Findings of proton magnetic resonance spectometry in the dorsolateral prefrontal cortex in adolescents with first episodes of psychosis

Meta-analytic evidence of elevated choline, reduced N-acetylaspartate, and normal creatine in schizophrenia and their moderation by measurement quality, echo time, and medication status

BACKGROUND

Brain metabolite abnormalities measured with magnetic resonance spectroscopy (MRS) provide insight into pathological processes in schizophrenia. Prior meta-analyses have not yet answered important questions about the influence of clinical and technical factors on neurometabolite abnormalities and brain region differences. To address these gaps, we performed an updated meta-analysis of N-acetylaspartate (NAA), choline, and creatine levels in patients with schizophrenia and assessed the moderating effects of medication status, echo time, measurement quality, and other factors.

METHODS

We searched citations from three earlier meta-analyses and the PubMed database after the most recent meta-analysis to identify studies for screening. In total, 113 publications reporting 366 regional metabolite datasets met our inclusion criteria and reported findings in medial prefrontal cortex (MPFC), dorsolateral prefrontal cortex, frontal white matter, hippocampus, thalamus, and basal ganglia from a total of 4445 patient and 3944 control observations.

RESULTS

Patients with schizophrenia had reduced NAA in five of the six brain regions, with a statistically significant sparing of the basal ganglia. Patients had elevated choline in the basal ganglia and both prefrontal cortical regions. Patient creatine levels were normal in all six regions. In some regions, the NAA and choline differences were greater in studies enrolling predominantly medicated patients compared to studies enrolling predominantly unmedicated patients. Patient NAA levels were more reduced in hippocampus and frontal white matter in studies using longer echo times than those using shorter echo times. MPFC choline and NAA abnormalities were greater in studies reporting better metabolite measurement quality.

CONCLUSIONS

Choline is elevated in the basal ganglia and prefrontal cortical regions, suggesting regionally increased membrane turnover or glial activation in schizophrenia. The basal ganglia are significantly spared from the well-established widespread reduction of NAA in schizophrenia suggesting a regional difference in disease-associated factors affecting NAA. The echo time findings agree with prior reports and suggest microstructural changes cause faster NAA T2 relaxation in hippocampus and frontal white matter in schizophrenia. Separating the effects of medication status and illness chronicity on NAA and choline abnormalities will require further patient-level studies. Metabolite measurement quality was shown to be a critical factor in MRS studies of schizophrenia.

Alterations of neurometabolism in the dorsolateral prefrontal cortex and thalamus in transition to psychosis patients change under treatment as usual - A two years follow-up 1H/31P-MR-spectroscopy study

BACKGROUND

The ultra-high risk (UHR) paradigm allows early contact with patients developing acute psychosis and the study of treatment effects on the underlying pathology.

METHODS

29 patients with first acute psychosis according to CAARMS criteria (transition patients, TP) (T0) and thereof 22 patients after two-year follow-up (mean 788 d) (T1) underwent ¹H-/³¹P-MR spectroscopy of the prefrontal (DLPFC) and anterior midcingulate (aMCC) cortices and the thalamus. N-acetylaspartate (NAA), glutamate (Glu, Glx), energy (PCr, ATP) and phospholipid metabolites (PME, PDE) were compared to 27 healthy controls by ANCOVA and correlated with patients' symptom ratings (BPRS-E, SCL-90R). For longitudinal analysis, linear mixed model (LMM) and ANCOVA for repeated measures were used.

RESULTS

DLPFC: In patients, NAA and PME were decreased bilaterally and Glu on the left side at T0. Left-sided Glu and NAA (trend) and bilateral Glx increased during follow-up. Thalamus: In TP, bilateral NAA, left-sided Glu and right-sided Glx were decreased at T0; bilateral NAA and left-sided Glx increased during follow-up. aMCC: In TP, bilateral NAA, right-sided Glu, and bilateral PME and PDE were decreased, while left-sided PCr was increased at T0. No changes were observed during follow-up.

CONCLUSION

Regardless of the long-term diagnosis, the psychotic state of illness includes disturbed neuronal function in the DLPFC, thalamus and aMCC. Treatment-as-usual (TAU), including antipsychotic/antidepressant medication and supportive psychotherapy, had an effect on the thalamo-frontal area but not or less pronounced on the neurometabolic deficits of the aMCC.

Influence of muscarinic M1 receptor antagonism on brain choline levels and functional connectivity in medication-free subjects with psychosis: A placebo controlled, cross-over study

An increasing number of studies implicate the muscarinic cholinergic system in cognitive dysfunction associated with psychosis. This study examined the effect of muscarinic M₁ receptor modulation on anterior cingulate cortex (ACC) and striatal choline concentrations and the relation with cognitive performance, as well as functional connectivity of cognitive networks. Thirty medication-free subjects with a psychosis spectrum disorder and 30 gender, age and IQ-matched healthy control subjects underwent ¹H-proton magnetic resonance spectroscopy (¹H-MRS) twice, once after placebo and once after a single dose of biperiden (M₁ receptor antagonist, 4 mg). A subset of 19 psychotic subjects and 28 controls underwent resting-state functional magnetic resonance imaging (rs-fMRI) as well. No significant differences were found in ACC and striatal choline levels, nor in functional connectivity, between the two groups after placebo. Moreover, M₁ antagonism did not significantly affect choline levels or functional connectivity. No correlations were found between choline levels and cognition as well as psychotic symptoms. Our findings do not support an association between the cholinergic system and cognition and psychotic symptoms. However, the lack of group differences in choline concentrations and functional connectivity, both after biperiden and placebo, may indicate that there were no severe cholinergic abnormalities present in our sample.

Relationships between dorsolateral prefrontal cortex metabolic change and cognitive impairment in first-episode neuroleptic-naive schizophrenia patients

The present study aimed to explore the possible associations between the dorsolateral prefrontal cortex (DLPFC) metabolites and the cognitive function in first-episode schizophrenia (FES).This study included 58 patients with FES (29 males and 29 females; mean age, 22.66 ± 7.64 years) recruited from the First Affiliated Hospital, College of Medicine, Zhejiang University, and 43 locally recruited healthy controls (16 males and 27 females; mean age, 23.07 ± 7.49 years). The single-voxel proton magnetic resonance spectroscopy was used to measure the levels of N-acetylaspartate (NAA); complex of glutamate, glutamine, and γ-aminobutyric acid (Glx); choline-containing compounds; and myo-inositol in the DLPFC. The ratios of metabolites to creatine (Cr) were calculated. The cognitive function was assessed by Measurement and Treatment Research to Improve Cognition in Schizophrenia Consensus Cognitive Battery (MCCB). Correlation analysis was used to assess the relationships between the DLPFC metabolites and the cognitive function.Compared with the healthy controls, the patients with FES showed significantly reduced scores in each part of the MCCB, significantly reduced NAA/Cr, and significantly increased Glx/Cr in the left DLPFC. Poor performance in verbal learning and visual learning was correlated to the reduced NAA/Cr ratio in the left DLPFC.These findings suggest that a lower NAA/Cr ratio in the left DLPFC is associated with the cognitive deficits in patients with FES, and may be an early biochemical marker for the cognitive impairment in schizophrenia.

A review of altered biochemistry in the anterior cingulate cortex of first-episode psychosis

Relevant biochemicals of the brain can be quantified in vivo, non-invasively, using proton Magnetic Resonance Spectroscopy (¹H MRS). This includes metabolites associated with neural general functioning, energetics, membrane phospholipid metabolism and neurotransmission. Moreover, there is substantial evidence of implication of the frontal and prefrontal areas in the pathogenesis of psychotic disorders such as schizophrenia. In particular, the anterior cingulate cortex (ACC) plays an important role in cognitive control of emotional and non-emotional processes. Thus the study of its extent of biochemistry dysfunction in the early stages of psychosis is of particular interest in gaining a greater understanding of its aetiology. In this review, we selected ¹H MRS studies focused on the ACC of first-episode psychosis (FEP). Four studies reported increased glutamatergic levels in FEP, while other four showed preserved concentrations. Moreover, findings on FEP do not fully mirror those in chronic patients. Due to conflicting findings, larger longitudinal ¹H MRS studies are expected to further explore glutamatergic neurotransmission in ACC of FEP in order to have a better understanding of the glutamatergic mechanisms underlying psychosis, possibly using ultra high field MR scanners.

[Role of astrocytes in alterations of glutamatergic neurotransmission in schizophrenia]

The glutamatergic hypothesis of schizophrenia based on the hypofunction of the N-methyl-D-aspartate-type glutamate receptors (NMDA-R) is one of the most widely implicated hypothesis that explains the origin of positive and negative symptoms of illness as well as cognitive deficits. The author considered a neuromorphological aspect of this hypothesis related to the glial astrocytes function. The literature on the astrocyte ability to regulate glutamate neurotransmission is reviewed. Astrocyte abnormalities in schizophrenia include the disturbances of glutamate reuptake, recycling and turnover of endogenous NMDA-R ligands. The results of the experimental and clinical studies that target levels of endogenous NMDA-R ligands, their enzymes and transporters for treatment of schizophrenia symptoms are discussed. Further studies studies are needed to develop this strategy.

[The search of the "intact" structural and functional brain systems as a paradigm shift in schizophrenia research]

OBJECTIVE

The search of the structural and functional brain characteristics is one of the most studied directions in the modern biological psychiatry. However, in spite of the numerous studies the results are still controversial. As the necessity of the shift of the current paradigm in schizophrenia research evolves it has been suggested to discriminate not only abnormal but stable functioning neuronal circuits as well. Consequently, the aim is formulated as the search of the minimal brain damage sufficient for disease development.

MATERIAL AND METHODS

Author analyzed the auditory oddball P300 latency (as a marker of information processing speed), N-acetylaspartate level in the dorsolateral prefrontal cortex (as a marker of neuronal integrity in this brain area) and fractional anisotropy of the fasciculus uncindtus which connects the frontal and temporal lobes (as a marker of white matter bundles microstructure) in 30 patients with schizophrenia and 27 healthy people.

RESULTS AND CONCLUSION

The findings showed that all the tested characteristics are not "obligatory" for schizophrenia.

[Reactivity of perineuronal astrocytes in the prefrontal cortex in schizophrenia: an ultrastructural morphometric study]

OBJECTIVE

Previously the ultrastructural alterations of astrocytes have been reported in schizophrenia. Reduced dendritic arborization of the neurons in layer 5 of the prefrontal cortex has been found in schizophrenia. Authors hypothesized that the abnormalities in perineuronal astrocytes (PA) might contribute to these neuronal changes. It was aimed to study the ultrastructure of PA in the prefrontal cortex in schizophrenia.

MATERIAL AND METHODS

Postmortem electron microscopic morphometric study of PA was performed in layer 5, area 10 of the prefrontal cortex in 39 cases of schizophrenia and 37 controls.

RESULTS

No significant group differences were found in areas of cell, nucleus, cytoplasm, volume fraction (Vv) of lipofuscin granules and areal density of PA. However, in the subgroup of women with schizophrenia, the areal density of PA was significantly lower and the area of PA was significantly higher as compared to the subgroup of healthy women (-52%, p<0,01; +32%, p<0.05 respectively) and to the subgroup of men with schizophrenia (-56%, p<0,01; +23%, p<0,05 respectively). The area of PA nucleus was negatively correlated with the duration of disease (r= -0.37, p=0.02) and positively with the age of disease onset (ADO) (r=0,47, p<0,01). Areas of PA and of PA nucleus were significantly lower in early ADO (<21 y.o.) as compared to the adult ADO (>21 y.o.) (-24%, p<0.05). Vv of lypofuscin granules was correlated with the age in control group (r=0.52, p=0.001), but not in schizophrenia group (r=0.13, p=0.4).

CONCLUSION

Significant differences in PA reactivity in the prefrontal cortex in the schizophrenia are associated with gender and age at onset of the disease.

T2 relaxation effects on apparent N-acetylaspartate concentration in proton magnetic resonance studies of schizophrenia

Over the past two decades, many magnetic resonance spectroscopy (MRS) studies reported lower N-acetylaspartate (NAA) in key brain regions of patients with schizophrenia (SZ) compared to healthy subjects. A smaller number of studies report no difference in NAA. Many sources of variance may contribute to these discordant results including heterogeneity of the SZ subject populations and methodological differences such as MRS acquisition parameters, and post-acquisition analytic methods. The current study reviewed proton MRS literature reporting measurements of NAA in SZ with a focus on methodology. Studies which reported lower NAA were significantly more likely to have used longer echo times (TEs), while studies with shorter TEs reported no concentration difference. This suggests that NAA quantitation using MRS was affected by the choice of TE, and that published MRS literature reporting NAA in SZ using a long TE is confounded by apparent differential T2 relaxation effects between SZ and healthy control groups. Future MRS studies should measure T2 relaxation times. This would allow for spectral concentration measurements to be appropriately corrected for these relaxation effects. In addition, as metabolite concentration and T2 relaxation times are completely independent variables, this could offer distinct information about the metabolite of interest.

Metabolomic imaging of prostate cancer with magnetic resonance spectroscopy and mass spectrometry

Metabolomic imaging of prostate cancer (PCa) aims to improve in vivo imaging capability so that PCa tumors can be localized noninvasively to guide biopsy and evaluated for aggressiveness prior to prostatectomy, as well as to assess and monitor PCa growth in patients with asymptomatic PCa newly diagnosed by biopsy. Metabolomics studies global variations of metabolites with which malignancy conditions can be evaluated by profiling the entire measurable metabolome, instead of focusing only on certain metabolites or isolated metabolic pathways. At present, PCa metabolomics is mainly studied by magnetic resonance spectroscopy (MRS) and mass spectrometry (MS). With MRS imaging, the anatomic image, obtained from magnetic resonance imaging, is mapped with values of disease condition-specific metabolomic profiles calculated from MRS of each location. For example, imaging of removed whole prostates has demonstrated the ability of metabolomic profiles to differentiate cancerous foci from histologically benign regions. Additionally, MS metabolomic imaging of prostate biopsies has uncovered metabolomic expression patterns that could discriminate between PCa and benign tissue. Metabolomic imaging offers the potential to identify cancer lesions to guide prostate biopsy and evaluate PCa aggressiveness noninvasively in vivo, or ex vivo to increase the power of pathology analysis. Potentially, this imaging ability could be applied not only to PCa, but also to different tissues and organs to evaluate other human malignancies and metabolic diseases.

N-Acetyl-Aspartate Level is Decreased in the Prefrontal Cortex in Subjects At-Risk for Schizophrenia

Reduced N-acetyl-aspartate (NAA) levels have been reported in the prefrontal cortex (PFC) in patients with schizophrenia using proton magnetic resonance spectroscopy. However, it is unclear whether this NAA reduction predates the illness onset and is reported in subjects at-risk for developing schizophrenia (HRS). The aim of this study was to assess NAA levels in the PFC in HRS. We hypothesized that HRS display lower NAA levels than healthy controls in the PFC. Studies assessing levels of NAA/Creatine (NAA/Cr) in the PFC in HRS were extracted from literature. Meta-analysis tools were used to compute effect sizes of nine selected studies meeting our inclusion criteria (clinical and/or genetic HRS, groups of HRS, and healthy controls matched for age and gender, spectral acquisition in the PFC). We reported that HRS exhibited a significant lower NAA/Cr level (2.15 ± 0.29; n = 208) than healthy controls (2.21 ± 0.32; n = 234) in the PFC with a medium pooled effect size [Hedges's g = -0.42; 95% confidence interval: (-0.61; -0.23); p < 0.0001] corresponding to an average 5.7% of NAA/Cr decrease. Secondary analysis revealed that this reduction was observed in young HRS (<40 years old) who have not reached the peak age of risk for schizophrenia (-11%, g = -0.82, p < 0.00001) but not in old HRS (>40 years old) who have already passed the peak age (g = 0.11, p = 0.56), when they are compared with their matched healthy controls. Our findings suggest that the NAA/Cr reduction in the PFC reported in patients with schizophrenia is observable only in HRS who have not passed the peak age of risk for schizophrenia. NAA/Cr level in the PFC could therefore be considered as a biological vulnerability marker of schizophrenia.

Proton magnetic resonance spectroscopy in pediatric obsessive-compulsive disorder: longitudinal study before and after treatment

Abnormalities in neurochemical compounds in obsessive-compulsive disorder (OCD) may help increase our knowledge of neurobiological abnormalities in the fronto-subcortical circuits. The aims of this exploratory study were to identify with in vivo magnetic resonance spectroscopy ((1)H-MRS) the possible alterations in neurometabolites in a group of drug naïve children and adolescents with OCD in comparison with a control group and to determine whether there was any effect of treatment on the metabolite levels. Eleven OCD children and adolescents (age range 9-17 years; 6 male, 5 female) and twelve healthy subjects with similar age, sex and estimated intellectual quotient were studied. Proton magnetic resonance spectroscopy at 1.5 T was used. We placed 3 voxels, one bilaterally located involving anterior cingulate-medial frontal regions, and one in each striatal region involving the caudate and putaminal regions. Concentrations of creatine (Cr), myo-inositol (mI), total Cho (glycerophosphocholine+phosphocholine), total NAA (N-acetyl aspartate+N-acetyl aspartylglutamate), and total Glx (glutamate+glutamine) were calculated. We found significantly lower concentrations of total Cho in left striatum in OCD patients compared with healthy subjects. The difference in Cho concentrations in left striatum between the two groups did not change over time and persisted at follow-up assessment. Like the control subjects, OCD patients undergoing pharmacological treatment and clinical recovery showed no significant changes in neurometabolic activity between the first and second evaluations.

Proton magnetic resonance spectroscopy and thought disorder in childhood schizophrenia

OBJECTIVE

Although magnetic resonance spectroscopy has identified metabolic abnormalities in adult and childhood schizophrenia, no prior studies have investigated the relationship between neurometabolites and thought disorder. This study examined this association in language-related brain regions using proton magnetic resonance spectroscopic imaging ((1)H MRSI).

METHOD

MRSI was acquired bilaterally from 28 youth with childhood-onset schizophrenia and 34 healthy control subjects in inferior frontal, middle frontal, and superior temporal gyri at 1.5T and short echo time (TR/TE = 1500/30 ms). CSF-corrected "total NAA" (tNAA; N-acetyl-aspartate + N-acetyl-aspartyl-glutamate), glutamate + glutamine (Glx), creatine + phosphocreatine (Cr + PCr), choline compounds (Cho), and myo-inositol (mI) were assayed in manually drawn regions-of-interest partitioned into gray matter, white matter, and CSF and then coregistered with MRSI. Speech samples of all subjects were coded for thought disorder.

RESULTS

In the schizophrenia group, the severity of formal thought disorder correlated significantly with tNAA in the left inferior frontal and superior temporal gyri and with Cr + PCr in left superior temporal gyrus.

CONCLUSIONS

Neurometabolite concentrations in language-related brain regions are associated with thought disorder in childhood-onset schizophrenia.

Proton magnetic resonance spectroscopy and illness stage in schizophrenia--a systematic review and meta-analysis

BACKGROUND

It is not known whether regional brain N-acetyl aspartate (NAA) changes in the progression from prodrome to chronic schizophrenia. We used effect size meta-analysis to determine which brain regions show the most robust reductions in NAA first episode and chronic schizophrenia as measured by proton magnetic resonance spectroscopy and to determine whether these changes are present in individuals at high risk of developing schizophrenia.

METHODS

We identified 131 articles, of which 97 met inclusion criteria. Data were separated by stage of illness (at risk, first episode schizophrenia, chronic schizophrenia) and by brain region. For each region, mean and SD of the NAA measure was extracted.

RESULTS

Significant reductions in NAA levels were found in frontal lobe, temporal lobe, and thalamus in both patient groups (effect size > .3; p < .01). In individuals at high risk of schizophrenia (of whom approximately 20% would be expected to undergo transition to psychosis), significant NAA reductions were present in thalamus (effect size = .78; p < .05), with reductions at trend level only in temporal lobe (effect size = .32; p < .1), and no reductions in frontal lobe (effect size = .05; p = .5).

CONCLUSIONS

These data suggest that schizophrenia is associated with loss of neuronal integrity in frontal and temporal cortices and in the thalamus and suggest that these changes in the frontal and temporal lobe might occur in the transition between the at-risk phase and the first episode.

From bench to bedside: translating new research from genetics and neuroimaging into treatment development for early-onset schizophrenia

OBJECTIVE

Children and adolescents with schizophrenia share a similar pattern of phenomenological, genetic and cognitive abnormalities to adults with schizophrenia. However, an early-onset of schizophrenia (EOS) (prior to 18 years of age) is associated with a higher frequency of risk indicators associated with schizophrenia (e.g. developmental delays and familial spectrum disorders) and a worse long-term outcome. This overview examines recent research on the neurobiological alterations, possible causes, developmental trajectory and treatment of EOS and attempts to identify gaps in the field.

METHOD

The authors provide a selective review of major findings from genetics, neuroimaging and treatment studies of pediatric schizophrenia that were presented at a workshop sponsored by the National Institute of Mental Health. These data are synthesized in conjunction with preclinical studies into a model of the pathophysiology of EOS.

RESULTS

EOS is associated with a high frequency of cytogenetic abnormalities (e.g. velocardiofacial syndrome, sex chromosome anomalies) and other rare denovo chromosomal aberrations. Brain imaging research in adolescents with EOS has revealed a progressive loss of cortical grey matter post-onset of psychosis and subtle abnormalities in white matter microstructure. Although EOS patients are more likely to be treatment-refractory than their adult counterparts, there are substantial data that this subgroup is particularly responsive to clozapine.

CONCLUSIONS

Genetic or environmental factors operating during adolescence that reduce frontal capacity might contribute to an EOS in susceptible individuals. Additional longitudinal studies of adolescents with schizophrenia are needed to better understand the relationship between structural changes in fronto-limbic regions, stress responsivity, and cognitive and neurochemical development.

Proton MR spectroscopy correlates of frontal lobe function in healthy children

BACKGROUND AND PURPOSE

Neuroimaging methods have been used to improve our understanding of the topographic organization of the brain. In our study, proton (1)H-MR spectroscopic imaging was used to evaluate frontal lobe function. The goal was to determine the relationship between neuropsychological measures of frontal lobe function and levels of a surrogate neuronal marker, N-acetylaspartate (NAA), in typically developing healthy children and adolescents.

MATERIALS AND METHODS

Fifty-one healthy children (25 girls; 6.2-18.3 years of age; mean age, 12.3 +/- 3.6 years) were examined. All children completed a neuropsychological assessment including measures of attention, executive function, memory, language, and visual and motor skills. (1)H-MR spectroscopic imaging was performed by using a multisection spin-echo sequence at 1.5T. General linear model analysis of covariance was used to examine the relationship between the neuropsychological test scores and NAA/creatine (Cr) ratios, controlling for age and sex.

RESULTS

A positive relationship between frontal lobe white matter NAA/Cr ratio and performance on 2 neuropsychological tests associated with frontal lobe function was detected. The Purdue Pegboard right-hand scores were higher with increasing NAA/Cr in the left frontal white matter (P = .047), and Stanford-Binet-IV "Bead Memory" scores improved with increasing NAA/Cr ratio in the right frontal white matter (P = .032).

CONCLUSIONS

An association between frontal white matter NAA/Cr ratios and 1) measures of manual speed and dexterity, and 2) visual working memory was detected. Our data may provide a quantitative basis for assessment of frontal lobe impairments in disease states.

Echopraxia in schizophrenia: possible mechanisms

The aim of the current study was to present a possible mechanism underpinning echopraxia in schizophrenia. It is proposed that echopraxia occurs in schizophrenia when the mirror neuron system provides a representation to the inferior frontal gyrus (IFG) and the motor cortex (and via the IFG, to the anterior cingulate cortex) and that this potential becomes executed movement, when the disorder is associated with decreased inhibition and increased arousal.