Lecture neurodegenerative disorders 4: synucleopathies (Parkinson's) Flashcards
Name four characteristics of Parkinson’s disease.
Parkinson’s is a movement disorder, symptoms are:
- bradykinesia (slow movement)
- rigidity (stiff movement)
- Resting tremor (shaking movement)
- Postural instability
Another symptom can be hypomimia (decreased facial expressions)
What primary brain area is affected?
The substantia nigra, there’s loss of melanin containing dopaminergic neurons.
What pathway is affected in Parkinson’s Disease and what’s the importance of this pathway?
The nigrostriatal pathway is affected, this pathway consists of neurons reaching from the substantia nigra to the caudate nucleus and putamen. It’s important in movement control.
Shortly describe how the motor cortex regulates muscle activity in healthy state.
In healthy people, the motor cortex initiates two signals:
- one signal passes from the motor cortex to the reticular formation and spinal cord, which stimulates conctraction of muscles
- the other signal passes from the motor cortex to the basal ganglia. Here, dopamine dampens the effect of the motor signal. If dampening of the signal becomes too strong, acetylcholine can counteract the effect of dopamine, thus maintaining a balance in the force of the signals sent to the muscle.
Descibe how Parkinson’s results in increased muscle tension and tremor.
In PD, degeneration of the basal ganglia and with this dopaminergic neurons of the substantia nigra results in a decrease of available dopamine. While the motor cortex is still able to pass a signal to the reticular formation and spinal cord, this signal is no longer dampened by dopamine. In combination with acetylcholine still able to ‘inhibit the dampening effect of dopamine’, there’s uncontrolled muscle movement like increased muscle tension and tremor.
This pictures supports the previous questions. Just study.
Ok
How is PD diagnosed?
Diagnosis with DAT-SPECT (dopamine transporter-SPECT). Here, a radioactive tracer is injected into the blood , where it circulates around the body and makes its way into the brain. It binds to dopamine transporters found on dopamine neurons. This can be visualized with a SPECT-scan.
Like Alzheimer’s, there are also Braak stages for Parkinson’s. Describe these stages.
- Braak stages 1 and 2 → autonomic and olfactory disturbances
- Braak stages 3 and 4 → sleep and (pre)motor disturbances
- Braak stages 5 and 6 → emotional and cognitive disturbances
What aggregate initiates development of Braag stages and how does it spread?
Lewy body aggregates. These aggregates first arise in the brainstem and spread via the olfactory bulb to the prefrontal cortex.
What’s the first symptom that’s important for early diagnosis?
Loss of smell or reduced ability to smell due to the fact that the olfactory bulb is affected, which is responsible for the sensation of smell.
Based on this picture, what can be stated/concluded?
That there’s extensive pathology before diagnosis, where the first part of development of the disease is a presymptomatic phase and the last part is a symptomatic phase. Also seen in this picture.
What aggregates/neuronal inclusions belong to the pathology of Parkinson’s?
a-synuclein aggregates, also called Lewy bodies.
What is a-synuclein?
A small synaptic protein that is involved in (pre)synaptic vescile fusion.
Lewy bodies aggregate inside neuronal cell bodies (Lewy neurites). What kind of processes are disrupted/what does formation of Lewy bodies inside the cell cause?
- Oxidative stress
- Disruption of axonal transport
- Protein sequestration
- Mitochondrial dysfunction
- Synaptic dysfunction
- Inhibition of ubiquitin/proteasome system
Answer the following questions:
- How common is early-onset PD?
- If someone has early-onset PD, how high is the probability for a monogenic cause?
- Name risk genes for familial PD
- Name risk genes for sporadic PD
- Not common, only 15% is early-onset and 85% is late-onset PD.
- The probability for a monogenic cause is very high when it is early-onset PD.
- Risk genes are Parkin, Pink1, DJ1, LRRK2, SNCA
- Risk genes are LRRK2, Parkin, PINK1, DJ1 (rare, but very limited data)