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Objective: To investigate regional differences of relative metabolite concentrations in the brain of healthy dogs with short echo time, single voxel proton magnetic resonance spectroscopy ((1)H MRS) at 3.0 T., Animals: 10 Beagles., Procedures: Short echo time, single voxel (1)H MRS was performed at the level of the right and left basal ganglia, right and left thalamus, right and left parietal lobes, occipital lobe, and cerebellum. Data were analyzed with an automated fitting method (linear combination model). Metabolite concentrations relative to water content were obtained, including N-acetyl aspartate, total choline, creatine, myoinositol, the sum of glutamine and glutamate (glutamine-glutamate complex), and glutathione. Metabolite ratios with creatine as the reference metabolite were calculated. Concentration differences between right and left hemispheres and sexes were evaluated with a Wilcoxon signed rank test and among various regions of the brain with an independent t test and 1-way ANOVA., Results: No significant differences were detected between sexes and right and left hemispheres. All metabolites, except the glutamine-glutamate complex and glutathione, had regional concentrations that differed significantly. The creatine concentration was highest in the basal ganglia and cerebellum and lowest in the parietal lobes. The N-acetyl aspartate concentration was highest in the parietal lobes and lowest in the cerebellum. Total choline concentration was highest in the basal ganglia and lowest in the occipital lobe., Conclusions and Clinical Relevance: Metabolite concentrations differed among brain parenchymal regions in healthy dogs. This study may provide reference values for clinical and research studies involving (1)H MRS performed at 3.0 T.

Objective: To investigate clinical use of proton magnetic resonance spectroscopy ((1)H MRS) and to compare metabolic brain bioprofiles of dogs with and without hepatic encephalopathy., Animals: 6 dogs with hepatic encephalopathy and 12 control dogs., Procedures: Conventional MRI and single-voxel (1)H MRS were performed with a 3-T magnet. Images for routine MRI planes and sequences were obtained. Single-voxel (1)H MRS was performed with a point-resolved sequence with a short echo time (35 milliseconds) and voxel of interest placement at the level of the basal ganglia. Metabolites of interest included the glutamine-glutamate complex (sum quantification of glutamate and glutamine), myoinositol, N-acetyl aspartate, total choline, and creatine. Data were analyzed with postprocessing fitting algorithm software, and metabolite concentration relative to water and ratios with creatine as the reference metabolite were calculated., Results: Compared with control dogs, dogs with hepatic encephalopathy had specific changes, which included significantly higher concentration relative to water of the glutamine-glutamate complex and significantly lower concentration of myoinositol. Choline and N-acetyl aspartate concentrations were also slightly lower in dogs with hepatic encephalopathy than in control dogs. No differences in creatine concentration were detected between groups., Conclusions and Clinical Relevance: (1)H MRS aided in the diagnosis of hepatic encephalopathy in dogs, and findings supported the assumption that ammonia is a neurotoxin that manifests via glutamine-glutamate complex derangements. Use of (1)H MRS may provide clinically relevant information in patients with subclinical hepatic encephalopathy, equivocal results of bile acids tests, and equivocal ammonia concentrations or may be helpful in monitoring efficacy of medical management.

Background: Exposure to excessive levels of manganese (Mn) is known to induce psychiatric and motor disorders, including parkinsonian symptoms. Therefore, finding a reliable means for early detection of Mn neurotoxicity is desirable., Objectives: Our goal was to determine whether in vivo brain levels of γ-aminobutyric acid (GABA), N-acetylaspartate (NAA), and other brain metabolites in male smelters were altered as a consequence of Mn exposure., Methods: We used T1-weighted magnetic resonance imaging (MRI) to visualize Mn deposition in the brain. Magnetic resonance spectroscopy (MRS) was used to quantify concentrations of NAA, glutamate, and other brain metabolites in globus pallidus, putamen, thalamus, and frontal cortex from a well-established cohort of 10 male Mn-exposed smelters and 10 male age-matched control subjects. We used the MEGA-PRESS MRS sequence to determine GABA levels in a region encompassing the thalamus and adjacent parts of the basal ganglia [GABA-VOI (volume of interest)]., Results: Seven of 10 exposed subjects showed clear T1-hyperintense signals in the globus pallidus indicating Mn accumulation. We found a significant increase (82%; p = 0.014) in the ratio of GABA to total creatine (GABA/tCr) in the GABA-VOI of Mn-exposed subjects, as well as a distinct decrease (9%; p = 0.04) of NAA/tCr in frontal cortex that strongly correlated with cumulative Mn exposure (R = -0.93; p < 0.001)., Conclusions: We demonstrated elevated GABA levels in the thalamus and adjacent basal ganglia and decreased NAA levels in the frontal cortex, indicating neuronal dysfunction in a brain area not primarily targeted by Mn. Therefore, the noninvasive in vivo MRS measurement of GABA and NAA may prove to be a powerful tool for detecting presymptomatic effects of Mn neurotoxicity.

Purpose: To evaluate the reproducibility of neural activations induced by an anticipatory anxiety provocation challenge in healthy volunteers., Materials and Methods: Fourteen healthy male volunteers participated in two separate functional MRI (fMRI) sessions in which they underwent a paradigm based on anticipation of aversive transcutaneous electrical nerve stimulations. This paradigm consisted of alternating presentation of red circles associated with the likelihood that aversive stimuli may be given and blue circles during which the subjects knew that no shock could be given. Anxiety state was compared before the fMRI sessions and during the threat periods using clinical scales (Hamilton, STAI-Y1), the Bond and Lader Visual Analogue Scale, and self-rating scales of apprehension and stimulus aversivity., Results: The selected paradigm induced anticipatory anxiety of moderate intensity as suggested by clinical scales and apprehension rating, without any habituation to the somatosensory stimulus across sessions. Compared to rest periods, threat of the aversive stimulus induced clear brain activation in anticipatory anxiety-related areas: frontal/prefrontal cortex, insula, lentiform nucleus, temporal pole, and cingulate cortex. Anxiety symptoms and cerebral activity were reproducible across sessions., Conclusion: The fMRI paradigm and its assessment method include all criteria to speed up the evaluation and the development of new anxiolytics.

The X-linked McLeod neuroacanthocytosis syndrome is a multisystem disorder with central nervous system manifestations resembling Huntington's disease. We examined 5 McLeod patients and 5 asymptomatic heterozygous females with fast multiple spin-echo spectroscopic imaging. Three patients with pronounced psychiatric or cognitive manifestations had pathological N-acetyl aspartate/(creatine + choline) ratios in frontal, temporal, and insular areas, with an individual pattern. Two patients with a severe choreatic movement disorder had unilateral thalamic alterations. One patient with moderate movement disorder and personality disorder had bilateral occipital alterations. One female heterozygote had unilateral insular metabolic alterations, possibly indicating subclinical cerebral involvement. Although the prominent psychiatric and cognitive manifestations in McLeod patients suggest significant and widespread cortical abnormalities, previous neuroradiological and histopathological data had not revealed definite extrastriatal pathology. Our findings demonstrating metabolic abnormalities in different brain regions of McLeod patients might either reflect neuronal dysfunction due to impaired basal ganglia-thalamo-cortical circuits or subtle structural alterations in the particular cerebral areas., (Copyright 2006 S. Karger AG, Basel.)

This article reviews spectral editing techniques for in vivo 1H NMR spectroscopy of human brain tissue at moderate field strengths of 1.5-3 Tesla. Various aspects of 1H NMR spectroscopy are discussed with regard to in vivo applications. The parameter set [delta, J, n] (delta being the relative chemical shift, J the scalar coupling constant and n the number of coupled spins) is used to characterize the spin systems under investigation and to classify the editing techniques that are used in in vivo 1H NMR spectroscopy.

This article reviews spectral editing techniques for in vivo 1H NMR spectroscopy of human brain tissue at moderate field strengths of 1.5–3 Tesla. Various aspects of 1H NMR spectroscopy are discussed with regard to in vivo applications. The parameter set [δ, J, n] (δ being the relative chemical shift, J the scalar coupling constant and n the number of coupled spins) is used to characterize the spin systems under investigation and to classify the editing techniques that are used in in vivo 1H NMR spectroscopy. [Copyright &y& Elsevier]