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Neurology > 6. Parkinson's Disease > Flashcards

6. Parkinson's Disease Flashcards

1
Q

What is dopamine produced from?

A

Tyrosine -> L-dopa -> dopamine.

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2
Q

Where does the substantia nigra project to?

A

The striatum.

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3
Q

What is the Basal Ganglia?

A

Collection of subcortical nuclei
Consists of 3 main pathways: Direct, indirect, and Nigrostriatal

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4
Q

What makes up the basal ganglia? (5)

A

Complex internal connectivity involving 5 principle nuclei:

  1. Substantia Nigra (pars compacta & pars reticulata)
  2. Caudate & Putamen (together = striatum)
  3. Globus Pallidus (internal and external segments)
  4. Subthalamic Nucleus
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5
Q

Describe the basal ganglia circuit in the brain - direct and indirect pathways.

A

Direct pathway (excitatory):
Motor cortex – sends excitatory signals to caudate/putamen (dorsal striatum) – sends inhibitory signals to Gpi + Substantia nigra, pars reticulata (SNr) – sends inhibitory signals to thalamus – sends excitatory signals to the motor cortex - affect the planning of the movement by synapsing with the neurones of the corticospinal + corticobulbar tracts in the brainstem & spinal cord.

Hyper-activation: from motor cortex – sends excitatory signals to Subthalamic nucleus (STN)

Indirect pathway (inhibitory):
Motor cortex – sends excitatory signals to the caudate/putamen (dorsal striatum) – sends inhibitory signals to GPe – sends inhibitory signals to Subthalamic nucleus (STN) – sends excitatory signals to Gpi + SNr – sends inhibitory signals to thalamus – sends excitatory signals to the motor cortex – a decreased activity of the cortical motor neurones and consequentialsuppressionof the extemporaneous movement.

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6
Q

What is Parkinson’s Disease (PD)?

A
  • A neurodegenerative movement disorder caused by degeneration of dopaminergic neruones in the substantia nigra, resulting in a progressive reduction of dopamine in the basal ganglia
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7
Q

What is the typical age of onset of Parkinson’s disease?

A

65 yrs

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8
Q

Describe the epidemiology of PD.

A
  • Increasing prevalence with age
  • Peak age of onset is 55-65 yrs
  • M > F
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9
Q

What 1 main risk factor for other diseases, is protective in Parkinson’s disease?

A

Smoking

(Being a non-smoker have a higher risk of PD.)

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10
Q

Describe the pathophysiology of PD.

A
  1. Degeneration of dopaminergic neurones in the Substantia nigra pars compacta (SNpc).
  2. Reduction in the signals sent from SNpc to the striatum via dopaminergic neurones (I.E. the nigrostriatal pathway).
  3. Decrease in striatal dopamine levels.
  4. Reduction in direct-pathway action
  5. Resultant increase in the indirect-pathway (inhibitory)
  6. Causes increase in restrictive action on movement
    = Bradykinesia + rigidity.
  7. Associated with the presence of Lewy bodies.
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11
Q

Give 2 histopathological signs of Parkinson’s disease.

A
  1. Lewy bodies.
  2. Loss of dopaminergic neurones in the substantia nigra.
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12
Q

Give key genetic and environmental factors involved in the pathophysiology of PD.

A
  • Environmental factors:
    1. Pesticides
    2. Methyl-phenyl tetrahydropyridine (MPTP) - found in illegal opiates
  • Parkinson genes - mutations:
    1. PARKIN gene
    2. Alpha-synuclein gene
    3. PINK1 gene
  • Oxidative stress and mitochondrial dysfunction
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13
Q

What is the cardinal Parkinsonism triad comprised of?

A
  1. Bradykinesia (Parkinsonian gait)
    - Problems with doing up buttons, keyboard etc
    - Writing smaller
    - Walking deteriorated: Small stepped, dragging one foot etc
  2. Cogwheel rigidity
    - Pain
    - Problem turning in bed
  3. Pill-rolling tremor
    - At rest
    - May be unilateral
    - Only in Parkinson’s will you see issue with repetitive hand
    movements with worsening in rhythm the longer attempted
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14
Q

Describe the motor symptoms of Parkinson’s disease.

A
  1. Bradykinesia - problems with doing up buttons, writing smaller, small steps/shuffling, walking slowly, reduced arm swing.
  2. Rigidity - pain, problems turning in bed.
  3. Resting tremor.
  4. Postural instability.
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15
Q

Give 3 non-motor symptoms of Parkinson’s disease.

A

Depression
Dementia
Dribbling
Anosmia - reduced sense of smell.
Hallucinations
Constipation
Dysphagia
Heartburn
Urinary difficulties
Micrographia (writing smaller)

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16
Q

Would you describe the symptoms of parkinson’s disease as symmetrical or asymmetrical?

A

One side is always worse than the other - the symptoms are asymmetrical.

17
Q

You ask a patient, who you suspect might have PD, to walk up and down the corridor, so that you can assess their gait.

What features would be suggestive of PD?

A
  • Struggle to start walking.
  • Stooped posture.
  • Asymmetrical arm swing.
  • Small steps.
  • Shuffling gait.
  • Narrow base - making falls common.
  • Obstacles (e.g. doors) make them freeze + struggle to restart.
18
Q

Diagnosis of Parkinson’s Disease (PD).

A
  1. Diagnosis is CLINICAL -> based on history, symptoms and examination
  • NICE reccomends the UK Parkinson’s Disease Society Brain Bank Clinical Diagnostic Criteria

If diagnostic testing is warrented to due atypical features or unclear clinical diagnosis, dopaminergic agent trial can be done.

  1. Dopaminergic agent trial:
    • Should see an improvement in symptoms
    • Useful to confirm diagnosis
    • Can confirm by response to LEVODOPA
19
Q

What is the first-line treatment of PD?

A

If motor symptoms are affecting patients QOL:
→ Oral LEVODOPA along with a decarboxylase inhibitor
- E.G. are carbidopa and benserazide.
Combination drugs are:
1. Co-benyldopa (levodopa and benserazide)
2. Co-careldopa (levodopa and carbidopa)

  • If motor symptoms are not affecting patients QOL:
    → Dopamine agonist, Levodopa or MAO-B inhibitor
20
Q

What is the GOLD STANDARD treatment for PD?

A

Oral Levodopa (L-dopa)

21
Q

Give 3 side effects of Levodopa.

A
  1. Nausea
  2. Vomiting
  3. Arrhythmias
  4. Psychosis and visual hallucinations
22
Q

Give 4 motor complications of Levodopa treament.

A
  1. Wearing off
    - Medication doesn’t work as long as before
  2. On-Dyskinesias
    - Hyperkinetic, choreiform movements whenever drugs work
  3. Off-Dyskinesias
    - Fixed, painful dystonic posturing, typically of feet, when drugs don’t work
  4. Freezing
    - Unpredictable loss of mobility
23
Q

Give 3 examples of the dyskinesias associated with Levodopa treatment.

A
  1. Dystonia
    -> This is where excessive muscle contraction leads to abnormal postures or exaggerated movements.
  2. Chorea
    -> These are abnormal involuntary movements that can be jerking and random.
  3. Athetosis
    -> These are involuntary twisting or writhing movements usually in the fingers, hands or feet.
24
Q

Give the 4 different classes of medications for PD treatment.

A
  1. L-dopa.
  2. Monoamine Oxidase B (MAO-B) inhibitors.
  3. Catechol-O-methyl transferase (COMT) inhibitors.
  4. Dopamine Agonists.
25
Q

Give an example of a dopamine agonist.

A

Bromocriptine, Ropinirole, Cabergoline, Apomorphine

26
Q

Give 3 side effects of dopamine agonists.

A
  1. Pulmonary fibrosis
  2. Drowsiness
  3. Nausea
  4. Hallucinations
  5. Compulsive behaviour
27
Q

Give an example of a MAO inhibitor.

A

Selegiline, Rasagiline.

28
Q

How do MAO inhibitors work?

A

These inhibit MAO-B enzymes, which breakdown dopamine, thus they result in a reduction of dopamine breakdown, so dopamine remains for longer.

29
Q

Give 2 side effects of MAO inhibitors.

A
  1. Postural hypotension
  2. AF
30
Q

How do COMT inhibitors work?

A

These inhibit COMT, which breaks down dopamine.

31
Q

Give an example of a COMT inhibitor.

A

Entacapone, Tolcapone.

32
Q

Why can’t PD just be treated with dopamine?

A

Dopamine cannot cross the blood-brain barrier.

Levodopa is a precursor of dopamine and is able to cross the BBB and then be converted to dopamine within the brain.

33
Q

What non-pharmacological treatment options are available for Parkinson’s?

A
  1. Deep brain stimulation
  2. Surgical ablation of overactive basal ganglia circuits.
34
Q

How would you differentiate between Parkinson’s disease and Benign Essential Tumor? (Common exam question!)

A

PD:
1. Asymmetrical
2. 4-6 Hertz
3. Worse at rest
4. Improves with intentional movement
5. Other Parkinson’s features
6. No change with alcohol

BET:
1. Symmetrical
2. 5-8 Hertz
3. Improves at rest
4. Worse with intentional movement
5. No other Parkinson’s features
6. Improves with alcohol

35
Q

Differential diagnosis of PD.

A
  • Essential tremor
  • Metabolic abnormalities
  • Lewy body dementia

Neurology (20 decks)

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