Objective: One patient received oral levodopa during a study aiming for better\nunderstanding of the basal ganglia and of the mechanisms of deep brain\nstimulation of the subthalamic nucleus (STN DBS) with and without intravenous\n(IV) levodopa infusion in patients with Parkinson�s disease (PD). The\nresults from oral and IV levodopa treatment are presented. Methods: Five patients\nwith advanced PD were included in the original study. During planned\nSTN DBS surgery microdialysis probes were implanted in the right putamen\nand in the right and left globus pallidus interna (Gpi). During the study, microdialysis\nwas performed continuously and STN DBS, with and without IV levodopa\ninfusion, was performed according to a specific protocol. After DBS\nsurgery, but before STN DBS was started, one patient received oral levodopa/\nbenserazide and entacapone tablets out of protocol due to distressing parkinsonism.\nResults: The levodopa levels increased prompt in the central nervous\nsystem after the first PD medication intakes but declined after the last. Immediately\nthe levodopa seemed to be metabolized to dopamine (DA) since the\nlevels of DA correlated well with levodopa concentrations. Left STN DBS\nseemed to increase DA levels in left Gpi and right STN DBS seemed to increase\nDA levels in right Gpi while all STN stimulation seemed to increase the\nDA levels in right putamen. There was no obvious effect on levodopa levels.\nConclusions: The results indicate that PD patients still have capacity to metabolize\nlevodopa to DA despite advanced disease with on-off symptoms and\nprobably pronounced nigral degeneration. STN DBS seems to increase DA\nlevels with a more pronounced effect on ipsilateral structures in striatum.
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