The influence of season on glutamate and GABA levels in the healthy human brain investigated by magnetic resonance spectroscopy imaging

Seasonal changes in neurotransmitter systems have been demonstrated in imaging studies and are especially noticeable in diseased states such as seasonal affective disorder (SAD). These modulatory neurotransmitters, such as serotonin, are influencing glutamatergic and GABAergic neurotransmission. Furthermore, central components of the circadian pacemaker are regulated by GABA (the suprachiasmatic nucleus) or glutamate (e.g., the retinohypothalamic tract). Therefore, we explored seasonal differences in the GABAergic and glutamatergic system in 159 healthy individuals using magnetic resonance spectroscopy imaging with a GABA-edited 3D-MEGA-LASER sequence at 3T. We quantified GABA+/tCr, GABA+/Glx, and Glx/tCr ratios (GABA+, GABA+ macromolecules; Glx, glutamate + glutamine; tCr, total creatine) in five different subcortical brain regions. Differences between time periods throughout the year, seasonal patterns, and stationarity were tested using ANCOVA models, curve fitting approaches, and unit root and stationarity tests, respectively. Finally, Spearman correlation analyses between neurotransmitter ratios within each brain region and cumulated daylight and global radiation were performed. No seasonal or monthly differences, seasonal patterns, nor significant correlations could be shown in any region or ratio. Unit root and stationarity tests showed stable patterns of GABA+/tCr, GABA+/Glx, and Glx/tCr levels throughout the year, except for hippocampal Glx/tCr. Our results indicate that neurotransmitter levels of glutamate and GABA in healthy individuals are stable throughout the year. Hence, despite the important correction for age and gender in the analyses of MRS derived GABA and glutamate, a correction for seasonality in future studies does not seem necessary. Future investigations in SAD and other psychiatric patients will be of high interest.

Neonatal hyperbilirubinemia differentially alters the neurochemical profiles of the developing cerebellum and hippocampus in a preterm Gunn rat model

Neonatal hyperbilirubinemia (NHB) can lead to brain injury in newborn infants by affecting specific regions including the cerebellum and hippocampus. Extremely preterm infants are more vulnerable to bilirubin neurotoxicity, but the mechanism and extent of injury is not well understood. A preterm version of the Gunn rat model was utilized to investigate severe preterm NHB. Homozygous/jaundiced Gunn rat pups were injected (i.p.) on postnatal day (P) 5 with sulfadimethoxine, which increases serum free bilirubin capable of crossing the blood-brain barrier and causing brain injury. The neurochemical profiles of the cerebellum and hippocampus were determined using in vivo ¹ H MRS at 9.4 T on P30 and compared with those of heterozygous/non-jaundiced control rats. Transcript expression of related genes was determined by real-time quantitative PCR. MRI revealed significant morphological changes in the cerebellum of jaundiced rats. The concentrations of myo-inositol (+54%), glucose (+51%), N-acetylaspartylglutamate (+21%), and the sum of glycerophosphocholine and phosphocholine (+17%) were significantly higher in the cerebellum of the jaundiced group compared with the control group. Despite the lack of morphologic changes in the hippocampus, the concentration of myo-inositol (+9%) was higher and the concentrations of creatine (-8%) and of total creatine (-3%) were lower in the jaundiced group. In the hippocampus, expression of calcium/calmodulin dependent protein kinase II alpha (Camk2a), glucose transporter 1 (Glut1), and Glut3 transcripts were downregulated in the jaundiced group. In the cerebellum, glial fibrillary acidic protein (Gfap), myelin basic protein (Mbp), and Glut1 transcript expression was upregulated in the jaundiced group. These results indicate osmotic imbalance, gliosis, and changes in energy utilization and myelination, and demonstrate that preterm NHB critically affects brain development in a region-specific manner, with the cerebellum more severely impacted than the hippocampus.

Prevalence and Molecular Characterization of Methicillin-Resistant Staphylococci (MRS) and Mammaliicocci (MRM) in Dromedary Camels from Algeria: First Detection of SCCmec-mecC Hybrid in Methicillin-Resistant Mammaliicoccus lentus

Dromedary camels are an important source of food and income in many countries. However, it has been largely overlooked that they can also transmit antibiotic-resistant bacteria. The aim of this study was to identify the Staphylococcaceae bacteria composition of the nasal flora in dromedary camels and evaluate the presence of methicillin-resistant Mammaliicoccus (MRM) and methicillin-resistant Staphylococcus (MRS) in dromedary camels in Algeria. Nasal swabs were collected from 46 camels from seven farms located in two different regions of Algeria (M'sila and Ouargla). We used non-selective media to determine the nasal flora, and antibiotic-supplemented media to isolate MRS and MRM. The staphylococcal isolates were identified using an Autoflex Biotyper Mass Spectrometer (MALDI-TOF MS). The mecA and mecC genes were detected by PCR. Methicillin-resistant strains were further analysed by long-read whole genome sequencing (WGS). Thirteen known Staphylococcus and Mammaliicoccus species were identified in the nasal flora, of which half (49.2%) were coagulase-positive staphylococci. The results showed that four out of seven farms were positive for MRS and/or MRM, with a total of 16 isolates from 13 dromedary camels. The predominant species were M. lentus, S. epidermidis, and S. aureus. Three methicillin-resistant S. aureus (MRSA) were found to be ST6 and spa type t304. Among methicillin-resistant S. epidermidis (MRSE), ST61 was the predominant ST identified. Phylogenetic analysis showed clonal relatedness among M. lentus strains, while S. epidermidis strains were not closely related. Resistance genes were detected, including mecA, mecC, ermB, tet(K), and blaZ. An SCCmec type VIII element was found in a methicillin-resistant S. hominis (MRSH) belonging to the ST1 strain. An SCCmec-mecC hybrid element was detected in M. lentus, similar to what was previously detected in M. sciuri. This study highlights that dromedary camels may be a reservoir for MRS and MRM, and that they contain a specific set of SCCmec elements. This emphasizes the need for further research in this ecological niche from a One Health perspective.

In Vivo Magnetic Resonance Spectroscopy by J-Locked Chemical Shift Encoding for Determination of Neurochemical Concentration and Transverse Relaxation Time

Cell pathology in neuropsychiatric disorders has mainly been accessible by analyzing postmortem tissue samples. Although molecular transverse relaxation informs local cellular microenvironment via molecule-environment interactions, precise determination of the transverse relaxation times of molecules with scalar couplings (J), such as glutamate and glutamine, is difficult using current in vivo magnetic resonance spectroscopy (MRS) technologies, whose approach to measuring transverse relaxation has not changed for decades. We introduce an in vivo MRS technique that achieves chemical shift encoding with selectively locked J-couplings in each column of the acquired two-dimensional dataset, freeing up the entire row dimension for transverse relaxation encoding. This results in increased spectral resolution, minimized background signals, and markedly broadened dynamic range for transverse relaxation encoding. This technique enables determination of the transverse relaxation times of glutamate and glutamine in vivo with unprecedented high precision. Since glutamate predominantly resides in glutamatergic neurons and glutamine in glia in the brain, this noninvasive technique provides a way to probe cellular pathophysiology in neuropsychiatric disorders for characterizing disease progression and monitoring treatment response in a cell type-specific manner in vivo.

Motor cortex functional connectivity is associated with underlying neurochemistry in ALS

OBJECTIVE

To identify structural and neurochemical properties that underlie functional connectivity impairments of the primary motor cortex (PMC) and how these relate to clinical findings in amyotrophic lateral sclerosis (ALS).

METHODS

52 patients with ALS and 52 healthy controls, matched for age and sex, were enrolled from 5 centres across Canada for the Canadian ALS Neuroimaging Consortium study. Resting-state functional MRI, diffusion tensor imaging and magnetic resonance spectroscopy data were acquired. Functional connectivity maps, diffusion metrics and neurometabolite ratios were obtained from the analyses of the acquired multimodal data. A clinical assessment of foot tapping (frequency) was performed to examine upper motor neuron function in all participants.

RESULTS

Compared with healthy controls, the primary motor cortex in ALS showed reduced functional connectivity with sensory (T=5.21), frontal (T=3.70), temporal (T=3.80), putaminal (T=4.03) and adjacent motor (T=4.60) regions. In the primary motor cortex, N-acetyl aspartate (NAA, a neuronal marker) ratios and diffusion metrics (mean, axial and radial diffusivity, fractional anisotropy (FA)) were altered. Within the ALS cohort, foot tapping frequency correlated with NAA (r=0.347) and white matter FA (r=0.537). NAA levels showed associations with disturbed functional connectivity of the motor cortex.

CONCLUSION

In vivo neurochemistry may represent an effective imaging marker of impaired motor cortex functional connectivity in ALS.

Quantification of GABA concentration measured noninvasively in the human posterior cingulate cortex with 7 T ultra-short-TE MR spectroscopy

PURPOSE

The increased spectral dispersion achieved at ultra-high field permits quantification of γ-aminobutyric acid (GABA) concentrations at ultra-short-TE without editing. This work investigated the influence of spectral quality and different LCModel fitting approaches on quantification of GABA. Additionally, the sensitivity with which cross-sectional and longitudinal variations in GABA concentrations can be observed was characterized.

METHODS

In - vivo spectra were acquired in the posterior cingulate cortex of 10 volunteers at 7 T using a STEAM sequence. Synthetically altered spectra with different levels of GABA signals were used to investigate the reliability of GABA quantification with different LCModel fitting approaches and different realizations of SNR. The synthetically altered spectra were also used to characterize the sensitivity of GABA quantification.

RESULTS

The best LCModel fitting approach used stiff spline baseline, no soft constraints, and measured macromolecules in the basis set. With lower SNR, coefficients of variation increased dramatically. Longitudinal and cross-sectional variations in GABA of 10% could be detected with 79 and 48 participants per group, respectively. However, the small cohort may bias the calculation of the coefficients of variation and of the sample size that would be needed to detect variations in GABA.

CONCLUSION

Reliable quantification of normal and abnormal GABA concentrations was achieved for high quality 7 T spectra using LCModel fitting.

Clinical, pathological, and radiological features of 80 pediatric diffuse intrinsic pontine gliomas: A single-institute study

Objective

Diffuse intrinsic pontine gliomas (DIPGs) are rare but devastating diseases. This retrospective cross-sectional study aimed to investigate the clinical, radiological, and pathological features of DIPGs.

Materials and methods

The clinical data of 80 pediatric DIPGs under clinical treatment in Beijing Tiantan Hospital from July 2013 to July 2019 were retrospectively collected and studied. A follow-up evaluation was performed.

Results

This study included 48 men and 32 women. The most common symptoms were cranial nerve palsy (50.0%, 40/80 patients) and limb weakness (41.2%, 33/80 patients). Among the 80 patients, 24 cases were clinically diagnosed, 56 cases were pathologically verified, and 45 cases were tested for H3K27 alteration status, with 34 H3K27 alteration cases confirmed. Radiological results indicated that enhancement was common (65.0%, 52/80 patients). Cho/Cr was of predictive value for H3K27 alteration status (P = 0.012, cutoff value = 2.38, AUC = 0.801). Open cranial surgery followed by further chemotherapy and radiotherapy was beneficial for patients' overall survival. Cox regression analysis indicated H3K27 alteration to be the independent prognostic influencing factor for DIPGs in this series (P = 0.002).

Conclusion

DIPGs displayed a wide spectrum of clinical and imaging features. Surgery-suitable patients could benefit from postoperative comprehensive therapy for a better overall survival. H3K27 alteration was the independent prognostic influencing factor for DIPGs.

MR-Nucleomics: The study of pathological cellular processes with multinuclear magnetic resonance spectroscopy and imaging in vivo

Clinical medicine has experienced a rapid development in recent decades, during which therapies targeting specific cellular signaling pathways, or specific cell surface receptors, have been increasingly adopted. While these developments in clinical medicine call for improved precision in diagnosis and treatment monitoring, modern medical imaging methods are restricted mainly to anatomical imaging, lagging behind the requirements of precision medicine. Although positron emission tomography and single photon emission computed tomography have been used clinically for studies of metabolism, their applications have been limited by the exposure risk to ionizing radiation, the subsequent limitation in repeated and longitudinal studies, and the incapability in assessing downstream metabolism. Magnetic resonance spectroscopy (MRS) or spectroscopic imaging (MRSI) are, in theory, capable of assessing molecular activities in vivo, although they are often limited by sensitivity. Here, we review some recent developments in MRS and MRSI of multiple nuclei that have potential as molecular imaging tools in the clinic.

Neurophysiological assessment of cortical activity in DEPDC5- and NPRL3-related epileptic mTORopathies

BACKGROUND

Mutations in the GATOR1 complex genes, DEPDC5 and NPRL3, play a major role in the development of lesional and non-lesional focal epilepsy through increased mTORC1 signalling. We aimed to assess the effects of mTORC1 hyperactivation on GABAergic inhibitory circuits, in 3 and 5 individuals carrying DEPDC5 and NPRL3 mutations respectively using a multimodal approach including transcranial magnetic stimulation (TMS), magnetic resonance spectroscopy (MRS), and electroencephalography (EEG).

RESULTS

Inhibitory functions probed by TMS and MRS showed no effect of mutations on cortical GABAergic receptor-mediated inhibition and GABA concentration, in both cortical and subcortical regions. However, stronger EEG theta oscillations and stronger and more synchronous gamma oscillations were observed in DEPDC5 and NPRL3 mutations carriers.

CONCLUSIONS

These results suggest that DEPDC5 and NPRL3-related epileptic mTORopathies may not directly modulate GABAergic functions but are nonetheless characterized by a stronger neural entrainment that may be reflective of a cortical hyperexcitability mediated by increased mTORC1 signaling.

Fat in the brain: Facts and features

The presence of fat within a lesion in the brain is not only easy to identify on both CT/MRI but also can help narrow the differential. The purpose of this paper is to illustrate the spectrum of common and rare fat-containing lesions in the brain that are encountered in clinical practice. This paper intends to discuss 15 such lesions which are confirmed by MRI findings and histopathological correlation. We divided the spectrum of fat-containing lesions into lesions with adipose cells, lesions with cholesterol-rich content and tumours with lipomatous differentiation/transformation. Knowledge of these common and rare fat-containing lesions is essential for making the right diagnosis or narrowing the differential diagnosis.

Ketamine administration in idiopathic epileptic and healthy control dogs: Can we detect differences in brain metabolite response with spectroscopy?

Introduction

In recent years ketamine has increasingly become the focus of multimodal emergency management for epileptic seizures. However, little is known about the effect of ketamine on brain metabolites in epileptic patients. Magnetic resonance spectroscopy (MRS) is a non-invasive technique to estimate brain metabolites in vivo. Our aim was to measure the effect of ketamine on thalamic metabolites in idiopathic epileptic (IE) dogs using 3 Tesla MRS. We hypothesized that ketamine would increase the glutamine-glutamate (GLX)/creatine ratio in epileptic dogs with and without antiseizure drug treatment, but not in control dogs. Furthermore, we hypothesized that no different responses after ketamine administration in other measured brain metabolite ratios between the different groups would be detected.

Methods

In this controlled prospective experimental trial IE dogs with or without antiseizure drug treatment and healthy client-owned relatives of the breeds Border Collie and Greater Swiss Mountain Dog, were included. After sedation with butorphanol, induction with propofol and maintenance with sevoflurane in oxygen and air, a single voxel MRS at the level of the thalamus was performed before and 2 min after intravenous administration of 1 mg/kg ketamine. An automated data processing spectral fitting linear combination model algorithm was used to estimate all commonly measured metabolite ratios. A mixed ANOVA with the independent variables ketamine administration and group allocation was performed for all measured metabolites. A p < 0.05 was considered statistically significant.

Results

Twelve healthy control dogs, 10 untreated IE and 12 treated IE dogs were included. No significant effects for GLX/creatine were found. However, increased glucose/creatine ratios were found (p < 0.001) with no effect of group allocation. Furthermore, increases in the GABA/creatine ratio were found in IEU dogs.

Discussion

MRS was able to detect changes in metabolite/creatine ratios after intravenous administration of 1 mg/kg ketamine in dogs and no evidence was found that excitatory effects are induced in the thalamus. Although it is beyond the scope of this study to investigate the antiseizure potential of ketamine in dogs, results of this research suggest that the effect of ketamine on the brain metabolites could be dependent on the concentrations of brain metabolites before administration.

Measuring Brain Temperature in Youth Bipolar Disorder Using a Novel Magnetic Resonance Imaging Approach: A Proof-of-concept Study

BACKGROUND

There is evidence of alterations in mitochondrial energy metabolism and cerebral blood flow (CBF) in adults and youth with bipolar disorder (BD). Brain thermoregulation is based on the balance of heat-producing metabolism and heat-dissipating mechanisms, including CBF.

OBJECTIVE

To examine brain temperature, and its relation to CBF, in relation to BD and mood symptom severity in youth.

METHODS

This study included 25 youth participants (age 17.4 ± 1.7 years; 13 BD, 12 control group (CG)). Magnetic resonance spectroscopy data were acquired to obtain brain temperature in the left anterior cingulate cortex (ACC) and the left precuneus. Regional estimates of CBF were provided by arterial spin labeling imaging. Analyses used general linear regression models, covarying for age, sex, and psychiatric medications.

RESULTS

Brain temperature was significantly higher in BD compared to CG in the precuneus. A higher ratio of brain temperature to CBF was significantly associated with greater depression symptom severity in both the ACC and precuneus within BD. Analyses examining the relationship of brain temperature or CBF with depression severity score did not reveal any significant finding in the ACC or the precuneus.

CONCLUSION

The current study provides preliminary evidence of increased brain temperature in youth with BD, in whom reduced thermoregulatory capacity is putatively associated with depression symptom severity. Evaluation of brain temperature and CBF in conjunction may provide valuable insight beyond what can be gleaned by either metric alone. Larger prospective studies are warranted to further evaluate brain temperature and its association with CBF concerning BD.

Alterations to Cerebral Perfusion, Metabolite Profiles, and Neuronal Morphology in the Hippocampus and Cortex of Male and Female Mice during Chronic Exposure to a High-Salt Diet

Excess dietary salt reduces resting cerebral blood flow (CBF) and vascular reactivity, which can limit the fueling of neuronal metabolism. It is hitherto unknown whether metabolic derangements induced by high-salt-diet (HSD) exposure during adulthood are reversed by reducing salt intake. In this study, male and female mice were fed an HSD from 9 to 16 months of age, followed by a normal-salt diet (ND) thereafter until 23 months of age. Controls were continuously fed either ND or HSD. CBF and metabolite profiles were determined longitudinally by arterial spin labeling magnetic resonance imaging and magnetic resonance spectroscopy, respectively. HSD reduced cortical and hippocampal CBF, which recovered after dietary salt normalization, and affected hippocampal but not cortical metabolite profiles. Compared to ND, HSD increased hippocampal glutamine and phosphocreatine levels and decreased creatine and choline levels. Dietary reversal only allowed recovery of glutamine levels. Histology analyses revealed that HSD reduced the dendritic arborization and spine density of cortical and hippocampal neurons, which were not recovered after dietary salt normalization. We conclude that sustained HSD exposure throughout adulthood causes permanent structural and metabolic alterations to the mouse brain that are not fully normalized by lowering dietary salt during aging.

Hypoxic ischemic brain injury with status myoclonus in a case with post-operative massive pulmonary thromboembolism: A diagnostic and therapeutic challenge

Thromboembolic event is an important and widely regarded risk factor, influencing the outcome and overall survival in post-operative cases with second highest association with gynaecological surgeries. Here we report a 52 years old female who underwent total laparoscopic hysterectomy with bilateral salpingo-oophorectomy (TLH+BSO) presented to our emergency in unconscious and intubated state on her post-operative day-1 with cardiorespiratory failure. Based on the immediate investigations after successful resuscitation, an initial diagnosis of massive pulmonary thromboembolism was made following supportive and conservative management. Interestingly on subsequent days she started to display episodic non-rhythmic symmetric myoclonic jerks persisting for seconds to minutes; resembling 'post-hypoxic' or 'post-anoxic' status myoclonus due to hypoxic ischemic brain injury. Further neuro-electrophysiological examination revealed rhythmic well-formed delta activity on both sides symmetrically with a transformation into theta activity with forward displacement on subsequent days, bilaterally over the same areas. Later on, magnetic resonance imaging with magnetic resonance-spectroscopic findings also corroborated to hypoxic ischemic brain injury related changes over bilateral basal ganglia mostly in caudate nucleus. Post operative venous thromboembolism is a major clinical challenge and a subject of constant intensive care yet the neurological sequalae of such event is given less priority despite of its major contribution on overall prognostic and survival index.

Prognosis Prediction Using Magnetic Resonance Spectroscopy and Oligoclonal Bands in Central Nervous System Methotrexate-associated Lymphoproliferative Disorder

Central nervous system methotrexate-associated lymphoproliferative disorder (CNS-MTX-LPD) is rare, but its spontaneous regression has been observed in some patients after withdrawal of agents. We herein report three cases of primary CNS-MTX-LPD that received oral MTX for rheumatoid arthritis. Epstein-Barr virus and oligoclonal bands (OCBs) were positive, while proton magnetic resonance spectroscopy (¹H-MRS) showed an elevated lipid peak and slightly elevated choline/N-acetylaspartate ratio in common. After MTX withdrawal, brain lesions showed spontaneous regression in all cases. Our patient's ¹H-MRS findings and OCBs may reflect a non-monoclonal lymphoproliferative histology as benign-type lesions in CNS-MTX-LPD.

Case report: MELAS and concomitant presumed antiphospholipid antibody syndrome in an adult woman

Mitochondrial encephalomyopathy, lactic acidosis, stroke-like episodes, and other features (short stature, headaches, seizures, and sensorineural hearing loss) constitute characteristics of MELAS syndrome. MELAS is a rare condition due to mutations in maternally inherited mitochondrial DNA with levels of heteroplasmy possibly related to late adulthood presentation. A previously reported MELAS case coexisted with presumed Antiphospholipid Antibody Syndrome (APLAS), but the connection between MELAS and a potential APLAS is unclear. A 29-year-old woman presented with mild right-sided sensorimotor symptoms and mixed aphasia in November 2021. She presented again in May 2022 for unrelenting headaches and was found to have a new right hemisphere syndrome with mild left-sided sensorimotor symptoms, hemineglect, and anosognosia. Characteristic lab and imaging studies were obtained. During the first presentation (October 2021), the discovery of anticardiolipin IgM antibodies (aCL) (and their replication 3 months later) led to a diagnosis of APLAS, and Warfarin was initiated. During the second admission (May 2022), a new stroke-like lesion on the right hemisphere with characteristic features not suggestive of ischemia was detected, which led to a diagnosis of MELAS (m3243A > G mutation). Although MELAS and APLAS could co-exist, alternatively, it is possible that antiphospholipid antibodies might be generated when the strongly anionic Cardiolipin-Hydroperoxide from the inner mitochondrial membrane is exposed to immune component cells upon cell lysis. Thus, the presence of aCL in patients with stroke-like lesions might masquerade as an APLAS, but should probably be questioned if only aCL are repeatedly found and imaging findings are not characteristic for ischemic lesions.

Harnessing the Power of Advanced Fetal Neuroimaging to Understand In Utero Footprints for Later Neuropsychiatric Disorders

Adverse intrauterine events may profoundly impact fetal risk for future adult diseases. The mechanisms underlying this increased vulnerability are complex and remain poorly understood. Contemporary advances in fetal magnetic resonance imaging (MRI) have provided clinicians and scientists with unprecedented access to in vivo human fetal brain development to begin to identify emerging endophenotypes of neuropsychiatric disorders such as autism spectrum disorder, attention-deficit/hyperactivity disorder, and schizophrenia. In this review, we discuss salient findings of normal fetal neurodevelopment from studies using advanced, multimodal MRI that have provided unparalleled characterization of in utero prenatal brain morphology, metabolism, microstructure, and functional connectivity. We appraise the clinical utility of these normative data in identifying high-risk fetuses before birth. We highlight available studies that have investigated the predictive validity of advanced prenatal brain MRI findings and long-term neurodevelopmental outcomes. We then discuss how ex utero quantitative MRI findings can inform in utero investigations toward the pursuit of early biomarkers of risk. Lastly, we explore future opportunities to advance our understanding of the prenatal origins of neuropsychiatric disorders using precision fetal imaging.

Positron Emission Tomography Assessments of Phosphodiesterase 10A in Patients With Schizophrenia

BACKGROUND AND HYPOTHESIS

Phosphodiesterase 10A (PDE10A) is a highly expressed enzyme in the basal ganglia, where cortical glutamatergic and midbrain dopaminergic inputs are integrated. Therapeutic PDE10A inhibition effects on schizophrenia have been reported previously, but the status of this molecule in the living patients with schizophrenia remains elusive. Therefore, this study aimed to investigate the central PDE10A status in patients with schizophrenia and examine its relationship with psychopathology, cognition, and corticostriatal glutamate levels.

STUDY DESIGN

This study included 27 patients with schizophrenia, with 5 antipsychotic-free cases, and 27 healthy controls. Positron emission tomography with [18F]MNI-659, a specific PDE10A radioligand, was employed to quantify PDE10A availability by measuring non-displaceable binding potential (BPND) of the ligand in the limbic, executive, and sensorimotor striatal functional subregions, and in the pallidum. BPND estimates were compared between patients and controls while controlling for age and gender. BPND correlations were examined with behavioral and clinical measures, along with regional glutamate levels quantified by the magnetic resonance spectroscopy.

STUDY RESULTS

Multivariate analysis of covariance demonstrated a significant main effect of diagnosis on BPND (p = .03). A posthoc test showed a trend-level higher sensorimotor striatal BPND in patients, although it did not survive multiple comparison corrections. BPND in controls in this subregion was significantly and negatively correlated with the Tower of London scores, a cognitive subtest. Striatal or dorsolateral prefrontal glutamate levels did not correlate significantly with BPND in either group.

CONCLUSIONS

The results suggest altered striatal PDE10A availability and associated local neural dysfunctions in patients with schizophrenia.

Multi-Reflectance-Spectroscopy, Part I: Theory and Calculations Using Simulated Milk Samples

Optical methods are appropriate for monitoring of constituents in suspensions and emulsions. A simple multi-wavelength, multi-reflectance spectroscopic technique, called MRS-Technology, is introduced. Two different signals of a sample are measured: the reflectance from a small and from a large measuring volume corresponding to the reduced scattering coefficient μSCA' and to the sum of μSCA' and the absorption coefficient μ_ABS, respectively. Analytical relations between the MRS reflectance and μ_ABS as well as μSCA' are derived. The investigations on MRS method are carried out using milk as an example. For this purpose "virtual" milk samples are defined. μ_ABS and μSCA' are calculated by means of the Mie scattering theory in the ultraviolet-visible-shortwave near-infrared (UV-Vis-SWNIR) spectral range. Using this data analytical reflectances can be calculated based on MRS theory as well as numerical reflectances obtained by Monte Carlo (MC) simulation. Analytical and numerical results are compared and investigated. The spectral behavior of the analytical reflectances is very similar to that of the numerical MC reflectances in the case of medium and low absorptions. By means of simple multilinear regression techniques (MLR), simple correlations between fat and protein volume fractions and reflectances could be generated with acceptable root mean square error (RMSE) values. Each correlation shows that best results will be achieved by using reflectances at sample-specific wavelengths for small and large measuring volumes of a sample indicating the potential of the MRS-Technology.

NIfTI-MRS: A standard data format for magnetic resonance spectroscopy

PURPOSE

Multiple data formats in the MRS community currently hinder data sharing and integration. NIfTI-MRS is proposed as a standard spectroscopy data format, implemented as an extension to the Neuroimaging informatics technology initiative (NIfTI) format. This standardized format can facilitate data sharing and algorithm development as well as ease integration of MRS analysis alongside other imaging modalities.

METHODS

A file format using the NIfTI header extension framework incorporates essential spectroscopic metadata and additional encoding dimensions. A detailed description of the specification is provided. An open-source command-line conversion program is implemented to convert single-voxel and spectroscopic imaging data to NIfTI-MRS. Visualization of data in NIfTI-MRS is provided by development of a dedicated plugin for FSLeyes, the FMRIB Software Library (FSL) image viewer.

RESULTS

Online documentation and 10 example datasets in the proposed format are provided. Code examples of NIfTI-MRS readers are implemented in common programming languages. Conversion software, spec2nii, currently converts 14 formats where data is stored in image-space to NIfTI-MRS, including Digital Imaging and Communications in Medicine (DICOM) and vendor proprietary formats.

CONCLUSION

NIfTI-MRS aims to solve issues arising from multiple data formats being used in the MRS community. Through a single conversion point, processing and analysis of MRS data are simplified, thereby lowering the barrier to use of MRS. Furthermore, it can serve as the basis for open data sharing, collaboration, and interoperability of analysis programs. Greater standardization and harmonization become possible. By aligning with the dominant format in neuroimaging, NIfTI-MRS enables the use of mature tools present in the imaging community, demonstrated in this work by using a dedicated imaging tool, FSLeyes, for visualization.

Emerging findings of glutamate-glutamine imbalance in the medial prefrontal cortex in attention deficit/hyperactivity disorder: systematic review and meta-analysis of spectroscopy studies

One of the main challenges in investigating the neurobiology of ADHD is our limited capacity to study its neurochemistry in vivo. Magnetic resonance spectroscopy (MRS) estimates metabolite concentrations within the brain, but approaches and findings have been heterogeneous. To assess differences in brain metabolites between patients with ADHD and healthy controls, we searched 12 databases screening for MRS studies. Studies were divided into 'children and adolescents' and 'adults' and meta-analyses were performed for each brain region with more than five studies. The quality of studies was assessed by the Newcastle-Ottawa Scale. Thirty-three studies met our eligibility criteria, including 874 patients with ADHD. Primary analyses revealed that the right medial frontal area of children with ADHD presented higher concentrations of a composite of glutamate and glutamine (p = 0.02, SMD = 0.53). Glutamate might be implicated in pruning and neurodegenerative processes as an excitotoxin, while glutamine excess might signal a glutamate depletion that could hinder neurotrophic activity. Both neuro metabolites could be implicated in the differential cortical thinning observed in patients with ADHD across all ages. Notably, more homogeneous designs and reporting guidelines are the key factors to determine how suitable MRS is for research and, perhaps, for clinical psychiatry. Results of this meta-analysis provided an overall map of the brain regions evaluated so far, addressed the role of glutamatergic metabolites in the pathophysiology of ADHD, and pointed to new perspectives for consistent use of the tool in the field.

Label-Free Assessment of Mannitol Accumulation Following Osmotic Blood-Brain Barrier Opening Using Chemical Exchange Saturation Transfer Magnetic Resonance Imaging

PURPOSE

Mannitol is a hyperosmolar agent for reducing intracranial pressure and inducing osmotic blood-brain barrier opening (OBBBO). There is a great clinical need for a non-invasive method to optimize the safety of mannitol dosing. The aim of this study was to develop a label-free Chemical Exchange Saturation Transfer (CEST)-based MRI approach for detecting intracranial accumulation of mannitol following OBBBO.

METHODS

In vitro MRI was conducted to measure the CEST properties of D-mannitol of different concentrations and pH. In vivo MRI and MRS measurements were conducted on Sprague-Dawley rats using a Biospec 11.7T horizontal MRI scanner. Rats were catheterized at the internal carotid artery (ICA) and randomly grouped to receive either 1 mL or 3 mL D-mannitol. CEST MR images were acquired before and at 20 min after the infusion.

RESULTS

In vitro MRI showed that mannitol has a strong, broad CEST contrast at around 0.8 ppm with a mM CEST MRI detectability. In vivo studies showed that CEST MRI could effectively detect mannitol in the brain. The low dose mannitol treatment led to OBBBO but no significant mannitol accumulation, whereas the high dose regimen resulted in both OBBBO and mannitol accumulation. The CEST MRI findings were consistent with ¹H-MRS and Gd-enhanced MRI assessments.

CONCLUSION

We demonstrated that CEST MRI can be used for non-invasive, label-free detection of mannitol accumulation in the brain following BBBO treatment. This method may be useful as a rapid imaging tool to optimize the dosing of mannitol-based OBBBO and improve its safety and efficacy.

The role of glutamate and GABA in cognitive dysfunction in schizophrenia and mood disorders - A systematic review of magnetic resonance spectroscopy studies

Epidemiologic, genetic, and neurobiological studies suggest considerable overlap between schizophrenia and mood disorders. Importantly, both disorders are associated with a broad range of cognitive deficits as well as altered glutamatergic and GABAergic neurometabolism. We conducted a systematic review of magnetic resonance spectroscopy (MRS) studies investigating the relationship between glutamatergic and GABAergic neurometabolites and cognition in schizophrenia spectrum disorders and mood disorders. A literature search in Pubmed of studies published before April 15, 2019 was conducted and 37 studies were deemed eligible for systematic review. We found that alterations in glutamatergic and GABAergic neurotransmission have been identified relatively consistently in both schizophrenia and mood disorders. However, because of the vast heterogeneity of published studies in terms of illness stage, medication exposure, MRS acquisition parameters and data post-processing strategies, we still do not understand the relationship between those neurotransmitters and cognitive dysfunction in mental illness, which is a critical initial step for rational drug development. Our findings emphasize the need for coordinated multi-center studies that characterize cognitive function and its biological substrates in large and well-defined clinical populations, using harmonized imaging sequences and analytical methods with the goal to elucidate the underlying pathophysiological mechanisms and to inform future clinical trials.

Behavior during aging of bone-marrow fatty-acids profile in women's calcaneus to search for early potential osteoporotic biomarkers: a 1H-MR Spectroscopy study

AIM

Identify new potential biomarkers of osteoporosis at an early stage, by magnetic resonance spectroscopy (MRS), studying early changes in the metabolic profile of bone-marrow fatty acids in women's calcanei during healthy aging and osteoporosis status.

METHODS

Single voxel MRS was performed by using a point resolved spectroscopy (PRESS) sequence at 3T. Thirty-four Caucasian women (age range: 22-59 years) were recruited to investigate calcaneus bone marrow. The cohort was constituted of four groups according to age, menopausal status, and T-score evaluated after a DXA examination on the femoral neck. Women were classified in young control (n = 11, mean age = 26.5 ± 3.8 y, age range: 22-34 years), perimenopausal groups (n = 11, mean age = 42.0 ± 3.6 y, age range: 37-47 years), postmenopausal group (n = 9, mean age = 55.4 ± 2.9 y, age range: 50-59 years, mean T-score = -1.70 ± 0.50) and osteoporotic group (n = 6, mean age = 53.0 ± 2.8 y, age range: 50-58 years, mean T-score = -2.54 ± 0.10). The total lipid content (TL), the Unsaturation Index (UI), and the fraction of unsaturated/polyunsaturated fatty acid (f_UFA and f_PUFA) were calculated.

RESULTS

TL was significantly correlated with age (r = 0.73, p < 0.001). TL increases linearly with age in the young + perimenopausal population (r = 0.92, p < 0.001) but this trend is not significant in the postmenopausal subject (r = 0.48, p = 0.07). No significant correlation was found between T-Score and TL in postmenopausal and osteoporotic women, whereas a significant correlation was found between TL and time interval (t_p) between the age at menopause and the age of the subject at the MRS examination. Conversely, no correlation was found between T-score and t_p. The unsaturation index (UI) does not significantly discriminate between osteoporotic, peri- and postmenopausal women. On the other hand, f_UFA is significantly different in peri-menopausal and osteoporotic subjects (p = 0.02), while f_PUFA is significantly different both between peri- and postmenopausal women (p = 0.05) and postmenopausal and osteoporotic subjects (p = 0.03). Both f_UFA and f_PUFA did not correlate with subjects' age.

CONCLUSION

In the female calcaneus, f_UFA and f_PUFA are promising measurable quantities for the characterization of bone marrow's composition potentially correlated with the development of osteoporosis, whereas UI does not differentiate between subjects of varying osteoporotic status. The fact that the TL in the calcaneus is correlated with t_p, indicates that active metabolic changes are still occurring in these subjects, giving complementary information to the DXA about the changes in bone marrow's composition which may affect the whole bone health.

The Roles of Imaging Biomarkers in the Management of Chronic Neuropathic Pain

Chronic neuropathic pain (CNP) affects around 10% of the general population and has a significant social, emotional, and economic impact. Current diagnosis techniques rely mainly on patient-reported outcomes and symptoms, which leads to significant diagnostic heterogeneity and subsequent challenges in management and assessment of outcomes. As such, it is necessary to review the approach to a pathology that occurs so frequently, with such burdensome and complex implications. Recent research has shown that imaging methods can detect subtle neuroplastic changes in the central and peripheral nervous system, which can be correlated with neuropathic symptoms and may serve as potential markers. The aim of this paper is to review available imaging methods used for diagnosing and assessing therapeutic efficacy in CNP for both the preclinical and clinical setting. Of course, further research is required to standardize and improve detection accuracy, but available data indicate that imaging is a valuable tool that can impact the management of CNP.