Combined 1H and 31P MR spectroscopic imaging: impaired energy metabolism in severe carotid stenosis and changes upon treatment

Could Phosphorous MR Spectroscopy Help Predict the Severity of Vasospasm? A Pilot Study

One of the main causes of the dismal prognosis in patients who survive the initial bleeding after aneurysmal subarachnoidal hemorrhage is the delayed cerebral ischaemia caused by vasospasm. Studies suggest that cerebral magnesium and pH may potentially play a role in the pathophysiology of this adverse event. Using phosphorous magnetic resonance spectrocopy (31P-MRS), we calculated the cerebral magnesium (Mg) and pH levels in 13 patients who suffered from aSAH. The values between the group that developed clinically significant vasospasm (n = 7) and the group that did not (n = 6) were compared. The results of this study show significantly lower cerebral Mg levels (p = 0.019) and higher pH levels (p < 0.001) in the cumulative group (all brain voxels together) in patients who developed clinically significant vasospasm. Further clinical studies on a larger group of carefully selected patients are needed in order to predict clinically significant vasospasm.

Vascular disease risk factors in multiple sclerosis: Effect on metabolism and brain volumes

BACKGROUND

Vascular disease risk factors (VDRF) such as hypertension, hyperlipidemia, obesity, diabetes and heart disease likely play a role in disease progression in people with multiple sclerosis (PwMS) (Marrie, Rudick et al. 2010). Studies exploring the mechanistic connection between vascular disease and MS disease progression are scant. We hypothesized that phosphate energy metabolism impairment in PwMS with VDRFs (VDRF+) will be greater compared to PwMS without VDRFs (VDRF-) and is related to increased brain atrophy in VDRF+. To test this hypothesis, we planned to study the differences in the high energy phosphate (HEP) metabolites in cerebral gray matter as assessed by 31P magnetic resonance spectroscopic imaging (MRSI) and MRI brain volumetric in the VDRF+ and VDRF- PwMS at four different timepoints over a 3 yearlong period using a 7T MR system. We present here the results from the cross-sectional evaluation of HEP metabolites and brain volumes. We also evaluated the differences in clinical impairment, blood metabolic biomarkers and quality of life in VDRF+ and VDRF- PwMS in this cohort.

METHODS

Group differences in high energy phosphate metabolites were assessed from a volume of interest in the occipital region using linear mixed models. Brain parenchymal and white matter lesion volumes were determined from MR anatomic images. We present here the cross-sectional analysis of the baseline data collected as part of a longitudinal 3 yearlong study where we obtained baseline and subsequent 6-monthly clinical and laboratory data and annual 7T MRI volumetric and 31P MR spectroscopic imaging (MRSI) data on 52 PwMS with and without VDRF. Key clinical and laboratory outcomes included: body mass index (BMI), waist and thigh circumferences and disability [Expanded Disability Status Scale (EDSS)], safety (complete blood count with differential, complete metabolic), lipid panel including total cholesterol and HbA1C. We analyzed clinical and laboratory data for the group differences using student's t or χ2 test. We investigated relationship between phosphate metabolites and VDRF using mixed effect linear regression.

RESULTS

Complete MRI data were available for 29 VDRF+, age 56.3 (6.8) years [mean (SD)] (83% female), and 23 VDRF-, age 52.5 (7.5) years (57% female) individuals with MS. The mean value of normalized adenosine triphosphate (ATP) (calculated as the ratio of ATP to total phosphate signal in a voxel) was decreased by 4.5% (p < .05) in VDRF+ compared to VDRF- MS group. White matter lesion (WML) volume fraction in VDRF+ individuals {0.007 (0.007)} was more than doubled compared to VDRF- participants {0.003 (0.006), p= .02}.

CONCLUSIONS

We found significantly lower brain ATP and higher inorganic phosphate (Pi) in those PwMS with VDRFs compared to those without. ATP depletion may reflect mitochondrial dysfunction. Ongoing longitudinal data analysis from this study, not presented here, will evaluate the relationship of phosphate metabolites, brain atrophy and disease progression in PwMS with and without vascular disease.

Phosphorus metabolism in the brain of cognitively normal midlife individuals at risk for Alzheimer's disease

BACKGROUND

Neurometabolic abnormalities and amyloid-beta plaque deposition are important early pathophysiologic changes in Alzheimer's disease (AD). This study investigated the relationship between high-energy phosphorus-containing metabolites, glucose uptake, and amyloid plaque using phosphorus magnetic resonance spectroscopy (³¹P-MRS) and positron emission tomography (PET).

METHODS

We measured ³¹P-MRS, fluorodeoxyglucose (FDG)-PET, and Pittsburgh Compound B (PiB)-PET in a cohort of 20 cognitively normal middle-aged adults at risk for AD. We assessed ³¹P-MRS reliability by scanning a separate cohort of 13 healthy volunteers twice each. We calculated the coefficient-of-variation (CV) of metabolite ratios phosphocreatine-to-adenosine triphosphate (PCr/α-ATP), inorganic phosphate (Pi)-to-α-ATP, and phosphomonoesters-to-phosphodiesters (PME/PDE), and pH in pre-defined brain regions. We performed linear regression analysis to determine the relationship between ³¹P measurements and tracer uptake, and Dunn's multiple comparison tests to investigate regional differences in phosphorus metabolism. Finally, we performed linear regression analysis on ³¹P-MRS measurements in both cohorts to investigate the relationship of phosphorus metabolism with age.

RESULTS

Most regional ³¹P metabolite ratio and pH inter- and intra-day CVs were well below 10%. There was an inverse relationship between FDG-SUV levels and metabolite ratios PCr/α-ATP, Pi/α-ATP, and PME/PDE in several brain regions in the AD risk group. There were also several regional differences among ³¹P metabolites and pH in the AD risk group including elevated PCr/α-ATP, depressed PME/PDE, and elevated pH in the temporal cortices. Increased PCr/α-ATP throughout the brain was associated with aging.

CONCLUSIONS

Phosphorus spectroscopy in the brain can be performed with high repeatability. Phosphorus metabolism varies with region and age, and is related to glucose uptake in adults at risk for AD. Phosphorus spectroscopy may be a valuable approach to study early changes in brain energetics in high-risk populations.

Energy metabolism measured by 31P magnetic resonance spectroscopy in the healthy human brain

BACKGROUND AND PURPOSE

Phosphorous magnetic resonance spectroscopy (31P-MRS) allows a non-invasive analysis of phosphorus-containing compounds in vivo. The present study investigated the influence of brain region, hemisphere, age, sex and brain volume on 31P-MRS metabolites in healthy adults.

MATERIALS AND METHODS

Supratentorial brain 31P-MRS spectra of 125 prospectively recruited healthy volunteers (64 female, 61 male) aged 20 to 85 years (mean: 49.4 ± 16.9 years) were examined with a 3D-31P-MRS sequence at 3T, and the compounds phosphocreatine (PCr), inorganic phosphate (Pi) and adenosine triphosphate (ATP) were measured. From this data, the metabolite ratios PCr/ATP, Pi/ATP and PCr/Pi were calculated for different brain regions. In addition, volumes of gray matter, white matter and cerebrospinal fluid were determined.

RESULTS

For all metabolite ratios significant regional differences and in several regions sex differences were found. In some brain regions and for some metabolites hemispheric differences were detected. In addition, changes with aging were found, which differed between women and men.

CONCLUSIONS

The present results indicate that 31P-MRS metabolism varies throughout the brain, with age and between sexes, and therefore have important practical implications for the design and the interpretation of future 31P-MRS studies under physiological conditions and in patients with various cerebral diseases.

Changes in Brain Energy and Membrane Metabolism in Glioblastoma following Chemoradiation

Brain parenchyma infiltration with glioblastoma (GB) cannot be entirely visualized by conventional magnetic resonance imaging (MRI). The aim of this study was to investigate changes in the energy and membrane metabolism measured with phosphorous MR spectroscopy (31P-MRS) in the presumably “normal-appearing” brain following chemoradiation therapy (CRT) in GB patients in comparison to healthy controls. Twenty (seven female, thirteen male) GB patients underwent a 31P-MRS scan prior to surgery (baseline) and after three months of standard CRT (follow-up examination. The regions of interest “contrast-enhancing (CE) tumor” (if present), “adjacent to the (former) tumor”, “ipsilateral distant” hemisphere, and “contralateral” hemisphere were compared, differentiating between patients with stable (SD) and progressive disease (PD). Metabolite ratios PCr/ATP, Pi/ATP, PCr/Pi, PME/PDE, PME/PCr, and PDE/ATP were investigated. In PD, energy and membrane metabolism in CE tumor areas have a tendency to “normalize” under therapy. In different “normal-appearing” brain areas of GB patients, the energy and membrane metabolism either “normalized” or were “disturbed”, in comparison to baseline or controls. Differences were also detected between patients with SD and PD. 31P-MRS might contribute as an additional imaging biomarker for outcome measurement, which remains to be investigated in a larger cohort.

Phosphorous Magnetic Resonance Spectroscopy to Detect Regional Differences of Energy and Membrane Metabolism in Naïve Glioblastoma Multiforme

Simple Summary

Glioblastoma multiforme is a highly aggressive brain tumor, tending to infiltrate even larger zones of brain tissue than visible on conventional magnetic resonance imaging. By application of phosphorus magnetic resonance spectroscopy in patients with naïve glioblastoma multiforme, we tried to demonstrate changes in energy and membrane metabolism not only in affected regions but also in distant brain regions, the opposite brain hemisphere, and in comparison to healthy volunteers. We found reduced energetic states and signs of increased cell membrane turnover in regions of visible tumor and differences to and between the “normal-appearing” brains of glioblastoma patients and the brains of healthy volunteers. Our pilot study confirmed the feasibility of the method, so differences between various genetic mutations or clinical applicability for follow-up monitoring can be assessed in larger cohorts.

Abstract

Background: Glioblastoma multiforme (GBM) is a highly malignant primary brain tumor with infiltration of, on conventional imaging, normal-appearing brain parenchyma. Phosphorus magnetic resonance spectroscopy (31P-MRS) enables the investigation of different energy and membrane metabolites. The aim of this study is to investigate regional differences of 31P-metabolites in GBM brains. Methods: In this study, we investigated 32 patients (13 female and 19 male; mean age 63 years) with naïve GBM using 31P-MRS and conventional MRI. Contrast-enhancing (CE), T2-hyperintense, adjacent and distant ipsilateral areas of the contralateral brain and the brains of age- and gender-matched healthy volunteers were assessed. Moreover, the 31P-MRS results were correlated with quantitative diffusion parameters. Results: Several metabolite ratios between the energy-dependent metabolites and/or the membrane metabolites differed significantly between the CE areas, the T2-hyperintense areas, the more distant areas, and even the brains of healthy volunteers. pH values and Mg²⁺ concentrations were highest in visible tumor areas and decreased with distance from them. These results are in accordance with the literature and correlated with quantitative diffusion parameters. Conclusions: This pilot study shows that 31P-MRS is feasible to show regional differences of energy and membrane metabolism in brains with naïve GBM, particularly between the different “normal-appearing” regions and between the contralateral hemisphere and healthy controls. Differences between various genetic mutations or clinical applicability for follow-up monitoring have to be assessed in a larger cohort.

The pH sensitivity of APT-CEST using phosphorus spectroscopy as a reference method

The pH value is a potential physiological marker for clinical diagnosis as it is altered in pathologies such as tumors. While intracellular pH can be measured noninvasively via phosphorus spectroscopy (³¹ P MRSI), Amide Proton Transfer-Chemical Exchange Saturation Transfer (APT-CEST) MRI has been suggested as an alternative method for pH quantification. To assess the suitability of APT-CEST contrast for pH quantification, two approaches (magnetization transfer ratio asymmetry [MTR_asym ] and Lorentzian difference analysis [LDA]) for analyzing the Z-spectrum have been correlated with pH values obtained by ³¹ P MRSI. Fourteen patients with glioblastoma and 12 healthy controls were included. In contrast to MTR_asym , the LDA is modeling the direct water saturation and the semi-solid magnetization transfer, allowing a separate evaluation of the aliphatic nuclear Overhauser effect and the APT-CEST. The results of our study show that the pH values obtained by ³¹ P MRSI correspond well with both methods describing the APT-CEST contrast. Two-sample t-test showed significant differences in MTR_asym , LDA and pH obtained by ³¹ P MRSI for regions of interest in glioblastoma, contralateral control areas and normal appearing white matter (P < 0.001). A slightly improved correlation between the amide signal and pH was found after performing LDA (r = 0.78) compared with MTR_asym (r = 0.70). While both methods can be used to monitor pH changes, the LDA approach appears to be better suited.

Revascularization of High-Grade Carotid Stenosis Restores Global Cerebral Energy Metabolism

Background and Purpose- Chronic cerebral hemodynamic impairment due to high-grade occlusive carotid disease may lead to compromised energy metabolism. This might result in chronic subtle tissue damage, even in patients without overt brain infarction. The aim of this study was to investigate hypoperfusion-related changes of cerebral energy metabolism and their potential restitution after revascularization. For this purpose, 3-dimensional ³¹P magnetic resonance spectroscopy and oxygenation-sensitive T2' magnetic resonance imaging were used (with 1/T2'=1/T2*-1/T2), which were expected to cross-validate each other. Methods- Ten patients with unilateral high-grade carotid artery stenosis resulting in a transient ischemic attack or a nondisabling cerebral ischemia were included. Then, high-energy metabolites, intracellular pH, and oxygenation-sensitive quantitative (q)T2' values were determined in noninfarcted hypoperfused areas delineated on time-to-peak maps from perfusion-weighted imaging and in unaffected contralateral areas before and shortly after carotid stenting/endarterectomy. Repeated measures ANOVA was used to test for intervention effects. Results- Within dependent hypoperfused areas ipsilateral to the stenosis, qT2' was significantly decreased ( P<0.05) as compared to corresponding contralateral areas before carotid intervention. There was a significant effect of carotid intervention on qT2' values in both hemispheres ( P<0.001). No differences between hemispheres were found for qT2' after revascularization. Intracellular pH and qT2' values showed a significant negative relationship ( P=0.005) irrespective of time point and hemisphere. Conclusions- After revascularization of unilateral high-grade carotid stenosis, previously decreased qT2' in the dependent hypoperfused territory as marker of hypoxia reincreases not only in the dependent territory but also in corresponding contralateral brain tissue. This might indicate a restriction of the whole-brain oxygen metabolism in case of unilateral high-grade carotid stenosis and an improvement of whole-brain oxygenation after revascularization that goes beyond acute clinically apparent affection of the dependent territory. Furthermore, tissue oxygen supply seems to be closely linked to intracellular pH.

Results of Phosphorus Magnetic Resonance Spectroscopy for Brain Metastases Correlate with Histopathologic Results

BACKGROUND

Brain metastases (BMs) are classically well-circumscribed lesions. Still, the amount of edema in these neoplasms suggests either mechanisms of infiltration or defense. A better understanding of the mechanisms within the edema of BMs seems reasonable to preoperatively identify areas of potential infiltration and resect them. BMs represent tumors with high energy demand and cell turnover; therefore, they qualify for preoperative investigation with phosphorus-31 magnetic resonance spectroscopy (31PMRS), which reveals information about those characteristics.

METHODS

Ten patients with BMs were included in this trial. All underwent preoperative standard magnetic resonance imaging with additional 31PMRS. In all patients, 1 voxel within the contrast-enhancing tumor (CE+), 1 voxel at the border (including CE+ areas and surrounding T2-hyperintensive [T2+] areas), and 1 distant voxel purely including T2+ areas were determined by a neuroradiologist and a neurosurgeon. A frameless stereotactic biopsy was performed after craniotomy. Subsequently, the metabolites of the 31PMRS were analyzed and compared with the histopathologic results.

RESULTS

Ratios, reflecting resynthesis (CE+/border/T2+: 1.109 ± 0.192/1.112 ± 0.158/1.083 ± 0.097), hydrolysis (0.303 ± 0.089/0.360 ± 0.122/0.321 ± 0.089), energy demand (4.227 ± 2.35/3.453 ± 1.284/3.599 ± 0.833), and membrane turnover (1.239 ± 0.2611/3.453 ± 1.284/3.599 ± 0.283) were calculated and compared intraindividually with a voxel from the contralateral side (resynthesis/hydrolysis/energy demand/membrane turnover: 1.063 ± 0.085/0.335 ± 0.073/3.317 ± 0.7573/0.784 ± 0.186), respectively. Resynthesis showed a trend toward higher ratios in CE+ and border biopsies without reaching statistical significances. This trend was also seen concerning energy demand. Membrane turnover was significantly higher in CE+, border zone, and also in the T2+ areas compared with controls (P > 0.001).

CONCLUSIONS

31PMRS in BMs provides information on metabolic changes in tumor and surrounding edema. There is proof of enhanced metabolism in tissue without histologic tumor manifestation.

Fast data acquisition techniques in magnetic resonance spectroscopic imaging

Magnetic resonance spectroscopic imaging (MRSI) is an important technique for assessing the spatial variation of metabolites in vivo. The long scan times in MRSI limit clinical applicability due to patient discomfort, increased costs, motion artifacts, and limited protocol flexibility. Faster acquisition strategies can address these limitations and could potentially facilitate increased adoption of MRSI into routine clinical protocols with minimal addition to the current anatomical and functional acquisition protocols in terms of imaging time. Not surprisingly, a lot of effort has been devoted to the development of faster MRSI techniques that aim to capture the same underlying metabolic information (relative metabolite peak areas and spatial distribution) as obtained by conventional MRSI, in greatly reduced time. The gain in imaging time results, in some cases, in a loss of signal-to-noise ratio and/or in spatial and spectral blurring. This review examines the current techniques and advances in fast MRSI in two and three spatial dimensions and their applications. This review categorizes the acceleration techniques according to their strategy for acquisition of the k-space. Techniques such as fast/turbo-spin echo MRSI, echo-planar spectroscopic imaging, and non-Cartesian MRSI effectively cover the full k-space in a more efficient manner per T_R . On the other hand, techniques such as parallel imaging and compressed sensing acquire fewer k-space points and employ advanced reconstruction algorithms to recreate the spatial-spectral information, which maintains statistical fidelity in test conditions (ie no statistically significant differences on voxel-wise comparisions) with the fully sampled data. The advantages and limitations of each state-of-the-art technique are reviewed in detail, concluding with a note on future directions and challenges in the field of fast spectroscopic imaging.

Cerebral Phosphorus Magnetic Resonance Spectroscopy in a Patient with Giant Cell Arteritis and Endovascular Therapy

With phosphorus magnetic resonance spectroscopy (31P MRS) energy metabolites can be visualised. In this case study, we report on a patient with stenosis and wall contrast enhancement in the left internal carotid and the right vertebral artery, due to giant cell arteritis. 31P MRS revealed a decreased inorganic phosphate-to-phosphocreatine ratio (Pi/PCr) in regions with a prolonged mean transit time (MTT). After systemic therapy and angioplasty of the right vertebral artery, the stenosis and the symptoms improved and the area of prolonged MTT became smaller. However, a new decrease in Pi/PCr in areas that developed moderately prolonged MTT was observed.

In vivo ³¹P magnetic resonance spectroscopic imaging (MRSI) for metabolic profiling of human breast cancer xenografts

PURPOSE

To study cancer associated with abnormal metabolism of phospholipids, of which several have been proposed as biomarkers for malignancy or to monitor response to anticancer therapy. We explored 3D (31) P magnetic resonance spectroscopic imaging (MRSI) at high magnetic field for in vivo assessment of individual phospholipids in two patient-derived breast cancer xenografts representing good and poor prognosis (luminal- and basal-like tumors).

MATERIALS AND METHODS

Metabolic profiles from luminal-like and basal-like xenograft tumors were obtained in vivo using 3D (31) P MRSI at 11.7T and from tissue extracts in vitro at 14.1T. Gene expression analysis was performed in order to support metabolic differences between the two xenografts.

RESULTS

In vivo (31) P MR spectra were obtained in which the prominent resonances from phospholipid metabolites were detected at a high signal-to-noise ratio (SNR >7.5). Metabolic profiles obtained in vivo were in agreement with those obtained in vitro and could be used to discriminate between the two xenograft models, based on the levels of phosphocholine, phosphoethanolamine, glycerophosphocholine, and glycerophosphoethanolamine. The differences in phospholipid metabolite concentration could partly be explained by gene expression profiles.

CONCLUSION

Noninvasive metabolic profiling by 3D (31) P MRSI can discriminate between subtypes of breast cancer based on different concentrations of choline- and ethanolamine-containing phospholipids.

Handgrip-Related Activation in the Primary Motor Cortex Relates to Underlying Neuronal Metabolism After Stroke

BACKGROUND

Abnormal task-related activation in primary motor cortices (M1) has been consistently found in functional imaging studies of subcortical stroke. Whether the abnormal activations are associated with neuronal alterations in the same or homologous area is not known.

OBJECTIVE

Our goal was to establish the relationships between M1 measures of motor-task-related activation and a neuronal marker, N-acetylaspartate (NAA), in patients with severe to mild hemiparesis.

METHODS

A total of 18 survivors of an ischemic subcortical stroke (confirmed on T2-weighted images) at more than six months post-onset and 16 age- and sex-matched right-handed healthy controls underwent functional MRI during a handgrip task (impaired hand in patients, dominant hand in controls) and proton magnetic resonance spectroscopy ((1)H-MRS) imaging. Spatial extent and magnitude of blood oxygen level-dependent response (or activation) and NAA levels were measured in each M1. Relationships between activation and NAA were determined.

RESULTS

Compared with controls, patients had a greater extent of contralesional (ipsilateral to impaired hand, P < .001) activation and a higher magnitude of activation and lower NAA in both ipsilesional (P = .008 and P < .001, respectively) and contralesional (P < .0001, P < .05) M1. There were significant negative correlations between extent of activation and NAA in each M1 (P = .02) and a trend between contralesional activation and ipsilesional NAA (P = .08) in patients but not in controls.

CONCLUSIONS

Our results suggest that after stroke greater neuronal recruitment could be a compensatory response to lower neuronal metabolism. Thus, dual-modality imaging may be a powerful tool for providing complementary probes of post-stroke brain reorganization.

Motor and premotor cortices in subcortical stroke: proton magnetic resonance spectroscopy measures and arm motor impairment

BACKGROUND

Although functional imaging and neurophysiological approaches reveal alterations in motor and premotor areas after stroke, insights into neurobiological events underlying these alterations are limited in human studies.

OBJECTIVE

We tested whether cerebral metabolites related to neuronal and glial compartments are altered in the hand representation in bilateral motor and premotor areas and correlated with distal and proximal arm motor impairment in hemiparetic persons.

METHODS

In 20 participants at >6 months postonset of a subcortical ischemic stroke and 16 age- and sex-matched healthy controls, the concentrations of N-acetylaspartate and myo-inositol were quantified by proton magnetic resonance spectroscopy. Regions of interest identified by functional magnetic resonance imaging included primary (M1), dorsal premotor (PMd), and supplementary (SMA) motor areas. Relationships between metabolite concentrations and distal (hand) and proximal (shoulder/elbow) motor impairment using Fugl-Meyer Upper Extremity (FMUE) subscores were explored.

RESULTS

N-Acetylaspartate was lower in M1 (P = .04) and SMA (P = .004) and myo-inositol was higher in M1 (P = .003) and PMd (P = .03) in the injured (ipsilesional) hemisphere after stroke compared with the left hemisphere in controls. N-Acetylaspartate in ipsilesional M1 was positively correlated with hand FMUE subscores (P = .04). Significant positive correlations were also found between N-acetylaspartate in ipsilesional M1, PMd, and SMA and in contralesional M1 and shoulder/elbow FMUE subscores (P = .02, .01, .02, and .02, respectively).

CONCLUSIONS

Our preliminary results demonstrated that proton magnetic resonance spectroscopy is a sensitive method to quantify relevant neuronal changes in spared motor cortex after stroke and consequently increase our knowledge of the factors leading from these changes to arm motor impairment.

Neuronal-glial alterations in non-primary motor areas in chronic subcortical stroke

Whether functional changes of the non-primary motor areas, e.g., dorsal premotor (PMd) and supplementary motor (SMA) areas, after stroke, reflect reorganization phenomena or recruitment of a pre-existing motor network remains to be clarified. We hypothesized that cellular changes in these areas would be consistent with their involvement in post-stroke reorganization. Specifically, we expected that neuronal and glial compartments would be altered in radiologically normal-appearing, i.e., spared, PMd and SMA in patients with arm paresis. Twenty survivors of a single ischemic subcortical stroke and 16 age-matched healthy controls were included. At more than six months after stroke, metabolites related to neuronal and glial compartments: N-acetylaspartate, myo-inositol, and glutamate/glutamine, were quantified by proton magnetic resonance spectroscopy in PMd and SMA in both injured (ipsilesional) and un-injured (contralesional) hemispheres. Correlations between metabolites were also calculated. Finally, relationships between metabolite concentrations and arm motor impairment (total and proximal Fugl-Meyer Upper Extremity, FMUE, scores) were analyzed. Compared to controls, stroke survivors showed significantly higher ipsilesional PMd myo-inositol and lower SMA N-acetylaspartate. Significantly lower metabolite correlations were found between ipsilesional and contralesional SMA. Ipsilesional N-acetylaspartate was significantly related to proximal FMUE scores. This study provides evidence of abnormalities in metabolites, specific to neuronal and glial compartments, across spared non-primary motor areas. Ipsilesional alterations were related to proximal arm motor impairment. Our results suggest the involvement of these areas in post-stroke reorganization.

Metabolic gray matter changes of adolescents with anorexia nervosa in combined MR proton and phosphorus spectroscopy

INTRODUCTION

There are hints for changes in phospholipid membrane metabolism and structure in the brain of adolescents with anorexia nervosa (AN) using either proton ((1)H) or phosphorus ((31)P) magnetic resonance spectroscopic imaging (MRSI). We aimed to specify these pathological metabolite changes by combining both methods with additional focus on the neuronal metabolites glutamate (Glu) and N-acetyl-l-aspartate (NAA).

METHODS

Twenty-one female patients (mean 14.4  ±  1.9 years) and 29 female controls (mean 16  ±  1.6 years) underwent (1)H and (31)P MRSI at 3 T applied to the centrum semiovale including the anterior cingulate cortex. We assessed gray matter (GM) and white matter (WM) metabolite concentration changes of the frontal and parietal brain measuring choline(Cho)- and ethanolamine(Eth)-containing compounds, Glutamate (Glu) and glutamine (Gln) and their sum (Glx), myoinositol, NAA, and high-energy phosphates.

RESULTS

For (1)H MRSI, a clear discrimination between GM and WM concentrations was possible, showing an increase of Glx (p < 0.001), NAA (frontal p < 0.05), pooled creatine (tCr) (p < 0.001), and choline (tCho) (p < 0.05) in the GM of AN patients. The lipid catabolites glycerophosphocholine (p < 0.07) and glycerophosphoethanolamine (p < 0.03) were increased in the parietal region.

CONCLUSIONS

Significant changes in GM metabolite concentrations were observed in AN possibly triggered by elevated excitotoxin Glu. Increased tCho may indicate modifications of membrane phospholipids due to increased catabolism in the parietal region. Since no significant changes in phosphorylated choline compounds were found for the frontal region, the tCho increase in this region may hint to fluidity changes.

Phosphorus and proton magnetic resonance spectroscopy demonstrates mitochondrial dysfunction in early and advanced Parkinson's disease

Mitochondrial dysfunction hypothetically contributes to neuronal degeneration in patients with Parkinson's disease. While several in vitro data exist, the measurement of cerebral mitochondrial dysfunction in living patients with Parkinson's disease is challenging. Anatomical magnetic resonance imaging combined with phosphorus and proton magnetic resonance spectroscopic imaging provides information about the functional integrity of mitochondria in specific brain areas. We measured partial volume corrected concentrations of low-energy metabolites and high-energy phosphates with sufficient resolution to focus on pathology related target areas in Parkinson's disease. Combined phosphorus and proton magnetic resonance spectroscopic imaging in the mesostriatal region was performed in 16 early and 13 advanced patients with Parkinson's disease and compared to 19 age-matched controls at 3 Tesla. In the putamen and midbrain of both Parkinson's disease groups, we found a bilateral reduction of high-energy phosphates such as adenosine triphophosphate and phosphocreatine as final acceptors of energy from mitochondrial oxidative phosphorylation. In contrast, low-energy metabolites such as adenosine diphophosphate and inorganic phosphate were within normal ranges. These results provide strong in vivo evidence that mitochondrial dysfunction of mesostriatal neurons is a central and persistent phenomenon in the pathogenesis cascade of Parkinson's disease which occurs early in the course of the disease.

Posterior paralimbic and frontal metabolite impairments in asymptomatic hypertension with different treatment outcomes

Hypertension is associated with cognitive decline in elderly persons. We studied asymptomatic hypertensive subjects using brain magnetic resonance (MR) spectroscopy to evaluate metabolite impairments before the appearance of symptoms in patients with different treatment outcomes. In all, 14 healthy controls and 37 asymptomatic hypertensive patients (17 controlled and 20 resistant) underwent brain structural MR and MR spectroscopy of the posterior paralimbic (PPL) area and left frontal white matter. Ischemic burden (IB), global cortical atrophy and microbleeds were analyzed with visual scales. Metabolite ratios involving N-acetyl-aspartate (NAA), creatine (Cr), choline (Cho) and myoinositol (mI) were computed. Ultrasound measurements, including intima-media thickness, plaques and hemodynamic ratios, were obtained. Intergroup differences in IB, atrophy and metabolite ratios, and the atrophy and IB relationship were assessed with parametric and nonparametric statistical tests. In addition, the impacts of demographic, analytic and clinical factors, ischemia and atrophy, and ultrasound measurements on metabolite ratios were assessed. The significance level was set at P<or=0.05. Higher atrophy scores presented with higher total or frontal IB (P<0.05). However, there was no intergroup difference in atrophy and IB. PPL mI/Cr was increased in resistant hypertension (P<0.021), whereas frontal NAA/Cr (P<0.007) showed opposite trends between controlled (increased ratios) and resistant (decreased ratios) hypertension. Unlike PPL mI/Cr, frontal NAA/Cr showed significant correlations with the lipid profile and ultrasound measurements. PPL mI/Cr increases in resistant hypertension, and frontal NAA/Cr diverges between controlled and resistant hypertension before physical and neuropsychological symptoms appear.