Parkinson's

Question 1

What is Parkinson’s?

Answer 1

First referred to as shaking palsy by James Parkinson in 1817, Parkinson’s is a disorder of motor function associated with dopaminergic neuronal death in the substantia nigra.

Question 2

What are the main symptoms of PD?

Answer 2

• Muscle rigidity
• Akinesia (absence of movement)
• Tremor at rest

Question 3

What is the cause?

Answer 3

Cause of neuronal death is unknown. Likely to be due to ongoing loss as part of ageing. Early onset due to head traumas or viral infection.

Question 4

What is the normal pathway?

Answer 4

1. Substantia nigra contains dopamine neurons which project into the striatum
2. The striatum projects to the thalamus via the globus pallidus and recieves inputs from the cortex
3. This circuitry allows motor programmes to be established
4. There are also inhibitory GABA projections from the striatum back to the substantia nigra and intrinsic excitatory cholinergic striatal neurons which need dopamine for movement control.

Question 5

So what happens when dopamine is lost and how does this relate to the symptoms?

Answer 5

Degeneration of dopamine neurons (70-80%) concentrated in substantia nigra part of the brain means that dopamine is depleted from nigrostriatal projection zones in striatum.

Loss of dopamine from nigrostriatal projection causes basal gangla to lock up hence symptom of akinesia.

Loss of dopamine control in cholinergic striatal neurons responsible for tremor in PD.