Developmental brain changes investigated with proton magnetic resonance spectroscopy

Changes in brain metabolite levels across childhood

Metabolites play important roles in brain development and their levels change rapidly in the prenatal period and during infancy. Metabolite levels are thought to stabilize during childhood, but the development of neurochemistry across early-middle childhood remains understudied. We examined the developmental changes of key metabolites (total N-acetylaspartate, tNAA; total choline, tCho; total creatine, tCr; glutamate+glutamine, Glx; and myo-inositol, mI) using short echo-time magnetic resonance spectroscopy (MRS) in the anterior cingulate cortex (ACC) and the left temporo-parietal cortex (LTP) using a mixed cross-sectional/longitudinal design in children aged 2-11 years (ACC: N=101 children, 112 observations; LTP: N=95 children, 318 observations). We found age-related effects for all metabolites. tNAA increased with age in both regions, while tCho decreased with age in both regions. tCr increased with age in the LTP only, and mI decreased with age in the ACC only. Glx did not show linear age effects in either region, but a follow-up analysis in only participants with ≥3 datapoints in the LTP revealed a quadratic effect of age following an inverted U-shape. These substantial changes in neurochemistry throughout childhood likely underlie various processes of structural and functional brain development.

Developmental Functioning of Toddlers At-Risk for Autism With and Without Down Syndrome

PURPOSE

Due to the difficulties in differentiating between impairments associated with intellectual disability and ASD symptomology, DS often leads to delayed or misdiagnoses of ASD.

METHOD

An ANOVA was run to investigate the effects of ASD risk and DS on overall developmental functioning across three groups: ASD+, DS-, and DS+ (n = 138). A MANOVA was run to investigate the differences of group on five developmental subdomains.

RESULTS

The results revealed significant group differences in the overall developmental functioning and each developmental subdomain. Children in the DS+ group demonstrated significantly lower overall developmental functioning, as well as lower adaptive, cognitive, motor, and communication skills compared to their peers; however, children in the DS- group demonstrated significantly better social skills compared to their peers in the ASD+ group.

DISCUSSION

These findings support the need for early screening and identification of ASD among those with DS.

Multivariate approach for longitudinal analysis of brain metabolite levels from ages 5-11 years in children with perinatal HIV infection

Treatment guidelines recommend that children with perinatal HIV infection (PHIV) initiate antiretroviral therapy (ART) early in life and remain on it lifelong. As part of a longitudinal study examining the long-term consequences of PHIV and early ART on the developing brain, 89 PHIV children and a control group of 85 HIV uninfected children (HIV-) received neuroimaging at ages 5, 7, 9 and 11 years, including single voxel magnetic resonance spectroscopy (MRS) in three brain regions, namely the basal ganglia (BG), midfrontal gray matter (MFGM) and peritrigonal white matter (PWM). We analysed age-related changes in absolute metabolite concentrations using a multivariate approach traditionally applied to ecological data, the Correlated Response Model (CRM) and compared these to results obtained from a multilevel mixed effect modelling (MMEM) approach. Both approaches produce similar outcomes in relation to HIV status and age effects on longitudinal trajectories. Both methods found similar age-related increases in both PHIV and HIV- children in almost all metabolites across regions. We found significantly elevated GPC+PCh across regions (95% CI=[0.033; 0.105] in BG; 95% CI=[0.021; 0.099] in PWM; 95% CI=[0.059; 0.137] in MFGM) and elevated mI in MFGM (95% CI=[0.131; 0.407]) among children living with PHIV compared to HIV- children; additionally the CRM model also indicated elevated mI in BG (95% CI=[0.008; 0.248]). These findings suggest persistent inflammation across the brain in young children living with HIV despite early ART initiation.

On the acquisition of the water signal during water suppression: High-speed MR spectroscopic imaging with water referencing and concurrent functional MRI

This study evaluated the utility of concurrent water signal acquisition as part of the water suppression in MR spectroscopic imaging (MRSI), to allow simultaneous water referencing for metabolite quantification, and to concurrently acquire functional MRI (fMRI) data. We integrated a spatial-spectral binomial water excitation RF pulse and a short spatial-spectral echo-planar readout into the water suppression module of 2D and 3D proton-echo-planar-spectroscopic-imaging (PEPSI) with a voxel size as small as 4 x 4 x 6 mm³ . Metabolite quantification in reference to tissue water was validated in healthy controls for different prelocalization methods (spin-echo, PRESS and semi-LASER) and the clinical feasibility of a 3-minute 3D semi-Laser PEPSI scan (TR/TE: 1250/32 ms) with water referencing in patients with brain tumors was demonstrated. Spectral quality, SNR, Cramer-Rao-lower-bounds and water suppression efficiency were comparable with conventional PEPSI. Metabolite concentration values in reference to tissue water, using custom LCModel-based spectral fitting with relaxation correction, were in the range of previous studies and independent of the prelocalization method used. Next, we added a phase-encoding undersampled echo-volumar imaging (EVI) module during water suppression to concurrently acquire metabolite maps with water referencing and fMRI data during task execution and resting state in healthy controls. Integration of multimodal signal acquisition prolongated minimum TR by less than 50 ms on average. Visual and motor activation in concurrent fMRI/MRSI (TR: 1250-1500 ms, voxel size: 4 x 4 x 6 mm³ ) was readily detectable in single-task blocks with percent signal change comparable with conventional fMRI. Resting-state connectivity in sensory and motor networks was detectable in 4 minutes. This hybrid water suppression approach for multimodal imaging has the potential to significantly reduce scan time and extend neuroscience research and clinical applications through concurrent quantitative MRSI and fMRI acquisitions.

Magnetic Resonance Spectroscopy in Children With Developmental Delay: Time to Look Beyond Conventional Magnetic Resonance Imaging (MRI)

Developmental delay (DD) is an important long-term neuromorbidity owing to various insults to the developing brain and neuroimaging plays a key role in evaluating these children. Magnetic resonance spectroscopy (MRS) is the only noninvasive method to determine the levels of various metabolites in the brain which aids in delineating the underlying abnormalities. A total of 48 children aged between 6 months to 6 years with developmental delay were included and evaluated with neuroimaging in our study. Sensitivity of MRS in children with DD and DD plus (DD along with seizures, abnormal motor findings, behavior, brainstem evoked response audiometry, visual assessment, and microcephaly) was 81.2% and 89.6% respectively. 86.6% of children with microcephaly had abnormal MRS. MRS detected abnormalities in two-thirds of children with normal magnetic resonance imaging (MRI). Children with behavioral abnormalities had significantly lower N-acetyl aspartate (NAA)-creatine and NAA-choline ratios on MRS. Thus, MRS is additive to MRI in delineating the underlying pathophysiology in children with DD.

NMR-based metabolomics in pediatric drug resistant epilepsy - preliminary results

Epilepsy in children is the most frequent, heterogeneous and difficult to classify chronic neurologic condition with the etiology found in 35–40% of patients. Our aim is to detect the metabolic differences between the epileptic children and the children with no neurological abnormalities in order to define the metabolic background for therapy monitoring. The studied group included 28 epilepsy patients (median age 12 months) examined with a diagnostic protocol including EEG, videoEEG, 24-hour-EEG, tests for inborn errors of metabolism, chromosomal analysis and molecular study. The reference group consisted of 20 patients (median age 20 months) with no neurological symptoms, no development delay nor chronic diseases. ¹H-NMR serum spectra were acquired on 400 MHz spectrometer and analyzed using multivariate and univariate approach with the application of correction for age variation. The epilepsy group was characterized by increased levels of serum N-acetyl-glycoproteins, lactate, creatine, glycine and lipids, whereas the levels of citrate were decreased as compared to the reference group. Choline, lactate, formate and dimethylsulfone were significantly correlated with age. NMR-based metabolomics could provide information on the dynamic metabolic processes in drug-resistant epilepsy yielding not only disease-specific biomarkers but also profound insights into the disease course, treatment effects or drug toxicity.

From fetus to older age: A review of brain metabolic changes across the lifespan

INTRODUCTION

The knowledge of metabolic changes across the lifespan is poorly understood. Thus we systematically reviewed the available literature to determine the changes in brain biochemical composition from fetus to older age and tried to explain them in the context of neural, cognitive, and behavioural changes.

METHODS

The search identified 1262 articles regarding proton magnetic resonance spectroscopy (1H MRS) examinations through December 2017. The following data was extracted: age range of the subjects, number of subjects studied, brain regions studied, MRS sequence used, echo time, MR system, method of statistical analysis, metabolites analyzed, significant differences in metabolites concentrations with age as well as the way of presentation of the results.

RESULTS

82 studies that described brain metabolite changes with age were identified. Reports on metabolic changes related to healthy aging were analyzed and discussed among six basic age groups: fetuses, infants, children, adolescents, adults, and the elderly as well as between groups and during the whole lifetime.

DISCUSSION

The results presented in the reviewed papers provide evidence that normal aging is associated with a number of metabolic changes characteristic for every period of life. Therefore, it can be concluded that the age matching is essential for comparative studies of disease states using 1H MRS.

Longitudinal increases of brain metabolite levels in 5-10 year old children

Longitudinal magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) studies reveal significant changes in brain structure and structural networks that occur together with cognitive and behavioral maturation in childhood. However, the underlying cellular changes accompanying brain maturation are less understood. Examining regional age-related changes in metabolite levels provides insight into the physiology of neurodevelopment. Magnetic resonance spectroscopy (MRS) measures localize brain metabolism. The majority of neuroimaging studies of healthy development are from the developed world. In a longitudinal MRS study of 64 South African children aged 5 to 10 years old (29 female; 29 HIV exposed, uninfected), we examined the age-related trajectories of creatine (Cr+PCr), N-acetyl-aspartate (NAA), the combined NAA+N-acetyl-aspartyl-glutamate (NAAG), choline (GPC+PCh), glutamate (Glu) and the combined Glu+glutamine (Glu+Gln) in voxels within gray and white matter, as well as subcortically in the basal ganglia (BG). In frontal gray matter, we found age-related increases in Cr+PCr, NAA, NAA+NAAG and Glu+Gln levels pointing to synaptic activity likely related to learning. In the BG we observed increased levels of Glu, Glu+Gln and NAA+NAAG with age that point to subcortical synaptic reorganization. In white matter, we found increased levels of Cr+PCr, NAA, NAA+NAAG, Glu and Glu+Gln with age, implicating these metabolites in ongoing myelination. We observed no sex-age or HIV exposure-age interactions, indicating that physiological changes are independent of sex during this time period. The metabolite trajectories presented, therefore, provide a critical benchmark of normal cellular growth for a low socioeconomic pediatric population in the developing world against which pathology and abnormal development may be compared.

An MRspec database query and visualization engine with applications as a clinical diagnostic and research tool

PURPOSE

Proton magnetic resonance spectroscopy (MRspec), one of the very few techniques for in vivo assessment of neuro-metabolic profiles, is often complicated by lack of standard population norms and paucity of computational tools.

METHODS

7035 scans and clinical information from 4430 pediatric patients were collected from 2008 to 2014. Scans were conducted using a 1.5T (n=3664) or 3T scanner (n=3371), and with either a long (144ms, n=5559) or short echo time (35ms, n=1476). 3055 of these scans were localized in the basal ganglia (BG), 1211 in parieto-occipital white matter (WM). 34 metabolites were quantified using LCModel. A web application using MySQL, Python and Flask was developed to facilitate the exploration of the data set.

RESULTS

Already piloting the application revealed numerous insights. (1), N-acetylaspartate (NAA) increased throughout all ages. During early infancy, total choline was highly varied and myo-inositol demonstrated a downward trend. (2), Total creatine (tCr) and creatine increased throughout childhood and adolescence, though phosphocreatine (PCr) remained constant beyond 200days. (3), tCr was higher in BG than WM. (4), No obvious gender-related differences were observed. (5), Field strength affects quantification using LCModel for some metabolites, most prominently for tCr and total NAA. (6), Outlier analysis identified patients treated with vigabatrin through elevated γ-aminobutyrate, and patients with Klippel-Feil syndrome, Leigh disease and L2-hydroxyglutaric aciduria through low choline in BG.

CONCLUSIONS

We have established the largest MRSpec database and developed a robust and flexible computational tool for facilitating the exploration of vast metabolite datasets that proved its value for discovering neurochemical trends for clinical diagnosis, treatment monitoring, and research. Open access will lead to its widespread use, improving the diagnostic yield and contributing to better understanding of metabolic processes and conditions in the brain.

Changes of brain metabolite concentrations during maturation in different brain regions measured by chemical shift imaging

INTRODUCTION

We examined the effect of maturation on the regional distribution of brain metabolite concentrations using multivoxel chemical shift imaging.

METHODS

From our pool of pediatric MRI examinations, we retrospectively selected patients showing a normal cerebral MRI scan or no pathologic signal abnormalities at the level of the two-dimensional 1H MRS-CSI sequence and an age-appropriate global neurological development, except for focal neurological deficits. Seventy-one patients (4.5 months-20 years) were identified. Using LC Model, spectra were evaluated from voxels in the white matter, caudate head, and corpus callosum.

RESULTS

The concentration of total N-acetylaspartate increased in all regions during infancy and childhood except in the right caudate head where it remained constant. The concentration of total creatine decreased in the caudate nucleus and splenium and minimally in the frontal white matter and genu. It remained largely constant in the parietal white matter. The concentration of choline-containing compounds had the tendency to decrease in all regions except in the parietal white matter where it remained constant. The concentration of myoinositol decreased slightly in the splenium and right frontal white matter, remained constant on the left side and in the caudate nucleus, and rose slightly in the parietal white matter and genu.

CONCLUSION

CSI determined metabolite concentrations in multiple cerebral regions during routine MRI. The obtained data will be helpful in future pediatric CSI measurements deciding whether the ratios of the main metabolites are within the range of normal values or have to be considered as probably pathologic.

Magnetic resonance spectroscopic analysis of neurometabolite changes in the developing rat brain at 7T

We utilized proton magnetic resonance spectroscopy to evaluate the metabolic profile of the hippocampus and anterior cingulate cortex of the developing rat brain from postnatal days 14-70. Measured metabolite concentrations were modeled using linear, exponential, or logarithmic functions and the time point at which the data reached plateau (i.e. when the portion of the data could be fit to horizontal line) was estimated and was interpreted as the time when the brain has reached maturity with respect to that metabolite. N-acetyl-aspartate and myo-inositol increased within the observed period. Gluthathione did not vary significantly, while taurine decreased initially and then stabilized. Phosphocreatine and total creatine had a tendency to increase towards the end of the experiment. Some differences between our data and the published literature were observed in the concentrations and dynamics of phosphocreatine, myo-inositol, and GABA in the hippocampus and creatine, GABA, glutamine, choline and N-acetyl-aspartate in the cortex. Such differences may be attributed to experimental conditions, analysis approaches and animal species. The latter is supported by differences between in-house rat colony and rats from Charles River Labs. Spectroscopy provides a valuable tool for non-invasive brain neurochemical profiling for use in developmental neurobiology research. Special attention needs to be paid to important sources of variation like animal strain and commercial source.

Applications of Magnetic Resonance Spectroscopy to Psychiatry

The inaccessibility of the human brain to biochemical studies has historically challenged the ability of in vestigators to elucidate the pathophysiology of psychiatric syndromes. Magnetic resonance spectroscopy (MRS) now provides a noninvasive means of assessing neurochemistry in vivo. Since the first application of the technique to the study of the human brain, many new advances have been made. This new technology broadens the applications of the MRS. The major principles of the technique and compounds currently available for study are discussed in this article. A brief review of current and future applications of the technology to the field of psychiatry are discussed. NEUROSCIENTIST 5:192-196, 1999

Normal development

Numerous events are involved in brain development, some of which are detected by neuroimaging. Major changes in brain morphology are depicted by brain imaging during the fetal period while changes in brain composition can be demonstrated in both pre- and postnatal periods. Although ultrasonography and computed tomography can show changes in brain morphology, these techniques are insensitive to myelination that is one of the most important events occurring during brain maturation. Magnetic resonance imaging (MRI) is therefore the method of choice to evaluate brain maturation. MRI also gives insight into the microstructure of brain tissue through diffusion-weighted imaging and diffusion tensor imaging. Metabolic changes are also part of brain maturation and are assessed by proton magnetic resonance spectroscopy. Understanding and knowledge of the different steps in brain development are required to be able to detect morphologic and structural changes on neuroimaging. Consequently alterations in normal development can be depicted.

Four-and-one-half years' experience in monitoring of reproducibility of an MR spectroscopy system--application of in vitro results to interpretation of in vivo data

The primary purpose of this work was to assess long-term in vitro reproducibility of metabolite levels measured using 1H MRS (proton magnetic resonance spectroscopy). The secondary purpose was to use the in vitro results for interpretation of 1H MRS in vivo spectra acquired from patients diagnosed with Canavan disease. 1H MRS measurements were performed in the period from April 2006 to September 2010. 118 short and 116 long echo spectra were acquired from a stable phantom during this period. Change-point analysis of the in vitro N-acetylaspartate levels was exploited in the computation of fT factor (ratio of the actual to the reference N-acetylaspartate level normalized by the reciprocity principle). This coefficient was utilized in the interpretation of in vivo spectra analyzed using absolute reference technique. The monitored time period was divided into six time intervals based on short echo in vitro data (seven time intervals based on long echo in vitro data) characterized by fT coefficient ranging from 0.97 to 1.09 (based on short echo data) and from 1.0 to 1.11 (based on long echo data). Application of this coefficient to interpretation of in vivo spectra confirmed increased N-acetylaspartate level in Canavan disease. Long-term monitoring of an MRS system reproducibility, allowing for absolute referencing of metabolite levels, facilitates interpretation of metabolic changes in white matter disorders.

Neurochemical evaluation of brain function with 1H magnetic resonance spectroscopy in patients with fragile X syndrome

Fragile X syndrome (FXS) is the most common hereditary disorder of intellectual disability. Cognitive deficits involve executive function, attention, learning and memory. Advanced neuroimaging techniques are available, and (1)H magnetic resonance spectroscopy (MRS) can be used as a complementary method to MR imaging to understand disease processes in brain, by in vivo demonstration of brain metabolites. MRS was performed in 13 male patients with FXS full mutation, and 13 age- and sex-matched healthy controls. FXS diagnosis was based on clinical evaluation, followed by detection of FMR1 full mutation. Axial T2 TSE, sagittal T1 SE and coronal 3D MPRAGE images were obtained for both morphological imaging and voxel localization. Following evaluation of conventional images, multivoxel MRS (CSI) through supraventricular white matter and single voxel MRS (svs) with an intermediate echo time (TE:135 ms) from the cerebellar vermis were performed. Choline/Creatine (Cho/Cr), N-acetyl aspartate/Creatine (NAA/Cr), and Choline/N-acetyl aspartate (Cho/NAA) ratios were examined at right frontal (RF), left frontal (LF), right parietal (RP), left parietal (LP), and cerebellar vermian (C) white matter. Statistical analyses were done using t-test and Mann-Whitney U tests. A statistically significant difference was observed in RP Cho/NAA ratio (cell membrane marker/neuroaxonal marker), FXS patients having lower levels than controls (P = 0.016). The results should be evaluated cautiously in parallel to consequences in brain metabolism leading to alterations in neurotransmitter levels, osmoregulation, energy metabolism and oxidative stress response described in animal models. MRS may serve to define a metabolic signature and biomarkers associated with FXS.

A two-year longitudinal pilot MRI study of the brainstem in autism

Research has demonstrated the potential role of the brainstem in the pathobiology of autism. Previous studies have suggested reductions in brainstem volume and a relationship between this structure and sensory abnormalities. However, little is known regarding the developmental aspects of the brainstem across childhood and adolescence. The goal of this pilot study was to examine brainstem development via MRI volumetry using a longitudinal research design. Participants included 23 boys with autism and 23 matched controls (age range=8-17 years), all without intellectual disability. Participants underwent structural MRI scans once at baseline and again at two-year follow-up. Brainstem volumetric measurements were performed using the BRAINS2 software package. There were no significant group differences in age, gender, handedness, and total brain volume; however, full-scale IQ was higher in controls. Autism and control groups showed different patterns of growth in brainstem volume. While whole brainstem volume remained stable in controls over the two-year period, the autism group showed increases with age reaching volumes comparable to controls by age 15 years. This increase of whole brainstem volume was primarily driven by bilateral increases in gray matter volume. Findings from this preliminary study are suggestive of developmental brainstem abnormalities in autism primarily involving gray matter structures. These findings are consistent with autism being conceptualized as a neurodevelopmental disorder with alterations in brain-growth trajectories. More longitudinal MRI studies are needed integrating longitudinal cognitive/behavioral data to confirm and elucidate the clinical significance of these atypical growth patterns.

Decreased frontal N-acetylaspartate levels in adolescents concurrently using both methamphetamine and marijuana

INTRODUCTION

The potential neurochemical toxicity associated with methamphetamine (MA) or marijuana (MJ) use on the developing adolescent brain is unclear, particularly with regard to individuals with concomitant use of MA and MJ (MA+MJ). In this study, proton magnetic resonance spectroscopy (MRS) was utilized to measure in vivo brain N-acetylaspartate plus N-acetylaspartyl glutamate (tNAA, an indicator of intact neuronal integrity) levels.

METHODS

Three adolescent groups from Cape Town, South Africa completed MRS scans as well as clinical measures including a drug use history. Subjects included (1) nine MA (age=15.7±1.37), (2) eight MA+MJ (age=16.2±1.16) using adolescents and (3) ten healthy controls (age=16.8±0.62). Single voxel spectra were acquired from midfrontal gray matter using a point-resolved spectroscopy sequence (PRESS). The MRS data were post-processed in the fully automated approach for quantitation of metabolite ratios to phosphocreatine plus creatine (PCr+Cr).

RESULTS

A significant reduction in frontal tNAA/PCr+Cr ratios was seen in the MA+MJ group compared to the healthy controls (p=0.01, by 7.2%) and to the MA group (p=0.04, by 6.9%). Significant relationships were also observed between decreased tNAA/PCr+Cr ratios and drug use history of MA or MJ (total cumulative lifetime dose, age of onset, and duration of MA and MJ exposure) only in the MA+MJ group (all p<0.05).

CONCLUSIONS

These findings suggest that in adolescents, concomitant heavy MA+MJ use may contribute to altered brain metabolites in frontal gray matter. The significant associations between the abnormal tNAA/PCr+Cr ratios and the drug use history suggest that MA+MJ abuse may induce neurotoxicity in a dose-responsive manner in adolescent brain.

Developmental aspects of temporal and spatial visual attention: insights from the attentional blink and visual search tasks

Frontal regions of the human cortex are thought to reach full maturation last in the course of development. The present report examines such development in the context of attentional tasks in the temporal (e.g., the attentional blink, AB, paradigm) and spatial (e.g., the visual search, VS, paradigm) domains. Here we show that the recovery from AB is progressively longer with younger age by studying 7-, 12-, 15-year-olds, and adults participating on a modified AB task. By contrast, we found no difference between 7-year-olds and adults in a VS task using the same target stimuli as in the AB task. This differential pattern of development between temporal and spatial attention is discussed in relation to visual working memory development, clinical populations, and general mechanisms of cortical development.

High gamma-aminobutyric acid level in cortical tubers in epileptic infants with tuberous sclerosis complex measured with the MEGA-editing J-difference method and a three-Tesla clinical MRI Instrument

The purpose of this study was to estimate the gamma-aminobutyric acid (GABA) and glutamate plus glutamine (Glx) concentrations in the cortical tubers of patients with tuberous sclerosis complex (TSC) using the MEGA-editing J-difference method and a stimulated echo-acquisition mode with a short echo time, and to determine which abnormality was more dominant between GABA and Glx in patients with TSC with epilepsy. This study included six patients with TSC (mean age, 4.3 years) and seven control subjects (mean age, 4.8 years). Measurements were obtained with a three-Tesla apparatus and postprocessing was conducted with an LCModel. The GABA level in the cortical gray matter (cgGABA) was calculated as a result of segmentation in voxels and from the literature values for gray and white matter ratios for GABA. Increased GABA and myo-inositol (mI) concentrations and a decreased N-acetyl aspartate (NAA) concentration were observed in the cortical tubers. The cgGABA level, and cgGABA/NAA and cgGABA/Glx ratios were also higher in patients with TSC than in control subjects. No significant difference was found in Glx concentration between patients with TSC and control subjects. Although the number of patients with TSC in this study was small, the increase in GABA and no significant change in Glx were consistent with previous neurochemical studies and support the hypothesis that brain GABA plays a key role in the pathophysiology of epilepsy during the process of neuronal development.

Cholinergic dysfunction in fragile X syndrome and potential intervention: a preliminary 1H MRS study

Males with fragile X syndrome (FRAX) are at risk for significant cognitive and behavioral deficits, particularly those involving executive prefrontal systems. Disruption of the cholinergic system secondary to fragile X mental retardation protein deficiency may contribute to the cognitive-behavioral impairments associated with fragile X. We measured choline in the dorsolateral prefrontal cortex of nine males with FRAX and 9 age-matched typically developing controls using (1)H magnetic resonance spectroscopy. Right choline/creatine was significantly reduced in the fragile X group compared to controls. In controls, both left and right choline was significantly positively correlated with intelligence and age was significantly negatively correlated with left choline. There were no correlations in the fragile X group. Subjects with FRAX participating in a pilot open-label trial of donepezil, an acetylcholinesterase inhibitor, demonstrated significantly improved cognitive-behavioral function. Studies utilizing biochemical neuroimaging techniques such as these have the potential to significantly impact the design of treatment strategies for FRAX and other genetic disorders by helping identify neurochemical targets for intervention as well as serving as metrics for treatment efficacy.

Brain development in infantile-onset Pompe disease treated by enzyme replacement therapy

The primary manifestations of Pompe disease are muscle weakness and cardiomyopathy. Although accumulation of glycogen has also been seen in the nervous system in patients, the significance of brain involvement in infantile-onset Pompe disease is not clear. In this study, brain development in five cases of infantile-onset Pompe disease, whose survivals have been prolonged by enzyme replacement therapy (ERT), were studied by brain magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). The results revealed delay in myelination milestones in all patients at a median age of 6 mo upon the initiation of treatment. After ERT, four of the five cases showed good progression in myelination, even though mild dilatation of the ventricles was still observed. In the case with no response to ERT in the muscles, however, brain myelination was slow and follow-up MRI and MRS studies suggested both neuron and myelination loss. Therefore, myelination defects are common in infantile-onset Pompe disease. Improvement in brain myelination could be seen in those who survive by effective treatment, although we do not know whether ERT does have a direct therapeutic effect on the brain.

Metabolite profile in the basal ganglia of children with cerebral palsy: a proton magnetic resonance spectroscopy study

This prospective study determined metabolite profile in the left and right basal ganglia of children with spastic cerebral palsy (CP) compared with children without disabilities, by using proton magnetic resonance spectroscopy (1HMRS). Twenty-three patients with spastic CP (12 males, 11 females; mean age 11y 9mo [SD 4y 2mo], range 4-17y) were examined. Twenty children had spastic diplegia and three had quadriplegia. Twenty-four normally developing children (13 females, 11 males; mean age 10y 3mo [SD 4y 8mo], range 4-17y) served as a comparison group. The relative concentrations of N-acetylaspartate (NAA), choline (Cho), myo-inositol (mI), and gamma-aminobutyric acid (GABA) were measured relative to creatine (Cr) and different combinations of metabolites within 8cm3 brain voxels. Children with CP showed reduced ratios of NAA:Cr, NAA:Cho, NAA:mI, and GABA:Cr in the basal ganglia relative to a matched comparison group. Patients demonstrated a significant age-dependent increase in NAA:Cr and NAA:Cho in the basal ganglia. No sex-dependent difference was shown in children with CP nor in the comparison group for all tested metabolite ratios. Significant correlation between Apgar score and ratio of mI:Cr in the group with CP was found. None of the tested metabolite ratios were correlated with the severity scale of CP in children with CP. NAA:Cr ratios were negatively correlated with learning disability in patients with CP. Results indicate the association of the metabolite ratios in basal ganglia with learning disability.

White matter proton MR spectroscopy in children with isolated developmental delay: does it mean delayed myelination?

RATIONALE AND OBJECTIVES

Isolated developmental delay (IDD) is a common disorder in preschool and school-age children. Conventional magnetic resonance imaging (MRI) usually does not disclose abnormalities, but a myelination delay is suspected as causative or associated factor. N-acetyl-aspartate is a surrogate marker of neuronal integrity but also of axonal integrity. The goal of our study is to determine whether magnetic resonance spectroscopy (MRS) is able to detect alterations in the white matter supporting the hypothesis of delayed myelination in children with IDD and normal MRI.

MATERIALS AND METHODS

In this cross-sectional study, we enrolled 12 consecutive children meeting the criteria if IDD and aged between 3 and 12 years (mean 7.25 years) and 11 healthy children as control group (mean age 7.18, range 3-12 years) on whom we performed conventional MRI and MRS. We did not include children with abnormal MRI. Single voxel (8 cm(3)) was placed in the white matter of the left centrum semiovale. The mode of acquisition was probe-p (PRESS technique) with a TR of 2500 milliseconds and a TE of 30 milliseconds. We measured the metabolite concentration of n-acetyl-aspartate (NAA), choline (Ch), creatine (Cr) y myo-inositol (mI), and ratios of NAA, Ch, and mI to creatine.

RESULTS

In children with IDD, we found a significant decrease of the following ratios: NAA/Cr (P < .016), NAA/Ch (P < .026), and NAA/mI (P < .023) in relation to controls. The mean NAA/Cr ratio in IDD children was 1.92 (SD 0.14), and in controls it was 2.09 (SD 0.14); t = 2.62, fd (freedom degrees) = 21, P < .016. No differences were seen in the remaining ratios.

CONCLUSIONS

The lower NAA/Cr ratio in children with IDD in relation to controls may be a promising marker of this disorder and supports the hypothesis of delayed myelination. MRS can provide important information in children with neurodevelopmental disorders.

Contribution of proton magnetic resonance spectroscopy to the evaluation of children with unexplained developmental delay

Developmental delay (DD) in children is a common socioeconomic problem with a prevalence of 1-2%. The cause of DD in children is often unknown, and magnetic resonance imaging plays an important role in evaluating children with DD, estimating long-term prognosis, and guiding therapeutic options. The aim of our study on children with DD was to elucidate 1) whether magnetic resonance spectroscopy (MRS) reveals abnormalities in cerebral metabolism and 2) whether there is a correlation between the cognitive performance and the concentration of brain metabolites, especially N-acetylaspartate (NAA), named in the literature a neuronal marker. Using proton MRS of deep gray and central white matter, we measured concentrations of brain metabolites in 48 children, who were aged 1 mo to 13 y and had unexplained DD [developmental quotient (DQ) between <50 and 85] and normal magnetic resonance imaging examinations, and compared them with those of 23 age-matched normal control children. Children with DD were divided into three groups: mild (DQ 76-85), moderate (DQ 51-75), and severe (DQ <50). We found no significant differences in metabolite concentrations, neither among the three groups of children with DD nor between patients and age-matched normal control children. Independent of the degree of mental retardation, the NAA concentrations of handicapped patients and normal children were comparable. We conclude that 1) brain metabolites, especially NAA, in children with unexplained DD are within normal limits, and 2) in most cases, proton MRS adds little information concerning cause of unexplained DD.

BOLD fMRI signal increases with age in selected brain regions in children

To determine whether the BOLD signal used in fMRI is age dependent in childhood, 332 healthy children (age 4.9-18.9 years) performed tasks in a periodic block design during 3 T fMRI: (1) a verb generation task interleaved with a finger tapping task; (2) a word-picture matching task interleaved with an image discrimination task. Significant correlations between percent signal change in BOLD effect and age occurred in left Broca's, middle frontal, Wernicke's, and inferior parietal regions, and anterior cingulate during the verb generation task; in precentral, postcentral, middle frontal, supplementary motor, and precuneus regions during the finger tapping task; and in bilateral lingula gyri during the word-picture matching task. Thus, BOLD effect increases with age in children during sensorimotor and language tasks.

Imaging data in autism: from structure to malfunction

During the last two decades, neuroimaging studies have improved our knowledge of brain development and contributed to our understanding of disorders involving the developing brain. Differences in cerebral anatomy have been determined in autism spectrum disorder (ASD). Morphological studies by magnetic resonance imaging have provided evidence of structural differences in ASD compared with the normal population. This has enhanced our view of autism as a neurobiological disorder corresponding with different stages and events in brain development. Alterations in volume of the total brain and specifically the cerebellum, frontal lobe, and limbic system have been identified. There appears to be a pattern of increased and then decreased rate of brain growth over time. We integrate these observations with neurobehavioral findings to provide a developmental hypothesis of the pathophysiology of autism.

Localized 1H-MR spectroscopy in moyamoya disease before and after revascularization surgery

OBJECTIVE

To evaluate, using localized proton magnetic resonance spectroscopy ((1)H-MRS), the cerebral metabolic change apparent after revascularization surgery in patients with moyamoya disease.

MATERIALS AND METHODS

Sixteen children with moyamoya disease and eight age-matched normal controls underwent MR imaging, MR angiography, conventional angiography, and (99m)Tc- ECD SPECT. Frontal white matter and the basal ganglia of both hemispheres were subjected to localized (1)H-MRS, and after revascularization surgery, four patients underwent follow-up (1)H-MRS.

RESULTS

Decreased NAA/Cr ratios (1.35+/-0.14 in patients vs. 1.55+/-0.24 in controls) and Cho/Cr ratios (0.96+/-0.13 in patients vs. 1.10+/-0.11 in controls) were observed in frontal white matter. After revascularization surgery, NAA/Cr and Cho/Cr ratios in this region increased. In the basal ganglia, there is no abnormal metabolic ratios.

CONCLUSION

Localized (1)H-MRS revealed abnormal metabolic change in both hemispheres of children with moyamoya disease. Because of its non-invasive nature, (1)H-MRS is potentially useful for the preoperative evaluation of metabolic abnormalities and their postoperative monitoring.

Maturation of the human fetal brain as observed by 1H MR spectroscopy

Proton MRS was used to monitor cerebral metabolite tissue levels in 35 normal fetuses during development in the gestational age range of 30-41 weeks. First, MRI in three orthogonal orientations was performed. A volume of interest (VOI) (15-43 cc) of fetal brain tissue was then selected for (1)H MRS. For localization, two pulse sequences (stimulated echo acquisition mode (STEAM) at TE = 20 ms, and point-resolved spectroscopy (PRESS) at TE = 135 ms) were applied. The MR spectra of the brain showed signals for inositol (Ino), choline (Cho), creatine (Cr), and N-acetyl (NA) compounds. From 30 to 41 weeks the absolute tissue level of NA, and the ratios of NA/Cr and NA/Cho increased, whereas the ratio of Cho/Cr decreased. These changes reflect maturation of the brain. Considering the diagnostic value of proton MRS in pediatric neurology, this new approach may also be useful for characterizing pathological conditions in the fetal brain.

Hydrogen proton magnetic resonance spectroscopy in autism: preliminary evidence of elevated choline/creatine ratio

Hydrogen proton magnetic resonance spectroscopy is only beginning to be studied in autistic individuals. We report an association between hydrogen proton magnetic resonance spectroscopy choline/creatine ratios and severity of autism as measured by the Children's Autistic Rating Scale (Pearson r = .657, P = .04) in 10 autistic children. Hydrogen proton magnetic resonance spectroscopy choline/creatine ratio measures the concentration of cytosolic choline including free choline used in the synthesis of acetylcholine. Elevation in this ratio has been interpreted as a result of membrane degradation such as caused by a tumor or, alternatively, as a result of choline synthesis associated with increased cellular proliferation. Recent neuropathologic evidence has implicated disruption of acetylcholine transmission in the brains of autistic adults. A case-controlled study of hydrogen proton magnetic resonance spectroscopy choline/creatine ratios is warranted.

In vivo quantitative proton MRSI study of brain development from childhood to adolescence

PURPOSE

To quantify regional variations in metabolite levels in the developing brain using quantitative proton MR spectroscopic imaging (MRSI).

MATERIALS AND METHODS

Fifteen healthy subjects three to 19 years old were examined by in vivo multislice proton MRSI. Concentrations of N-acetyl aspartate (NAA), total choline (Cho), total creatine (Cr), and peak area ratios were determined in selected frontal and parietal gray and white matter regions, basal ganglia, and thalamus.

RESULTS

In cortical gray matter regions, the ratio of NAA/Cho increased to a maximum at 10 years and decreased thereafter (P = 0.010). In contrast, in white matter, average ratios NAA/Cho increased linearly with age (P = 0.045). In individual brain regions, age-related changes in NAA/Cho were found in the putamen (P = 0.044). No significant age-related changes in NAA, Cho, Cr, or other metabolite ratios could be determined.

CONCLUSION

Consistent with recent studies using other structural and functional neuroimaging techniques, our data suggest that small but significant changes occur in regional cerebral metabolism during childhood and adolescence. Non-linear age related changes of NAA/Cho in frontal and parietal areas, resembling previously reported age related changes in rates of glucose utilization and cortical volumes, may be associated with dendritic and synaptic development and regression. Linear age-related changes of NAA/Cho in white matter are also in agreement with age-related increases in white matter volumes, and may reflect progressive increases in axonal diameter and myelination.

Increased thalamic N-acetylaspartate in male patients with familial bipolar I disorder

N-Acetylaspartate (NAA) in the anterior and mediodorsal thalamic regions was measured using proton magnetic resonance spectroscopic imaging (1H-MRSI) in 15 euthymic male patients with familial bipolar I disorder and compared to values in 15 male control subjects to determine if there was evidence for altered neuronal/axonal integrity. MRI tissue segmentation methods were also utilized to obtain tissue-contribution estimates for each MRSI voxel. Relative to the comparison group, the patients with bipolar I disorder demonstrated significantly higher NAA and creatine in both the right and left thalamus. NAA was also significantly higher in the left thalamus compared to the right in both bipolar I patients and controls. There were no group or lateralized differences in the percentages of different tissue types within the MRSI voxels, suggesting that the thalamic NAA and creatine alterations were not an artifact of variations in tissue type percentages in the MRSI voxels. There was also no significant association between NAA or creatine and illness duration. The findings of increased thalamic NAA bilaterally may represent neuronal hypertrophy or hyperplasia, reduced glial cell density, or abnormal synaptic and dendritic pruning. Increased thalamic creatine bilaterally may represent altered cellular energy metabolism and is consistent with prior studies demonstrating changes in thalamic metabolism in mood disorders.

Developmental neuroimaging of children using magnetic resonance techniques

Cognitive and motor development in children remain fascinating processes that are uniquely human. Progress has been made in recent years in elucidating the prenatal process of human brain development. In addition, much information exists regarding the behavioral aspects of postnatal human development. However, little is known about the relationship between anatomic postnatal central nervous system development and the accretion of functional milestones observed in children from the neonatal period through adolescence. Recently, powerful qualitative and quantitative magnetic resonance techniques have been developed that will permit detailed inquiry into the connection between the developing brain and the developing mind. In this review, first, the steps of prenatal and postnatal brain development are reviewed briefly. Subsequently, recent magnetic resonance imaging data related to human brain development during the fetal, neonatal, and later childhood periods are presented. Finally, functional magnetic resonance imaging (fMRI) is discussed. Specific examples of its usefulness are provided. Magnetic resonance imaging techniques such as quantitative MRI, volumetric MRI, diffusion tensor imaging, and functional magnetic resonance imaging (fMRI) when combined with neurologic and neuropsychologic evaluation, will provide new insights into the cognitive development of children. MRDD Research Reviews 6:68-80, 2000.

Regional age dependence of human brain metabolites from infancy to adulthood as detected by quantitative localized proton MRS

Regional changes of metabolite concentrations during human brain development were assessed by quantitative localized proton magnetic resonance spectroscopy in vivo. Apart from measurements in young healthy adults, the study was based on regional spectra from 97 children who were either healthy or suffered from mental retardation, movement disorders, epilepsies, neoplasm, or vascular malformation. Metabolite quantitation focused on cortical gray and white matter, cerebellum, thalamus, and basal ganglia in six age groups from infancy to adulthood. During infancy and childhood, the concentration of the neuroaxonally located N-acetylasparate increased in gray matter, cerebellum, and thalamus, whereas a constant level was detected in white matter. These findings are in line with regional differences in the formation of synaptic connections during early development and suggest a role of N-acetylaspartate as a marker of functioning neuroaxonal tissue rather than of the mere presence of nerve cells. This view is further supported by high concentrations of taurine in gray matter and cerebellum during infancy, because taurine is also believed to be involved in the process of synapse formation. Remarkably, in basal ganglia both N-acetylaspartate and taurine remain constant at relatively high concentrations. Other metabolite changes during maturation include increases of N-acetylaspartylglutamate, especially in thalamus and white matter, and a decrease of glutamine in white matter. Despite regional differences and some small changes during the first year of life, the concentrations of creatine, phosphocreatine, choline-containing compounds, myoinositol, and glutamate remain constant afterward. The creatine to phosphocreatine concentration ratio yields 2:1 throughout the human brain irrespective of region or age. The observed increase of the proton resonance line-width with age is most pronounced in basal ganglia and corresponds to the age-related and tissue-dependent increase of brain iron.

Brain metabolic alterations in Cushing's syndrome as monitored by proton magnetic resonance spectroscopy

Proton magnetic resonance spectroscopy ((1)H MRS) was used to evaluate changes in cerebral metabolites in 13 patients with Cushing's syndrome (including seven with pituitary corticotroph adenomas and six with primary adrenal disease) as compared to 40 normal subjects. Data were recorded in the frontal, thalamic and temporal areas; quantification of the MRS signals demonstrated a statistically significant decrease of the Cho/Cr ratio in the frontal and thalamic areas but not in the temporal area for patients with Cushing's syndrome. The largest decrease in Cho/Cr was measured in the thalamic area of patients with a Cushing's syndrome secondary to an adrenal disease. No statistically significant changes in the NAA/Cr ratio were measured in any of the areas studied. These results suggest that the quantification of choline levels could be helpful for monitoring the cerebral metabolite alterations in patients with hypercortisolism.

Preliminary study of frontal lobe 1H MR spectroscopy in childhood-onset schizophrenia

Cerebral 1H MR spectra were recorded in 13 children and adolescents with schizophrenia and 12 healthy children and adolescents. Stimulated echo acquisition mode (STEAM) sequence was used to localize an 8-ml voxel bilaterally in the frontal gray matter. The frontal gray matter metabolite ratios for NAA/Cr, Ch/Cr, Glx/Cr, and mI/Cr in schizophrenic children and adolescents were 1.08 +/- .28, .64 +/- .23, 1.09 +/- .30, and .60 +/- .24, respectively. In comparison, these ratios were 1.59 +/- .35, .74 +/- .27, 1.23 +/- .36, and .58 +/- .29 in healthy children and adolescents. Decrease in the frontal lobe NAA/Cr of schizophrenic children and adolescents was statistically significant (P < .001). In contrast, the MR spectra localized bilaterally in the occipital gray matter (8 ml) showed no significant changes between the patients and the controls. In the occipital gray matter, the metabolite ratios were 1.21 +/- .26,.52 +/- .08, 1.00 +/- .11, and.55 +/- .12 inpatients versus 1.30 +/- .23, .45 +/- .10, 1.15 +/- .20, and .48 +/- .19 in controls. Our preliminary finding of reduced NAA/Cr ratio in the frontal gray matter is consistent with the neurodevelopmental models emphasizing dysfunction of frontal lobe areas in patients with schizophrenia.

Proton magnetic resonance spectroscopy of the brain in three cases of Rett syndrome: comparison with autism and normal controls

Rett syndrome (RS) is a clinically defined disorder characterized by autistic behavior, and cognitive and motor skill loss early in life. We performed 1H-MRS of the brain in 3 cases of RS in comparison with in autism and controls. The older patient with RS demonstrated decreased N-acetylaspartate (NAA)/choline (Cho) and NAA/creatine (Cr) ratios when compared with the autism and control groups, whereas the younger patients did not demonstrate these decreased metabolite ratios. The Cho/Cr ratio did not differ among Rett syndrome, autism and controls. Since the clinical stage did not differ among the 3 cases of RS, it was suggested that NAA was decreased with increasing age and was not related with the clinical stage of RS. The NAA/Cho, NAA/Cr and Cho/Cr ratios did not differ between autism and controls. The present data suggest that there may be a secondary degenerative process of late onset in RS, which pathophysiologically differs from autism.

Proton magnetic resonance spectroscopy of the brain in patients with Prader-Willi syndrome

Five patients with Prader-Willi syndrome underwent magnetic resonance imaging and proton magnetic resonance spectroscopy. Magnetic resonance images revealed mild abnormalities, including slight ventriculomegaly, cortical atrophy, and a small brainstem, in all cases. The N-acetylaspartate/Choline (NAA/Cho) and N-acetylaspartate/Creatine (NAA/Cr) ratios were decreased in one (Case 1) and two (Cases 1 and 4) patients, respectively. The Choline/Creatine (Cho/Cr) ratio did not differ from those in control subjects. Thus, in patients with Prader-Willi syndrome, it is thought that there may be neuron loss or a neuron dysfunction caused by a chromosome abnormality. Statistically significant relationships were observed between IQ (DQ) and the NAA/Cho and Cho/Cr ratios: r = 0.895 (P < .05, NAA/Cho ratio) and r = -0.898 (P < .05, Cho/Cr ratio). This suggests that the parietal lobe pathology detected on 1H-magnetic resonance spectroscopy may be associated with more global brain damage and with loss of cognitive functions.

A theory of neurolinguistic development

This article offers a developmental theory of language and the neural systems that lead to and subserve linguistic capabilities. Early perceptual experience and discontinuities in linguistic development suggest that language develops in four phases that occur in a fixed, interdependent sequence. In each phase of language, a unique ontogenetic function is accomplished. These functions have proprietary neural systems that vary in their degree of specialization. Of particular interest is an analytical mechanism that is responsible for linguistic grammar. This mechanism is time-locked and can only be turned on in the third phase. Confirming evidence is provided by children who are delayed in the second phase of the language learning process. These children store insufficient lexical material to activate their analytic mechanism. Inactivation behaves like damage, shifting language functions to homologous mechanisms in the nondominant hemisphere, thereby increasing functional and anatomical symmetry across the hemispheres. This atypical assembly of neurolinguistic resources produces functional but imperfect command of spoken language and may complicate learning of written language. The theory thus offers a different role for genetics and early experience, and a different interpretation of neuroanatomic findings, from those entertained in most other proposals on developmental language disorders.

Magnetic resonance imaging of the brain and cerebral proton spectroscopy in patients with systemic lupus erythematosus

OBJECTIVE

To investigate the prevalence and extent of cerebral changes in patients with systemic lupus erythematosus (SLE) by magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS).

METHODS

SLE patients (47 women) and controls (25 women) underwent 1.5T MRI. A semiautomated segmentation technique calculated cerebrospinal fluid (CSF) and brain volumes. Proton MRS of the frontal and parieto-occipital white matter yielded metabolite ratios of N-acetyl groups (NA), choline, and creatine.

RESULTS

Compared with the control group, the SLE patients more often had cerebral atrophy on MRI (32% versus 0%), confirmed by an increase in the CSF to intracranial volume ratio. The patients also had old infarcts and hemorrhages (8.5% versus 0%) and more small white matter lesions (23% versus 8% had > 5 such lesions). MRS showed relative reduction of NA peaks. Although no patient was studied when acutely ill, prior neurologic involvement was related to abnormal findings.

CONCLUSION

MRI and MRS are helpful in the investigation of cerebral complications of SLE. There are chronic changes which may be ischemic in nature. Their precise cause, consequences, and prevention are current challenges.

Lactate, N-acetylaspartate, choline and creatine concentrations, and spin-spin relaxation in thalamic and occipito-parietal regions of developing human brain

Previous studies of the brains of normal infants demonstrated lower lactate (Lac)/choline (Cho), Lac/creatine (Cr), and Lac/ N-acetylaspartate (Naa) peak-area ratios in the thalamic region (predominantly gray matter) compared with occipitoparietal (mainly unmyelinated white matter) values. In the present study, thalamic Cho, Cr, and Naa concentrations between 32-42 weeks' gestational plus postnatal age were greater than occipito-parietal: 4.6 +/- 0.8 (mean +/- SE), 10.5 +/- 2.0, and 9.0 +/- 0.7 versus 1.8 +/- 0.6, 5.8 +/- 1.5, and 3.4 +/- 1.1 mmol/kg wet weight, respectively: Lac concentrations were similar, 2.7 +/- 0.6 and 3.3 +/- 1.3 mmol/kg wet weight, respectively. In the thalamic region, Cho and Naa T2s increased, and Cho and Lac concentrations decreased, during development. Lower thalamic Lac peak-area ratios are principally due to higher thalamic concentrations of Cho, Cr, and Naa rather than less Lac. The high thalamic Cho concentration may relate to active myelination; the high thalamic Naa concentration may be due to advanced gray-matter development including active myelination. Lac concentration is higher in neonatal than in adult brain.

Proton magnetic resonance spectroscopy of the brain in normal preterm and term infants, and early changes after perinatal hypoxia-ischemia

The aims of this study were 1) to define normal perinatal maturational changes in proton metabolite peak-area ratios in two regions of the neonatal brain, the thalamic and occipitoparietal regions, and 2) to investigate abnormalities of these ratios after perinatal hypoxia-ischemia. Fifty-four infants were studied: 35 normal control infants at 31-42 wk of gestational plus postnatal age, and 19 "asphyxiated" infants suspected of cerebral hypoxic-ischemic injury. Proton spectra were collected at 2.4 tesla from (2 cm)3 voxels using the point-resolved spectroscopy technique with a 270-ms echo time. Lactate was detected in all infants studied. In the normal infants, lactate relative to N-acetylaspartate (NAA), choline and creatine was significantly greater in the occipitoparietal region than in the thalamus, and fell with increasing maturity in both regions, whereas NAA/ choline increased. The 19 asphyxiated infants were studied on a total of 34 occasions during the 1st wk of life (median age 1.8 d), at gestational plus postnatal ages of 27-41 wk. Maximum lactate/NAA was above 95% confidence limits for the control data in one or both regions in 11 of the 19 infants. Minimum NAA/choline was below 95% confidence limits in only one asphyxiated infants, who was later found to have congenital hypothyroidism. SD scores for lactate, relative to NAA, choline, and creatine, were higher in both regions in the asphyxiated infants compared with the normal infants, particularly in the thalamus. Early results of 1-y follow-up examinations indicate that raised lactate/NAA carries a poor long-term prognosis.

Proton magnetic resonance spectroscopy on childhood-onset dentatorubral-pallidoluysian atrophy (DRPLA)

To evaluate brain dysfunction of childhood-onset dentatorubral-pallidoluysian atrophy (DRPLA), three children with progressive myoclonus epilepsy, who were diagnosed as having DRPLA by DNA analysis, for the first time, underwent a study of proton magnetic resonance spectroscopy (1H-MRS). 1H-MRS obtained from both the parietal and basal ganglia regions disclosed markedly reduced ratios of N-acetylaspartate to both choline and creatine. Especially regarding the basal ganglia region, the latter (ratio of N-acetylaspartate to creatine) closely correlated to severity of genetic abnormality, i.e. number of expanded CAG repeats, suggesting that the degree of neuronal loss in the region strongly depends on genetic factors. 1H-MRS must be a valuable tool to clarify the pathophysiology of DRPLA.