Increased glutamate + glutamine levels in the thalamus of patients with essential tremor: A preliminary proton MR spectroscopic study.

INTRODUCTION: The aim of this study was to investigate the thalamic biochemical profile in patients with essential tremor (ET), using proton magnetic resonance spectroscopy (1H-MRS), and to explore the correlations between clinical and biochemical data. METHODS: Sixteen patients with ET and 14 healthy controls participated in this study. After conventional MR imaging, single-voxel 1H-MRS (TR = 2000 ms; TE = 28 ms) was performed by using a PROBE-SV system implemented on a 3-T scanner. A voxel of 10 × 10 × 15 mm involving the ventrointermediate (Vim) nucleus was acquired in each thalamus of all subjects. Peak areas of N-acetyl-aspartate + N-acetyl-aspartyl-glutamate (NAA), creatine + phosphocreatine (Cr), glycerophosphocholine + phosphocholine (Cho), and glutamate + glutamine (Glx) were calculated using a version 6.3-1 K of the fitting program LCModel for each voxel. Comparative and correlation analyses were performed on the NAA, Cr, Cho, and Glx concentrations, as well as on the values of the NAA/Cr, a neural density marker, Cho/Cr, a membrane marker, and Glx/Cr, an intracellular neurotransmitter marker. RESULTS: Patients with ET showed a significant increase in Glx concentration and Glx/Cr ratio values in both thalami, compared to healthy controls, whereas no difference inter-group was found for the other metabolites and NAA/Cr and Cho/Cr ratio values. Of note, the tremor severity was positively related to increased Glx concentrations and Glx/Cr ratio values in ET group. CONCLUSIONS: Our study shows that 1H-MRS can highlight in vivo metabolic abnormalities in the thalami of ET patients, supporting the evidence that the increase of thalamic glutamatergic transmission can play a role in developing of tremor in ET.

Thalamic neurometabolic alterations in tremulous Parkinson's disease: A preliminary proton MR spectroscopy study.

INTRODUCTION: The objective of this study was to investigate the thalamic biochemical changes in tremor-dominant Parkinson's disease (tPD) patients in comparison with essential tremor with resting tremor (rET) patients, by using proton MR spectroscopy (1H-MRS). METHODS: Fourteen tPD patients, 12 rET patients and 10 controls participated in this study. All patients underwent dopamine transporter single-photon emission computed tomography (DAT-SPECT) with 123I-ioflupane, and a short-echo single-voxel 1H-MRS on a 3T scanner. A voxel of 10 × 15 × 10 mm involving the Vim nucleus was acquired in both thalami of all subjects. Peak areas of N-acetyl-aspartate (NAA), creatine (Cr), glycerophosphocholine (Cho), and glutamate (Glu) were measured for each voxel using LCModel. The NAA/Cr, Cho/Cr, and Glu/Cr ratios were then calculated. RESULTS: DAT-SPECT was abnormal in tPD patients, whereas it was normal in rET patients. Patients with tPD showed a significant reduction of NAA/Cr and Cho/Cr in the thalami compared to rET and healthy controls; whereas there were no significant differences between rET patients and controls. The combination of thalamic NAA/Cr and Cho/Cr ratios showed a 100% accuracy in distinguishing tPD patients from rET patients and controls. CONCLUSIONS: This study provides preliminary evidence that thalamic neurometabolic abnormalities occur in tremor-dominant phenotype of PD, and suggests that 1H-MRS can help differentiate patients with tPD from those with rET.

Determinants of serum manganese levels in an Italian population.

Manganese (Mn) is both essential and toxic for humans, mainly depending on the total levels and its species. Main sources of exposure include food and air pollution, particularly motorized traffic. We sought to determine the potential influence of these sources on serum total levels of Mn and Mn species. We selected a random sample of municipality residents from an Italian urban municipality, from whom we collected detailed personal information, dietary habits and a blood sample for serum Mn determination. We also assessed outdoor air Mn exposure, by modeling levels of particulate matter ≤10 µm (PM10) from motorized traffic at the residence of geocoded subjects. Serum Mn species generally showed higher levels in males and positive correlation with age, while no such differences were found according to smoking habits or use of dietary supplements. Among nutrients, only iron intake showed a relation with Mn [an inverse correlation with Mn­ferritin (Mn­Fer) and a direct one with inorganic­Mn (Inorg­Mn)]. Meat consumption directly correlated and fish and seafood inversely correlated with total Mn, Mn­transferrin (Mn­Tf) and Mn-citrate (Mn-Cit). Fruits and vegetables, including legumes and nuts, generally showed a positive correlation with all Mn species, especially Mn­Cit, and an inverse one with Inorg­Mn. Odds ratios (ORs) of having serum Mn levels above median value increased with increasing PM10 tertiles, with an OR for highest­to­lowest tertile of 7.40 (1.36­40.25) in multivariate analysis. Analyses for Mn species did not highlight a clear comparable pattern. In conclusion, our results seem to demonstrate that PM10 exposure positively influences total Mn serum levels, while single Mn species show conflicting results.

Importance of Multimodal MRI in Characterizing Brain Tissue and Its Potential Application for Individual Age Prediction.

This study presents a voxel-based multiple regression analysis of different magnetic resonance image modalities, including anatomical T1-weighted, T2(*) relaxometry, and diffusion tensor imaging. Quantitative parameters sensitive to complementary brain tissue alterations, including morphometric atrophy, mineralization, microstructural damage, and anisotropy loss, were compared in a linear physiological aging model in 140 healthy subjects (range 20-74 years). The performance of different predictors and the identification of the best biomarker of age-induced structural variation were compared without a priori anatomical knowledge. The best quantitative predictors in several brain regions were iron deposition and microstructural damage, rather than macroscopic tissue atrophy. Age variations were best resolved with a combination of markers, suggesting that multiple predictors better capture age-induced tissue alterations. The results of the linear model were used to predict apparent age in different regions of individual brain. This approach pointed to a number of novel applications that could potentially help highlighting areas particularly vulnerable to disease.

Brain tissues atrophy is not always the best structural biomarker of physiological aging: A multimodal cross-sectional study.

This study presents a voxel-based multiple regression analysis of different magnetic resonance image modalities, including anatomical T1-weighted, T2* relaxometry, and diffusion tensor imaging. Quantitative parameters sensitive to complementary brain tissue alterations, including morphometric atrophy, mineralization, microstructural damage, and anisotropy loss, were compared in a linear physiological aging model in 140 healthy subjects (range 20-74 years). The performance of different predictors and the identification of the best biomarker of age-induced structural variation were compared without a priori anatomical knowledge. The best quantitative predictors in several brain regions were iron deposition and microstructural damage, rather than macroscopic tissue atrophy. Age variations were best resolved with a combination of markers, suggesting that multiple predictors better capture age-induced tissue alterations. These findings highlight the importance of a combined evaluation of multimodal biomarkers for the study of aging and point to a number of novel applications for the method described.

Serial MRI findings in brain anoxia leading to Lance-Adams syndrome: a case report.

Although in literature almost 150 patients with Lance-Adams Syndrome (LAS) have been reported, neuroradiological evaluations were often performed in late stages and there is no serial study evaluating LAS from early stages. We herein report a serial neuroimaging study demonstrating early and transient involvement of cerebellum and thalami in a LAS patient. We may hypothesize that a transient cerebral hypoxia provoked a permanent synaptic rearrangements of the neuronal networks involved in the pathogenesis of post-hypoxic myoclonus in our patient.

Hippocampi, thalami, and accumbens microstructural damage in schizophrenia: a volumetry, diffusivity, and neuropsychological study.

Volumetric abnormalities in the subcortical structures have been described in schizophrenia. However, it still has to be clarified if subtle microstructural damage is also present. Thus, we aimed to detect subcortical volume and mean diffusivity (MD) alterations in 45 patients with diagnosis of schizophrenia compared with 45 age-, gender-, and educational attainment-matched healthy comparison (HC) participants, by using a combined volumetry and diffusion tensor imaging (DTI) method. A secondary aim was to identify the neuropsychological correlates of subcortical abnormalities in the schizophrenic group. We found thalami and hippocampi bilaterally and left accumbens to show MD increase in the schizophrenic group. No volumetric decrease was found. Moreover, significant correlations between the MD values in subcortical structures (right thalamus and hippocampus and left accumbens) and working memory performance were found. Thus, subcortical microstructural alterations are present in schizophrenia even in absence of volumetric abnormalities. Furthermore, microstructural damage in subcortical areas is linked to working memory, suggesting the presence of a subtle microstructural subcortical dysfunction in the pathoetiological mechanism underlying high cognitive load performances in schizophrenia. Finally, our findings indicate that MD is a more sensitive marker of brain tissue deficits than signal intensity variations measured in T1-weighted imaging data, consistently with previous reports. Thus, DTI appears to be an invaluable tool to investigate subcortical pathology in schizophrenia, greatly enhancing the ability to detect subtle brain changes in this complex disorder.

Magnetic resonance imaging markers of Parkinson's disease nigrostriatal signature.

One objective of modern neuroimaging is to identify markers that can aid in diagnosis, disease progression monitoring and long-term drug impact analysis. In this study, Parkinson-associated physiopathological modifications were characterized in six subcortical structures by simultaneously measuring quantitative magnetic resonance parameters sensitive to complementary tissue characteristics (i.e. volume atrophy, iron deposition and microstructural damage). Thirty patients with Parkinson's disease and 22 control subjects underwent 3-T magnetic resonance imaging with T2*-weighted, whole-brain T1-weighted and diffusion tensor imaging scans. The mean R2* value, mean diffusivity and fractional anisotropy in the pallidum, putamen, caudate nucleus, thalamus, substantia nigra and red nucleus were compared between patients with Parkinson's disease and control subjects. Comparisons were also performed using voxel-based analysis of R2*, mean diffusivity and fractional anisotropy maps to determine which subregion of the basal ganglia showed the greater difference for each parameter. Averages of each subregion were then used in a logistic regression analysis. Compared with control subjects, patients with Parkinson's disease displayed significantly higher R2* values in the substantia nigra, lower fractional anisotropy values in the substantia nigra and thalamus, and higher mean diffusivity values in the thalamus. Voxel-based analyses confirmed these results and, in addition, showed a significant difference in the mean diffusivity in the striatum. The combination of three markers was sufficient to obtain a 95% global accuracy (area under the receiver operating characteristic curve) for discriminating patients with Parkinson's disease from controls. The markers comprising discriminating combinations were R2* in the substantia nigra, fractional anisotropy in the substantia nigra and mean diffusivity in the putamen or caudate nucleus. Remarkably, the predictive markers involved the nigrostriatal structures that characterize Parkinson's physiopathology. Furthermore, highly discriminating combinations included markers from three different magnetic resonance parameters (R2*, mean diffusivity and fractional anisotropy). These findings demonstrate that multimodal magnetic resonance imaging of subcortical grey matter structures is useful for the evaluation of Parkinson's disease and, possibly, of other subcortical pathologies.

Mental representations of action: the neural correlates of the verbal and motor components.

Recent theories have hypothesized that semantic representations of action verbs and mental representations of action may be supported by partially overlapping, distributed brain networks. An fMRI experiment in healthy participants was designed to identify the common and specific regions in three different tasks from a common set of object drawings (manipulable man-made objects (MMO) and biological objects (MBO)): the generation of action words (GenA), the mental simulation of action (MSoA) and the mime of an action with the right hand (MimA). A fourth task, object naming (ON), was used as control for input/output effects. A null conjunction identified a common neural network consisting of nine regions distributed over premotor, parietal and occipital cortices. Within this common network, GenA elicited significantly more activation than either ON or MSoA in the left inferior frontal region, while MSoA elicited significantly more activation than either ON or GenA in the left superior parietal lobule. Both MSoA and GenA activated the left inferior parietal lobule more than ON. Furthermore, the left superior parietal cortex was activated to a greater extent by MMO than by MBO regardless of the tasks. These results suggest that action-denoting verbs and motor representations of the same actions activate a common frontal-parietal network. The left inferior parietal cortex and the left superior parietal cortex are likely to be involved in the retrieval of spatial-temporal features of object manipulation; the former might relate to the grasping and manipulation of any object while the latter might be linked to specific object-related gestures.

Combined volumetry and DTI in subcortical structures of mild cognitive impairment and Alzheimer's disease patients.

The aim of this work was to investigate the hypothesis that multimodal MRI is able to detect the progressive disruption of volume and microstructure of subcortical structures in patients with amnestic mild cognitive impairment (a-MCI) and mild Alzheimer's disease (AD) in comparison with healthy controls (CTRL). We combined volumetric and diffusion tensor imaging (DTI) techniques in a cross-sectional study including 30 a-MCI, 30 AD patients, and 30 age-matched CTRL. We employed a fully automated model-based segmentation algorithm on 3 Tesla MRI anatomical images and accurate coregistration of DTI to anatomical images to extract regional values of DTI parameters. Both the hippocampi significantly and progressively decreased in volume from CTRL through MCI to AD. Both the thalami showed a progressive and significant decrease in volume from CTRL to AD. Mean diffusivity (MD) values increased progressively across the three groups in the bilateral hippocampus, amygdala, and in the right caudate. No differences in fractional anisotropy (FA) values were found. Two distinct but overlapping patterns of progression of structural (i.e., atrophy) and microstructural (i.e., MD increase) damage were observed. Particularly, the pattern of atrophy was mirrored by the increasing value of the averaged MD, which provided a further indicator of subtle tissue disruption in the hippocampal structure in mild AD patients. Combining different MRI modalities can allow identifying sensitive indicators of the subtle pathogenic mechanisms that occur in subcortical areas of AD patients.

Aging of subcortical nuclei: microstructural, mineralization and atrophy modifications measured in vivo using MRI.

In the present study, we characterized the physiological aging of deep grey matter nuclei by simultaneously measuring quantitative magnetic resonance parameters sensitive to complementary tissue characteristics (volume atrophy, iron deposition, microstructural damage) in seven different structures in 100 healthy subjects. Large age-related variations were observed in the thalamus, putamen and caudate. No significant correlations with age were observed in the hippocampus, amygdala, pallidum, or accumbens. Multiple regression analyses of advanced imaging data revealed that the best predictors of physiological aging were the mean relaxation time (T2*) of the putamen and the volume and mean diffusivity of the thalamus. These three parameters accounted for over 70% of the age variance in a linear model comprising 100 healthy subjects, aged from 20 to 70 years. Importantly, the statistical analyses highlighted characteristic patterns of variation for the measurements in the various structures evaluated in this study. These findings contribute in establishing a baseline for comparison with pathological changes in the basal ganglia and thalamus.

Volume and iron content in basal ganglia and thalamus.

Magnetic resonance imaging (MRI) studies have highlighted the possibility to investigate brain iron content in vivo. In this study, we combined T2* relaxometry and automatic segmentation of basal ganglia based on T1-weighted images in healthy subjects, with the aim of characterizing age related changes in volume and iron-related relaxivity values (R2*) of these structures. Thirty healthy subjects underwent MR imaging at 3 Tesla. Mean R2* values and volumes were calculated for the selected subcortical structures (pallidum, putamen, thalamus and caudate nucleus). Our results showed a correlation between R2* values and iron concentration as calculated from published post-mortem data. Furthermore, we observed a shrinkage/iron increase with a different pattern in the anatomical regions selected in this work, suggesting that the age-related changes on these MR parameters are specific to the subcortical structure considered. In particular, the putamen demonstrated a decrease of volume and an increase of iron level, with the posterior region of this structure appearing more disposed to iron deposition. Our work suggests that combining volumetry and iron estimation in MRI permits to investigate in vivo neurophysiological and neuropathological changes of basal ganglia.