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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
what is the pathology of degenerative diseases
simple neuronal atrophy and subsequent gliosis
26
what is dementia
an acquired and persistent generalised disturbance of higher mental functions in an otherwise fully alert person
27
where do neurodegenerative diseases typically affect
functionally related neuronal groups
28
is dementia part of the normal ageing process
no
29
what are the primary dementias
alzheimers lewy body picks disease (fronto-temporal dementia) huntingtons
30
what are the secondary dementias
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
what are the most common subtypes of dementia
alzheimers vascular lewey body frontotemporal (picks)
32
what is the epidemiology of alzheimers
``` 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
what happens to symptoms of alzheimers when onset later
is more severe
34
what is the presentation of alzherimers
insidious impairment of higher intellectual function with alterations in mood and behaviour
35
what are the late features of alzheimers
progressive disorientation, memory loss, aphasia = indicates severe cortical dysfunction profound disability, muteness and immobility
36
what causes death in alzheimers
secondary cause e,g, bronchopneumonia
37
what is the pathology of alzheimers
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
what parts of brain are spared in Alzheimers
occipital lobe, brainstem, cerebellum
39
what are the microscopic features of alzheimers
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
what is the importance of amyloid Abeta in alzheimers
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
what do Abeta oligomers activate
NMDA receptors causing excitotoxicity which causes neuronal damage in alzheimers
42
what are the histological features of amyloid angiopathy
extracellular eosinophillic accumulation polymerised beta pleated sheats formed by Abeta stains with congo red disrupts BBB- serum leaking, oedema, local hypoxia
43
what are the clinical features of lewy bodies dementia
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
what are the clinical features of parkinsonism
Loss of facial expression, stooping, shuffling gait, slow initiation of movements, stiffness and pill rolling tremor
45
what conditions do you get parkinsonism in
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
what are the pathological features of lewy bodies dementia
degeneration of the substantia nigra - pallor
47
what is seen microscopically in lewy bodies dementia
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
what are the clinical features of huntingtons disease
``` 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
what is the inheritance pattern of huntingtons
AD | on chromosome 4P (additional CAG repeats- disease penetrant when >35 repeats)
50
what is seen pathologically in huntingtons
atrophy of basal ganglia, caudate nucleus and putamen cortical atrophy occurs later compensatory expansion in the ventricles
51
what is seen histologically in huntingtons
simple neuronal atrophy | pronounced astrocytic gliosis
52
what is fronto-temporal dementia
(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
what are the symptoms of fronto-temporal dementia
personality and behavioural change speech and communication problems changes in eating habits reduced attention span duration of disease usually 2-10 years
54
what is seen pathologically in fronto-temporal dementia
extreme atrophy of cerebral cortex in frontal the temporal lobes neuronal loss and gliosis
55
what is seen histologically in fronto-temporal dementia
``` pick cells (swollen neurones) intracytoplasmic filamentous inclusions (picks bodies) ```
56
what is multi-infarct dementia (MID)
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
who gets MID
men middle age hypertensives >60s
58
why are patients with MID so prone to depression and anxiety
as have insight- aware of their mental deficits
59
how do you distinguish MID from alzheimers
abrupt onset stepwise progression history of hptx or stroke evidence of stroke will be seen on CT/ MRI
60
what are the pathological findings of MID
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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