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A recent publication in JCBFM, "Static autoregulation in humans" gives rise to critical comments. Autoregulation of cerebral blood flow implies that flow is rather constant within a certain blood pressure (BP) range with a lower and an upper pressure limit. The physiology at the two limits is very different, making comparison of the brain's vulnerability at the limits questionable. The recent publication in JCBFM claims a narrow autoregulatory range based on pooling of data from several studies. However, we argue that such pooling blurs the autoregulatory limits. We summarize the classical literature, therefrom we argue for a broad autoregulatory range.
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BACKGROUND: Increased gray matter volume (GMV) following electroconvulsive therapy (ECT) has been well-documented, with limited studies reporting a subsequent decrease in GMV afterwards. OBJECTIVE: This study characterized the reversion pattern of GMV after ECT and its association with clinical depression outcome, using multi-site triple time-point data from the Global ECT-MRI Research Collaboration (GEMRIC). METHODS: 86 subjects from the GEMRIC database were included, and GMV in 84 regions-of-interest (ROI) was obtained from automatic segmentation of T1 MRI images at three timepoints: pre-ECT (T0), within one-week post-ECT (T1), and one to six months post-ECT (T2). RM-ANOVAs were used to assess longitudinal changes and LMM analyses explored associations between GMV changes and demographical and clinical characteristics. RESULTS: 63 of the 84 ROIs showed a significant increase-and-decrease pattern (RM-ANOVA, Bonferroni corrected p < 0.00059). Post hoc tests indicated a consistent pattern in each of these 63 ROIs: significant increase from T0 to T1inGMV, followed by significant decrease from T1 to T2 and no difference between T0 and T2, except for both amygdalae, right hippocampus and pars triangularis, which showed the same increase and decrease but GMV at T2 remained higher compared to T0. No consistent relationship was found between GMV change pattern and clinical status. CONCLUSION: The GEMRIC cohort confirmed a rapid increase of GMV after ECT followed by reversion of GMV one to six months thereafter. The lack of association between the GMV change pattern and depression outcome scores implies a transient neurobiological effect of ECT unrelated to clinical improvement.
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Neurostimulation is a mainstream treatment option for major depression. Neuromodulation techniques apply repetitive magnetic or electrical stimulation to some neural target but significantly differ in their invasiveness, spatial selectivity, mechanism of action, and efficacy. Despite these differences, recent analyses of transcranial magnetic stimulation (TMS) and deep brain stimulation (DBS)-treated individuals converged on a common neural network that might have a causal role in treatment response. We set out to investigate if the neuronal underpinnings of electroconvulsive therapy (ECT) are similarly associated with this causal depression network (CDN). Our aim here is to provide a comprehensive analysis in three cohorts of patients segregated by electrode placement (N = 246 with right unilateral, 79 with bitemporal, and 61 with mixed) who underwent ECT. We conducted a data-driven, unsupervised multivariate neuroimaging analysis Principal Component Analysis (PCA) of the cortical and subcortical volume changes and electric field (EF) distribution to explore changes within the CDN associated with antidepressant outcomes. Despite the different treatment modalities (ECT vs TMS and DBS) and methodological approaches (structural vs functional networks), we found a highly similar pattern of change within the CDN in the three cohorts of patients (spatial similarity across 85 regions: r = 0.65, 0.58, 0.40, df = 83). Most importantly, the expression of this pattern correlated with clinical outcomes (t = -2.35, p = 0.019). This evidence further supports that treatment interventions converge on a CDN in depression. Optimizing modulation of this network could serve to improve the outcome of neurostimulation in depression.
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OBJECTIVE: Single-photon emission computed tomography (SPECT) with the tracer 99m Tc-HMPAO is a method to visualize the cerebral hyperperfusion during an epileptic seizure and thus localize the epileptogenic zone and seizure propagation. Subtraction of interictal from Ictal SPECT Co-registered to MRI (SISCOM) visualizes areas with relative increases in cerebral blood flow. The purpose of this retrospective study is to explore the added value of visualizing areas of hypoperfusion as well as hyperperfusion, so-called reversed SISCOM. METHODS: Fifty-six patients operated for epilepsy who had been investigated with SISCOM were included in the analysis. The patients were divided into two groups based on seizure duration after tracer injection, above or below 30 s. The preoperative SISCOM description was compared to the area of resection and given a concordance score. The 56 SISCOM were recalculated visualizing also areas of hypoperfusion and again compared to the site of resection using the same scale of concordance. The reversed SISCOM were categorized into three subgroups: "Altered Conclusion," "Confirmed Conclusion," and "Adds Nothing." If an area of hyperperfusion had an area of hypoperfusion in close proximity, it was re-interpreted as noise, thus possibly altering the conclusion. If the areas of hypoperfusion were in the opposite hemisphere it was interpreted as confirming factor. Further the concordance scores from conventional SISCOM and reversed SISCOM was compared to surgical outcome to explore the difference in sensitivity, positive predictive value (PPV), and odds ratio. RESULTS: In approximately half of the cases reversed SISCOM added additional value, meaning either altered the conclusion or confirmed the conclusion. The sensitivity, PPV, and odds ratio was also better in the subgroup of long, >30 s seizure duration after injection, and got worse in the group with short, <30 s seizure duration after injection. SIGNIFICANCE: Adding reversed SISCOM performed better than conventional SISCOM at predicting good surgical outcome.
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Epilepsia , Humanos , Estudos Retrospectivos , Epilepsia/diagnóstico por imagem , Epilepsia/cirurgia , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Tecnécio Tc 99m Exametazima , Convulsões/diagnóstico por imagem , Convulsões/cirurgiaRESUMO
OBJECTIVE: This retrospective study investigates the predictive value of ictal subtraction single-photon emission computed tomography (SPECT) co-registered to magnetic resonance imaging (MRI) (SISCOM) for successful epilepsy surgery. METHODS: 57 patients examined with SISCOM as a part of epilepsy surgery evaluation were divided into two groups based on seizure duration after tracer injection (group 1: Seizure duration above or equal to 30 s, group 2: Seizure duration under 30 s). SISCOM was compared to the surgical site and categorized as good or poor concordance. Subsequently, Odds ratios (ORs) and positive predictive values (PPVs) were calculated for each group for good surgical outcome, freedom from disabling seizures. RESULTS: The PPVs and ORs for good surgical outcome was 74.1% and 5.71 for group 1 and 40% and 0.22 for group 2. SISCOM had a similar positive predictive value regardless of whether the focus was in the same or neighboring lobe, but same hemisphere as the resection. CONCLUSION: In conclusion, the implementation of a precise definition for a well-executed ictal SPECT scan with respect to seizure duration after injection enhances the positive predictive value (PPV) and odds ratio (OR) for successful surgical outcome, surpassing previous findings, whether the focus in resected lobe or the neighboring.
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Epilepsia , Humanos , Estudos Retrospectivos , Epilepsia/diagnóstico por imagem , Epilepsia/cirurgia , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Convulsões/diagnóstico por imagem , Convulsões/cirurgia , Tecnécio Tc 99m ExametazimaRESUMO
The history of Danish neuroscience starts with an account of impressive contributions made at the 17th century. Thomas Bartholin was the first Danish neuroscientist, and his disciple Nicolaus Steno became internationally one of the most prominent neuroscientists in this period. From the start, Danish neuroscience was linked to clinical disciplines. This continued in the 19th and first half of the 20th centuries with new initiatives linking basic neuroscience to clinical neurology and psychiatry in the same scientific environment. Subsequently, from the middle of the 20th century, basic neuroscience was developing rapidly within the preclinical university sector. Clinical neuroscience continued and was even reinforced during this period with important translational research and a close co-operation between basic and clinical neuroscience. To distinguish 'history' from 'present time' is not easy, as many historical events continue in present time. Therefore, we decided to consider 'History' as new major scientific developments in Denmark, which were launched before the end of the 20th century. With this aim, scientists mentioned will have been born, with a few exceptions, no later than the early 1960s. However, we often refer to more recent publications in documenting the developments of initiatives launched before the end of the last century. In addition, several scientists have moved to Denmark after the beginning of the present century, and they certainly are contributing to the present status of Danish neuroscience-but, again, this is not the History of Danish neuroscience.
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Neurociências , Psiquiatria , Humanos , Dinamarca , História do Século XX , Neurociências/história , Psiquiatria/história , História do Século XIX , História do Século XVIIRESUMO
BACKGROUND AND PURPOSE: Magnetic resonance spectroscopy (MRS)-a method of analysing metabolites in vivo-has been utilized in several studies of brain glioma biomarkers at lower field strengths. At ultra-high field strengths, MRS provides an improved signal-to-noise-ratio and spectral resolution, but 7T studies on patients with gliomas are sparse. The purpose of this exploratory study was to evaluate the potential clinical implication of the use of single-voxel MRS at 7T to assess metabolic information on lesions in a pilot cohort of patients with grade II and III gliomas. METHODS: We scanned seven patients and seven healthy controls using the semi-localization by adiabatic-selective refocusing sequence on a Philips Achieva 7T system with a standard dual-transmit head coil. The metabolic ratios were calculated relative to water and total creatine. Additionally, 2-hydroxyglutarate (2-HG) MRS was carried out in four of the patients, and the 2-HG concentration was calculated relative to water. RESULTS: When comparing the tumour data to control regions in both patients and healthy controls, we found that the choline/creatine and myo-inositol/creatine ratios were significantly increased and that the N-acetylaspartate/creatine and the neurotransmitter glutamate/creatine ratios were significantly decreased. The N-acetylaspartate/water and glutamate/water ratios were also significantly decreased. The lactate/water and lactate/creatine ratios showed increases, although not significant. The GABA/water ratio was significantly decreased, but the GABA/creatine ratio was not. MRS spectra showed the presence of 2-HG in three of the four patients studied. Three of the patients, including the MRS 2-HG-negative patient, were operated on, and all of them had the IDH mutation. CONCLUSION: Our findings were consistent with the existing literature on 3T and 7T MRS.
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PURPOSE: Diffuse low-grade gliomas (DLGGs) are low-malignancy brain tumors originating from the glial cells of the brain growing continuously and infiltratively along the neural axons and infiltrating the surrounding brain tissue. DLGGs usually transform into higher malignancy, causing progressive disability and premature death. MRI scans are valuable when assessing soft tissue abnormalities, but, due to the infiltrative properties of DLGGs, delineating the tumor borders is a challenging task. Therefore, the aim of this study was to explore the difference in gross tumor volume (GTV) of DLGGs delineated from 7 Tesla and 3 Tesla MRI scans. METHOD: Patients were recruited at the department of neurosurgery and were scanned in both a 7T and a 3T MRI scanner prior to the operation. Two observers delineated the tumors using semi-automatic delineation software. The results from each observer were blinded to the other observer's delineation. RESULTS: Comparing GTVs from 7T and 3T, the percentage difference varied up to 40.4% on the T2-weighted images. The percentage difference in GTV varied up to 15.3% on the fluid-attenuated inversion recovery (FLAIR) images. On the T2-weighted images, most cases varied by approximately 15%; on the FLAIR sequence, half of the cases varied by approximately 5% and the other half by approximately 15%. The overall inter-observer agreement was near perfect, with an intraclass correlation of 0.969. The intraclass correlation was better on the FLAIR sequence than on the T2 sequence. CONCLUSION: Overall, the GTVs delineated from 7T images were smaller. The increase in field strength improved the inter-observer agreement only on the FLAIR sequence.
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Exposure to moderate hypoxia in humans leads to cerebral lactate production, which occurs even when the cerebral metabolic rate of oxygen (CMRO2) is unaffected. We searched for the mechanism of this lactate production by testing the hypothesis of upregulation of cerebral glycolysis mediated by hypoxic sensing. Describing the pathways counteracting brain hypoxia could help us understand brain diseases associated with hypoxia. A total of 65 subjects participated in this study: 30 subjects were exposed to poikilocapnic hypoxia, 14 were exposed to isocapnic hypoxia, and 21 were exposed to carbon monoxide (CO). Using this setup, we examined whether lactate production reacts to an overall reduction in arterial oxygen concentration or solely to reduced arterial oxygen partial pressure. We measured cerebral blood flow (CBF), CMRO2, and lactate concentrations by magnetic resonance imaging and spectroscopy. CBF increased (P < 10-4), whereas the CMRO2 remained unaffected (P > 0.076) in all groups, as expected. Lactate increased in groups inhaling hypoxic air (poikilocapnic hypoxia: $0.0136\ \frac{\mathrm{mmol}/\mathrm{L}}{\Delta{\mathrm{S}}_{\mathrm{a}}{\mathrm{O}}_2}$, P < 10-6; isocapnic hypoxia: $0.0142\ \frac{\mathrm{mmol}/\mathrm{L}}{\Delta{\mathrm{S}}_{\mathrm{a}}{\mathrm{O}}_2}$, P = 0.003) but was unaffected by CO (P = 0.36). Lactate production was not associated with reduced CMRO2. These results point toward a mechanism of lactate production by upregulation of glycolysis mediated by sensing a reduced arterial oxygen pressure. The released lactate may act as a signaling molecule engaged in vasodilation.
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Encéfalo , Ácido Láctico , Encéfalo/fisiologia , Circulação Cerebrovascular/fisiologia , Humanos , Hipóxia/complicações , Hipóxia/metabolismo , Oxigênio , Consumo de OxigênioRESUMO
Psychotic major depression (PMD) is hypothesized to be a distinct clinical entity from nonpsychotic major depression (NPMD). However, neurobiological evidence supporting this notion is scarce. The aim of this study is to identify gray matter volume (GMV) differences between PMD and NPMD and their longitudinal change following electroconvulsive therapy (ECT). Structural magnetic resonance imaging (MRI) data from 8 independent sites in the Global ECT-MRI Research Collaboration (GEMRIC) database (n = 108; 56 PMD and 52 NPMD; mean age 71.7 in PMD and 70.2 in NPMD) were analyzed. All participants underwent MRI before and after ECT. First, cross-sectional whole-brain voxel-wise GMV comparisons between PMD and NPMD were conducted at both time points. Second, in a flexible factorial model, a main effect of time and a group-by-time interaction were examined to identify longitudinal effects of ECT on GMV and longitudinal differential effects of ECT between PMD and NPMD, respectively. Compared with NPMD, PMD showed lower GMV in the prefrontal, temporal and parietal cortex before ECT; PMD showed lower GMV in the medial prefrontal cortex (MPFC) after ECT. Although there was a significant main effect of time on GMV in several brain regions in both PMD and NPMD, there was no significant group-by-time interaction. Lower GMV in the MPFC was consistently identified in PMD, suggesting this may be a trait-like neural substrate of PMD. Longitudinal effect of ECT on GMV may not explain superior ECT response in PMD, and further investigation is needed.
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Depressão/fisiopatologia , Idoso , Idoso de 80 Anos ou mais , Espessura Cortical do Cérebro , Eletroconvulsoterapia/métodos , Eletroconvulsoterapia/estatística & dados numéricos , Feminino , Humanos , Imageamento por Ressonância Magnética/métodos , Imageamento por Ressonância Magnética/estatística & dados numéricos , Masculino , Pessoa de Meia-IdadeRESUMO
BACKGROUND: Evidence suggests that fronto-limbic brain regions and connecting white matter fibre tracts in the left hemisphere are more sensitive to glucocorticoids than in the right hemisphere. It is unknown whether treatment with glucocorticoids in childhood is associated with microstructural differences of the uncinate fasciculus and cingulum bundle, which connect fronto-limbic brain regions. Here, we tested the hypothesis that prior glucocorticoid treatment would be associated with differences in fractional anisotropy (FA) of the left relative to right uncinate fasciculus and cingulum bundle. METHODS: We performed diffusion-weighted imaging in 28 children and adolescents aged 7-16 years previously treated with glucocorticoids for nephrotic syndrome or rheumatic disease and 28 healthy controls. RESULTS: Patients displayed significantly different asymmetry in the microstructure of uncinate fasciculus with higher left but similar right uncinate fasciculus FA and axial diffusivity compared to controls. No apparent differences were observed for the cingulum. Notably, higher cumulative glucocorticoid doses were significantly associated with higher uncinate fasciculus FA and axial diffusivity bilaterally. CONCLUSIONS: Our findings indicate that previous glucocorticoid treatment for non-cerebral diseases in children and adolescents is associated with long-term changes in the microstructure of the uncinate fasciculi, and that higher cumulative glucocorticoid doses have a proportional impact on the microstructure. IMPACT: It is unknown if treatment with glucocorticoids in childhood have long-term effects on fronto-limbic white matter microstructure. The study examined if children and adolescents previously treated with glucocorticoids for nephrotic syndrome or rheumatic disorder differed in fronto-limbic white matter microstructure compared to healthy controls. The nephrotic and rheumatic patients had higher left but similar right uncinate fasciculus FA and axial diffusivity. Higher bilateral uncinate fasciculus FA and axial diffusivity was associated with higher cumulative glucocorticoid doses. We revealed new evidence suggesting that previous glucocorticoid treatment for non-cerebral diseases in children and adolescents is associated with long-term changes in uncinate fasciculi microstructure.
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Síndrome Nefrótica , Substância Branca , Adolescente , Anisotropia , Encéfalo , Criança , Imagem de Tensor de Difusão/métodos , Feminino , Glucocorticoides/uso terapêutico , Humanos , Masculino , Síndrome Nefrótica/diagnóstico por imagem , Síndrome Nefrótica/tratamento farmacológico , Fascículo Uncinado , Substância Branca/diagnóstico por imagemRESUMO
In the pons, glutamatergic mechanisms are involved in regulating inhibitory descending pain modulation, serotoninergic neurotransmission as well as modulating the sensory transmission of the trigeminovascular system. Migraine involves altered pontine activation and structural changes, while biochemical, genetic and clinical evidence suggests that altered interictal pontine glutamate levels may be an important pathophysiological feature of migraine abetting to attack initiation. Migraine without aura patients were scanned outside attacks using a proton magnetic resonance spectroscopy protocol optimized for the pons at 3 Tesla. The measurements were performed on two separate days to increase accuracy and compared to similar repeated measurements in healthy controls. We found that interictal glutamate (i.e. Glx) levels in the pons of migraine patients (n = 33) were not different from healthy controls (n = 16) (p = 0.098), while total creatine levels were markedly increased in patients (9%, p = 0.009). There was no correlation of glutamate or total creatine levels to migraine frequency, days since the last attack, usual pain intensity of attacks or disease duration. In conclusion, migraine is not associated with altered interictal pontine glutamate levels. However, the novel finding of increased total creatine levels suggests that disequilibrium in the pontine energy metabolism could be an important feature of migraine pathophysiology.
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Enxaqueca sem Aura , Creatina , Ácido Glutâmico , Humanos , Imageamento por Ressonância Magnética , Ponte/diagnóstico por imagem , Espectroscopia de Prótons por Ressonância MagnéticaRESUMO
Background: Obesity is a frequent somatic comorbidity of major depression, and it has been associated with worse clinical outcomes and brain structural abnormalities. Converging evidence suggests that electroconvulsive therapy (ECT) induces both clinical improvements and increased subcortical grey matter volume in patients with depression. However, it remains unknown whether increased body weight modulates the clinical response and structural neuroplasticity that occur with ECT. Methods: To address this question, we conducted a longitudinal investigation of structural MRI data from the Global ECT-MRI Research Collaboration (GEMRIC) in 223 patients who were experiencing a major depressive episode (10 scanning sites). Structural MRI data were acquired before and after ECT, and we assessed change in subcortical grey matter volume using FreeSurfer and Quarc. Results: Higher body mass index (BMI) was associated with a significantly lower increase in subcortical grey matter volume following ECT. We observed significant negative associations between BMI and change in subcortical grey matter volume, with pronounced effects in the thalamus and putamen, where obese participants showed increases in grey matter volume that were 43.3% and 49.6%, respectively, of the increases found in participants with normal weight. As well, BMI significantly moderated the association between subcortical grey matter volume change and clinical response to ECT. We observed no significant association between BMI and clinical response to ECT. Limitations: Because only baseline BMI values were available, we were unable to study BMI changes during ECT and their potential association with clinical and grey matter volume change. Conclusion: Future studies should take into account the relevance of body weight as a modulator of structural neuroplasticity during ECT treatment and aim to further explore the functional relevance of this novel finding.
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Peso Corporal , Encéfalo/patologia , Transtorno Depressivo Maior/patologia , Transtorno Depressivo Maior/terapia , Eletroconvulsoterapia , Substância Cinzenta/patologia , Encéfalo/diagnóstico por imagem , Transtorno Depressivo Maior/diagnóstico por imagem , Feminino , Substância Cinzenta/diagnóstico por imagem , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
Migraine is a complex disorder, involving peripheral and central brain structures, where mechanisms and site of attack initiation are an unresolved puzzle. While abnormal pontine neuronal activation during migraine attacks has been reported, exact implication of this finding is unknown. Evidence suggests an important role of glutamate in migraine, implying a possible association of pontine hyperactivity to increased glutamate levels. Migraine without aura patients were scanned during attacks after calcitonin gene-related peptide and sildenafil in a double-blind, randomized, double-dummy, cross-over design, on two separate study days, by proton magnetic resonance spectroscopy and pseudo-continuous arterial spin labeling at 3T. Headache characteristics were recorded until 24 h after drug administrations. Twenty-six patients were scanned during migraine, yielding a total of 41 attacks. Cerebral blood flow increased in dorsolateral pons, ipsilateral to pain side during attacks, compared to outside attacks (13.6%, p = 0.009). Glutamate levels in the same area remained unchanged during attacks (p = 0.873), while total creatine levels increased (3.5%, p = 0.041). In conclusion, dorsolateral pontine activation during migraine was not associated with higher glutamate levels. However, the concurrently increased total creatine levels may suggest an altered energy metabolism, which should be investigated in future studies to elucidate the role of pons in acute migraine.
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Ácido Glutâmico/metabolismo , Imageamento por Ressonância Magnética , Transtornos de Enxaqueca/patologia , Ponte/metabolismo , Espectroscopia de Prótons por Ressonância Magnética , Adulto , Artérias/química , Artérias/fisiopatologia , Peptídeo Relacionado com Gene de Calcitonina/farmacologia , Peptídeo Relacionado com Gene de Calcitonina/uso terapêutico , Circulação Cerebrovascular/efeitos dos fármacos , Circulação Cerebrovascular/fisiologia , Creatina/metabolismo , Método Duplo-Cego , Metabolismo Energético/efeitos dos fármacos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Transtornos de Enxaqueca/tratamento farmacológico , Ponte/irrigação sanguínea , Ponte/fisiopatologia , Citrato de Sildenafila/farmacologia , Citrato de Sildenafila/uso terapêutico , Marcadores de Spin , Vasodilatadores/farmacologia , Vasodilatadores/uso terapêutico , Adulto JovemRESUMO
The middle meningeal artery is a proposed surrogate marker for activation of trigeminal nociceptors during migraine. Previous studies focused on the extracranial part of the artery; hence, vasoreactivity in the intradural arteries during migraine is unknown. Thirty-four patients with migraine without aura were given sildenafil on one day and calcitonin gene-related peptide on another in double-blind crossover fashion. Patients were scanned with 3.0 T MR angiography before drug administration and again 6 hours later during induced attacks of migraine. We measured circumference of the intradural segment of the middle meningeal artery before and during induced migraine attacks. The middle cerebral and superficial temporal arteries were also examined. Fourteen patients had attacks during the second scan after both study drugs and 11 had a migraine after either one or the other, resulting in a total of 39 attacks included in the final analysis. Mean circumference of the intradural middle meningeal artery at baseline was 3.18 mm with an increase of 0.11 mm during attacks (P = 0.005), corresponding to a relative dilation of 3.6% [95% CI: 1.4%-5.7%]. Middle cerebral artery dilated by 9.4% [95% CI: 7.1%-11.7%] and superficial temporal artery by 2.3% [95% CI: 0.2%-4.4%]. Our study shows that the intradural middle meningeal artery and the middle cerebral artery are dilated during migraine induced by calcitonin gene-related peptide as well as sildenafil. We propose that intradural vasculature is affected by migraine-driven activation of trigeminal afferents during migraine attacks.
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Transtornos de Enxaqueca , Peptídeo Relacionado com Gene de Calcitonina , Dilatação , Humanos , Artérias Meníngeas/diagnóstico por imagem , Transtornos de Enxaqueca/induzido quimicamente , Transtornos de Enxaqueca/diagnóstico por imagem , Citrato de SildenafilaRESUMO
Glutamate detection in pons and thalamus using proton magnetic resonance spectroscopy (1H-MRS) after an intervention is of interest for studying various brain disorders. However, 1H-MRS in these brain regions is challenging and time-consuming, especially in longitudinal study designs. 1H-MRS of more cortical structures at the ultrahigh magnetic field strength of 7T yields an improved spectral output, including separation of the glutamate signal from the glutamine signal, in a shorter and more feasible scan time, as compared to conventional clinical field strengths. For this purpose, we compared the feasibility of 1H-MRS at 3T and 7T in pons and thalamus by applying a longitudinal study design of repeated measures on same day and three separate days at both field strength in five healthy participants. Total 1H-MRS acquisition time was reduced by a factor 3.75 for pons and by a factor 3 for thalamus at 7T as compared to 3T. We found higher spectral signal-to-noise ratio (SNR) (p < 0.001), lower linewidth (p = 0.001) and lower Cramér-Rao lower bounds (CRLB) (p < 0.001) for the combined glutamate and glutamine signal (Glx) in thalamus at 7T as compared to 3T. In pons, CRLB of Glx and SNR were lower at 7T (p = 0.002 and p = 0.006), with no differences in linewidth compared to 3T. Mean within-subject variability of Glx concentration estimates was lower at 7T compared to 3T for both pons and thalamus. At 7T, it was possible to assess glutamate and γ-aminobutyric acid (GABA) simultaneously in pons and thalamus. In conclusion, 1H-MRS at 7T resulted in improved spectral quality while allowing shorter scan times than at 3T as well as estimation of the pure glutamate signal in pons and thalamus. This opens up the opportunity for multimodal study designs and multiregional subcortical 1H-MRS research. Glutamate and GABA measurement at 7T in pons and thalamus is advantageous for future investigations of excitatory-inhibitory mechanisms in brain disorders.
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OBJECTIVES: Brain dysfunction is a serious complication after cardiac surgery. In the Perfusion Pressure Cerebral Infarcts trial, we allocated cardiac surgery patients to a mean arterial pressure of either 70-80 or 40-50 mmHg during cardiopulmonary bypass (CPB). In this secondary analysis, we compared selected cerebral metabolites using magnetic resonance spectroscopy hypothesizing that a postoperative decrease in occipital grey matter (GM) N-acetylaspartate-to-total-creatine ratio, indicative of ischaemic injury, would be found in the high-target group. METHODS: Of the 197 patients randomized in the Perfusion Pressure Cerebral Infarcts trial, 55 and 42 patients had complete and useful data from GM and white matter (WM), respectively. Spectroscopies were done preoperatively and on postoperative days 3-6. Cognitive function was assessed prior to surgery, at discharge and at 3 months. We predefined the statistical significance level to be 0.01. RESULTS: A postoperative decrease was found in GM N-acetylaspartate-to-total-creatine ratio in the high-target group [mean difference -0.09 (95% confidence interval -0.14 to -0.04), P = 0.014]. No significant differences were found in other metabolite ratios investigated in GM or WM. No significant association was found between changes in metabolite ratios and new cerebral infarcts, WM lesion score or cognitive dysfunction. CONCLUSIONS: A higher mean arterial pressure during CPB was associated with signs of impaired cerebral metabolism, though not at the predefined significance level of 0.01. No significant association was found between metabolite ratio changes and neuroradiological pathology or change in cognitive function. CLINICAL TRIAL REGISTRATION NUMBER: Clinicaltrials.gov: NCT02185885.
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Lesões Encefálicas , Procedimentos Cirúrgicos Cardíacos , Pressão Sanguínea , Encéfalo , Procedimentos Cirúrgicos Cardíacos/efeitos adversos , Ponte Cardiopulmonar/efeitos adversos , Humanos , PerfusãoRESUMO
BACKGROUND: Treatment options for the subgroup of people who develop long-lasting symptoms following mild traumatic brain injury are limited. Transcranial pulsating low-frequency electromagnetic stimulation (T-PEMF) in other patient groups has shown promising results in several studies with proposed neuroprotective and anti-inflammatory effects. OBJECTIVE: The present pilot study was conducted to access feasibility and tolerability of T-PEMF in treating post-concussion syndrome. METHODS: Seven patients with post-concussion syndrome received 5 weeks of daily 30 minutes T-PEMF treatment with evaluation after 2 and 5 weeks and 3 months after ending treatment. RESULTS: Compliance was high as all subject completed the full treatment. Two patients however experienced a worsening of their concussion symptoms during the course of treatment. The remaining patients had some discomfort in relation to treatment, mainly headache, but passing and less for each treatment. The majority (n = 5) had a reduction in symptoms overall, up to 61% (2%-61%) based on the Rivermead Post-Concussion Symptoms Questionnaire. CONCLUSION: Further studies on T-PEMF as a treatment option for post-concussion syndrome are warranted.