1H magnetic resonance spectroscopy at 3 T in cryptogenic and mesial temporal lobe epilepsy

Riederer, Franz; Bittšanský, Michal; Schmidt, Christian A.; Mlynárik, Vladı́mir; Baumgartner, Christoph; Moser, Ewald; Serles, Wolfgang

doi:10.1002/nbm.1029

Cited by 41 publications

(33 citation statements)

References 32 publications

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“…). Hippocampal Glu is a metabolite of particular clinical interest, as demonstrated in studies seeking surrogate markers for diagnostics or therapy monitoring in Alzheimer's disease and schizophrenia .…”

Section: Discussionmentioning

confidence: 99%

“…The hippocampus, a brain structure located deep in the temporal lobe, plays an essential role in learning, memory formation and stress regulation . Hippocampus dysfunction is thought to be involved in several neurological, psychiatric and metabolic diseases, including Alzheimer's disease , temporal lobe epilepsy , schizophrenia and diabetes . Importantly, hippocampal function can be affected by both pharmacological treatments and non‐pharmacological treatments, such as exercise training .…”

Section: Introductionmentioning

confidence: 99%

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Feasibility and reproducibility of neurochemical profile quantification in the human hippocampus at 3 T

et al. 2015

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summary Hippocampal dysfunction is known to be associated with several neurological and neuropsychiatric disorders such as Alzheimer's disease, epilepsy, schizophrenia and depression, therefore there has been significant clinical interest to study hippocampal neurochemistry. However the hippocampus is a challenging region to study using 1H MRS, hence the use of MRS for clinical research in this region has been limited. Therefore, our goal was to investigate the feasibility of obtaining high quality hippocampal spectra that allow reliable quantification of a neurochemical profile and to establish inter-session reproducibility of hippocampal MRS, including reproducibility of voxel placement, spectral quality and neurochemical concentrations. Ten healthy volunteers were scanned in two consequent sessions using a standard clinical 3T MR scanner. Neurochemical profiles were obtained with a short-echo (TE=28ms) semi-LASER localization sequence from a relatively small (~4mL) voxel that covered ~62% of the hippocampal volume as calculated from segmentation of T1-weighted images. Voxel composition was highly reproducible between sessions, with test-retest coefficients-of-variance (CV) of 3.5% and 7.5% for gray and white matter volume fraction, respectively. Excellent signal-to-noise ratio (~54 based on the N-acetylaspartate (NAA)-methyl peak in non-apodized spectra) and linewidths (~9 Hz for water) were achieved reproducibly in all subjects. The spectral quality allowed quantification of NAA, total choline, total creatine, myo-inositol and glutamate with high scan-rescan reproducibility (CV ≤ 6%) and quantification precision (Cramér-Rao lower bounds, CRLB < 9%). Four other metabolites, including glutathione and glucose, were quantified with scan-rescan CV below 20%. Therefore, the highly optimized, short echo semi-LASER sequence together with FASTMAP shimming substantially improved the reproducibility and number of quantifiable metabolites relative to prior reports. In addition, the between-session variation in metabolite concentrations, as well as CRLB were lower than between-subject variation of the concentrations for most metabolites indicating that the method has the sensitivity to detect inter-individual differences in the healthy brain.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Feasibility and reproducibility of neurochemical profile quantification in the human hippocampus at 3 T

et al. 2015

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“…However, in studies of neurodegenerative diseases, other areas of the brain, such as the basal ganglia and medial temporal lobe, could be interesting as these are known to be sites of early biochemical changes and therefore potentially enable the early detection of the disease (7). As an example, MRS of the temporal lobe has been used extensively in studies of epilepsy (7)(8)(9)(10)(11), schizophrenia (12) and, in particular, Alzheimer's disease (13)(14)(15)(16)(17). However, obtaining high-quality 1 H MRS from this region is highly challenging.…”

Section: Introductionmentioning

confidence: 99%

Improvements in high‐field localized MRS of the medial temporal lobe in humans using new deformable high‐dielectric materials

et al. 2010

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The intrinsic nonuniformities in the transmit radiofrequency field from standard quadrature volume resonators at high field are particularly problematic for localized MRS in areas such as the temporal lobe, where a low signal-to-noise ratio and poor metabolite quantification result from destructive B₁⁺ field interference, in addition to line broadening and signal loss from strong susceptibility gradients. MRS of the temporal lobe has been performed in a number of neurodegenerative diseases at clinical fields, but a relatively low signal-to-noise ratio has prevented the reliable quantification of, for example, glutamate and glutamine, which are thought to play a key role in disease progression. Using a recently developed high-dielectric-constant material placed around the head, localized MRS of the medial temporal lobe using the stimulated echo acquisition mode sequence was acquired at 7 T. The presence of the material increased the signal-to-noise ratio of MRS by a factor of two without significantly reducing the sensitivity in other areas of the brain, as shown by the measured B₁⁺ maps. An increase in the receive sensitivity B₁⁻ was also measured close to the pads. The spectral linewidth of the unsuppressed water peak within the voxel of interest was reduced slightly by the introduction of the dielectric pads (although not to a statistically significant degree), a result confirmed by using a pad composed of lipid. Using LCmodel for quantitative analysis of metabolite concentrations, the increase in signal-to-noise ratio and the slight decrease in spectral linewidth contributed to statistically significant reductions in the Cramer-Rao lower bounds (CRLBs), also allowing the levels of glutamate and glutamine to be quantified with CRLBs below 20%.

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“…1 H-MRS has been confirmed as a satisfactory method for the diagnosis and assessment of epilepsies, especially TLE (22)(23)(24). This study has characterized it as a practical preoperative and non-invasive tool for assessing hippocampal sclerosis in patients with TLE.…”

Section: Discussionmentioning

confidence: 90%

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NMR in Biomedicine

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ABSTRACT:We assessed 1 H-MRS as a screening tool for detection of hippocampal sclerosis in patients with temporal lobe epilepsy (TLE).1 H-MRS was carried out in the hippocampus of 23 patients with unilateral TLE. Metabolite alterations detected by 1 H-MRS correlated with degree of segmental neuronal cell loss and amount of astrogliosis. Positive correlation was found between total N-Acetylaspartate (tNAA) reduction and neuronal density in hippocampal CA1 (P < 0.001), CA3 (P ¼ 0.015), and CA4 subfields (P ¼ 0.031) and the dentate gyrus (P ¼ 0.006). Neuronal cell loss in CA1 turned out to be the most predictive and only significant variable for tNAA reduction (P ¼ 0.027). The association between myo-inositol (m-Ins) and astroglial glial fibrillary acidic protein (GFAP) expression revealed significantly increased m-Ins concentrations associated with diffuse astrogliosis (m-Ins ¼ 6.4 AE 1.1 institutional units) compared with gliosis restricted to isolated sectors of the hippocampus (i.e. hilus) (m-Ins ¼ 5.2 AE 1.2 institutional units) (P ¼ 0.039). A negative correlation was found between m-Ins and neuronal loss in the CA4 subfield of the hippocampus (P ¼ 0.028). Our results support 1 H-MRS as a suitable non-invasive method for preoperative identification of hippocampal sclerosis in patients with TLE. The extent of tNAA reduction correlates with hippocampal neuronal cell density. Furthermore, m-Ins is associated with the extent of hippocampal astrogliosis.

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1H magnetic resonance spectroscopy at 3 T in cryptogenic and mesial temporal lobe epilepsy

Cited by 41 publications

References 32 publications

Feasibility and reproducibility of neurochemical profile quantification in the human hippocampus at 3 T

Feasibility and reproducibility of neurochemical profile quantification in the human hippocampus at 3 T

Improvements in high‐field localized MRS of the medial temporal lobe in humans using new deformable high‐dielectric materials

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