Differences at brain SPECT between depressed females with and without adult ADHD and healthy controls: etiological considerations

Background

Comorbidity between Attention Deficit Hyperactivity Disorder (ADHD) and mood disorders is common. Alterations of the cerebellum and frontal regions have been reported in neuro-imaging studies of ADHD and major depression.

Methods

Thirty chronically depressed adult females of whom 16 had scores below, and 14 scores above, cut-offs on the 25-items Wender Utah Retrospective Scale (WURS-25) and the Wender-Reimherr Adult Attention Deficit Disorder Scale (WRAADDS) were divided into subgroups designated "Depression" and "Depression + ADHD", respectively. Twenty-one of the patients had some audiological symptom, tinnitus and/or hearing impairment. The patients were investigated with other rating scales and ^99mTc-HMPAO SPECT. Controls for ^99mTc-HMPAO SPECT were 16 healthy females. SPECT was analyzed by both statistical parametric mapping (SPM2) and the computerized brain atlas (CBA). Discriminant analysis was performed on the volumes of interest generated by the CBA, and on the scores from rating scales with the highest group differences.

Results

The mean score of a depression rating scale (MADRS-S) was significantly lower in the "Depression" subgroup compared to in the "Depression + ADHD" subgroup. There was significantly decreased tracer uptake within the bilateral cerebellum at both SPM and CBA in the "Depression + ADHD" subgroup compared to in the controls. No decrease of cerebellar tracer uptake was observed in "Depression". Significantly increased tracer uptake was found at SPM within some bilateral frontal regions (Brodmann areas 8, 9, 10, 32) in the "Depression + ADHD" subgroup compared to in "Depression". An accuracy of 100% was obtained for the discrimination between the patient groups when thalamic uptake was used in the analysis along with scores from Socialization and Impulsivity scales.

Conclusion

The findings confirm the previous observation of a cerebellar involvement in ADHD. Higher bilateral frontal ^99mTc-HMPAO uptake in "Depression + ADHD" compared to in "Depression" indicate a difference between these subgroups. ^99mTc-HMPAO uptake mechanisms are discussed.

Diffusion-weighted imaging in multiple system atrophy: a comparison between clinical subtypes

Multiple system atrophy can be classified into two main types, a Parkinsonian (MSA-P) and a cerebellar (MSA-C) variant based on clinical presentation. We obtained diffusion-weighted magnetic resonance imaging (DWI) in 9 MSA-P and 12 MSA-C patients and 11 controls, and correlated DWI changes with disease duration and severity. We found that Trace (D) values in the entire and anterior putamen were significantly higher in MSA-P than in MSA-C patients and controls, whereas Trace (D) values in the cerebellum and middle cerebellar peduncle (MCP) were significantly higher in MSA-C than in MSA-P patients and controls. Increased disease duration was significantly correlated with increased Trace (D) values in pons of MSA-P patients, and in cerebellum and MCP of MSA-C patients. Both UMSARS and UPDRS motor scores positively correlated with entire and posterior putaminal Trace (D) values in MSA-P patients. The diffusivity changes parallel phenotypical and pathologic differences between MSA-P and MSA-C patients, suggesting that DWI is a feasible tool for in vivo evaluation of neurodegeneration in MSA. Based on our findings, Trace (D) measurements in the putamen and pons in MSA-P patients and in the cerebellum and MCP in MSA-C patients could serve as quantitative markers for microstructural damage in the course of disease.

Synthesis, radiolabeling and preliminary in vivo evaluation of [18F]FE-PE2I, a new probe for the dopamine transporter

A new dopamine transporter (DAT) ligand, (E)-N-(3-iodoprop-2-enyl)-2beta-carbofluoroethoxy-3beta-(4'-methyl-phenyl) nortropane (FE-PE2I, 6), derived from PE2I (1), was prepared and found to be a potent inhibitor of rodent DAT in vitro. Compound 6 was radiolabelled with fluorine-18 (t(1/2)=109.8 min) for PET studies in monkeys. In vivo PET measurements showed a regional distribution in brain that corresponds to the known distribution of DAT. This binding was specific, reversible and the kinetics of [(18)F]6 binding in brain were faster than for its lead compound, [(11)C]1. The possible presence of a hydroxymethyl-radiometabolite formed by oxidation in the 3beta-benzylic position of [(18)F]6 warrants further detailed evaluation of the metabolism of [(18)F]6. [(18)F]6 is a potential radioligand for imaging DATs in the human brain with PET.

Advancement in PET quantification using 3D-OP-OSEM point spread function reconstruction with the HRRT

PURPOSE

Image reconstruction including the modelling of the point spread function (PSF) is an approach improving the resolution of the PET images. This study assessed the quantitative improvements provided by the implementation of the PSF modelling in the reconstruction of the PET data using the High Resolution Research Tomograph (HRRT).

METHODS

Measurements were performed on the NEMA-IEC/2001 (Image Quality) phantom for image quality and on an anthropomorphic brain phantom (STEPBRAIN). PSF reconstruction was also applied to PET measurements in two cynomolgus monkeys examined with [(18)F]FE-PE2I (dopamine transporter) and with [11C]MNPA (D2 receptor), and in one human subject examined with [11C]raclopride (D2 receptor).

RESULTS

PSF reconstruction increased the recovery coefficient (RC) in the NEMA phantom by 11-40% and the grey to white matter ratio in the STEPBRAIN phantom by 17%. PSF reconstruction increased binding potential (BP (ND)) in the striatum and midbrain by 14 and 18% in the [18F]FE-PE2I study, and striatal BP (ND) by 6 and 10% in the [11C]MNPA and [11C]raclopride studies.

CONCLUSION

PSF reconstruction improved quantification by increasing the RC and thus reducing the partial volume effect. This method provides improved conditions for PET quantification in clinical studies with the HRRT system, particularly when targeting receptor populations in small brain structures.

Saturated norepinephrine transporter occupancy by atomoxetine relevant to clinical doses: a rhesus monkey study with (S,S)-[(18)F]FMeNER-D (2)

PURPOSE

In a previous PET study on norepinephrine transporter (NET) occupancy in the nonhuman primate brain, the relationship between NET occupancy and atomoxetine plasma concentration, and occupancies among different brain regions, were not demonstrated adequately. It may therefore be difficult to translate the results to the clinical situations. In the present study, the detailed change of NET occupancy was investigated among a wider range of doses in a more advanced manner.

METHODS

Two rhesus monkeys were examined using a high-resolution PET system with (S,S)-[(18)F]FMeNER-D(2) under baseline conditions and after steady-state infusion of different doses of atomoxetine (0.003 to 0.12 mg/kg per hour). NET occupancy of the thalamus, brainstem and anterior cingulate cortex was calculated using BP(ND) obtained with the simplified reference tissue model.

RESULTS

NET occupancy increased regionally and uniformly as the plasma concentration of atomoxetine increased. The estimated Kd value (the amount to occupy 50% of NET) in the thalamus was 16 ng/ml.

CONCLUSION

The results indicate that clinical doses of atomoxetine would occupy NET almost completely.

Changes in cortical dopamine D1 receptor binding associated with cognitive training

Working memory is a key function for human cognition, dependent on adequate dopamine neurotransmission. Here we show that the training of working memory, which improves working memory capacity, is associated with changes in the density of cortical dopamine D1 receptors. Fourteen hours of training over 5 weeks was associated with changes in both prefrontal and parietal D1 binding potential. This plasticity of the dopamine D1 receptor system demonstrates a reciprocal interplay between mental activity and brain biochemistry in vivo.

[18F]flumazenil binding to central benzodiazepine receptor studies by PET--quantitative analysis and comparisons with [11C]flumazenil

[(11)C]flumazenil is the reference radioligand for Positron Emission Tomography (PET) studies of central benzodiazepine (BZ) receptors. Fluorine is available in the flumazenil molecule and [(18)F]flumazenil has recently been prepared. The aim of the present PET-study in 8 male subjects was to examine the binding of [(18)F]flumazenil in the human brain by direct comparison with [(11)C]flumazenil. Each subject participated in two 93-minute PET-measurements with [(11)C]flumazenil and [(18)F]flumazenil, respectively. Data were analyzed using compartment models with metabolite-corrected arterial plasma input and reference tissue models using the pons as reference region. There was no evident difference between the kinetic behaviors of the two ligands. Overall, the noise in the time activity curves for [(18)F]flumazenil was lower at late time points, and the variance of the kinetic parameters was lower than for [(11)C]flumazenil. In BZ receptor rich regions, such as the neocortex, the 3-compartment model was statistically favored, whereas the 2-compartment model was favored in the pons. Binding potential values obtained by the reference tissue models were in good agreement with those obtained by the kinetic analysis. There was no support for the presence of specific binding in the pons. In conclusion, the binding and the kinetic behavior of [(11)C]flumazenil and [(18)F]flumazenil were similar. The present analysis supports the use of pons as reference region in simplified protocols without arterial blood sampling. [(18)F]flumazenil should thus be an excellent choice for applied studies at centers not having a cyclotron.

Sex differences in the serotonin 1A receptor and serotonin transporter binding in the human brain measured by PET

Women and men differ in serotonin associated psychiatric conditions, such as depression, anxiety and suicide. Despite this, very few studies focus on sex differences in the serotonin system. Of the biomarkers in the serotonin system, serotonin(1A) (5-HT(1A)) receptor is implicated in depression, and anxiety and serotonin transporter (5-HTT) is a target for selective serotonin reuptake inhibitors, psychotropic drugs used in the treatment of these disorders. The objective of the present study was to study sex related differences in the 5-HT(1A) receptor and 5-HTT binding potentials (BP(ND)s) in healthy humans, in vivo. Positron emission tomography and selective radioligands [(11)C]WAY100635 and [(11)C]MADAM were used to evaluate binding potentials for 5-HT(1A) receptors (14 women and 14 men) and 5-HTT (8 women and 10 men). The binding potentials were estimated both on the level of anatomical regions and voxel wise, derived by the simplified reference tissue model and wavelet/Logan plot parametric image techniques respectively. Compared to men, women had significantly higher 5-HT(1A) receptor and lower 5-HTT binding potentials in a wide array of cortical and subcortical brain regions. In women, there was a positive correlation between 5-HT(1A) receptor and 5-HTT binding potentials for the region of hippocampus. Sex differences in 5-HT(1A) receptor and 5-HTT BP(ND) may reflect biological distinctions in the serotonin system contributing to sex differences in the prevalence of psychiatric disorders such as depression and anxiety. The result of the present study may help in understanding sex differences in drug treatment responses to drugs affecting the serotonin system.

Imaging the norepinephrine transporter with positron emission tomography: initial human studies with (S,S)-[18F]FMeNER-D2

INTRODUCTION

(S,S)-[(18)F]FMeNER-D(2) is a recently developed positron emission tomography (PET) ligand for in vivo quantification of norepinephrine transporter. A monkey occupancy study with the radioligand indicated that (S,S)-[(18)F]FMeNER-D(2) can be useful for quantitative PET analysis. In this preliminary study, regional distributions in the living human brain were evaluated.

MATERIALS AND METHODS

Brain PET measurements were performed for a total of 255 min after the injection of 188.3 +/- 5.7 MBq of (S,S)-[(18)F]FMeNER-D(2) in four healthy male subjects. Regions of interests were drawn on the thalamus and the caudate in the coregistered MRI/PET images.

RESULTS

(S,S)-[(18)F]FMeNER-D(2) displayed good brain penetration and selective retention in regions rich in norepinephrine reuptake sites. The transient peak equilibrium was reached during the PET measurements. The ratios of radioactivity uptake in the thalamus to that in the caudate were 1.50 +/- 0.06 for the time period of 90-255 min.

CONCLUSION

The present preliminary investigation indicates that (S,S)-[(18)F]FMeNER-D(2) has suitable characteristics for probing the norepinephrine reuptake system with PET in the human brain.

Neuroimaging follow-up in a case of Rasmussen's encephalitis with dyskinesias

We describe a case of adult-onset biphasic Rasmussen's encephalitis who presented seizures and left dyskinesias at the onset and, after 1 year, language disorder. Serial MRI and [(18)F] FDG-PET scans were performed showing involvement of the right cerebral hemisphere in the first phase and of the contralateral one in the second.

Parkinsonism and essential tremor in a family with pseudo-dominant inheritance of PARK2: an FP-CIT SPECT study

We report a family with 5 affected individuals manifesting either essential tremor (ET), Parkinsonism, or both, consistent with pseudo-dominant inheritance of PARK2. Two homozygotes presented postural and kinetic tremor several years before the onset of Parkinsonism. Postural and kinetic tremor mimicking ET was the only feature in 1 homozygous and 2 heterozygous carriers of the mutation. Striatal dopamine transporter density was reduced in accordance with phenotype and number of mutated alleles. In 3 homozygotes and 1 heterozygote, a 2-year follow-up single photon emission computed tomography suggested no progression of nigrostriatal deficit.

Identification by [99mTc]ECD SPECT of anterior cingulate hypoperfusion in progressive supranuclear palsy, in comparison with Parkinson's disease

PURPOSE

Progressive supranuclear palsy (PSP) is an akinetic-rigid syndrome that can be difficult to differentiate from Parkinson's disease (PD), particularly at an early stage. [99mTc]ethyl cysteinate dimer (ECD) SPECT could represent a widely available tool to assist in the differential diagnosis. In this study we used voxel-based analysis and Computerised Brain Atlas (CBA)-based principal component analysis (PCA) of [99mTc]ECD SPECT data to test whether: (1) specific patterns of rCBF abnormalities can differentiate PSP from controls and PD; (2) networks of dysfunctional brain regions can be found in PSP vs controls and PD.

METHODS

Nine PD patients, 16 PSP patients and ten controls were studied with [99mTc]ECD SPECT using a brain-dedicated device (Ceraspect). Voxel-based analysis was performed with statistical parametric mapping. PCA was applied to volume of interest data after spatial normalisation to CBA.

RESULTS

The voxel-based analysis showed hypoperfusion of the anterior cingulate and medial frontal cortex in PSP compared with controls and PD. In PSP patients the rCBF impairment extended to the pre-supplementary motor area and prefrontal cortex, areas involved in executive function and motor networks. Compared with PSP patients, PD patients showed a mild rCBF decrease in associative visual areas which could be related to the known impairment of visuospatial function. The PCA identified three principal components differentiating PSP patients from controls and/or PD patients that included groups of cortical and subcortical brain regions with relatively decreased (cingulate cortex, prefrontal cortex and caudate) or increased (parietal cortex) rCBF, representing distinct functional networks in PSP.

CONCLUSION

Anterior cingulate hypoperfusion seems to be an early, distinct brain abnormality in PSP as compared with PD.

PINK1 homozygous W437X mutation in a patient with apparent dominant transmission of parkinsonism

We analyzed the PINK1 gene in 58 patients with early-onset Parkinsonism and detected the homozygous mutation W437X in 1 patient. The clinical phenotype was characterized by early onset (22 years of age), good response to levodopa, early fluctuations and dyskinesias, and psychiatric symptoms. The mother, heterozygote for W437X mutation, was affected by Parkinson's disease and 3 further relatives were reported affected, according to an autosomal dominant transmission.