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A Positron Emission Tomographic Study

Stéphane Thobois, MD, PhD; François Vingerhoets, MD, PhD; Valerie Fraix, MD; Jing Xie-Brustolin, MD, PhD; Hélène Mollion, MD; Nicolas Costes, MS; Patrick Mertens, MD, PhD; Alim-Louis Benabid, MD, PhD; Pierre Pollak, MD; Emmanuel Broussolle, MD, PhD

Arch Neurol. 2004;61:1705-1709.

Background  In patients with advanced Parkinson disease (PD) who are undergoing long-term treatment with a dopaminergic medication, a down-regulation of striatal dopamine D₂ receptor expression has been demonstrated and interpreted as a consequence of either the disease itself or dopaminergic drug administration.

Objective  To compare, using positron emission tomography, the striatal binding of raclopride carbon C 11, a dopamine D₂ receptor ligand, in PD patients who completely discontinued dopaminergic therapy (off drug) with that in PD patients who continued receiving dopaminergic therapy (on drug) after undergoing subthalamic nucleus stimulation.

Main Outcome Measures  The positron emission tomographic data were acquired in off-stimulation and, for 12 hours, off-medication conditions. Five off-drug PD patients, 7 on-drug PD patients, and 8 healthy subjects participated.

Results  In off-drug PD patients, the putaminal raclopride C 11 binding was 24% higher than in on-drug PD patients. The same tendency was noted for the caudate nucleus, but was not significant (P=.07). Compared with control subjects, the putaminal raclopride C 11 binding was increased by 21% in off-drug and was normal in on-drug PD patients. Compared with controls, the caudate raclopride C 11 binding was reduced by 23% in on-drug and was normal in off-drug PD patients. Further analysis using statistical parametric mapping showed a significant increase of binding bilaterally in the caudate nucleus and putamen in off-drug compared with on-drug PD patients (P=.002 at cluster level).

Conclusions  The down-regulation of dopamine D₂ receptors probably relates to the long-term and intermittent administration of dopaminergic treatments rather than to disease progression. This phenomenon is reversed by the complete withdrawal of dopaminergic drugs. Furthermore, an up-regulation of putaminal dopamine D₂ receptors is demonstrated in late-stage PD after dopaminergic drug withdrawal.

Author Affiliations: Neurological Department D, The Pierre Wertheimer Neurological Hospital and INSERM U 534, Lyon, France (Drs Thobois, Xie-Brustolin, Mollion, and Broussolle); Cyclotron Unit (CERMEP) (Drs Thobois and Broussolle and Mr Costes) and Neurosurgical Department A (Dr Mertens), The Pierre Wertheimer Neurological Hospital, Lyon; Sobell Department of Motor Neurosciences and Movement Disorders, Institute of Neurology, London, England (Dr Thobois); Neurological Department, CHUV, Lausanne, Switzerland (Dr Vingerhoets); and Neurological and Neurosurgical Departments and INSERM U 318, CHU, Grenoble, France (Drs Fraix, Benabid, and Pollak).

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