Maria-Joao Ribeiro

Slower progression of Parkinson's disease with ropinirole versus levodopa: The REAL-PET study

Preclinical studies suggest ropinirole (a D2/D3 dopamine agonist) may be neuroprotective in Parkinsons disease (PD), and a pilot clinical study using 18F‐dopa positron emission tomography (PET) suggested a slower loss of striatal dopamine storage with ropinirole compared with levodopa. This prospective, 2‐year, randomized, double‐blind, multinational study compared the rates of loss of dopamine‐terminal function in de novo patients with clinical and 18F‐dopa PET evidence of early PD, randomized 1 to 1 to receive either ropinirole or levodopa. The primary outcome measure was reduction in putamen 18F‐dopa uptake (Ki) between baseline and 2‐year PET. Of 186, 162 randomized patients were eligible for analysis. A blinded, central, region‐of‐interest analysis showed a significantly lower reduction (p = 0.022) in putamen Ki over 2 years with ropinirole (−13.4%; n = 68) compared with levodopa (−20.3%; n = 59; 95% confidence interval [CI], 0.65–13.06). Statistical parametric mapping localized lesser reductions in 18F‐dopa uptake in the putamen and substantia nigra with ropinirole. The greatest Ki decrease in each group was in the putamen (ropinirole, −14.1%; levodopa, −22.9%; 95% CI, 4.24–13.3), but the decrease was significantly lower with ropinirole compared with levodopa (p < 0.001). Ropinirole is associated with slower progression of PD than levodopa as assessed by 18F‐dopa PET. Ann Neurol 2003

Effect of fetal neural transplants in patients with Huntington's disease 6 years after surgery: a long-term follow-up study

BACKGROUND Although we have shown in three out of five patients with Huntingtons disease that motor and cognitive improvements 2 years after intracerebral fetal neural grafts are correlated with recovery of brain metabolic activity in grafted striatal areas and connected regions of the cerebral cortex, neural grafts are not known to have protective effects on the host brain per se. We undertook long-term follow-up of previously reported patients with the disease to ascertain the nature and extent of any secondary decline after grafting. METHODS Five patients with Huntingtons disease from our pilot study were assessed annually with the unified Huntingtons disease rating scale, neuropsychological tests, and MRI, for up to 6 years after neural grafting. Resting cerebral activity was recorded at 2 and 6 years. FINDINGS Clinical improvement plateaued after 2 years and then faded off variably 4-6 years after surgery. Dystonia deteriorated consistently, whereas chorea did not. Cognitive performance remained stable on non-timed tests, whereas progression of motor disability was shown by deterioration on timed tests. Hypometabolism also affected the brain heterogeneously, sparing the benefits in the frontal cortex and at the precise location of the grafts, but showing a progressive deterioration in other areas. Two patients who had no benefit from grafting at 2 years continued to decline in the same way as non-grafted patients. INTERPRETATION Neuronal transplantation in Huntingtons disease provides a period of several years of improvement and stability, but not a permanent cure for the disease. Improvement of the surgical procedure and in patient selection could improve the therapeutic value, but neuroprotective treatment seems to be unavoidable in the disease.

A multidisciplinary study of patients with early-onset PD with and without parkin mutations

Objective: To establish phenotype–genotype correlations in early-onset Parkinson disease (EOPD), we performed neurologic, neuropsychological, and psychiatric evaluations in a series of patients with and without parkin mutations. Background: Parkin (PARK2) gene mutations are the major cause of autosomal recessive parkinsonism. The usual clinical features are early-onset typical PD with a slow clinical course, an excellent response to low doses of levodopa, frequent treatment-induced dyskinesias, and the absence of dementia. Methods: A total of 44 patients with EOPD (21 with and 23 without parkin mutations) and 9 unaffected single heterozygous carriers of parkin mutations underwent extensive clinical, neuropsychological, and psychiatric examinations. Results: The neurologic, neuropsychological, and psychiatric features were similar in all patients, except for significantly lower daily doses of dopaminergic treatment and greater delay in the development of levodopa-related fluctuations (p < 0.05) in parkin mutation carriers compared to noncarriers. There was no major difference between the two groups in terms of general cognitive efficiency. Psychiatric manifestations (depression) were more frequent in patients than in healthy single heterozygous parkin carriers but did not differ between the two groups of patients. Conclusion: Carriers of parkin mutations are clinically indistinguishable from other patients with young-onset Parkinson disease (PD) on an individual basis. Severe generalized loss of dopaminergic neurons in the substantia nigra pars compacta in these patients is associated with an excellent response to low doses of dopa-equivalent and delayed fluctuations, but cognitive impairment and special behavioral or psychiatric symptoms were not more severe than in other patients with early-onset PD.

Assessment of 11C-PE2I Binding to the Neuronal Dopamine Transporter in Humans with the High-Spatial-Resolution PET Scanner HRRT

The high-resolution research tomograph (HRRT), dedicated to brain imaging, may offer new perspectives for identifying small brain nuclei that remain neglected by the spatial resolution of conventional scanners. However, the use of HRRT for neuroimaging applications still needs to be fully assessed. The present study aimed at evaluating the HRRT for measurement of the dopamine transporter (DAT) binding to validate its quantification and explore the gain induced by the increased spatial resolution in comparison with conventional PET scanners. Methods: Fifteen and 11 healthy subjects were examined using the selective DAT radioligand 11C-PE2I with HRRT and HR+ scanners, respectively. Quantification of the DAT binding was assessed by the calculation of binding potential (BP) values using the simplified reference tissue model in anatomic regions of interest (ROIs) defined on the dorsal striatum and in a standardized ROI defined on the midbrain. Results: Quantification of 11C-PE2I binding to the DAT measured in the midbrain and striatum with both scanners at the same spatial resolution (smoothed HRRT images) exhibited similar BP values and intersubject variability, thus validating the quantification of DAT binding on the HRRT. For age-paired comparison, BP values of subjects examined with HRRT were significantly higher than those of the subjects examined with HR+. The increase ranged from 29% in the caudate and 35% in the putamen to 92% in the midbrain. The decline in DAT binding with age in the striatum was in good agreement between both scanners and literature, whereas no significant decrease in DAT binding with age was observed in the midbrain with either HRRT or HR+. Conclusion: HRRT allows quantitative measurements of neurotransmission processes in small brain nuclei and allows recovering higher values as compared with coarser spatial resolution PET scanners. High-spatial-resolution PET appears promising for a more accurate detection of neurobiologic modifications and also for the exploration of subtle modifications in small and complex brain structures largely affected by the partial-volume effect.

Transplantation in Parkinson's disease: PET changes correlate with the amount of grafted tissue.

An erratum for this article appears in the January, 2004 issue of Movement Disorders (Mov Disord 2004;12:119).

Striatal and extrastriatal dopamine transporter in cannabis and tobacco addiction: a high‐resolution PET study

The dopamine (DA) system is known to be involved in the reward and dependence mechanisms of addiction. However, modifications in dopaminergic neurotransmission associated with long‐term tobacco and cannabis use have been poorly documented in vivo. In order to assess striatal and extrastriatal dopamine transporter (DAT) availability in tobacco and cannabis addiction, three groups of male age‐matched subjects were compared: 11 healthy non‐smoker subjects, 14 tobacco‐dependent smokers (17.6 ± 5.3 cigarettes/day for 12.1 ± 8.5 years) and 13 cannabis and tobacco smokers (CTS) (4.8 ± 5.3 cannabis joints/day for 8.7 ± 3.9 years). DAT availability was examined in positron emission tomography (HRRT) with a high resolution research tomograph after injection of [11C]PE2I, a selective DAT radioligand. Region of interest and voxel‐by‐voxel approaches using a simplified reference tissue model were performed for the between‐group comparison of DAT availability. Measurements in the dorsal striatum from both analyses were concordant and showed a mean 20% lower DAT availability in drug users compared with controls. Whole‐brain analysis also revealed lower DAT availability in the ventral striatum, the midbrain, the middle cingulate and the thalamus (ranging from −15 to −30%). The DAT availability was slightly lower in all regions in CTS than in subjects who smoke tobacco only, but the difference does not reach a significant level. These results support the existence of a decrease in DAT availability associated with tobacco and cannabis addictions involving all dopaminergic brain circuits. These findings are consistent with the idea of a global decrease in cerebral DA activity in dependent subjects.

A Multitracer Dopaminergic PET Study of Young-Onset Parkinsonian Patients With and Without Parkin Gene Mutations

The impact of parkin gene mutations on nigrostriatal dopaminergic degeneration is not well established. The purpose of this study was to characterize by PET using 18F-fluoro-l-3,4-dihydroxyphenylalanine (18F-fluoro-l-DOPA), 11C-PE2I, and 11C-raclopride the pattern of dopaminergic lesions in young-onset Parkinson disease (YOPD) patients with or without mutations of the parkin gene and to correlate the clinical and neuropsychologic characteristics of these patients with PET results. Methods: A total of 35 YOPD patients were enrolled (16 with parkin mutation, 19 without). The uptake constant (Ki) of 18F-fluoro-l-DOPA and the binding potential (BP) of 11C-PE2I (BPDAT) and of 11C-raclopride (BPD2) were calculated in the striatum. Comparisons were made between the 2 groups of YOPD and between controls and patients. For each radiotracer, parametric images were obtained, and statistical parametric mapping (SPM) analysis using a voxel-by-voxel statistical t test was performed. Correlations between the cognitive and motor status and PET results were analyzed. Results: In YOPD patients, 18F-fluoro-l-DOPA Ki values were reduced to 68% (caudate) and 40% (putamen) of normal values (P < 0.0001). This decrease was symmetric and comparable for nonparkin and parkin patients. No correlation was found between the Ki values and cognitive or motor status. 11C-PE2I BPDAT values in YOPD patients were decreased to 56% (caudate) and 41% (putamen) of normal values (P < 0.0001) and did not differ between the 2 YOPD populations. The mean 11C-raclopride BPD2 values were reduced to 72% (caudate) and 84% (putamen) of the normal values (P < 0.02) and did not differ between nonparkin and parkin patients. SPM analyses showed in patients an additional decrease of 11C-raclopride in the frontal cortex and a decrease of 18F-fluoro-l-DOPA and 11C-PE2I uptake in the substantia nigra bilaterally (P < 0.05, false-discovery rate–corrected). Conclusion: Carriers of parkin mutations are indistinguishable on PET markers of dopaminergic dysfunction from other YOPD patients with long disease duration.

Value of 18F–fluoro-l-dopa PET in the Preoperative Localization of Focal Lesions in Congenital Hyperinsulinism

PURPOSE To retrospectively compare fluorine 18 ((18)F) fluoro-L-dopa positron emission tomography (PET) and pancreatic venous sampling (PVS) in the preoperative differentiation of diffuse from focal congenital hyperinsulinism (CHI) and localization of focal lesions. MATERIALS AND METHODS This study was approved by the institutional ethical committee, and informed consent for the research study was obtained from the parents of all subjects. Fifty-one patients evaluated for focal CHI between January 1, 1995, and January 31, 2008, were included. Thirty five underwent PVS evaluation alone, and 16 underwent a PET evaluation alone. The sensitivity values of each technique for the diagnosis and localization of focal lesions were compared in regard to results of surgery and pathologic analyses. In each patient, perioperative treatment was reviewed, and the presence of postoperative hypoglycemia was assessed as evidence of incomplete resection. Comparisons of the sensitivity values and recurrence rates were performed by using the Fisher exact test in regard to the number of patients. Comparisons of median age, weight, or number of biopsies were performed with a two-tailed unpaired Mann-Whitney U test. A difference with P < .05 was considered significant. RESULTS For PVS and PET groups, there was no error in differentiating focal from diffuse forms. PVS was not completed in four of 35 patients. In 27 (87%) of 31 patients in whom PVS was completed and 13 (81%) of 16 patients in whom PET was completed, preoperative localization of the focal lesion was in accordance with the surgical findings (P = .7). Although not significant, the number of biopsies performed before discovering the focal lesion was higher in the PET group compared with the PVS group (P = .06). Inadequate localization occurred in two (6%) patients in the PVS group and five (31%) patients in the PET group at initial preoperative imaging study; these patients underwent repeat surgery for residual CHI (P = .03). CONCLUSION (18)F-fluoro-L-dopa PET is equivalent to PVS in the characterization of CHI but does not provide localization of the lesion as precisely as does PVS.

Comparison of clinical data sets acquired on different tomographs using 6-18F-l-dopa

Abstract.Longitudinal positron emission tomography (PET) studies of 6-18F-l-dopa uptake in the striatum are used to assess the progression of Parkinson’s disease or the survival of neuronal cells grafted in parkinsonian patients. These studies are performed over several years, and data analysis may suffer from the change from old tomographs to new machines with better sensitivity and spatial resolution. Furthermore, such studies on parkinsonian patients may be accomplished in either 2D or 3D acquisition mode. The aforementioned improvements offer great benefits for the study of neurodegenerative diseases, especially those affecting the striatum. However, direct comparison of data is not straightforward owing to variation in scanner characteristics. In this study, we assessed the feasibility of comparing the 6-18F-l-dopa striatal uptake values (Kc) measured in two groups of healthy subjects using two tomographs of different generations.We re-studied and compared acquisitions performed on 14 healthy subjects using 6-18F-l-dopa. Half of these studies had been performed in 2D acquisition mode using an ECAT 953B. The other half had been performed in 3D acquisition mode using an ECAT EXACT HR+. Different reconstruction protocols were used and the Kc values obtained were statistically compared.The results showed that lowering the transverse spatial resolution of images obtained with the scanner having the better spatial resolution, so that it more closely matched that of the other machine, allowed similar Kc values to be obtained in healthy subjects.This study shows that quantitative results of 6-18F-l-dopa scans can be matched between different scanners with different intrinsic resolutions. This can be accomplished using adequate modifications of the reconstruction parameters. Such modifications can be used to help in the longitudinal monitoring of parkinsonian patients using different tomographs.

Functional Imaging of the Pancreas: The Role of [ 18 F]Fluoro- L -DOPA PET in the Diagnosis of Hyperinsulinism of Infancy

Congenital hyperinsulinism (HI) of infancy, the most frequent cause of hypoglycaemia in young children, is a neuro-endocrine disease secondary to either focal adenomatous hyperplasia or a diffuse abnormal pancreatic insulin secretion. This inappropriate secretion of insulin induces severe hypoglycaemias that require aggressive treatment to prevent the high risk of irreversible brain damage. Focal and diffuse forms of HI share a similar clinical presentation, but their treatment is dramatically different. Selective surgical resection can cure focal HI whilst diffuse forms require near-total pancreatectomy if resistant to medical treatment. Until recently, preoperative differential diagnosis was based on pancreatic venous sampling, an invasive method, technically difficult to perform, which requires general anaesthesia. The pancreas is one of the most heavily innervated peripheral organs in the body, and its functional imaging with positron emission tomography (PET) is difficult to perform, in part because of the vast number of physiological roles and cell types that characterize this organ. However, HI, as all neuro-endocrine diseases, is notable for the ability to take up amine precursors and to convert them into biogenic amines. Therefore, we have evaluated the use of PET with [18F]fluoro-L-DOPA, a precursor of catecholamines, to image the pancreas and distinguish focal from diffuse HI.