A

decrease in size and weight of brain due to cortical atrophy - in frontal, temporal and parietal lobes

widening of sulci and narrowing of gyri

compensatory dilatation of the ventricles, 2ndary hydrocephalus ex vacuo

38
Q

what parts of brain are spared in Alzheimers

A

occipital lobe, brainstem, cerebellum

39
Q

what are the microscopic features of alzheimers

A

extensive neuronal loss with associated astrocyte proliferation - simple neuronal atrophy and gliosis

neurofibrillary tangles - esp in hippocampus and temporal lobe

neuritic plaques - Abeta amyloid plaques, surrounded by astrocytes and microglia

amyloid angiopathy

40
Q

what is the importance of amyloid Abeta in alzheimers

A

Abeta is produced by the cleavage of amyloid precursor protein APP (central element of neuritic plaques)

APP is on chromosome 21- early onset alzheimers in trisomy 21 (down s)

mutations of presenilin linked in familial alzheimers

apolipoprotein E- allele e4

41
Q

what do Abeta oligomers activate

A

NMDA receptors causing excitotoxicity which causes neuronal damage in alzheimers

42
Q

what are the histological features of amyloid angiopathy

A

extracellular eosinophillic accumulation

polymerised beta pleated sheats formed by Abeta

stains with congo red

disrupts BBB- serum leaking, oedema, local hypoxia

43
Q

what are the clinical features of lewy bodies dementia

A

progressive dementia
hallucinations
fluctuating levels of attention/ cognition (on day to day basis)
memory affected later than in alzheimers
features of parkinsonism present at onset or emerge shortly after

44
Q

what are the clinical features of parkinsonism

A

Loss of facial expression, stooping, shuffling gait, slow initiation of movements, stiffness and pill rolling tremor

45
Q

what conditions do you get parkinsonism in

A

ones where the nigro-striatial dopaminergic pathways are affected

  • parkinsons
  • lewy body dementia
  • drugs
  • trauma
  • multi system atrophy
  • progressive supranuclear palsy
  • cortico-basal degeneration
46
Q

what are the pathological features of lewy bodies dementia

A

degeneration of the substantia nigra - pallor

47
Q

what is seen microscopically in lewy bodies dementia

A

loss of pigmented neurones
reactive gliosis, microglial accumulation

remaining neurones may show lewy bodies
-Single / multiple intracytoplasmic, eosinophillic, round/ elongated bodies that have a dense core and a surrounding pale halo
(Aggregates of a‐synuclein and ubiquitin)

48
Q

what are the clinical features of huntingtons disease

A 
relentlessly progressive neuropsychiatric disorder 
onset usually 35-50 
emotional, cognitive and motor disturbance 
-chorea
-myoclonus 
-clumsiness 
slurred speech 
-depression 
-irritability 
-apathy

develop dementia later

49
Q

what is the inheritance pattern of huntingtons

A

AD

on chromosome 4P (additional CAG repeats- disease penetrant when >35 repeats)

50
Q

what is seen pathologically in huntingtons

A

atrophy of basal ganglia, caudate nucleus and putamen
cortical atrophy occurs later
compensatory expansion in the ventricles

51
Q

what is seen histologically in huntingtons

A

simple neuronal atrophy

pronounced astrocytic gliosis

52
Q

what is fronto-temporal dementia

A

(picks disease)
progressive dementia commencing in middle life (50-60s) characterised by progressive changes in character and social deterioration causing impairment of intellect, memory and language

53
Q

what are the symptoms of fronto-temporal dementia

A

personality and behavioural change
speech and communication problems
changes in eating habits
reduced attention span

duration of disease usually 2-10 years

54
Q

what is seen pathologically in fronto-temporal dementia

A

extreme atrophy of cerebral cortex in frontal the temporal lobes
neuronal loss and gliosis

55
Q

what is seen histologically in fronto-temporal dementia

A 
pick cells (swollen neurones)
intracytoplasmic filamentous inclusions (picks bodies)
56
Q

what is multi-infarct dementia (MID)

A

disorder involving a deterioration in mental functioning due to cumulative damage to the brain through hypoxia or anoxia as a result of multiple blood clots within the blood vessels supplying the brain

Successive, multiple cerebral infarctions cause increasingly larger areas of cell death and damage. When a sufficient area of the brain is damaged, dementia results.

57
Q

who gets MID

A

men
middle age hypertensives
>60s

58
Q

why are patients with MID so prone to depression and anxiety

A

as have insight- aware of their mental deficits

59
Q

how do you distinguish MID from alzheimers

A

abrupt onset
stepwise progression
history of hptx or stroke
evidence of stroke will be seen on CT/ MRI

60
Q

what are the pathological findings of MID

A

large vessel infarcts

  • more common
  • scattered through hemispheres
  • atheroma of large cerebral arteries provoke thromboembolsim

small vessel (lacuna) infarcts)

  • rarer
  • central, subcortical distribution
  • related to long standing hypertension and arteriosclerosis of small vessels

Neurology (35 decks)

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