Parkinson's disease is a movement disorder characterised by: tremor at rest, rigidity, bradykinesia
Aetiology
The exact cause of Parkinson's disease is unknown
Risk factors
Advancing age is the greatest risk factor
Positive family history
Early onset (below 40 years) increases probability of genetic cause
Male gender
Environmental factors e.g. pesticide exposure, prior head injury, rural living, beta blocker use
Genetic link - monogenetic forms have been identified e.g. LRRK2 and PARKIN
Pathophysiology
Although the exact pathophysiology is unknown, it is believed to result from the accumulation of ‘Lewy bodies’, intracellular inclusions primarily composed of misfolded alpha synuclein
These bodies form and lead to neuronal death in the dopaminergic cells of the substantia nigra of the basal ganglia, thereby causing the characteristic symptoms
Both dominant and recessive familial variants of Parkinson's disease have been identified
Pathological hallmarks
Sections through the brainstem reveals loss of the normally dark black pigment in the substantia nigra and locus coeruleus
Pigment loss correlates with dopaminergic cell loss
Lewy bodies
Subtypes of PD
Motor features in PD are heterogenous, but there are broadly 2 subtypes:
Tremor dominant PD (with relative absence of other motor symptoms)
Non-tremor dominant PD (such as akinestic-rigid syndrome and postural instability gait disorder)
