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Brain Disorders > Huntington's Disease > Flashcards

Huntington's Disease Flashcards

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1
Q

How common is HD in the caucasian population?

A

1/10,000 – 1/20,000
30-50 yrs

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2
Q

What is juvenile HD?

A

before 20yrs with behavioural disturbances & learning difficulties

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3
Q

How is HD inherited?

A

Autosomal dominant pattern of inheritance -> only need one mutated allele from a single parent

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4
Q

What is the mutation associated with HD?

A

expanded CAG trinucleotide repeat in HTT gene (chromosome 4) -> produces mutant huntingtin protein with an elongated polyglutamine tract

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5
Q

How much is the CAG repeat typically expanded?

A

10-35 times

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6
Q

What is anticipation?

A

the severity of the disease tends to increase and symptoms appear at an earlier age in successive generations.

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7
Q

What does the mutated huntingtin protein lead to?

A

Toxic effects on nerve cells
disruption of cellular processes
Formation of protein aggregates within cells

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8
Q

What are 5 motor symptoms of HD?

A

Chorea
Dysarthria
Dysphagia
Bradykinesia
Dystonia -> abnormal posture

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9
Q

What are 5 cognitive symptoms of HD?

A

Depression
Dementia
Seizures
Compulsive behaviour
Apathy

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10
Q

What brain region is the anatomical basis of chorea?

A

Basal ganglia

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11
Q

What part of the brain becomes enlarged in HD?

A

Frontal horns of lateral ventricles

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12
Q

Which brain regions become atrophied?

A

caudate and putamen

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13
Q

What brain regions degernate?

A

Frontal & temporal cortices

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14
Q

What are the 5 grade classifications of HD?

A

Grade 0 – clinical evidence but no gross or microscopic abnormalities
Grade 1 – moderate fibrillary astrocytosis at microscopic level
Grade 2 – macroscopic changes in caudate & putamen
Grade 3 – lateral segment of globus pallidus showing fibrillary astrocytosis
Grade 4 – shrunken caudate, widen anterior horn of lateral ventricle & smaller nucleus accumbens

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15
Q

What other changes are seen in stage 3 and 4?

A

loss of thalamus, sub-thalamic, nucleus accumbens, white matter & cerebellum

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16
Q

What is the exact neuropathology of HD?

A

Projection from caudate & putamen to globus pallidus is diminished -> decreases tonic inhibition from GP to subthalamic nucelus -> thalamic excitation of cortex is increased -> inappropriate motor activity -> chorea

17
Q

What 4 ways can HD be detected?

A

Imaging -> loss of grey & white matter volume
Diffusion weighted MRI
Functional MRI
PET

18
Q

What compensatory mechanisms occur in pre manifest stage?

A

Neuroplasticity & network reconfiguration

19
Q

What drug is used to treat chorea?

A

Tetrabenazine

20
Q

What is the MoA of terabenazine?

A

Inhibitor of synaptic vesicular monoamine transporter 2 -> depletes DA, 5-HTT, NE, hitamine

21
Q

What are 3 other drugs used to treat HD symptoms?

A

Atypical neuroleptics -> DA blocking
Antidepressants
Gene therapy (research focus)

22
Q

What is the indirect pathway in HD?

A

medium spiny neurons that project to GP degenerate

23
Q

What do medium spiny neurons inhibit?

A

Activity of external GP cells
In HD these cells now become abnormally active

24
Q

What do the abnormally active external GP cells reduce?

A

Excitatory output of subthalamic nucleus to internal GP -> reduces inhibitory outflow of BG -> upper motor neurons activated

25
Q

Which non-motor BG loops are disrupted?

A

Emotional & cognitive loops deteriorate

26
Q

What mouse model is used to look at HD?

A

R6/1

27
Q

How was this HD mouse model treated?

A

Suppression of HTT using antisense oligonucleotides to act on neurotransmission & protein clearance

28
Q

What behavioral tests did the R6/1 mouse do?

A

balance beam/maze

29
Q

What 3 brain regions did they look at in thre R6/1 mouse?

A

mPFC, striatum & hippocampus

30
Q

What did they measure?

A

Tyrosine hydroxylase expression -> correlates to DA and NA clearance

31
Q

What did they find in the ASO treated R6/1 mouse?

A

Improved balance, spatial memory, recognition memory, motor coordination
Increased TH

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