On the correlation between perceptual inundation caused by realistic immersive environmental auditory scenes and the sensory gating inventory in schizophrenia

BACKGROUND

In schizophrenia, perceptual inundation related to sensory gating deficit can be evaluated "off-line" with the sensory gating inventory (SGI) and "on-line" during listening tests. However, no study investigated the relation between "off-line evaluation" and "on-line evaluation". The present study investigates this relationship.

METHODS

A sound corpus of 36 realistic environmental auditory scenes was obtained from a 3D immersive synthesizer. Twenty schizophrenic patients and twenty healthy subjects completed the SGI and evaluated the feeling of "inundation" from 1 ("null") to 5 ("maximum") for each auditory scene. Sensory gating deficit was evaluated in half of each population group with P50 suppression electrophysiological measure.

RESULTS

Evaluation of inundation during sound listening was significantly higher in schizophrenia (3.25) compared to the control group (2.40, P<.001). The evaluation of inundation during the listening test correlated significantly with the perceptual modulation (n=20, rho=.52, P=.029) and the over-inclusion dimensions (n=20, rho=.59, P=.01) of the SGI in schizophrenic patients and with the P50 suppression for the entire group of controls and patients who performed ERP recordings (n=20, rho=-.49, P=.027).

CONCLUSION

An evaluation of the external validity of the SGI was obtained through listening tests. The ability to control acoustic parameters of each of the realistic immersive environmental auditory scenes might in future research make it possible to identify acoustic triggers related to perceptual inundation in schizophrenia.

Aspects visuels et descriptifs de l’électroencéphalographie pendant les séances d’électroconvulsivothérapie

La surveillance électroencéphalographique (EEG) des séances d’électroconvulsivothérapie (ECT) est indispensable mais nécessite une connaissance minimale de la neurophysiologie et de la lecture de l’EléctroEncéphaloGramme (EEG) par le psychiatre. La lecture de l’EEG pendant les ECT nécessite un œil formé à la reconnaissance sur le tracé EEG de certaine forme spécifique, associée à l’utilisation d’un vocabulaire de description rigoureux. Ce poster a pour objectif de fournir une méthode illustrée de lecture de l’EEG pendant les ECT. Premièrement, les artefacts du signal EEG doivent être reconnus pour ne pas les confondre avec des activités épileptiformes. Deuxièmement, le déroulement de la crise doit être reconnu et décrit en phase : pré-critique, critiques (précritique, recrutante, tonique et clonique) et post-critique. Troisièmement, la qualification de la crise doit être posée par l’utilisation des termes de crise épileptique adéquate, optimale et prolongée. Cette démarche de lecture EEG pendant la séance ECT permet de détecter une crise épileptique prolongée afin de diminuer le risque à court terme d’état de mal épileptique post-ECT et à moyen terme le risque de mauvaise tolérance cognitive de la cure ECT. Elle permet également d’adapter de manière optimale les paramètres de stimulation à la prochaine séance d’ECT afin de maximiser l’efficacité des ECT. La lecture de l’EEG pendant les ECT ne résume pas l’entièreté de la conduite des cures ECT en psychiatrie. Cependant elle reste une démarche indispensable à l’aide à la prise de décision et souligne la place centrale que peut prendre la neurophysiologie clinique dans une stratégie thérapeutique psychiatrique.

[Towards a new approach of neurophysiology in clinical psychiatry: functional magnetic resonance imaging neurofeedback applied to emotional dysfunctions]

Emotions color in a singular way our everyday life and constitute important determinants of human cognition and behavior. Emotional regulation is an essential process involved in neuropathophysiology and therapeutic efficacy in many psychiatric disorders. Yet, traditional psychiatric therapeutic has focused on symptomatic rather than neurophysiological criteria. Therefore, it was proposed to teach patients to modify their own brain activity directly, in order to obtain a therapeutic effect. These techniques, which are named neurofeedback, were originally developed using electroencephalography. Recent technical advances in fMRI enable real-time acquisition, and open opportunities to its utilization in neurofeedback. This seems particularly interesting in emotion regulation, which, at a neurofunctional level, lies on cortico-limbic pathways that, in great parts, were previously identified by traditional fMRI paradigms. This emotion regulation plays a central role in the etiopathogeny psychiatric, especially depressive and anxious, disorders. It is possible to devise new therapeutic strategies and research approach for addressing directly the neurophysiological processes of emotion regulation by integrating the neurofunctional activities of a subject. These prospects seem to be in line with the neurophenomenology project, which proposes to establish a link between subjective experiences and objective neurophysiological measures.

[The measurement of electrodermal activity]

INTRODUCTION

Electrodermal activity (EDA) is an early physiological index and the subject of constant interest, in spite of the bad reputation attached to "lie detectors". This interest is expected to increase in the future, following the development of research related to the neurobiological aspect of emotions of which it is an index. Recent data provided by functional cerebral imaging has added to the significance of this index and should result in further interest.

AIM

The authors thus re-examined the various notions related to measuring EDA, and its practical aspect as well as its mechanisms. EDA should be useful both for authors wishing to use this variable and for readers wishing to form their own critical point of view.

LITERATURE FINDINGS

The article first defines the various terms used to qualify EDA. Then, it analyses the mechanisms occurring at the sweat glands' level, showing that a distinct innervation of the sweat glands causes sweat to be released in the excretory channels, thereby allowing the recording of a negative surface potential in parallel to the lowering of skin conductance. Arguments are then pointed out to illustrate that the potential's positive phase following this first answer occurs in the case of high intensity stimulations. The study of the central command of sudation demonstrates that, several areas are involved and that different functions such as thermal regulation and motricity may interfere with emotive reactions. Difficulties regarding the mode of measurement of these answers as to their number and amplitude are also brought to light.

DISCUSSION

A particular interest of measuring EDA is its ability to highlight individual characteristic and unconscious emotional reactivity. Subjects who constitutionally present many spontaneous and therefore habitual EDA can indeed be opposed to subjects whose EDA reflexes are very few and hardly habitual. A theory suggests that for the first category, whose subjects are named labiles, emotional control may be at the origin of EDA. This characteristic brings to mind the case of antisocial subjects whose rate of EDA is also reduced, although for the latter a primitive drop in behavioral inhibition is involved. The production of EDA in response to non-conscious emotive stimulations can be objectified in the rare cases of prosopagnosia. These subjects who are unable to recognize familiar faces can produce EDA when presented faces with an emotional load. These cases contrast with the delusional denial of the Capgras syndrome where subjects do not present EDA, suggesting that the dysfunction of visual analysis occurs at a different level. There are other rare cases represented by cortical blindness where EDA shows that an unconscious emotional analysis is preserved. These subjects are known however to be capable of unconscious visual discriminations, which are possibly accompanied by EDA. This possibility of a "blind vision" is experimentally studied via subliminal vision testing (backward masking tests). These demonstrate that a rudimentary visual analysis is carried out in the subcortical circuits while taking into account the affective aspect of stimulations.

CONCLUSION

Present or future data should allow a greater comprehension of electrodermal signals, making it possible to overcome the difficulties related to their interpretation and facilitate their applications.

[Electrophysiology and schizophrenic vulnerability: the P300 component as endophenotype candidate?]

INTRODUCTION

Studies on early stages of schizophrenia imply the observation of stable markers of vulnerability. Among other research fields, these early and objective markers, or potential endophenotypes, can be described in event-related potential (ERP) paradigms.

LITERATURE FINDINGS

The P300 component, elicited during the allocation of attentional resources, is the most studied ERP among people with schizophrenia. In this review, we first develop the notion of endophenotypes in schizophrenia, notably in terms of stability, heritability and specificity. We also give a short account of the P300 component, its typical description, the classical paradigms which elicit it, and several interpretations of its significance.

DISCUSSION

After reviewing the main features of the schizophrenic alterations of P300 (their topography, amplitude and latency), we discuss the relevance of P300 when described as a potential schizophrenic endophenotype. In spite of an important number of studies, results remain controversial and incomplete. First, P300 in schizophrenia shows complex patterns of temporal evolution, and thus can be described as either a stable trait or a state marker. Second, its heritability is still discussed among high-risk participants with genetic, schizotypal or clinical vulnerability. Third, the issue of its specificity is the less studied criteria. In line with the debate of its specificity, only little is known about specific alterations of P300 among unipolar or bipolar disorders. In the discussion, we describe a few possible origins of such controversial results in both empirical and conceptual perspectives, and we provide several experimental propositions in order to develop a more systematic exploration of P300 alterations.

Valeurs contrôles obtenues avec une séquence press 135 ms en neurospectroscopie monovoxel du proton

The clinical value of MR spectroscopy is now well established and this technique has been added to the current French classification of medical acts (CCAM). This paper presents a set of normal control values for 3 metabolite ratios obtained using a PRESS sequence with a TE of 135 ms at 1.5T: NAA/Cho, NAA/Cr and Cho/CR. Spectroscopy data acquisition were obtained from the following 12 anatomical regions: parieto-occipital white matter, centrum semiovale, frontal white matter, thalamus, basal ganglia, cerebellum (hemisphere, including dentate nucleus), brain stem (including pons, medulla and midbrain), anterior and posterior temporal lobe, parietal, occipital and pre-frontal cortices. The presented data allow radiologists equipped with a similar MR system to implement a clinical spectroscopy program without undergoing research protocols in order to obtain control values.

Proton magnetic resonance neurospectroscopy and EEG cartography in corticobasal degeneration: correlations with neuropsychological signs

OBJECTIVE

To document the asymmetrical functional brain lesions in corticobasal degeneration (CBD) using proton magnetic resonance neurospectroscopy (MRS) and EEG cartography (EEGq).

METHODS

Eight patients with probable CBD were included in the study after full neurological examination and extensive neuropsychological testing, single photon emission computed tomography, anatomical x ray tomodensitometry (TDM), magnetic resonance imaging, and MRS examination.

RESULTS

MR spectra were abnormal in all seven patients in whom the examination could be completed. The EEG was also always modified in the CBD patients, and the abnormalities were enhanced by activation procedures. There was a good correlation between MRS anomalies and clinical presentation, between EEG modifications and neuropsychological patterns, and between metabolic (MRS) impairment and electrophysiological (EEG) slowing.

CONCLUSIONS

These results confirm the asymmetrical features of CBD. Combined EEGq/MRS examinations at disease onset and during its subsequent course could provide strong diagnostic evidence of CBD.

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.

[Proton magnetic resonance spectrometry for the non-invasive exploration of human brain metabolism: current and future clinical applications]

Magnetic resonance spectrometry (MRS) is now a routine investigation method in neurology. In some situations, its diagnostic sensitivity is better than MRI. In this review, we propose a critical analysis of the large body of literature on brain MRS concerning a wide range of pathologies and many different protocols. The diagnostic value of MRS is not fully determined in all neurological diseases, but the specific properties of MRS (detection of neuron-specific and glial-specific metabolites, quantitative data, reversibility of metabolic lesions) make it a high-performance tool for quantifying neuron, glial and membrane abnormalities. After reviewing the methodological advances in MRS and discussing restrictions on interpretation of spectral data, we describe variations in metabolic patterns detected by MRS in different groups of diseases. The currently reasonable indications for MRS exploration are presented as well as new avenues for research. Based on MRS data, we propose a metabolic definition of encephalopathy which could be useful in better understanding the role of MRS in modern neurology.

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.

Magnetic resonance spectroscopy of serum and acute-phase proteins revisited: a multiparametric statistical analysis of metabolite variations in inflammatory, infectious and miscellaneous diseases

Proton MR spectra and biochemical assays have been recorded on the sera of 40 patients and ten controls in order to document the correlation between spectroscopic and biochemical variations in selected pathologies (cancer, inflammatory and infectious diseases, diabetes). N-acetyl proton resonances are essentially generated by the N-acetyl residues of the glucidic moieties borne by the most abundant acute-phase proteins (alpha1-acid glycoprotein, alpha1-antitrypsin and haptoglobin). These resonances are not correlated to immunoglobulins A, G and M levels. Principal component analysis shows that variations in spectroscopic and biochemical data are independent markers of the inflammatory status of patients but no additional sensitivity or specificity is obtained when the two sets of data are combined.

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.

[Brain proton magnetic resonance spectroscopy. Indications for diagnosis and follow-up of HIV-related encephalopathy in the adult]

NONINVASIVE EXPLORATION: Proton localized magnetic resonance spectroscopy (MRS) is a noninvasive human neurochemistry method based on the magnetic resonance phenomenon.

ADVANTAGES

This exploration of brain metabolism, performed without any injection, detects neuronal, glial, and membrane markers, and can be performed after an MRI examination without moving the patient.

INDICATIONS

In vivo brain MRS plays a major role (i) in early diagnosis of HIV-related encephalopathy, (ii) in differential diagnosis of HIV-related encephalopathy versus psychiatric symptoms or occurring in AIDS patients, (iii) in differential diagnosis of HIV-related encephalopathy versus other brain lesions related to AIDS, and (iv) in the follow-up of patient response to therapy. In these indications, MRS is frequently more reliable than neuropsychologic testing and more sensitive than MRI.

Brain metabolic profiles obtained by proton MRS in two forms of mitochondriopathies: Leber's hereditary optic neuropathy and chronic progressive external ophthalmoplegia

The status of brain metabolism has been evaluated using monovoxel short echo time (20 ms) 1H magnetic resonance spectroscopy in 6 patients with two forms of mitochondrial disorders without clinical cerebral involvement: 2 patients with Leber's hereditary optic neuropathy (LHON) and 4 patients with chronic progressive external ophthalmoplegia (CPEO). Patients with LHON displayed normal spectra. In all patients with CPEO, the brain metabolic profiles were abnormal, with no single uniform pattern. No typical cerebral metabolic profile was found even when these disorders were classified either by syndrome or by biochemical defect. No lactate signal was detected. The metabolic alterations observed in CPEO patients contrasted with the absence of clinical signs of encephalopathy. The absence of a typical metabolic profile reflects the large variability in the clinical expression of biochemical defects in mitochondriopathies, and the lack of convergence between genetic deletions, biochemical anomalies and clinical syndromes.

Brain proton magnetic resonance spectroscopy in HIV-related encephalopathy: identification of evolving metabolic patterns in relation to dementia and therapy

Proton MRS has proved useful in the early diagnosis of HIV-related encephalopathy. The modifications of brain metabolism in HIV-related encephalopathy can be classified according to different metabolic patterns (Vion-Dury J et al. CR Acad Sci 1994;317:833-840). The present study describes the relative occurrence of these patterns and evaluates their evolution under zidovudine treatment. We have examined 112 HIV patients--35 neuroasymptomatic patients and 77 patients with ADC (AIDS dementia complex)--with localized proton MRS, using the PRESS 135-msec sequence. We have found the same metabolic modifications in N-acetylaspartate and choline-containing compounds as described in the literature. In addition, 14% of HIV patients with normal MRI displayed abnormal MRS, whatever their neurological status. The MRS-added diagnostic value in neuroasymptomatic patients reaches 30 %. The occurrence of undifferentiated (modification of NAA/Cho ratio only) and Cho (mainly an increase in choline signal) patterns is not significantly different in neuroasymptomatic and ADC patients. The NAA pattern (mainly a significant loss of NAA) is more frequent in ADC patients. Only ADC patients display the double pattern (with a significant increase in choline signal and a significant loss of NAA). Quantitated cerebral atrophy (bifrontal ratio) is related to the occurrence of NAA loss (in NAA and double patterns). An MRS follow-up study of 11 HIV patients showed that the clinical outcome was favorable after a 1000-mg/day zidovudine treatment in patients displaying an NAA pattern whereas this treatment had no effect on the patients displaying the Cho pattern. Consequently, MRS appears to be of great interest in predicting responsiveness to antiretroviral drugs and detecting early any resistance to treatment.

Cerebral metabolic alterations in human immunodeficiency virus-related encephalopathy detected by proton magnetic resonance spectroscopy. Comparison between sequences using short and long echo times

RATIONALE AND OBJECTIVES

The aim of this study is to evaluate comparatively the metabolic information afforded by proton magnetic resonance (MR) spectroscopy with stimulated-echo acquisition mode (STEAM) (echo time [TE], 20 mseconds) and point-resolved spectroscopy sequence (PRESS) (TE, 135 mseconds) spectra in HIV-related encephalopathy.

METHODS

Sixty-three human immunodeficiency virus (HIV) patients and 8 controls were examined by single-voxel proton MR spectroscopy at 1.5 tesla, using both PRESS (TE, 135 mseconds) and STEAM (TE, 20 mseconds) sequences performed during the same MR examination, in the same volume of interest. Cerebral atrophy was quantitated using bicaudate ratio (BCR) and bifrontal ratio (BFR).

RESULTS

With the STEAM (TE, 20 mseconds) spectra, mean N-acetylaspartate (NAA)/choline (Cho) and NAA/creatine and phosphocreatine (Cr-PCr) ratios are reduced in acquired immunodeficiency syndrome (AIDS) dementia complex (ADC) patients but not in neuroasymptomatics. The proportion of inositol signal is increased, that of NAA decreased in ADC patients. NAA/Cho and NAA/ Cr-PCr mean values measured with PRESS (TE, 135 mseconds) spectra are significantly reduced in ADC and neuroasymptomatic patients. Bifrontal ratio only correlates with NAA/Cr-PCr and NAA/Cho measured on the PRESS spectrum. PRESS (TE, 135 mseconds) spectra allow a definition of different metabolic patterns in HIV-related encephalopathy. At last, no correlation has been found between the NAA raw signals measured on the PRESS (TE, 135 mseconds) and STEAM (TE, 20 mseconds) spectra obtained in the same MR examination.

CONCLUSIONS

STEAM (TE, 20 mseconds) spectra provide more metabolic information-namely an evaluation of glial-neuronal status-than PRESS (TE, 135 mseconds) spectra, which afford a metabolic classification of the HIV-related encephalopathy. Because both sequences afford a similar diagnostic gain, MR spectroscopy examination probably requires spectrum acquisition with both sequences.

Cerebrospinal fluid metabolic profiles in multiple sclerosis and degenerative dementias obtained by high resolution proton magnetic resonance spectroscopy

We have analyzed the cerebrospinal fluid (CSF) of 19 patients with multiple sclerosis (MS), 12 patients with degenerative dementia and 17 control patients using in vitro high resolution proton magnetic resonance spectroscopy (MRS) at 400 MHz. The CSF metabolic profile is slightly modified in MS patients (increased lactate and fructose concentrations, decreased creatinine and phenylalanine concentrations) and is not correlated with the intensity of the intrathecal inflammation. Proton MRS of CSF does not differentiate relapsing-remitting MS and primary progressive MS. We have not detected any specific abnormal resonance in native or lyophilized CSF. The CSF metabolic profile of demented patients is much more altered (increased concentration of lactate, pyruvate, alanine, lysine, valine, leucine-isoleucine, tyrosine, glutamine) and is in agreement with a brain oxidative metabolism impairment as already described in Alzheimer's disease. Unassigned abnormal but non specific or constant resonances have been detected on MR spectra of demented patients. CSF inositol concentration is also increased in the CSF of patients with Alzheimer's disease. In vitro high resolution proton MRS of the CSF constitutes a new and original way to explore CSF for the differential and/or early diagnosis of dementias, as a complement to in vivo proton cerebral MRS.

[Future path of magnetic resonance spectroscopy in clinical medicine]

The metabolic exploration of skeletal muscle and brain by magnetic resonance spectroscopy (MRS) provides the basis of the main clinical applications of in vivo MRS on humans. Also, high resolution MRS is used in vitro to identify and assay the metabolites contained in physiological fluids (blood, urine, CSF). In these applications, MRS has became and will keep developing as the investigative tool of choice to perform non-invasively "live biochemistry" experiments on organs and tissues.

Value of Doppler echocardiography in the detection of low-grade rejections after cardiac transplantation

Modifications of the diastolic parameters pressure half-time (PHT) and isovolumic relaxation time (IVRT), recorded using cardiac Doppler echocardiography (CDE), were studied in 23 heart transplant recipients and compared to the results of 345 endomyocardial biopsies (EMB) performed on the same day. Two different protocols, analyzing respectively (1) a decrease of 20% or more in IVRT and/or PHT with respect to the mean and (2) a decrease of 20% or more in IVRT and/ or PHT with respect to its preceding value, were used to evaluate the efficiency of CDE in diagnosing mild and moderate rejections. When a mild rejection was detected by EMB, a statistically significant decrease was found in the average CDE parameter values of the patient population. However, these variations were weak and did not differ from the spontaneous variations observed in each patient in the absence of rejection. Thus, it is not surprising that the sensitivity of CDE in the detection of mild rejections was very low (45%) using the most sensitive protocol (variations of the parameters from their preceding value). We conclude that CDE alone does not seem to be sufficient to perform the noninvasive diagnosis of low-grade rejections and must be complemented by other noninvasive methods.

A multicenter proton magnetic resonance spectroscopy study of neurological complications of AIDS

Human immunodeficiency virus (HIV) infection as seen in Europe and the United States has predominantly been contracted through male homosexual sex or intravenous drug abuse. In infected subjects, the brain is frequently affected both clinically and neuropathologically. The aim of this multicenter study has been to evaluate the value of single-voxel proton magnetic resonance spectroscopy (MRS) in the assessment of the neurological complications of acquired immunodeficiency syndrome (AIDS). MRS (voxel size = 8 ml, TR/TE = 1600/135 msec) was performed in 137 HIV-1-seropositive patients and 64 healthy controls without risk factors at three clinical MR sites operating at 1.5 T. The first result of this multicenter trial is that good reproducibility of results among participating sites was found. This demonstrates the reliability and robustness of MRS in the study of in vivo brain metabolism. In HIV patients, there was no significant correlation between metabolite ratios of brain detected by MRS and CDC grouping of patients or CD4 count. In contrast, the variations of brain metabolite ratios (NA/Cr, NA/Cho, and Cho/Cr) were related to the occurrence of encephalopathy, brain atrophy, or diffuse white matter lesions. There was no significant difference in brain metabolites between male homosexual AIDS patients and male intravenous drug user AIDS patients, whatever their neurological status (neurosymptomatic or neuroasymptomatic). Thus, the mode of transmission of HIV infection does not appear to affect the cerebral changes observed in the proton spectra from AIDS patients. Because of its ease of implementation and high information content, single-voxel proton MRS is likely to play a significant role in the evaluation of HIV-related encephalopathies.

Localised proton magnetic resonance spectroscopy in X-linked adrenoleukodystrophy

We have performed localised proton magnetic resonance spectroscopy (MRS) of the brain on four patients with X-linked adrenoleukodystrophy (X-ALD). The spectrum is characterised at the beginning of the disease by a decrease in N-acetylaspartate and phosphocreatine-creatine content. Choline is strongly increased, and lactate can be detected in some cases. A proton signal from the CH2 groups borne by free intracellular very long chain fatty acids can also be observed. Later in the disease, the levels of all metabolites, in particular NAA, decrease significantly. The progression of neurometabolism documented by MRS correlates well with MRI and clinical progression on follow-up study. In one case, the metabolic profile recorded by proton MRS was abnormal before any change occurred on MRI. Proton MRS of the brain might be the method of choice for monitoring patients with X-ALD, to screen presumed cases and to study the effects of treatment.

Localized proton magnetic resonance spectroscopy of the brain differentiates the inborn metabolic encephalopathies in children

Localized brain proton magnetic resonance spectroscopy (MRS) has been performed using a STEAM (stimulated echo-acquisition mode) method with a short-echo time (20 ms) in 10 children suffering from different lysosomal diseases, 6 boys with X-linked adrenoleukodystrophy (X-ALD) and 5 healthy children. Metabolic data from localized spectra were processed by principal component analysis (PCA) of 7 metabolic variables recorded on the MR spectra. PCA allows to delineate different clusters corresponding to the 2 pathological groups which are separated from each other and from the control group. The position of each spectrum on the patient map correlates with the clinical data and to the evolution of the patients subjected to a follow-up. These results also confirm the metabolic features characterizing the pathologies of the lysosome (increase in inositol) and the peroxisome (increase in choline and free lipids). PCA constitutes an alternative to the classical statistical methods to analyze and compare metabolic modifications in small populations of patients and allows to identify the most critical parameters defining the organization of the pathological populations. This analysis clearly increases the discrimination among pathologies based on the metabolic profiles obtained by MRS.

[Magnetic resonance spectroscopy: a new technique for the exploration of brain metabolism in pediatrics]

In vivo nuclear magnetic resonance spectroscopy (MRS) has been developed recently in order to analyze brain metabolism in adults and children. After a short presentation of the methods and of the metabolic signals detected by phosphorus and proton MRS of the brain, the impact of MRS in pediatrics is examined with two main indications: the study of cerebral maturation in normal or pathological neonates, and the study of inborn metabolic encephalopathies. In the near future, brain MRS will be performed routinely after conventional MRI, and will become a valuable metabolic complement to the anatomical evaluation of cerebral pathologies.

Phosphorus-31 in vivo magnetic resonance spectroscopy of bone fails to diagnose osteoporosis

The values of in vivo T1 relaxation time (T1) of phosphorus atoms of wrist bone have been measured by phosphorus-31 magnetic resonance spectroscopy (MRS) in 65 menopausal women separated into three groups: (1) age-matched women without any paraclinical or clinical osteoporosis; (2) patients with paraclinical osteoporosis detected only by dual photonic absorptiometry; and (3) women with clinical osteoporosis with vertebral fractures. No significant differences were found in T1 values in the presence of paraclinical or clinical osteoporosis as compared to control values. No relationships were found among the T1, the value of the Z-score, the value of bone mineral content, the age of patients, the number of their children, and the age of menopause. Phosphorus-31 magnetic resonance spectroscopy of the wrist fails to separate osteoporotic from nonosteoporotic women and cannot be clinically used at this time to perform a noninvasive diagnosis of osteoporosis.

Study of bone mineralization using phosphorus 31 nuclear magnetic resonance spectroscopy. Results in a population of women with osteoporosis

The phosphorus 31 nuclear magnetic resonance signal from the wrist bones was studied in controls covering a broad age range and in postmenopausal osteopenic women with or without osteoporosis. The signal, which was obtained in less than 10 minutes, was broad (30 ppm) and easy to distinguish from muscle signals. Results were reproducible in a given subject. Signal intensity increased with the diameter of the wrist. Because of difficulties with in vivo quantification, we were unable to derive an accurate measurement of bone mineral content from the bone signal. Analysis of in vivo relaxation times of bone phosphorus atoms failed to demonstrate significant differences between osteoporotic subjects and same-age controls. These apparently disappointing findings may be ascribable to technical problems, to which solutions may be within reach. Our study provides information on the difficulties of this method and on the modalities of use of 31P nuclear magnetic resonance spectroscopy for evaluation of disorders of phosphorus and calcium metabolism.

Localized brain proton MRS metabolic patterns in HIV-related encephalopathies

We have examined 9 healthy volunteers and 63 HIV-patients (16 asymptomatic patients and 47 patients with clinical AIDS-dementia complex, ADC) by magnetic resonance spectroscopy (MRS) and imaging (MRI) on a Siemens Magnetom SP63 (1.5 T). Proton MRS of the brain was performed at 63 MHz using the PRESS sequence (echo time = 135 ms, TR = 1.6 s). Four main results have been found: (1) HIV-related encephalopathy induces significant modifications of brain metabolism analyzed by MRS and the most sensitive metabolic parameter is the N-acetyl-aspartate/Choline ratio, (2) the correlation between MRS and MRI is good in 75% of patients, (3) in 4 of the 16 neuro-asymptomatic patients (i.e. 25%) a metabolic encephalopathy was found while MRI was still normal, and (4) MR spectra describe 3 different pathological metabolic patterns in the brain of HIV patients. Two patterns might correspond to the two entities of HIV-induced lesions i.e. HIV encephalitis and HIV-related progressive leukoencephalopathy.

Rapid evaluation of ethanol content and metabolism in human plasma using quantitative proton magnetic resonance spectroscopy

Proton magnetic resonance spectroscopy (MRS) was used to assay ethanol in plasma. Ethanol concentrations determined by MRS and conventional enzymatic methods are in excellent agreement. In addition to ethanol, acetone, acetate and beta-hydroxybutyrate can be quantified simultaneously in the same sample. Proton MRS of plasma offers a rapid evaluation of human ethanol metabolism and may be useful in screening for chronic alcoholism.

What might be the impact on neurology of the analysis of brain metabolism by in vivo magnetic resonance spectroscopy?

In vivo nuclear magnetic resonance spectroscopy (MRS) of the human brain is a recently developed technique which allows to assay noninvasively in vivo key molecules of brain metabolism. After a review of the origin of the signals detected by phosphorus and proton MRS of human brain, the impact of MRS on clinical neurology is examined. MRS of the brain does not purport to be a metabolic "biopsy", but unique applications for brain MRS are (1) quantitating the oxidative state of the brain and defining neuronal death, (2) assessing and mapping neuron damage, (3) evaluating membrane alterations, and (4) characterizing encephalopathies. In the near future brain MRS will be performed routinely after conventional MRI, as a valuable metabolic (and functional) complement to the anatomical evaluation of cerebral pathologies, particularly the toxic, metabolic and infectious encephalopathies.

A multiparametric data analysis showing the potential of localized proton MR spectroscopy of the brain in the metabolic characterization of neurological diseases

We conducted an extended clinical evaluation of localized proton magnetic resonance spectroscopy (MRS) of the brain, performed on various brain diseases using short stimulated echo times. Pathologies studied were mainly multiple sclerosis, stroke, leukoaraiosis, AIDS-related leukoencephalopathies and glial tumors. Other miscellaneous pathologies were also studied. Magnetic resonance examination of the brain was conducted on a Siemens Magnetom SP63 (equipped with a 1.5 T magnet). Localized proton MRS was performed on a routine basis immediately after imaging, using the STEAM (stimulated echo acquisition mode) with a short echo time (20 ms) combined with a CHESS (chemical shift selective excitation) sequence. One or two VOI (8 ml) were examined. Data on 125 spectra were processed by principal component analysis (PCA) and conventional variance analysis. The following metabolite resonances were studied: inositol-glycine, taurine-scyllo-inositol, choline derivatives, phosphocreatine-creatine, aspartate, glutamine glutamate, N-acetylaspartate, acetate and lactate. PCA demonstrates that the different metabolic variables are independent. The analysis of groups of spectra clearly demonstrates that the metabolic profiles detected by localized MRS in various pathologies (i) differ significantly from controls, and (ii) allow a metabolic discrimination between groups of pathologies. Results of PCA are confirmed by variance analysis. Strokes are characterized by an increase in lactate concentration and leukoaraiosis by a decrease in inositol-glycine resonance. AIDS-related leukodystrophies are characterized by increases in lactate and choline concentrations. Reduction in N-acetylaspartate which is observed in most pathologies is not significant in the small lesions of white matter. Lactate has often been found in MS plaques, but no variation in the choline/phosphocreatine ratio was observed. GABA was tentatively assigned in the spectrum of a patient with epilepsy under sodium valproate treatment. This study illustrates the clinical feasibility of the technique, the value of a multiparametric data analysis in the definition of the pertinent variables characterizing the metabolic impairment, and the impact of localized proton MR spectroscopy of the brain in the assessment of cerebral suffering.