Functional effects of striatal dysfunction in Parkinson disease

Area of Science:

• Neuroscience
• Neurology
• Medical Imaging

Background:

• Basal ganglia organization involves segregated pathways linking putamen and caudate function to motor and cognitive performance.
• Parkinson disease (PD) presents with both motor and cognitive impairments, suggesting potential disruptions in nigrostriatal dopaminergic pathways.

Purpose of the Study:

• To investigate if motor and cognitive impairments in Parkinson disease are selectively linked to disturbances in nigrostriatal dopaminergic function.
• To examine the role of regional cerebral glucose metabolism in these impairments.

Main Methods:

• Twenty patients with probable Parkinson disease underwent positron emission tomography (PET) scans.
• PET measurements included dopaminergic nigrostriatal function (using fluorodopa F 18) and regional glucose metabolism (using fludeoxyglucose F 18).
• Patients also underwent memory testing and evaluation of locomotor disability.

Main Results:

• All Parkinson disease patients showed significantly reduced striatal uptake rates of fluorodopa F 18 compared to controls.
• Putaminal fluorodopa F 18 uptake correlated with locomotor disability, but not memory performance.
• In advanced PD, reduced caudate fluorodopa F 18 uptake correlated with memory impairment (delayed recall), but not locomotor disability.
• No significant changes in regional glucose metabolic rates were observed.

Conclusions:

• Motor impairment in Parkinson disease is associated with altered dopamine neuronal integrity in the putamen.
• Cognitive impairment, specifically memory deficits in advanced PD, is linked to dysfunction in the caudate nucleus.
• These findings support a model of selective striatal pathway involvement in Parkinson disease symptomatology.