Neurodegeneration Flashcards
Describe the prevalence of Parkinson’s disease.
Age dependent (>65 years).
Describe some of the symptoms of Parkinson’s disease.
Resting tremor, rigidity, bradykinesia, hypokinesia, akinesia, flexed posture, postural instability.
What is thought to cause Parkinson’s disease?
It is thought to be multifactorial and heterogenous in aetiology but can be possibly caused by:
- Loss of dopaminergic neurones in the substantial nigra and noradrengeric neurones in the locus coeruleus.
- Lewy bodies develop in the neurones.
What is the most common neurodegenerative movement disorder ?
Parkinson’s disease
Describe the aetiology of Parkinson’s disease.
Thought to be multifactorial and heterogenous.
For what people may Parkinson’s disease be incorrectly diagnosed?
People who have; essential tremor, multiple strokes, Alzheimer’s disease, drug induced conditions, post encephalitis, Parkinson’s plus syndrome.
What are the risk factors for Parkinson’s disease?
- Increasing age
- 2 times more common in men than women.
- More common in caucasian’s
- 1.4x more common in families with relatives with PD (more common in siblings than in parents).
- Environmental factors (pesticides)
- Head trauma
- Infection
- Caffeine use
- Smoking
Describe the resting tremor clinical feature of Parkinson’s disease.
This is the most common first symptom and is usually asymmetric and most evident in one hand with the arm at rest.
Describe the Bradykinesia clinical feature of Parkinson’s disease.
- Difficulty with daily activities such as writing, shaving etc.
- Decreased blinking
- Slowed chewing and swallowing.
Describe the depression clinical feature of Parkinson’s.
Mild to moderate in 50% of patients.
Describe the rigidity clinical feature of Parkinson’s.
- Muscle tone increases in both flexor and extensor muscles providing a constant resistance to passive movements of the joints; stopped posture, anterioflexid head and flexed knees and elbows.
Describe the cognitive impairment clinical feature of Parkinson’s.
Mild cognitive decline including impaired visual and spatial perception and attention.
Slowness in execution of motor tasks and impairment of concentration.
Describe the how autonomic function is altered by Parkinson’s disease.
- Impotence
- Slower bowel motility
- Orthostatic hypotension
Describe how cognition and mood is altered by Parkinson’s disease.
- Slow executive functions
- Depression
- Apathy
- Frustration
What is apathy?
A lack of motivation and care about what is going on around you.
Describe the olfactory deficiencies caused by Parkinson’s disease.
Senses of smell and taste are altered/ disturbed.
Describe the postural instability caused by Parkinson’s disease.
Caused by loss of postural reflexes.
Leads to falls.
Describe how Parkinson’s disease causes affects funtion of the autonomic nervous system.
- Impaired GI motility
- Bladder dysfunction
- Sialorrhea
- Excessive head and neck sweating
- Orthostatic hypotension
What is Sialorrhea?
Poor facial and oral muscle control.
What are lewy bodies and where are they found during Parkinson’s disease?
Eosinophillic, round intracytoplasmic inclusions.
There are a lot in the substantial nigra pars compacta but can also be found in the locus coeruleus, motor nucleus of the vagus nerve, the hypothalamus, the nucleus basalts of Meynert, the cerebral cortes, the olfactory bulb and the autonomic nervous system.
What is the purpose of the Substantia nigra?
It is the main origin of the dopamingeric innervation of the striatum.
What is the purpose of the Extrapyramidal system ?
Processes information coming from the cortex to the striatum, retuning it back to the cortex through the thalamus.
What is the main function of the Striatum?
Regulation of posture and muscle tone.
Outline the process of dopamine synthesis and how this leads to altered gene expression and excitability of cells.
- Tyrosine is converted to DOPA and then to Dopamine.
- Dopamine is stored in the vesicles where it can act on a range of receptors.
- D3 and D2 receptors on the nerve terminals that are secreting Dopamine trigger changes within the cell by an internal feedback loop.
- Dopaminergic producing cells have transporters that allow Dopamine to be retaken-up into vesicles for storage.
- When Dopamine hits the post synaptic neurone, it activates various receptors, triggering changes in the second messengers and ion channels.
- This alters gene expression and excitability of cells.
In Parkinson’s disease, what causes inhibition of movement?
There is a reduction in the quantity of Dopamine produced by the substantial nigra. The net effect is that there is much less activation of the direct pathway and relatively more stimulation of the indirect pathway. The inhibition of movement is increased.
In terms of Hoehn and Yahr staging of Parkinson’s disease, describe stage 0
No clinical signs evident
In terms of Hoehn and Yahr staging of Parkinson’s disease, describe stage 1
Unilateral involvement
In terms of Hoehn and Yahr staging of Parkinson’s disease, describe stage II
Bilateral involvement but no postural abnormalities.
In terms of Hoehn and Yahr staging of Parkinson’s disease, describe stage III
Bilateral involvement with mild postural imbalance on examination or history of poor balance or falls; patient leads independent life.
In terms of Hoehn and Yahr staging of Parkinson’s disease, describe stage IV
Bilateral involvement with postural instability; patient requires substantial help.
In terms of Hoehn and Yahr staging of Parkinson’s disease, describe stage V
Severe, fully developed disease; patient restricted to bed or wheelchair.
When was the L-Dopa therapy for Parkinson’s disease first used/discovered?
Late 1950s
How does L-Dopa work to treat Parkinson’s disease?
It is a precursor of Dopamine that crosses the blood-brain barrier and could restore Dopamine levels and mortar functions in those treated with a Catecholamine depleting drug.
What are the problems with L-Dopa therapy for Parkinson’s disease?
- It has a short half-life
- Some L-Dopa will be converted to Dopamine before it reaches the brain.
What are the side effects of L-dopa therapy?
Nausea, vomiting, postural hypotension, hallucinations.
What is used to stop L-Dopa being converted to Dopamine before it reaches the brain?
L-dopa is always administered with an inhibitor of aromatic L-amino acid decarboxylase, so it doesn’t get converted to dopamine before it crosses the blood brain barrier. (The inhibitor commonly used is Carbidopa, which doesn’t cross the blood brain barrier).
What is L-Dopa degeneration and how is this helpful?
This is a secondary degeneration pathway using a COMT inhibition. L-Dopa metabolism is reduced and so L-Dopa half-life is increased. This reduced the dose of L-Dopa needed.
How do most treatments , other than L-dopa, generally work to treat Parkinson’s ?
They mimic Dopamine
How do Oral Dopamine Agonists treat Parkinson’s disease?
They act directly on Dopamine brain receptors.
They may delay onset of dyskinesia.
What are the side effects of using oral dopamine agonists to treat Parkinson’s ?
Nausea, vomiting, postural hypotension, hallucinations.
How do MAO-B inhibitors work to treat Parkinson’s and how is this beneficial?
They reduce dopamine breakdown in the brain by inhibiting dopamine metabolism.
This may delay the need for L-Dopa.