Parkinson’s disease (Idiopathic PD) Flashcards
What is PD?
- Chronic progressive neurodegenerative disorder
-Classified as a movement disorder but non-motor features
-Is related to other Parkinson’s related disorders
Incidence
In the uk 160 ppl affected per 100,000, annual incidence of 15-20 per 100,000
1.5 times more common in men than women
Rising prevalence with age (up to 2% of population >80)
Aetiology
-10-15% hereditary
-10-20% due to gene mutation
- May need a triggering factor, eg mild brain injury
Environmental factors
MPTP: Neurotoxin related to common pesticides- Damage to mitochondrial function from free radicals, oxidative stress in dopamine - producing neurones.
-Potential effects of manganese’s and copper
What is MPTP?
Is a chemical precursor to the neurotoxin MPP+, which causes permanent symptoms of Parkinson’s disease by destroying dopaminergic neurons in the substantia nigra of the brain
Basal Ganglia Functions
-Regulate planning, initiation & termination of movement including:
-Pre movement planning and preparation
-Gross intentional movements
-Gross rhythmic body movements e.g walking
-Sequencing and timing of movement
-controls well learn, long and complex movement amplitude
Basal ganglia functions
-Regulate muscle tone required for specific body movements (inhibitory influence)- too much or too little muscle tone would affect our ability to move effectively
-Control subconscious or stereotyped contractions of skeletal muscle e.g. (automatic arm swing when walking; laughing in response to a joke)
-Act to inhibit antagonistic or unnecessary movements- Input necessary to our ability to perform several moments at once
Summary of functions
Important for subconscious planning and execution of motor programmes which are finally executed through the motor systems of the motor cortex and spinal cord
Important in the control of complex unconscious & semi voluntary movements e.g walking
Required for the development of body postures/position needed for us to perform all our activities/movement
Pathophysiology
Apoptosis- The death of dopamine cells
resulting from programmed cell dehth
-Process initiated by the cell itself- cell genetic material enzymatically degraded
-This results in dopamine depletion
Decrease in dopamine levels
Dopamine levels fall, leading to compensatory changes in basal ganglia circuitry and clinical features of PD. Immunostaining techniques show lewy bodies in cerebral cortex due to initial pathology in the lowerbrainstem.
Lewy Bodies
Lewy bodies are accumulations of alpha synuclein, which may be passed from cell to cell.
Braak’s hypothesis of PD stages
Disease starts in lower brainstem and ascends via vagus nerve, causing Lewy pathology.
Threshold theory
Alpha synuclein accumulation is a common cause of PD, linked to lower functional thresholds in the peripheral NS.
