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- Parkinson disease (PD) is a progressive neurodegenerative movement disorder.
- Hallmark symptoms of PD include: bradykinesia plus at least one of the following – rest tremor, rigidity, gait disturbance.
- Pathologically, PD is characterized by dopaminergic neuron death in the substantia nigra pars compacta (SNpc) of the midbrain.
- In early, pre-symptomatic stages of PD, pathological changes are thought to occur in the medulla oblongata, pontine tegmentum, and olfactory bulb.
- Motor symptom onset occurs after 60%-80% of the SNpc neurons are lost.
- From there, the disease continues to progress and eventually affects structures in the basal forebrain and neocortex.
- Lewy bodies, cytoplasmic inclusions composed of aggregated α-synuclein protein and proteolysis proteins including ubiquitin, are a second pathological signature of PD.
- The specific etiology and mechanism of PD neurodegeneration is still unknown.
- Cognitive impairment due to Parkinson disease is classified under the neurocognitive disorders (NCDs) section of the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5).