[Evaluation of dopaminergic presynaptic function by [F-18] DOPA PET]

Area of Science:

• Neuroscience
• Radiochemistry
• Medical Imaging

Context:

• Dopaminergic neuron function is crucial for motor control, cognition, and emotion.
• Parkinson's disease (PD) and Parkinson's disease with dementia (PDD) involve progressive neurodegeneration affecting dopaminergic systems.
• Positron Emission Tomography (PET) with [F-18] fluorodopa ([F-18] DOPA) visualizes dopa uptake, reflecting enzyme activity in dopaminergic terminals.

Purpose:

• To investigate dopaminergic function in the extrastriatal areas, including the brainstem, in PD and PDD using [F-18] DOPA PET and statistical image analysis.
• To differentiate dopaminergic deficits between PD and PDD, correlating them with cognitive impairment and Braak's staging.

Summary:

• [F-18] DOPA PET revealed significant declines in dopaminergic function (influx rate, Ki) in the striatum and midbrain of PD patients compared to controls.
• PDD patients exhibited more widespread reductions in [F-18] DOPA Ki, including the anterior cingulate and ventral striatum, indicating impaired mesolimbic and caudate dopaminergic function.
• Analysis of the brainstem showed a tendency for decreased [F-18] DOPA Ki in the raphe nucleus and locus ceruleus in PDD, suggesting these areas are affected in cognitive decline.

Impact:

• This study clarifies the neurochemical underpinnings of cognitive impairment in PDD, linking it to specific dopaminergic pathway dysfunctions.
• Findings support the hypothesis that mesolimbic dopaminergic system impairment contributes to cognitive deficits in PDD.
• The results correlate with Braak's staging of PD pathology, providing a neuroimaging correlate for disease progression.