New brain lesions with no impact on physical disability can impact cognition in early multiple sclerosis: A ten-year longitudinal study

OBJECTIVE

In early multiple sclerosis, although brain T2 lesions accrual are hallmark of the disease, only weak correlations were found between T2 lesions accrual and EDSS progression, the disability scale commonly used in multiple sclerosis studies. This may be related to the very poor sensitivity of EDSS to cognitive dysfunctions that may occur and progress from the first stage of the disease. In the present study, we aimed to demonstrate that cognitive deficits progress during the first ten years of MS and are significantly impacted by new T2 lesions.

METHODS

EDSS and extensive neuropsychological battery (22 measures) exploring memory, attention/speed of information processing and executive functions were assessed at baseline, Year 1 and Year 10 in 26 patients enrolled after their first clinical attack. To limit the bias of test-retest effect, only measures obtained at Year 1 and Year 10 were reported in the analysis. Raw scores of patients were transformed into z-scores using published normative data when available or scores of matched controls. Lesion probability mapping was used to assess the potential relationships between T2 lesions accumulation, cognitive decline and EDSS progression (P<0.05, FWE-corrected).

RESULTS

At Year 1, 27% of patients showed attention/speed of information processing deficits, 11.5% executive dysfunction and 11.5% memory impairment. During the follow-up, frequency and severity of executive dysfunction increased (from 11.5% of patients at Year 1 to 42% at Year 10, p<0.01) while no significant changes were evidenced for the other cognitive domains. Median EDSS increased from 0.5 [range: 0-3] at Year 1 to 2.5 [range: 0-6.5] at Year 10 (p<0.001). During the ten-year follow-up, lesions accumulation in the left cerebellum and semi-ovale centers was associated with EDSS progression. In contrast, most lesions accumulation in the frontal, parietal and temporal lobes were associated with cognitive decline but had no effect on EDSS progression.

CONCLUSION

The present study provides strong evidence that clinically silent T2 lesions impact cognition in early MS. In daily practice, early prevention of T2 lesions accrual may be useful to limit cognitive decline.

MRI/MRS of corpus callosum in patients with clinically isolated syndrome suggestive of multiple sclerosis

A trophy of corpus callosum (C C) related to axonal loss has previously been observed in patients at the early stage of clinically definite multiple sclerosis (CDMS). Atrophy increases with the progression of the disease. Nevertheless, no data concerning the onset of atrophy of C C are currently available. The purpose of this study is to determine if damage in callosal tissue was present at the earliest stage of MS, in a subgroup of patients presenting with a clinically isolated syndrome suggestive of MS (C ISSMS), fulfilling the dissemination in space criteria according to McDonald. Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) techniques were applied to measure C C volume, magnetization transfer ratio (MTR), mean diffusivity (MD), N-acetyl aspartate/choline-containing compounds (NAA/C ho) ratio, N-acetyl aspartate/total creatine (NA A/C r) ratio and C ho/C r ratio inside the C C of 46 C ISSMS patients and 24 sexand age-matched controls. No atrophy of C C was observed in the C ISSMS group. C C of patients was character ized by decreased MTR and increased MD. No change in the NA A/C r ratio was observed while the NA A/C ho ratio decreased and C ho/C r ratio increased in the splenium and the central anterio r part of C C. These abnormalities were present in patients with, but also without, macroscopic lesions inside the C C. O ur results indicate that diffuse structural and metabolic changes, which may be interpreted as representing predominantly myelin patho logy, occur in the C C at the earliest stage of MS before any atrophy is detected.

Onset and underpinnings of white matter atrophy at the very early stage of multiple sclerosis - a two-year longitudinal MRI/MRSI study of corpus callosum

Backgrounds Atrophy of corpus callosum (CC), a white matter structure linking the two hemispheres, is commonly observed in multiple sclerosis (MS). However, the occurrence and processes leading to this alteration are not yet determined.

Goal and methods To better characterize the onset and progression of CC atrophy from the early stage of MS, we performed a two-year follow-up magnetic resonance imaging/magnetic resonance spectroscopic imaging (MRI/MRSI) exploration of CC in 24 patients with clinically isolated syndrome. These patients were explored using the same protocol at month (M)6, M12 and M24. MRI/MRSI techniques were applied to measure CC volume, and relative concentrations of N-acetylaspartate (NAA), creatine/phosphocreatine (Cr) and choline-containing compounds (Cho). A group of matched controls was also explored.

Results Atrophy of CC, not present at baseline, was observed at M12 and progressed over the second year (M24). At baseline, a decrease in relative NAA level was observed in the anterior and posterior body of CC, with normalization during the follow-up period. In the anterior body, an increase in relative Cho level was observed, with normalization at M6. Normal relative Cr levels were observed at all time points in all sub-regions. The rate of CC atrophy was correlated with the change in the Expanded Disability Status Scale (EDSS) during the follow-up period.

Conclusion These results suggest that CC atrophy appears over a period of one year after the first acute inflammatory episode, and that this atrophy is accompanied, especially in the anterior body of CC, by a normalization of the relative Cho levels, marker of acute inflammation, and NAA levels, marker of neuronal dysfunction and/or loss.

Multimodal MR imaging (diffusion, perfusion, and spectroscopy): is it possible to distinguish oligodendroglial tumor grade and 1p/19q codeletion in the pretherapeutic diagnosis?

BACKGROUND AND PURPOSE

Pretherapeutic determination of tumor grade and genotype in grade II and III oligodendroglial tumors is clinically important but is still challenging. Tumor grade and 1p/19q status are currently the 2 most important factors in therapeutic decision making for patients with these tumors. Histopathology and cMRI studies are still limited in some cases. In the present study, we were interested in determining whether the combination of PWI, DWI, and MR spectroscopy could help distinguish oligodendroglial tumors according to their histopathologic grade and genotype.

MATERIALS AND METHODS

We retrospectively reviewed 50 adult patients with grade II and III oligodendrogliomas and oligoastrocytomas who had DWI, PWI, and MR spectroscopy at short and long TE data and known 1p/19q status. Univariate analyses and multivariate random forest models were performed to determine which criteria could differentiate between grades and genotypes.

RESULTS

ADC, rCBV, rCBF, and rK2 were significantly different between grade II and III oligodendroglial tumors. DWI, PWI, and MR spectroscopy showed no significant difference between tumors with and without 1p/19q loss. Separation between tumor grades and genotypes with cMRI alone showed 31% and 48% misclassification rates, respectively. Multimodal MR imaging helps to determine tumor grade and 1p/19q genotype more accurately (misclassification rates of 17% and 40%, respectively).

CONCLUSIONS

Although multimodal investigation of oligodendroglial tumors has a lower contribution to 1p/19q genotyping compared with cMRI alone, it greatly improves the accuracy of grading of these neoplasms. Use of multimodal MR imaging could thus provide valuable information that may assist clinicians in patient preoperative management and treatment decision making.

Is brain maturation comparable in fetuses and premature neonates at term equivalent age?

BACKGROUND AND PURPOSE

Improved knowledge of brain maturation in fetuses and premature neonates is crucial for the early detection of pathologies and would help determine whether MR data from the premature brain might be used to evaluate fetal maturation. Using diffusion-weighted MR imaging and (1)H-MR spectroscopy, we compared cerebral microstructure and metabolism in normal in utero fetuses imaged near term and premature neonates imaged at term equivalent.

MATERIALS AND METHODS

Forty-eight subjects were investigated: 24 in utero fetuses (mean gestational age, 37 ± 1 weeks) and 24 premature neonates (mean postconceptional age, 37 ± 1 weeks). ADC values were measured in cerebellum, pons, white matter, brain stem, basal ganglia, and thalamus. MR spectroscopy was performed in deep white matter.

RESULTS

Mean ADC values from fetuses and premature neonates were comparable except for the pons and the parietal white matter. ADC values were lower in the pons of premature neonates, whereas greater values were found in their parietal white matter compared with fetuses. Proton MR spectroscopy showed higher levels of NAA/H(2)O, Glx/H(2)O, tCr/H(2)O, and mIns/H(2)O in premature neonates compared with fetuses.

CONCLUSIONS

Our study provides evidence of subtle anomalies in the parietal white matter of healthy premature neonates. In addition, the reduced ADC values in the pons together with the increased levels of NAA/H(2)O, tCr/H(2)O, and Glx/H(2)O in the centrum semiovale suggest a more advanced maturation in some white matter regions. Our results indicate that MR data from the premature brain are not appropriate for the assessment of the fetal brain maturation.

Efficiency of cognitive control recruitment in the very early stage of multiple sclerosis: a one-year fMRI follow-up study

Functional magnetic resonance imaging (FMRI) studies have established that patients with multiple sclerosis show stronger activation in the lateral prefrontal cortices (LPFC) than healthy control subjects during effortful cognitive tasks. The aim of the present study was to assess the impact of these activation changes on cognitive performances. In addition to 19 controls, who were tested at a single time-point to define a standard pattern of fMRI activation during the performance of the Paced Auditory Serial Addition Task (PASAT), 13 patients with clinically isolated syndrome underwent a longitudinal fMRI examination while performing the PASAT at the beginning of the study (M0) and one year later (M12). Relative to the M0 scores, PASAT performances improved in eight patients (group A) and either decreased ( n = 4) or remained unchanged ( n = 1) (group B) in five patients at M12. Random effect analyses (SPM2; Wellcome Institute, London, England) were performed to compare intra-group time-related effects on brain activation (paired t-test between M0 and M12), and inter-group differences were also compared between the two groups of patients (analysis of covariance with PASAT performances as the covariate). Relative to group B, group A showed larger increase in activation between M0 and M12 in the right LPFC. In the whole group of patients, interaction analyses showed that the differences in the PASAT scores between M0 and M12 were correlated with the differences in activation observed in the right LPFC. This longitudinal study shows that in patients with early multiple sclerosis, the increased levels of activation in the right LPFC was associated with improved individual working memory and processing speed performances.

Multiparametric differentiation of posterior fossa tumors in children using diffusion-weighted imaging and short echo-time 1H-MR spectroscopy

PURPOSE

To assess the combined value of diffusion-weighted imaging (DWI) and proton magnetic resonance spectroscopy (1H-MRS) in differentiating medulloblastoma, ependymoma, pilocytic astrocytoma, and infiltrating glioma in a pediatric population.

MATERIALS AND METHODS

A total of 17 children with untreated posterior fossa tumors (seven medulloblastoma, four infiltrating glioma, two ependymoma, and four pilocytic astrocytoma), were investigated with conventional MRI, DWI, and MRS using a single-voxel technique. Within the nonnecrotic tumor core, apparent diffusion coefficient (ADC) values using a standardized region of interest (ROI) were retrieved. Quantification of water signal and analysis of metabolite signals from MRS measurements in the same tumorous area were reviewed using multivariant linear discriminant analysis.

RESULTS

Combination of ADC values and metabolites, which were normalized using water as an internal standard, allowed discrimination between the four tumor groups with a likelihood below 1 x 10(-9). Positive predictive value was 1 in all cases. Tumors could not be discriminated when using metabolite ratios or ADC values alone, nor could they be differentiated using creatine (Cr) as an internal reference even in combination with ADC values.

CONCLUSION

Linear discriminant analysis using DWI and MRS using water as internal reference, fully discriminates the four most frequent posterior fossa tumors in children.

Neuroimaging of neonatal encephalopathies

Neonatal brain disorders consist of a wide chapter including brain malformations, hypoxic-ischemic encephalopathy (HIE), intracranial infections, perinatal trauma and metabolic encephalopathy. We will focus here on HIE, intracranial infections (especially materno-fetal infection with or without prolonged and/or premature rupture of membranes) and metabolic encephalopathy, those three conditions being the most frequent so far in our experience. Neonatal stroke is also analyzed. Moreover minor perinatal events might be superimposed on an already damaged (infective, edematous, metabolically abnormal or maldeveloped) brain, highlighting the main role and potential benefits of neuroimaging during the neonatal period. The different methods of brain imaging are thus reported with their advantages and disadvantages.

MR imaging of brain maturation

Magnetic resonance imaging (MRI) is the imaging tool of choice to evaluate brain maturation and especially brain myelination. Magnetic resonance imaging also provides functional insight through diffusion images and proton spectroscopy. In this review the MRI techniques are analyzed for both pre- and postnatal periods. The origin of MR signal changes is also detailed in order to understand normal myelination evolution and the consequences on brain maturation of the different pathologies encountered prior and after birth. Because MRI is "blind" in terms of signal on conventional sequences after 2 years of age, a particular attention is given to diffusion images and proton spectroscopy of the developing brain.

[Brain magnetic resonance spectroscopy]

MR spectroscopy (MRS) sequences allow noninvasive exploration of brain metabolism during a MRI examination. Their day-to-day use in a clinical setting has recently been improved by simple programming of sequences and automated quantification of metabolites. However, a few simple rules should be observed in the choice of sequences and the location of the voxels so as to obtain an informative, high-quality examination. The research applications of MR spectroscopy, where use of this examination seeks to better understand the pathophysiology of the disease, must be distinguished from its clinical indications, where MRS provides information that can be used directly in patient management. The most significant of the clinical uses are imaging intracranial tumors (positive and differential diagnosis, extension, treatment follow-up), diffuse brain injury, encephalopathies (especially hepatic and HIV-related), and the diagnosis of metabolic disorders.

[Indications for cerebral MR proton spectroscopy in 2007]

Magnetic resonance spectroscopy (MRS) is being increasingly performed alongside the more conventional MRI sequences in the exploration of neurological disorders. It is however important to clearly differentiate its clinical applications aiming at improving the differential diagnosis or the prognostic evaluation of the patient, from the research protocols, when MRS can contribute to a better understanding of the pathophysiology of the disease or to the evaluation of new treatments. The most important applications in clinical practice are intracranial space occupying lesions (especially the positive diagnosis of intracranial abscesses and gliomatosis cerebri and the differential diagnosis between edema and tumor infiltration), alcoholic, hepatic, and HIV-related encephalopathies and the exploration of metabolic diseases. Among the research applications, MRS is widely used in multiple sclerosis, ischemia and brain injury, epilepsy and neuro degenerative diseases.

Diffusion-weighted imaging in normal fetal brain maturation

Diffusion-weighted imaging (DWI) provides information about tissue maturation not seen on conventional magnetic resonance imaging. The aim of this study is to analyze the evolution over time of the apparent diffusion coefficient (ADC) of normal fetal brain in utero. DWI was performed on 78 fetuses, ranging from 23 to 37 gestational weeks (GW). All children showed at follow-up a normal neurological evaluation. ADC values were obtained in the deep white matter (DWM) of the centrum semiovale, the frontal, parietal, occipital and temporal lobe, in the cerebellar hemisphere, the brainstem, the basal ganglia (BG) and the thalamus. Mean ADC values in supratentorial DWM areas (1.68 +/- 0.05 mm(2)/s) were higher compared with the cerebellar hemisphere (1.25 +/- 0.06 mm(2)/s) and lowest in the pons (1.11 +/- 0.05 mm(2)/s). Thalamus and BG showed intermediate values (1.25 +/- 0.04 mm(2)/s). Brainstem, cerebellar hemisphere and thalamus showed a linear negative correlation with gestational age. Supratentorial areas revealed an increase in ADC values, followed by a decrease after the 30th GW. This study provides a normative data set that allows insights in the normal fetal brain maturation in utero, which has not yet been observed in previous studies on premature babies.

Infratentorial pediatric brain tumors: the value of new imaging modalities

The correct assessment of the four most frequent infratentorial brain tumors in children (medulloblastoma, ependymoma, pilocytic astrocytoma and infiltrating glioma) has always been problematic. They are known to often resemble one another on conventional magnetic resonance (MR) imaging. We tested the hypothesis whether the combined strength of diffusion-weighted imaging (DWI) and proton MR spectroscopy (MRS) could help differentiate these tumors. Seventeen children with untreated posterior fossa tumors were investigated between January 2005 and January 2006 with conventional MR imaging and combined DWI and MR spectroscopy using a single-voxel technique at short and long echo time (TE) of 30 ms and 135 ms respectively. Apparent diffusion coefficient (ADC) values were retrieved after regions of interest were manually positioned within non necrotic tumor core. Water signal was quantified and metabolite signals were compared and analyzed using linear discriminant analysis. When a combination of ADC values and normalized metabolites was used, all tumors could be discriminated against one other. This could only be achieved when metabolites were normalized using water as an internal standard. They could not be discriminated when using metabolite ratios or ADC values alone, nor could they be differentiated using creatine (Cr) as an internal reference even in combination with ADC values. In conclusion, linear discriminant analysis and multiparametric combination of DWI and MRS, although not replacing histology, fully discriminates the four most frequent posterior fossa tumors in children, but metabolites have to be normalized using water and not Cr signal as an internal reference.

Spectroscopie par résonance magnétique des tumeurs cérébrales

MR spectroscopy (MRS) can complement MRI in the evaluation of intracranial tumors. Before treatment, MRS can contribute to the differential diagnosis between tumor and non tumoral lesion (especially intracranial abscesses), to assess the aggressiveness of a glial tumor or to determine its extension to better delineate the surgical removal or the target volume of radiotherapy. During treatment follow-up, MRS helps differentiate recurrent tumor from radionecrosis or physiological post-surgical contrast enhancement. The current studies are trying to determine if the indications of MRS, alone or in association with other MR sequences can further be extended in the study of brain tumors, in particular the follow-up of lesions undergoing chemo or radiotherapy.

Intracellular sodium increase and susceptibility to ischaemia in hearts from type 2 diabetic db/db mice

AIMS/HYPOTHESIS

An important determinant of sensitivity to ischaemia is altered ion homeostasis, especially disturbances in intracellular Na(+) (Na(i)(+)) handling. As no study has so far investigated this in type 2 diabetes, we examined susceptibility to ischaemia-reperfusion in isolated hearts from diabetic db/db and control db/+ mice and determined whether and to what extent the amount of (Na(i)(+)) increase during a transient period of ischaemia could contribute to functional alterations upon reperfusion.

METHODS

Isovolumic hearts were exposed to 30-min global ischaemia and then reperfused. (23)Na nuclear magnetic resonance (NMR) spectroscopy was used to monitor[Formula: see text] and (31)P NMR spectroscopy to monitor intracellular pH (pH(i)).

RESULTS

A higher duration of ventricular tachycardia and the degeneration of ventricular tachycardia into ventricular fibrillation were observed upon reperfusion in db/db hearts. The recovery of left ventricular developed pressure was reduced. The increase in[Formula: see text] induced by ischaemia was higher in db/db hearts than in control hearts, and the rate of pH(i) recovery was increased during reperfusion. The inhibition of Na(+)/H(+) exchange by cariporide significantly reduced (Na(i)(+)) gain at the end of ischaemia. This was associated with a lower incidence of ventricular tachycardia in both heart groups, and with an inhibition of the degeneration of ventricular tachycardia into ventricular fibrillation in db/db hearts.

CONCLUSIONS/INTERPRETATION

These findings strongly support the hypothesis that increased (Na(i)(+)) plays a causative role in the enhanced sensitivity to ischaemia observed in db/db diabetic hearts.

1H-MRS imaging in intractable frontal lobe epilepsies characterized by depth electrode recording

Presurgical evaluation of frontal lobe epilepsy (FLE) remains a challenging issue and frequently requires invasive depth electrode recording. In this study, we aimed at evaluating the potential usefulness of a non-invasive technique such as proton magnetic resonance spectroscopic imaging ((1)H-MRSI) in the presurgical evaluation of FLE and at investigating the potential electrophysiological correlates of the metabolic disturbances as defined by (1)H-MRSI. We compared the distribution of (1)H-MRSI abnormalities with the electrophysiological abnormalities defined by stereo-electroencephalography (SEEG) recording in 12 patients presenting with several subtypes of FLE. We also used 12 control subjects in order to obtain normative (1)H-MRSI data. We used a multilevel (1)H-MRSI protocol to better sample the principal regions of the frontal lobe. We also applied a metabolic mapping technique allowing a visual display of metabolic data. A significant decrease of both N-acetyl-aspartate/phosphocreatine-creatine and N-acetyl-aspartate/(choline-compounds + phosphocreatine-creatine) ratios was observed in regions involved in the epileptogenic zone (EZ) and/or the irritative zone (IZ) compared to regions without electrical abnormalities in the same patients (P = 0.044 and P = 0.018, respectively), and also compared to controls (P = 0.004 and P = 0.0001, respectively). No significant differences in metabolic ratios were observed between those regions involved in the EZ and those involved in the IZ only. Our results suggest a link between the relative decrease of N-acetyl-aspartate and the EZ as well as the IZ in FLE. Thus, multilevel (1)H-MRSI protocol may add pertinent information during the non-invasive presurgical evaluation of FLE.

Functional MRI study of PASAT in normal subjects

The paced auditory serial addition test (PASAT) is routinely used to evaluate the cognitive part of the multiple sclerosis functional composite (MSFC) score, the new reference index of patient disability. PASAT is sensitive to subtle cognitive impairment related to MS, although the cognitive components of this test still remain unclear. In order to better characterize brain systems involved during this complex task, functional magnetic resonance imaging (fMRI) experiments were conducted during PASAT in a population of ten normal subjects. The paradigm consisted of a series of 61 single-digit numbers delivered every 3 s. After each number, subjects were asked to overt vocalize the result of the addition of the two last numbers heard. A control task consisting of the repetition of the same series of single-digit numbers was used. Statistical group analysis was performed using the random effect procedure (SPM 99). Cortical activation was observed in the left prefrontal cortex, the supplementary motor area, the lateral premotor cortex, the cingulate gyrus, the left parietal lobe, the left superior temporal gyrus, the left temporal pole, and visual associative areas. fMRI activations underlying PASAT were consistent with an involvement of verbal working memory and the semantic memory retrieval network which could be related to arithmetic fact retrieval. This study on normal subjects could provide a base for the understanding of the potential abnormal cortical activation in MS patients performing this test for a cognitive evaluation.

Modulation of effective connectivity inside the working memory network in patients at the earliest stage of multiple sclerosis

fMRI and structural equation modeling (SEM) were used to study effective connectivity inside the working memory network in patients at the earliest stage of multiple sclerosis (MS), while performing paced auditory serial addition test (PASAT), a sensitive task to reveal subtle cognitive impairments related to working memory and information speed processing. The path model used for SEM included bilateral connections between left and right BA 46, left and right BA 40, left and right anterior cingulate cortex (ACC), left BA 44 and left BA 40, right BA 44 and right BA 40, and unidirectional ipsilateral connections from BA 46 to BA 44, from ACC to BA 46, and from ACC to BA 44. Experimental data from the two groups fit accurately the working memory model, in patients [chi20(2) = 13, P = 0.877] as well as in controls [chi20(2) = 13.54, P = 0.853]. The omnibus test indicated a significant difference of model fits in patients and in controls [chi40(2) = 160.07, P < 0.0001]. Connectivity strengths from right BA 46 to left BA 46, from left ACC to left BA 46 were lower in patients than in controls, and higher from right ACC to right BA 46, from left to right and from right to left ACC (stacked model). Effective connectivity inside the working memory network appears altered in patients at the earliest stage of MS. Modulation of effective connectivity is present in patients inside the executive subsystems of working memory, and could be related to adaptive cognitive control processes that may limit the clinical manifestation of MS.

High cerebral scyllo-inositol: a new marker of brain metabolism disturbances induced by chronic alcoholism

Cerebral metabolic changes that concur to motor and/or cognitive disorders in actively drinking alcoholics are not well established. We tested the hypothesis that chronic alcoholics exhibit profound alterations in the cerebral metabolism of scyllo-inositol. Brain metabolism was explored in nine actively drinking and 11 recently detoxified chronic alcoholics by in vivo brain (1)H-MRS and in vitro(1)H-MRS of blood serum and cerebrospinal fluid. The cohort was composed of individuals with acute, subacute or chronic encephalopathy or without any clinical encephalopathy. Chronic alcoholism is associated with a hitherto unrecognized accumulation of brain scyllo-inositol. Our results suggest that scyllo-inositol is produced within the central nervous system and shows a diffuse but heterogenous distribution in brain where it can persist several weeks after detoxification. Its highest levels were observed in subjects with a clinically symptomatic alcohol-related encephalopathy. When detected, brain scyllo-inositol takes part in a metabolic encephalopathy since it is associated with reduced N-acetylaspartate and increased creatine. High levels of cerebral scyllo-inositol are correlated with altered glial and neuronal metabolism. Our findings suggest that the accumulation of scyllo-inositol may precede and take part in the development of symptomatic alcoholic metabolic encephalopathy.

Multimodal magnetic resonance imaging of the central nervous system

The physiological and biochemical properties of the diseased brain that can be explored with magnetic resonance imaging (MRI) are increasing. Progress in MR-based technology affords a large panel of MRI sequences that explore different phenomena and, thus, provide complementary informations. The diagnostic accuracy of MRI is improved by the combination of all MR modalities. However, this abundance of data requires an efficient multiparametric analysis to fully achieve the goal of the multimodal strategy. We will discuss the potential impact of this advanced MRI analysis in the clinical management and the therapeutical strategies of the most common brain pathologies (intracranial tumors, multiple sclerosis, stroke, epilepsy and dementia). This non-invasive approach is of utmost importance since it already improves the diagnosis and the therapeutic choice in the management of several central nervous system diseases.

Fetal brain injury

Improvements in MRI techniques widen the indications for fetal brain imaging and fetal brain injury represents the third indication of fetal brain magnetic resonance imaging (MRI) after the evaluation of suspected central nervous system (CNS) malformations and ventricular dilatation. Optimal MR imaging technique is necessary in order to collect as much data as possible about the fetal brain. Diffusion images can be used routinely in addition to the standard protocol of fetal brain MRI that consists of T1 and T2 weighted images of the fetal brain. Monovoxel proton magnetic resonance spectroscopy can also be performed in utero, but this technique is still more part of research protocol than of routine clinical protocol. Fetal brain injury includes hypoxia-ischemia, congenital infections (especially toxoplasmosis and cytomegalovirus infections), brain damage due to malformation such as vascular brain malformation and heart malformation, pregnancies at risk of fetal brain damage, and even inherited metabolic diseases, especially mitochondrial diseases. MRI findings in fetal brain injury consist of acute or chronic lesions that can be seen alone or in combination. Acute response of the fetal brain is less commonly seen than the chronic response compared to the brain response encountered in the postnatal period.

Metabolic counterpart of decreased apparent diffusion coefficient during hyperacute ischemic stroke: a brain proton magnetic resonance spectroscopic imaging study

BACKGROUND AND PURPOSE

Recent studies have shown that the brain ischemic area defined by the map of decreased apparent diffusion coefficient (ADC) obtained by diffusion-weighted imaging (DWI) during the first hours of ischemic stroke includes a significant part of ischemic penumbra. We hypothesize that the misjudgment of the final infarct size by ADC mapping may be related to a restricted ability of DWI to capture variations in the intensity of cellular suffering. In an attempt to characterize metabolically the hypoperfused brain parenchyma, we studied the relationship between ADC values and brain metabolic parameters measured by proton MR spectroscopic imaging (SI).

METHODS

Six patients with hyperacute ischemic stroke were explored within the first 7 hours after onset with the use of a MR protocol including T2*-weighted MRI, DWI, SI, perfusion-weighted imaging, and MR angiography.

RESULTS

This study demonstrates, for the first time, a wide gradient of ischemia-related metabolic anomalies within the abnormal area delineated by DWI during hyperacute ischemic stroke. In the narrow range of decreased mean ADC values (0.60 to 0.40 x 10(-9) m2 x s(-1)), a 33% decrease in mean ADC is associated with a 122% increase in lactate/N-acetyl aspartate ratio. Mean ADC values never fall below 0.40 x 10(-9) m2 x s(-1) within the severely affected ischemic tissue, while SI still detects a large metabolic heterogeneity inside areas showing similar decreased mean ADC values close to this threshold.

CONCLUSIONS

Our results indicate that the region of very low mean ADC values observed during hyperacute ischemic stroke contains areas of various tissue damage intensity characterized by SI in relation to different stages of cellular metabolic injury. This observation may explain why ADC mapping does not reliably predict final infarct size.

Citrulline/malate promotes aerobic energy production in human exercising muscle

BACKGROUND

Previous studies have shown an antiasthenic effect of citrulline/malate (CM) but the mechanism of action at the muscular level remains unknown.

OBJECTIVE

To investigate the effects of CM supplementation on muscle energetics.

METHODS

Eighteen men complaining of fatigue but with no documented disease were included in the study. A rest-exercise (finger flexions)-recovery protocol was performed twice before (D-7 and D0), three times during (D3, D8, D15), and once after (D22) 15 days of oral supplementation with 6 g/day CM. Metabolism of the flexor digitorum superficialis was analysed by (31)P magnetic resonance spectroscopy at 4.7 T.

RESULTS

Metabolic variables measured twice before CM ingestion showed no differences, indicating good reproducibility of measurements and no learning effect from repeating the exercise protocol. CM ingestion resulted in a significant reduction in the sensation of fatigue, a 34% increase in the rate of oxidative ATP production during exercise, and a 20% increase in the rate of phosphocreatine recovery after exercise, indicating a larger contribution of oxidative ATP synthesis to energy production. Considering subjects individually and variables characterising aerobic function, extrema were measured after either eight or 15 days of treatment, indicating chronological heterogeneity of treatment induced changes. One way analysis of variance confirmed improved aerobic function, which may be the result of an enhanced malate supply activating ATP production from the tricarboxylic acid cycle through anaplerotic reactions.

CONCLUSION

The changes in muscle metabolism produced by CM treatment indicate that CM may promote aerobic energy production.

Investigation of fluoroquinolone-induced myalgia using (31)P magnetic resonance spectroscopy and in vitro contracture tests

OBJECTIVE

To investigate muscle function in patients with severe myalgia resulting from fluoroquinolone (FQ) treatment. We used histology, in vitro contracture tests (IVCTs), and (31)P magnetic resonance spectroscopy ((31)P MRS) to explore muscle contraction and metabolism.

METHODS

We studied 3 patients with myalgia, hyperalgia tendinopathy, and arthralgia following FQ treatment and 3 normal subjects after taking FQs. Results were compared with those of a control group of 9 subjects free of any muscle disease and not taking FQs. Muscle biopsies were performed on the left biceps, and IVCTs were performed in accordance with the protocol recommended by the European Malignant Hyperthermia Group. (31)P MR spectra of forearm flexor muscles were recorded at 4.7T throughout a rest-exercise-recovery protocol.

RESULTS

(31)P MRS showed a significant reduction of pH changes measured at the end of exercise and a faster rate of proton efflux measured during recovery in all patients. IVCTs diagnosed 1 patient as being susceptible to malignant hyperthermia. No specific histologic anomalies were observed in muscle biopsy samples, which showed normal mitochondria.

CONCLUSION

The adverse effects recorded in the 3 patients are related to a preexisting muscular anomaly revealed by FQ treatment.

[Applications of magnetic resonance spectrometry (MRS) in the study of metabolic disturbances affecting the brain in alcoholism]

The purpose of this article is to provide an overview of the current applications of magnetic resonance spectroscopy (MRS) to the investigation of cerebral metabolism in alcoholic patients. The specific metabolic changes associated with the intoxication process (tolerance, dependance), abstinence and alcohol-related diseases (alcoholic encephalopathy, cirrhosis, Gayet-Wernicke's encephalopathy, Marchiafava-Bignami syndrome) are described.

Time-dependent and indirect effect of inorganic phosphate on force production in rat gastrocnemius exercising muscle determined by 31P-MRS

The relationship of inorganic phosphate (P(i)) and its diprotonated form (H(2)PO(4)(-)) to isometric force (F) was analyzed non-invasively using 31P-magnetic resonance spectroscopy. Rat gastrocnemius muscles were electrically stimulated at six different frequencies in order to produce different levels of fatigue. A curvilinear relationship was demonstrated between force production and [P(i)] and [H(2)PO(4)(-)] accumulation. [P(i)] and [H(2)PO(4)(-)] were correlated with F at the end of the stimulation period but not when F was maximal at the early stage of the stimulation period. Interestingly, the respective [P(i)] and [H(2)PO(4)(-)] did not differ significantly between these two stages demonstrating that [P(i)] and [H(2)PO(4)(-)] cannot be considered as direct effectors of fatigue. This time-dependent and indirect effect of [P(i)] and [H(2)PO(4)(-)] on force production might be mediated by calcium ions.

Regional metabolite levels of the normal posterior fossa studied by proton chemical shift imaging

MR spectroscopy of the posterior fossa is pitted with numerous technical difficulties. It is, however, of great clinical interest in the study of the degenerative diseases and tumors of this area. We have developed a method to perform 2D CSI of this area, by using a sagittal slice and a careful positioning of outer volume saturation. We performed this acquisition in 30 healthy volunteers to determine the normal metabolic ratios in five voxels of this area (mesencephalon, pons, medulla oblongata, vermis, cerebellar white matter). The main technical difficulty was magnetic field inhomogeneity in the lower brainstem generated by dental alloys. However, 88% of the voxels were of sufficient quality to be analyzed. The statistically significant regional variations were a higher NAA/Cr ratio in the pons than in the medulla oblongata, higher Cho/Cr in the pons than in the mesencephalon and higher Cho/Cr in the cerebellar white matter than in the vermis. We conclude that 2D CSI of the brainstem, although technically delicate can be performed in most patients.

A noninvasive investigation of muscle energetics supports similarities between exertional heat stroke and malignant hyperthermia

Exertional heat stroke (EHS) is usually triggered by strenuous exercise performed under hot and humid environmental conditions. Although the pathogenesis of an EHS episode differs from that of a clinical malignant hyperthermia (MH) crisis, both conditions share some similarities in symptoms, such as the abnormal increase in core temperature. By use of (31)P magnetic resonance spectroscopy, we analyzed the muscle energetics of 26 post-EHS subjects for whom in vitro halothane/caffeine contracture tests were abnormal and investigated possible similarities with subjects susceptible to MH. An early decrease of pH was noted during the first minute of exercise in EHS subjects as compared with controls. EHS subjects were divided into two subgroups according to the diagnostic score previously developed for MH subjects. The 19 subjects (73%) with a score higher than 2 displayed significantly larger caffeine-induced and earlier ryanodine-induced contractures on muscle biopsies as compared with the rest of the group (7 subjects). The results demonstrate that muscle energetics are abnormal in subjects who have experienced EHS and suggest a possible link between MH and EH, although all EHS cannot be considered as MH.

Optimization of residual water signal removal by HLSVD on simulated short echo time proton MR spectra of the human brain

Suppression of the residual water signal from proton magnetic resonance (MR) spectra recorded in human brain is a prerequisite to an accurate quantification of cerebral metabolites. Several postacquisition methods of residual water signal suppression have been reported but none of them provide a complete elimination of the residual water signal, thereby preventing reliable quantification of brain metabolites. In the present study, the elimination of the residual water signal by the Hankel Lanczos singular value decomposition method has been evaluated and optimized to provide fast automated processing of spectra. Model free induction decays, reproducing the proton signal acquired in human brain localized MR spectroscopy at short echo times (e.g., 20 ms), have been generated. The optimal parameters in terms of number of components and dimension of the Hankel data matrix allowing complete elimination of the residual water signal are reported.

Simultaneous study of metabolism and function following cardioplegic arrest: a novel method of evaluation of the transplanted heart in the rat

BACKGROUND

Limitations of the isolated perfused rat heart model for heart preservation studies include short study time due to the lack of stability of the preparation. We aimed to develop a new experimental model based on heterotopic heart transplantation in the rat to achieve simultaneous (31)P magnetic resonance spectroscopy (MRS) and functional study of the transplanted heart during early and late blood reperfusion.

METHODS

Twenty-five Lewis rats underwent heterotopic abdominal isograft heart transplantation and were randomized in two groups. Hearts were harvested after cardioplegic arrest induced with Centre de Résonance Magnétique Biologique et Médicale (CRMBM) solution and then stored at 4 degrees C for a total ischemic time of 3 hours. Graft contractility measurement and simultaneous (31)P MRS were performed after 1 hour and 24 hours of blood reperfusion, respectively, in groups I (n = 12) and II (n =13).

RESULTS

Contractility improved during reperfusion. The mean rate pressure product plus or minus standard error of mean increased from 11,373 +/- 1,377 mm Hg/min in group I to 24,363 +/- 3,860 mm Hg/min in group II (P = 0.003), while mean dP/dtmax increased from 1,642 +/- 173 mm Hg/sec to 2,571 +/- 333 mm Hg/sec, respectively (p = 0.03). Simultaneously, both the phosphocreatine/adenosine triphosphate (ATP) and inorganic phosphate/ATP ratios decreased from group I to group II (p = 0.025 and p = 0.015, respectively), suggesting regeneration of the intracellular pool of ATP in group II.

CONCLUSIONS

Simultaneous functional and metabolic studies of the transplanted heart are feasible in rats. Improvement in contractility during late reperfusion is contemporary with significant changes in energetic metabolism. Our model should be useful for the further improvement of heart preservation, which may result in significant clinical progress.

Magnetic resonance spectroscopy of brain in epilepsy

The current applications of magnetic resonance spectroscopy (MRS) in the clinical management of epileptic patients are reviewed. A major contribution of MRS to epilepsy is its ability to determine lateralisation before surgical resection of the diseased brain region. Phosphorus-31 and proton single-voxel MRS identify abnormalities in high-energy metabolism, neuronal function and neurotransmitter levels, but information can only be obtained from restricted regions of the brain. Spectroscopic imaging techniques (also known as chemical shift imaging) provide a metabolic mapping of the whole brain. They expand the range of applications of MRS to other types of epilepsy (neocortical, frontal) than temporal lobe epilepsy, which is the most often studied. Also, spectral editing techniques in proton MRS make it possible to detect and monitor drug-induced variations of GABA in the human brain, opening new insights into patient response to drug therapy of epilepsy. MRS is playing an increasing role in the noninvasive characterisation and management of epileptic patients.

In vivo brain proton MR spectroscopy in a case of molybdenum cofactor deficiency

A 20-day-old infant with molybdenum cofactor deficiency, a rare encephalopathy, was investigated using cerebral MRI and proton MR spectroscopy. Images demonstrated extensive white-matter destruction with large cavities. The short-echo-time MR spectrum acquired in the parieto-occipital area was characterised by global loss of signal and accumulation of lactate. No additional signal in relation to the pathophysiology of the disease was detected. The brain metabolic abnormalities observed in this patient may reflect destruction of white matter and the presence of large cavities.

Brain metabolic impairment in non-cerebral and cerebral forms of X-linked adrenoleukodystrophy by proton MRS: identification of metabolic patterns by discriminant analysis

Cerebral metabolism in six children with X-linked adrenoleukodystrophy (X-ALD) was studied using 1H magnetic resonance spectroscopy (MRS), and the status of the patients was monitored for evaluating disease progression. Spectra were abnormal even in patients with no cerebral impairment. Four different metabolic patterns were identified, and a metabolic classification of the disease was proposed, from grade 0 to grade III. The evolution of the disease toward grade II appears to be systematic, but many patients did not evolve from this grade to grade III, which is the metabolic mark of severe progressive forms. Metabolic data of X-ALD were processed using discriminant analysis, which provides a classification accuracy of 95.2%. Proton cerebral MRS together with discriminant analysis may be useful during the follow-up in X-ALD for monitoring the evolution of the disease and the effects of therapy.

Localized proton magnetic resonance spectroscopy of the brain in children infected with human immunodeficiency virus with and without encephalopathy

Twenty children older than 2 y infected with human immunodeficiency virus (HIV) were examined by in vivo proton magnetic resonance spectroscopy (1H MRS) to study their cerebral metabolism and to identify metabolic profiles in relation with different stages of the disease. Patients were rated regarding their clinical and immunologic status according to the Centers for Disease Control classification and were divided into two groups: without encephalopathy (E-, n = 15) and with progressive encephalopathy (E+, n = 5). The acquisition was performed in the centrum semiovale using the short echo stimulated echo acquisition mode 20-ms sequence. The MRS profile was abnormal in all HIV-infected children compared with healthy age-matched controls (n = 7), even when magnetic resonance images were normal. A significant increase of the proportion of the lipid signals (ANOVA, p < 0.05) was found in all HIV-infected children. In addition, a significant decrease of the proportion of the N-acetylaspartate signal and a significant increase of the proportion of the myo-inositol signal (ANOVA, p < 0.05) characterized the E+ group. The principal component analysis performed on eight variables on 30 spectra confirms that the spectra of HIV-infected children differ from control spectra. The E+ group and the E- group are clearly separated on the map of subjects on the principal plane. The E- group lies in an intermediate position between the E+ group and the control group. The evolution of metabolic alterations in the brain of HIV-infected children can clearly be monitored by 1H MRS and associated with the occurrence of an encephalopathy.

Experimental protocol for clinical analysis of cerebrospinal fluid by high resolution proton magnetic resonance spectroscopy

High resolution magnetic resonance spectroscopy (MRS) of cerebrospinal fluid (CSF) is a non-destructive analytical method which allows rapid and simultaneous detection of molecules involved in intermediary and oxidative metabolic pathways. We developed a protocol suitable for routine MRS analysis of lyophilized CSF samples. This procedure guarantees sample integrity, from CSF collection to spectrum acquisition. MRS analysis of blood serum was included in our protocol as a complementary method to CSF analysis. This protocol can contribute to establish MRS of CSF as a new analytical tool to better understand the metabolic processes involved in neurological diseases.