Increased medial thalamic choline in pediatric obsessive-compulsive disorder as detected by quantitative in vivo spectroscopic imaging

Magnetic Resonance Spectroscopy (MRS) and Positron Emission Tomography (PET) Imaging in Obsessive-Compulsive Disorder

Obsessive-compulsive disorder (OCD) is characterised by structural and functional deficits in the cortico-striato-thalamic-cortical (CSTC) circuitry and abnormal neurochemical changes are thought to modulate these deficits. The hypothesis that an imbalanced concentration of the brain neurotransmitters, in particular glutamate (Glu) and gamma-amino-butyric acid (GABA), could impair the normal functioning of the CSTC, thus leading to OCD symptoms, has been tested in humans using magnetic resonance spectroscopy (MRS) and positron emission tomography (PET). This chapter summarises these neurochemical findings and represents an attempt to condense such scattered literature. We also discuss potential challenges in the field that may explain the inconsistent findings and suggest ways to overcome them. There is some convergent research from MRS pointing towards abnormalities in the brain concentration of neurometabolite markers of neuronal integrity, such as N-acetylaspartate (NAA) and choline (Cho). Lower NAA levels have been found in dorsal and rostral ACC of OCD patients (as compared to healthy volunteers), which increase after CBT and SSRI treatment, and higher Cho concentration has been reported in the thalamus of the OCD brain. However, findings for other neurometabolites are very inconsistent. Studies have reported abnormalities in the concentrations of creatine (Cr), GABA, glutamate (Glu), glutamine (Gln), Ins (myo-inositol), and serotonin (5-HT), but most of the results were not replicated. The question remains whether the NAA and Cho findings are genuinely the only neurochemical abnormalities in OCD or whether the lack of consistent findings for the other neurometabolites is caused by the lower magnetic field (1-3 Tesla (T)) used by the studies conducted so far, their small sample sizes or a lack of proper control for medication effects. To answer these questions and to further inform the biological underpinning of the symptoms and the cognitive problems at the basis of OCD we need better controlled studies using clear medicated vs unmedicated groups, larger sample sizes, stronger magnetic fields (e.g. at 7 T), and more consistency in the definition of the regions of interest.

Brain neurochemistry in unmedicated obsessive-compulsive disorder patients and effects of 12-week escitalopram treatment: 1 H-magnetic resonance spectroscopy study

AIM

The purpose of this study was to examine treatment-related neurochemical changes in 28 unmedicated obsessive-compulsive disorder (OCD) patients using ¹ H-magnetic resonance spectroscopy (¹ H-MRS).

METHODS

We included subjects diagnosed with OCD (n = 28), each with a total duration of illness of less than 5 years, as a study group and age- and sex-matched healthy controls (n = 26). The inclusion criteria for the OCD group were right-handed individuals aged 18 years or older who had not been on any specific treatment for OCD for the last at least 8 weeks and who had no other psychiatric comorbidity. A pre-post and case-control design was employed in which OCD patients underwent ¹ H-MRS at baseline and 12 weeks after treatment with escitalopram (n = 21). Clinical assessment was carried out using a semi-structured pro forma Yale-Brown Obsessive Compulsive Scale and the World Health Organization Disability Assessment Scale 2.0 before and after treatment. Volume-localized ¹ H-MRS was carried out with a 3-Tesla Philips MR scanner.

RESULTS

Our data suggested higher levels of myoinositol (mI), total choline (tCho), and glutamate+glutamine (Glx) in the medial thalamus at pre-assessment in OCD subjects as compared to healthy controls and a significant reduction in tCho and Glx after treatment in OCD subjects. The mI levels in the caudate nucleus and Glx levels in the anterior cingulate cortex were significantly correlated with disease severity on the Yale-Brown Obsessive Compulsive Scale.

CONCLUSION

Our study supports the hypothesis of a hyper-glutaminergic state (as suggested by increased Glx levels) and neurodegeneration (as suggested by increased tCho and mI in the thalamus) in cortico-striato-thalamocortical circuitry in OCD patients as suggested by previous studies using MRS as well as other functional imaging studies.

Anterior thalamic radiation structural and metabolic changes in obsessive-compulsive disorder: A combined DTI-MRS study

Numerous studies indicate the cortico-striato-thalamo-cortical (CSTC) circuit plays an important role in the pathophysiology of obsessive-compulsive disorder (OCD). The anterior thalamic radiation (ATR), as a major fiber in the fronto-thalamic circuitry, contributes to symptomology of OCD. However, the underlying biochemical mechanism in relation with its structural alteration remains not understood. This study investigated the structural abnormality of ATR and its correlation with thalamic metabolic alteration in OCD, using diffusion tensor image (DTI) and proton magnetic resonance spectroscopy (¹H-MRS). Twenty-six unmedicated adult OCD patients and twenty-six matched healthy controls participated in DTI study. Thirteen OCD patients and thirteen healthy controls, a subset of DTI participants, took part in MRS study. The results showed that mean fiber length of right ATR negatively correlated with ipsilateral thalamic choline (Cho) level in OCD patients. Additionally, significantly higher Cho concentration was detected in right thalamus of OCD patients compared to healthy controls. Moreover, the mean fractional anisotropy (FA) value of right ATR positively correlated with patients Yale-Brown Obsessive Compulsive Scale (YBOCS) total score, as well as YBOCS compulsion score. These results suggested the coupling of structural and metabolic changes in right ATR, which might serve as a multi-modal biomarker contributing to the pathogenesis of OCD.

Abnormalities in metabolite concentrations in tourette's disorder and obsessive-compulsive disorder-A proton magnetic resonance spectroscopy study

INTRODUCTION

Abnormal glutamatergic transmission in cortico-striato-thalamo-cortical (CSTC) circuits is thought to be involved in the pathophysiology of Tourette's disorder (TD) and obsessive-compulsive disorder (OCD). Using proton magnetic resonance spectroscopy, the current study aimed to investigate regional concentrations of glutamatergic compounds in TD and OCD patients in comparison to healthy control subjects (HC).

MATERIAL AND METHODS

Twenty-three TD patients, 20 OCD patients and 22 HC were included. Short echo-time single-voxel 3T MRS was obtained from dorsal anterior cingulate cortex (dACC) and midline bilateral thalamus.

RESULTS

The 3-group comparison showed a significant difference in choline concentration in the thalamus. Thalamic choline was highest in OCD patients, showing a significant difference with TD, and a trend compared to HC (post-hoc analyses). Glutamine in dACC correlated negatively with tic severity scores in TD patients, while glutamate in thalamus correlated positively with anxiety severity scores in OCD patients.

CONCLUSIONS

These findings suggest subtle differences in metabolites in CSTC areas between TD and OCD. Alterations of choline concentrations seem to be both regional (only in thalamus, not in dACC) and disease specific in OCD pathology. The findings need replication in larger groups, but encourage further research into glutamatergic metabolites in TD and OCD.

Cingulate and thalamic metabolites in obsessive-compulsive disorder

Focal brain metabolic effects detected by proton magnetic resonance spectroscopy (MRS) in obsessive-compulsive disorder (OCD) represent prospective indices of clinical status and guides to treatment design. Sampling bilateral pregenual anterior cingulate cortex (pACC), anterior middle cingulate cortex (aMCC), and thalamus in 40 adult patients and 16 healthy controls, we examined relationships of the neurometabolites glutamate+glutamine (Glx), creatine+phosphocreatine (Cr), and choline-compounds (Cho) with OCD diagnosis and multiple symptom types. The latter included OC core symptoms (Yale-Brown Obsessive-Compulsive Scale - YBOCS), depressive symptoms (Montgomery-Åsberg Depression Rating Scale - MADRS), and general functioning (Global Assessment Scale - GAS). pACC Glx was 9.7% higher in patients than controls. Within patients, Cr and Cho correlated negatively with YBOCS and MADRS, while Cr correlated positively with the GAS. In aMCC, Cr and Cho correlated negatively with MADRS, while Cr in thalamus correlated positively with GAS. These findings present moderate support for glutamatergic and cingulocentric perspectives on OCD. Based on our prior metabolic model of OCD, we offer one possible interpretation of these group and correlational effects as consequences of a corticothalamic state of elevated glutamatergic receptor activity alongside below-normal glutamatergic transporter activity.

Association between genetic variants of serotonergic and glutamatergic pathways and the concentration of neurometabolites of the anterior cingulate cortex in paediatric patients with obsessive-compulsive disorder

OBJECTIVES

The present study aimed to assess the relationship between variability in genes related to the pathophysiology of obsessive-compulsive disorder (OCD) and the concentration of different neurometabolites in the anterior cingulate cortex (ACC).

METHODS

We concomitantly assessed neurometabolite concentrations using 3-T (1)H-MRS and 262 single nucleotide polymorphism (SNPs) in 35 genes in 41 paediatric OCD patients.

RESULTS

There were significant associations, after Bonferroni correction, between the concentration of inositol, glutamate and glutamine, and total choline and five polymorphisms located in genes related to serotonin and glutamate (i.e., the vesicular monoamine transporter 1 gene, SLC18A1 [rs6586896]; the serotonin receptor 1B gene, HTR1B [rs6296 and rs6298]; and the glutamate receptor, ionotropic, AMPA1 gene, GRIA1 [rs707176 and rs2963944]).

CONCLUSIONS

The association observed between these polymorphisms and the neurometabolite concentrations could indicate the presence of a biological interaction between the serotonin and the glutamate pathways that could be involved in the pathophysiology of OCD. More studies with this methodology could increase our understanding of the aetiology and pathophysiology of OCD in children.

Decreased thalamic glutamate level in unmedicated adult obsessive-compulsive disorder patients detected by proton magnetic resonance spectroscopy

BACKGROUND

Previous neuroimaging studies implied that the dysfunction of cortico-striato-thalamo-cortical (CSTC) circuit served as the neural basis for the pathophysiology of obsessive-compulsive disorder (OCD). The imbalances in neuronal metabolite and neurotransmitter within CSTC circuit have been shown as the leading reasons of the OCD onset. The aim of this study is to investigate the metabolic alterations, especially the glutamatergic signal dysfunction within CSTC circuit, and the relationships between neural metabolites and the symptom severity of OCD patients.

METHODS

Single voxel magnetic resonance spectroscopy (MRS) was conducted in medial prefrontal cortex (mPFC) and bilateral thalamus areas for thirteen unmedicated adult OCD patients with age-, gender-, and education-matched healthy controls. Quantification and multivariate analysis were performed to identify vital metabolic biomarkers for patients and healthy controls group differentiation. Moreover, we performed Spearman׳s rank correlation analysis for OCD patients to examine the relationship between the metabolite concentration level and OCD symptomatology.

RESULTS

Patients with OCD showed significantly decreased glutamate level in mPFC (p=0.021) and right thalamus (p=0.039), and significantly increased choline compounds in left thalamus (p=0.044).The glutamate in right thalamus was shown as the most important metabolite for group separation from multivariate analysis (Q(2)=0.134) and was significantly correlated with the patients׳ compulsion scores (Spearman r=-0.674, p=0.016).

LIMITATIONS

Limited sample size, the use of creatine and phosphocreatine (Cr) ratios rather than absolute concentrations and unresolved glutamine (Gln) are limitations of the present study.

CONCLUSION

Our study results consolidated the hypothesis about glutamatergic signaling dysfunction in OCD. To our knowledge, it is the first finding about a reduced thalamic glutamate level in adult unmedicated OCD patients. The dysregulation of glutamate serves as a potential target for the OCD pharmacotherapy and the detailed mechanisms underlying the glutamate alterations within CSTC circuits merit further investigations.

Effects of intensive cognitive-behavioral therapy on cingulate neurochemistry in obsessive-compulsive disorder

The neurophysiological bases of cognitive-behavioral therapy (CBT) for obsessive-compulsive disorder (OCD) are incompletely understood. Previous studies, though sparse, implicate metabolic changes in pregenual anterior cingulate cortex (pACC) and anterior middle cingulate cortex (aMCC) as neural correlates of response to CBT. The goal of this pilot study was to determine the relationship between levels of the neurochemically interlinked metabolites glutamate + glutamine (Glx) and N-acetyl-aspartate + N-acetyl-aspartyl-glutamate (tNAA) in pACC and aMCC to pretreatment OCD diagnostic status and OCD response to CBT. Proton magnetic resonance spectroscopic imaging ((1)H MRSI) was acquired from pACC and aMCC in 10 OCD patients at baseline, 8 of whom had a repeat scan after 4 weeks of intensive CBT. pACC was also scanned (baseline only) in 8 age-matched healthy controls. OCD symptoms improved markedly in 8/8 patients after CBT. In right pACC, tNAA was significantly lower in OCD patients than controls at baseline and then increased significantly after CBT. Baseline tNAA also correlated with post-CBT change in OCD symptom severity. In left aMCC, Glx decreased significantly after intensive CBT. These findings add to evidence implicating the pACC and aMCC as loci of the metabolic effects of CBT in OCD, particularly effects on glutamatergic and N-acetyl compounds. Moreover, these metabolic responses occurred after just 4 weeks of intensive CBT, compared to 3 months for standard weekly CBT. Baseline levels of tNAA in the pACC may be associated with response to CBT for OCD. Lateralization of metabolite effects of CBT, previously observed in subcortical nuclei and white matter, may also occur in cingulate cortex. Tentative mechanisms for these effects are discussed. Comorbid depressive symptoms in OCD patients may have contributed to metabolite effects, although baseline and post-CBT change in depression ratings varied with choline-compounds and myo-inositol rather than Glx or tNAA.

A critical review of magnetic resonance spectroscopy studies of obsessive-compulsive disorder

Functional neuroimaging studies have converged to suggest that cortico-striatal-thalamo-cortical (CSTC) circuit dysfunction is a core pathophysiologic feature of obsessive-compulsive disorder (OCD). Now, complementary approaches examining regional neurochemistry are beginning to yield additional insights with regard to the neurobiology of aberrant CSTC circuitry in OCD. In particular, proton magnetic resonance spectroscopy, which allows for the in vivo quantification of various neurochemicals in the CSTC circuit and other brain regions, has recently been used extensively in studies of OCD patients. In this review, we summarize the diverse and often seemingly inconsistent findings of these studies, consider methodological factors that might help to explain these inconsistencies, and discuss several convergent findings that tentatively seem to be emerging. We conclude with suggestions for possible future proton magnetic resonance spectroscopy studies in OCD.

Reduction of N-acetylaspartate in the medial prefrontal cortex correlated with symptom severity in obsessive-compulsive disorder: meta-analyses of (1)H-MRS studies

Structural and functional neuroimaging findings suggest that disturbance of the cortico-striato-thalamo-cortical (CSTC) circuits may underlie obsessive-compulsive disorder (OCD). However, some studies with (1)H-magnetic resonance spectroscopy ((1)H-MRS) reported altered level of N-acetylaspartate (NAA), they yielded inconsistency in direction and location of abnormality within CSTC circuits. We conducted a comprehensive literature search and a meta-analysis of (1)H-MRS studies in OCD. Seventeen met the inclusion criteria for a meta-analysis. Data were separated by frontal cortex region: medial prefrontal cortex (mPFC), dorsolateral prefrontal cortex, orbitofrontal cortex, basal ganglia and thalamus. The mean and s.d. of the NAA measure were calculated for each region. A random effects model integrating 16 separate datasets with 225 OCD patients and 233 healthy comparison subjects demonstrated that OCD patients exhibit decreased NAA levels in the frontal cortex (P=0.025), but no significant changes in the basal ganglia (P=0.770) or thalamus (P=0.466). Sensitivity analysis in an anatomically specified subgroup consisting of datasets examining the mPFC demonstrated marginally significant reduction of NAA (P=0.061). Meta-regression revealed that NAA reduction in the mPFC was positively correlated with symptom severity measured by Yale-Brown Obsessive Compulsive Scale (P=0.011). The specific reduction of NAA in the mPFC and significant relationship between neurochemical alteration in the mPFC and symptom severity indicate that the mPFC is one of the brain regions that directly related to abnormal behavior in the pathophysiology of OCD. The current meta-analysis indicates that cortices and sub-cortices contribute in different ways to the etiology of OCD.

The effect of behavior therapy on caudate N-acetyl-l-aspartic acid in adults with obsessive-compulsive disorder

Previous studies suggest that baseline differences in neuronal markers between patients with obsessive-compulsive disorder (OCD) and healthy controls no longer exist following successful pharmacotherapy. The current study used proton magnetic resonance spectroscopy (MRS) to investigate differences in absolute concentrations of neurochemicals (i.e., N-acetyl-l-aspartic; NAA) in the head of the caudate nucleus (HOC) and orbital frontal white matter (OFWM) between 15 adults with OCD and a sex- and age-matched control group, as well as the effects of behavior therapy on these chemicals. Behavior therapy was associated with a significant increase in left HOC NAA. When the analyses were restricted to only pairings with complete data (OCD patient, control, post-treatment), the levels of left HOC NAA were significantly lower in patients compared to controls, and increased significantly with treatment. Exploratory analyses suggested that levels of NAA and Cr (creatine) in the right OFWM may be significantly lower in the OCD group than the control group. The results raise the possibility that successful behavioral treatment may be associated with increases in markers of neuronal viability, although other associations found in the literature were not replicated.

MRSI correlates of cognitive-behavioral therapy in pediatric obsessive-compulsive disorder

BACKGROUND

The brain mechanisms of cognitive-behavioral therapy (CBT), a highly effective treatment for pediatric obsessive-compulsive disorder (OCD), are unknown. Neuroimaging in adult OCD indicates that CBT is associated with metabolic changes in striatum, thalamus, and anterior cingulate cortex. We therefore probed putative metabolic effects of CBT on these brain structures in pediatric OCD using proton magnetic resonance spectroscopic imaging (1H MRSI).

METHOD

Five unmedicated OCD patients (4 ♀, 13.5±2.8) and 9 healthy controls (7 ♀, 13.0±2.5) underwent MRSI (1.5 T, repetition-time/echo-time=1500/30 ms) of bilateral putamen, thalamus and pregenual anterior cingulate cortex (pACC). Patients were rescanned after 12 weeks of exposure-based CBT. The Children's Yale-Brown Obsessive-Compulsive Scale (CY-BOCS) of OCD symptoms was administered before and after CBT.

RESULTS

Four of 5 patients responded to CBT (mean 32.8% CY-BOCS reduction). Multiple metabolite effects emerged. Pre-CBT, N-acetyl-aspartate+N-acetyl-aspartyl-glutamate (tNAA) in left pregenual anterior cingulate cortex (pACC) was 55.5% higher in patients than controls. Post-CBT, tNAA (15.0%) and Cr (23.9%) in left pACC decreased and choline compounds (Cho) in right thalamus increased (10.6%) in all 5 patients. In left thalamus, lower pre-CBT tNAA, glutamate+glutamine (Glx), and myo-inositol (mI) predicted greater post-CBT drop in CY-BOCS (r=0.98) and CY-BOCS decrease correlated with increased Cho.

CONCLUSIONS

Interpretations are offered in terms of the Glutamatergic Hypothesis of Pediatric OCD. Similar to 18FDG-PET in adults, objectively measurable regional MRSI metabolites may indicate pediatric OCD and predict its response to CBT.

The involvement of distinct neural systems in patients with obsessive-compulsive disorder with autogenous and reactive obsessions

OBJECTIVE

To investigate the regional metabolite abnormalities and changes after treatment in patients with OCD with autogenous and reactive obsessions.

METHOD

We assessed right anterior cingulate cortex (ACC) and amygdala-hippocampal region (Am + Hpp) N-acetyl-aspartate (NAA), choline (Cho) and creatine (Cr) concentrations and NAA/Cr and Cho/Cr ratios using single-voxel proton magnetic resonance spectroscopy in 15 patients with autogenous obsessions (OCD-A), 15 patients with reactive obsessions (OCD-R) and 15 healthy controls (HC). Measurements were repeated after 16 weeks of fluoxetine treatment.

RESULTS

Baseline ACC NAA/Cr ratios of both OCD groups were significantly lower than HC. OCD-A group had significantly lower baseline NAA/Cr ratios in the Am + Hpp than other groups. These differences were more likely to be explained by higher Cr levels in ACC. We found no significant differences and changes for Cho levels and Cho/Cr ratios between groups and within groups. Significant increase in NAA/Cr ratios of OCD-A group found in the Am + Hpp was more likely to be explained by increased NAA levels. No significant changes were found in ACC NAA/Cr ratios.

CONCLUSION

While disturbed energy metabolism in ACC might reflect a common pathology in patients with OCD regardless of symptom dimension, alterations in mesiotemporal lobe are more likely for autogenous obsessions.

Nutraceuticals in the treatment of obsessive compulsive disorder (OCD): a review of mechanistic and clinical evidence

Obsessive-compulsive disorder (OCD) is a debilitating mental illness which has a significant impact on quality of life. First-line SSRI treatments for OCD typically are of limited benefit to only 40-60% of patients, and are associated with a range of adverse side effects. Current preclinical research investigating nutraceuticals (natural products) for OCD, reveals encouraging novel activity in modulating key pathways suggested to be involved in the pathogenesis of OCD (glutamatergic and serotonergic pathway dysregulation). Emerging clinical evidence also appears to tentatively support certain nutrients and plant-based interventions with known active constituents which modulate these pathways: N-acetlycysteine, myo-inositol, glycine, and milk thistle (Silybum marianum). The serotonin precursor tryptophan is unlikely to be of use in treating OCD while 5-HTP may possibly be a more effective precursor strategy. However, there is currently no clinical evidence to test the efficacy of either of these substances. Currently the balance of clinical evidence does not support the use of St. John's wort (Hypericum perforatum) in OCD. While clinical research in this area is in its infancy, further research into nutraceuticals is warranted in light of the promising preclinical data regarding their mechanisms of action and their favourable side effect profiles in comparison to current SSRI treatments. It is recommended that future clinical trials of nutraceutical treatments for OCD utilize randomized placebo-controlled study designs and considerably larger sample sizes in order to properly test for efficacy.

Brain magnetic resonance spectroscopy in obsessive-compulsive disorder: the importance of considering subclinical symptoms of anxiety and depression

Brain metabolite concentrations have recently been assessed in different cerebral regions presumably targeted in patients with obsessive-compulsive disorder (OCD) using magnetic resonance spectroscopy (MRS). However, results have been divergent. Possible confounding variables, such as the cerebral localisation of investigated regions and metabolites considered, as well as subclinical symptoms of anxiety and depression, could have affected these MRS profiles. The main goal of this study was to assess MRS metabolite differences between 13 individuals with OCD and 12 matched healthy controls in seven brain regions potentially involved in OCD. The secondary objective was to assess the relationships between levels of anxiety and depression and brain metabolite concentrations. No difference was found for N-acetylaspartate, glutamate-glutamine, myo-inositol (mI) and choline relative to creatine (Cr) concentration in either the left or right orbitofrontal area, left or right median temporal lobe, left or right thalamus or the anterior cingulate cortex. A significant negative correlation between the mI/Cr in the left orbitofrontal area and the severity of OCD symptomatology was observed while subclinical anxiety and depression were closely related to brain metabolite ratios. Thus, these subclinical symptoms, commonly associated with OCD, should be considered in assessing brain metabolite concentrations and may be central to the comprehension of this disorder.

Increased N-Acetylaspartate/creatine ratio in the medial prefrontal cortex among unmedicated obsessive-compulsive disorder patients

AIMS

Changes in the fronto-striato-thalamo-cortical-circuit loop have been suggested in the pathogenesis of obsessive-compulsive disorder (OCD), and have been studied using (1)H magnetic resonance spectroscopy ((1)H MRS) with interesting findings. However, whether neural metabolites are abnormal in the medial prefrontal cortex in patients with OCD is unknown. The purpose of the present study was to investigate neural metabolites in this brain region in a sample of patients with OCD.

METHODS

Subjects were 21 unmedicated OCD patients, including 10 who were drug-naïve, and 19 healthy controls. Single-voxel (1)H MRS was used to study the medial prefrontal cortex for each subject. Levels of N-acetylaspartate (NAA), choline-containing compounds and myoinositol were measured in terms of their ratios with creatine (Cr).

RESULTS

The NAA/Cr ratio was significantly higher among OCD patients than among healthy controls (F = 4.76, P = 0.037). However, it did not correlate with patients' symptoms or with their illness durations. The NAA/Cr ratio also did not differ between drug-naïve and previously medicated patients. No significant group differences were found between OCD patients and normal controls for the choline-containing compounds/Cr or myoinositol/Cr ratios. In addition, a significant correlation between the NAA/Cr ratio and trait anxiety scores on the State-Trait Anxiety Inventory was found among the controls (r = 0.639, P = 0.010).

CONCLUSIONS

The N-Acetylaspartate level relative to creatine in the medial prefrontal cortex was increased among unmedicated OCD patients. This cannot be attributed to the effect of medications. The possible significance of this finding in the pathophysiology of OCD is discussed.

Translational neuroimaging research in pediatric obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a significant public health problem. Selective serotonin reuptake inhibitors (SSRIs) are the only FDA-approved medications for OCD. However, SSRIs are of limited efficacy in clinical practice. Given the persistence of symptoms and levels of treatment response, it is clear that the serotonin paradigm of OCD does not fully account for the neurobiology of the disorder, and that further translational research is needed. In this review, the glutamate hypothesis of pediatric OCD is explored, the neuroimaging evidence reviewed, and the translational impact highlighted. The traditional strategy of going from pharmacology to pathophysiology has failed to show real progress in our understanding of the neurobiology of psychiatric illness and, while still in the early stages, this work demonstrates the clear benefit of approaching psychiatric illness from the opposite direction.

Neurochemistry of the hippocampus in patients with obsessive-compulsive disorder

AIM

To date, despite possible neuroanatomical importance, no magnetic resonance spectroscopy (MRS) study on hippocampus has been performed in obsessive-compulsive disorder (OCD). The purpose of the present study was therefore to compare hippocampal chemicals in patients with OCD with those in healthy subjects with no psychopathology.

METHODS

Eighteen patients meeting DSM-IV criteria for OCD and 18 healthy controls were studied. The patients and controls underwent proton magnetic resonance spectroscopy ((1)H-MRS), and measures of N-acetyl-l-aspartate (NAA), choline (CHO), and creatine (CRE) in hippocampal regions were obtained.

RESULTS

Both NAA/CRE and NAA/CHO ratios in the hippocampus in patients with OCD were reduced relative to healthy controls. The anova showed a near-significant effect of diagnosis for NAA/CRE and a significant effect for NAA/CHO, but the anova did not show any significant effect even at a trend level for CHO/CRE. No main effect of hemisphere was found for any metabolite ratio.

CONCLUSIONS

The presence of neuronal degeneration is suggested in OCD. Future longitudinal neuroimaging and neuropsychological studies with larger patient samples are warranted in order to confirm these preliminary findings to better characterize the relevance of neurochemical abnormalities in hippocampus in the pathophysiology of OCD.

The neural bases of obsessive-compulsive disorder in children and adults

Functional imaging studies have reported with remarkable consistency hyperactivity in the orbitofrontal cortex (OFC), anterior cingulate cortex (ACC), and caudate nucleus of patients with obsessive-compulsive disorder (OCD). These findings have often been interpreted as evidence that abnormalities in cortico-basal ganglia-thalamo-cortical loops involving the OFC and ACC are causally related to OCD. This interpretation remains controversial, however, because such hyperactivity may represent either a cause or a consequence of the symptoms. This article analyzes the evidence for a causal role of these loops in producing OCD in children and adults. The article first reviews the strong evidence for anatomical abnormalities in these loops in patients with OCD. These findings are not sufficient to establish causality, however, because anatomical alterations may themselves be a consequence rather than a cause of the symptoms. The article then reviews three lines of evidence that, despite their own limitations, permit stronger causal inferences: the development of OCD following brain injury, pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection, and neurosurgical lesions that attenuate OCD. Converging evidence from these various lines of research supports a causal role for the cortico-basal ganglia-thalamo-cortical loops that involve the OFC and ACC in the pathogenesis of OCD in children and adults.

Paediatric obsessive-compulsive disorder, a neurodevelopmental disorder? Evidence from neuroimaging

OBJECTIVE

To present an overview of neuroimaging data on paediatric obsessive-compulsive disorder (OCD) and discuss implications for further research.

METHOD

Medline PsycINFO databases and reference lists were searched for relevant articles. All neuroimaging studies up to October 1, 2008 involving children and adolescents with obsessive-compulsive disorder were included.

RESULTS

Twenty-eight neuroimaging studies using various neuroimaging techniques (CT (2) MRI (15) MRS (8) and SPECT (2) fMRI (2) but no PET or DTI) including a total of 462 paediatric patients were identified. A number of findings indicate a dysfunction of the prefrontal-striatal-thalamic circuit with the involvement of other basal ganglia structures (putamen globus pallidus) and the thalamus in contrast to adult studies which report mainly involvement of the caudate nucleus and orbitofrontal cortex. Several findings point at an aberrant development of the brain in paediatric OCD, patients when compared with healthy controls.

CONCLUSION

Neuroimaging studies have contributed to our understanding of the neurobiological basis of paediatric OCD. This review provides an agenda for further theory driven research in particular aimed at identifying a critical window of abnormal maturation of prefrontal-striatal-thalamic and limbic circuitry in paediatric OCD patients.

Brain imaging in pediatric obsessive-compulsive disorder

OBJECTIVE

To review progress in understanding pediatric obsessive-compulsive disorder (OCD). The focus is on the frontal-striatal-thalamic model of OCD, neurobiological and genetic studies of the disorder, and their influence on recent advances in treatment.

METHOD

Computerized literature searches were conducted with the key words "obsessive-compulsive disorder" in conjunction with "pediatric," "genetics," and "imaging."

RESULTS

Neuroimaging studies find evidence to support the frontal-striatal-thalamic model. Genetic and neurochemical studies also implicate glutamate in the pathological finding of OCD. This has led to the application of glutamate-modulating agents to treat OCD.

CONCLUSIONS

Studies of pediatric OCD have led to a refined frontal-striatal-thalamic model of pathogenesis and are having an evidence-based impact on treatment. Despite this progress, fully explanatory models are still needed that would allow for accurate prognosis and the development of targeted and efficacious treatments.

Magnetic resonance spectroscopy in anxiety disorders

OBJECTIVE

Magnetic resonance spectroscopy (MRS) is a non-invasive in vivo method used to quantify metabolites that are relevant to a wide range of brain processes. This paper briefly describes neuroimaging using MRS and provides a systematic review of its application to anxiety disorders.

METHOD

A literature review was performed in the PubMed, Lilacs and Scielo databases using the keywords spectroscopy and anxiety disorder. References of selected articles were also hand-searched for additional citations.

RESULTS

Recent studies have shown that there are significant metabolic differences between patients with anxiety disorders and healthy controls in various regions of the brain. Changes were mainly found in N-acetylaspartate, which is associated with neuronal viability, but some of them were also seen in creatine, a substance that is thought to be relatively constant among individuals with different pathological conditions.

CONCLUSIONS

MRS is a sophisticated neuroimaging technique that has provided useful insights into the biochemical and neurobiological basis of many anxiety disorders. Nevertheless, its utilization in some anxiety disorders is still modest, particularly social phobia and generalised anxiety. Although it is an extremely useful advance in neuroimaging, further research in other brain areas and patient populations is highly advisable.

Proton magnetic resonance spectroscopy in obsessive-compulsive disorder: a pilot investigation comparing treatment responders and non-responders

Proton magnetic resonance spectroscopic imaging was performed to compare brain metabolism in patients with obsessive-compulsive OCD. Evaluation was done on responders and non-responders to pharmacotherapy and on healthy controls. The results showed significantly lower NAA/Cr ratios in the right basal ganglia in non-responders than in responders or in controls and higher Cho/Cr ratios in the right thalamus in non-responders than responders. Abnormal neuronal metabolism in the right basal ganglia and right thalamus may be indicating lack of response to treatment to selective serotonin reuptake inhibitor.

Decreased GABA levels in anterior cingulate and basal ganglia in medicated subjects with panic disorder: a proton magnetic resonance spectroscopy (1H-MRS) study

The purpose of this study was to investigate the brain gamma-aminobutyric acid (GABA) concentration and its relationship with clinical variables in patients with panic disorder (PD). Single voxel proton magnetic resonance spectroscopy ((1)H-MRS) scan was performed on 22 medicated subjects with PD and 25 age and sex-matched healthy comparison subjects. GABA and other metabolite levels were measured in the anterior cingulate cortex (ACC) and basal ganglia. GABA levels were significantly lower in the ACC and basal ganglia of PD patients relative to comparison subjects. Lactate and choline concentrations in the ACC in PD patients were also higher than in the comparison subjects. Our data suggested in part that alterations of the GABA function and the energy metabolism in ACC and basal ganglia may play an important role in the pathophysiology of panic disorder.

Bildgebungsbefunde bei Kindern und Jugendlichen mit ADHS, Tic-Störungen und Zwangserkrankungen

Zusammenfassung: ADHS, Tic-Störung, Tourette-Syndrom und Zwangsstörung sind gekennzeichnet durch Defizite in der Handlungskontrolle und treten überzufällig häufig komorbid auf. Es bestehen Hinweise auf eine gemeinsame neurobiologische Basis. Der folgende Übersichtsartikel fasst Ergebnisse aus Bildgebungsstudien zu diesen Störungen im Kindes- und Jugendalter zusammen, wobei strukturelle und funktionelle Befunde durch Magnetresonanztomographie einen Schwerpunkt einnehmen. Übereinstimmend zeigen sich im Vergleich zu gesunden Kontrollen morphologische Veränderungen im Bereich von Basalganglien und präfrontalem Kortex sowie abnorme Aktivierungen in fronto-striatalen Systemen. Vor allem beim ADHS und Tourette-Syndrom werden präfrontale Abweichungen gefunden, die beim letzteren milder ausgeprägt sind und unter Umständen auf Kompensationsmechanismen zurückzuführen sein könnten. Beim ADHS finden sich zusätzlich kleine, globale morphologische Veränderungen im gesamten Kortex und im Zerebellum, beim Tourette-Syndrom werden zudem Auffälligkeiten im okzipitalen Kortex beschrieben. Bei der Zwangserkrankung bestehen weitere strukturelle und funktionelle Aberrationen im Bereich von Amygdala und Thalamus und zudem orbito-frontale Funktionsveränderungen, die beim ADHS eher im ventralen präfrontalen Kortex zu finden sind. Diese Befunde scheinen insgesamt mit Störungen in kortiko-striato-thalamiko-kortikalen Regelkreisen assoziiert zu sein und u. a. in Verbindung mit Dysfunktionen im Bereich der Inhibition von motorischen Reaktionen, impulsiven Handlungen und unerwünschten Gedanken zu stehen. Generell wird die Aussagekraft und Vergleichbarkeit vieler Studien durch kleine und heterogene Gruppen sowie methodische Unterschiede eingeschränkt.

Parietal white matter abnormalities in obsessive-compulsive disorder: a magnetic resonance spectroscopy study at 3-Tesla

OBJECTIVE

To identify a neurochemical basis for the hypothesis that an aberrant cortico-subcortical circuit underlies obsessive-compulsive disorder (OCD). The white matter was also investigated because of recent research which suggests the altered connectivity of axons.

METHOD

Using 3-Tesla magnetic resonance spectroscopy, the relative concentrations of N-acetylaspartate (NAA) and choline-containing compounds (Cho) to creatine/phosphocreatine (Cr) were measured in the anterior cingulate, basal ganglia, thalamus, frontal and parietal white matter of 12 OCD patients, and 32 control subjects.

RESULTS

The mean concentration of Cho/Cr was significantly higher in the patients than in the controls, but only in the parietal white matter, while no significant group differences in NAA/Cr were observed in any of the brain regions. Parietal Cho/Cr correlated positively with the severity of OCD symptoms.

CONCLUSION

This finding provides indirect evidence for the parietal white matter involvement in OCD, thus suggesting a change in the phospholipids of myelinated axons and/or glia cells.

Glutamate-modulating drugs as novel pharmacotherapeutic agents in the treatment of obsessive-compulsive disorder

SUMMARY

Obsessive-compulsive disorder (OCD) is a common psychiatric disorder that produces significant morbidity. The introduction of serotonin reuptake inhibitors in the 1980s represented an important advance in the treatment of OCD. However, few patients show complete remission of their symptoms, and some patients show minimal improvement with existing treatments. We review current treatment strategies and initial data supporting the efficacy of glutamate modulating agents as a novel class of pharmaceuticals for the treatment of OCD. Functional neuroimaging studies repeatedly reported metabolic hyperactivity in the cortico-striato-thalamo-cortical circuitry in patients with OCD. Recent magnetic resonance spectroscopy studies provide evidence of elevated glutamate levels in several brain regions in patients suffering from OCD. These findings raised the possibility that agents that reduce glutamate hyperactivity or its consequences in the CNS might be efficacious as novel therapeutic interventions. Indeed, initial evidence from our group suggests that the antiglutamatergic agent riluzole (Rilutek), which was developed for the treatment of amyotrophic lateral sclerosis, is effective in treatment-resistant OCD. Case reports suggest that other agents that modulate glutamatergic activity may likewise be effective. This new application of glutamate modulating agents holds promise for the treatment of this disabling and often inadequately treated disease.

A magnetic resonance spectroscopy investigation of obsessive-compulsive disorder and anxiety

The aim of the current study was to use proton magnetic resonance spectroscopy (MRS) to investigate potential irregularities in neurochemical compounds in obsessive-compulsive disorder (OCD) and the extent to which these irregularities are related to state anxiety. Single voxel MRS was used to image the head of the caudate nucleus (HOC) and orbitofrontal white matter (OFWM) bilaterally in adult patients with OCD and a control group. The results indicated that patients with OCD had increased levels of a combined measure of glutamate and glutamine (Glx/Cr) and N-acetyl-l-aspartic acid (NAA/Cr) relative to creatine in the right OFWM and reduced levels of myo-inositol relative to creatine (mI/Cr) in the HOC bilaterally. Correlational analyses indicated that Glx/Cr in the OFWM was related to OCD symptoms, while mI/Cr in the HOC was related to trait and/or state anxiety. Reanalysis of the significant group differences controlling for state anxiety symptoms erased three of the four group differences. These results are discussed in context of the methodological difficulties facing this area of research.

Increased medial thalamic creatine-phosphocreatine found by proton magnetic resonance spectroscopy in children with obsessive-compulsive disorder versus major depression and healthy controls

Altered brain creatine-phosphocreatine levels might reflect changes in brain energy use and have been implicated in the pathogenesis of obsessive-compulsive disorder and major depressive disorder. We used proton magnetic resonance spectroscopy to measure absolute concentrations of creatine-phosphocreatine in the right and left medial thalami in 18 pediatric patients with major depressive disorder 9 to 17 years of age, 18 case-matched healthy controls, and 27 patients with obsessive-compulsive disorder 7 to 16 years old. The two patient groups were psychotropic drug naive and were not comorbid for the diagnosis of the comparison group. We found significantly increased left and right medial thalamic creatine-phosphocreatine concentrations in patients with obsessive-compulsive disorder compared with both healthy controls and patients with major depression. Creatine-phosphocreatine concentrations did not differ significantly between patients with major depression and healthy controls. Our data suggest that increased medial thalamic creatine-phosphocreatine concentrations in patients with untreated obsessive-compulsive disorder reflect altered energy use in the medial thalamus and might differentiate patients with obsessive-compulsive disorder from healthy controls and patients with major depression. Although these results must be considered preliminary, further study of the diagnostic specificity of creatine-phosphocreatine in obsessive-compulsive disorder is indicated.

Myelin oligodendrocyte glycoprotein (MOG) gene is associated with obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a severe neuropsychiatric disorder with a strong genetic component, and may involve autoimmune processes. Support for this latter hypothesis comes from the identification of a subgroup of children, described by the term pediatric autoimmune neuropsychiatric disorder associated with streptococcal infections (PANDAS), with onset of OCD symptoms following streptococcal infections. Genes involved in immune response therefore represent possible candidate genes for OCD, including the myelin oligodendrocyte glycoprotein (MOG) gene, which plays an important role in mediating the complement cascade in the immune system. Four polymorphisms in the MOG gene, a dinucleotide CA repeat (MOG2), a tetranucleotide TAAA repeat (MOG4), and 2 intronic single nucleotide polymorphisms, C1334T and C10991T, were investigated for the possibility of association with OCD using 160 nuclear families with an OCD proband. We examined the transmission of alleles of these four polymorphisms with the transmission disequilibrium test (TDT). A biased transmission of the 459-bp allele (allele 2: chi2 = 5.255, P = 0.022) of MOG4 was detected, while MOG2, C1334T, and C10991T showed no statistically significant bias in the transmission of alleles. The transmission of the C1334T.MOG2.C10991T.MOG4 haplotype 1.13.2.2 (chi2 = 6.426, P = 0.011) was also significant. Quantitative analysis using the family-based association test (FBAT) was significant for MOG4 in total Yale-Brown Obsessive-Compulsive Scale severity score (allele 2: z = 2.334, P = 0.020). Further investigations combining genetic, pathological, and pharmacological strategies, are warranted.

Pathophysiology of obsessive–compulsive disorder

Obsessive-compulsive disorder (OCD) is characterized by repetitive intrusive thoughts and compulsive time-consuming behaviors classified into three to five distinct symptom dimensions including: (1) aggressive/somatic obsessions with checking compulsions; (2) contamination concerns with washing compulsions; (3) symmetry obsessions with counting/ordering compulsions; (4) hoarding obsessions with collecting compulsions; and (5) sexual/religious concerns. Phenomenologically, OCD could be thought of as the irruption of internal signals centered on the erroneous perception that "something is wrong" in a specific situation. This generates severe anxiety, leading to recurrent behaviors aimed at reducing the emotional tension. In this paper, we examine how the abnormalities in brain activity reported in OCD can be interpreted in the light of physiology after consideration of various approaches (phenomenology, neuropsychology, neuroimmunology and neuroimagery) that contribute to proposing the central role of several cortical and subcortical regions, especially the orbitofrontal cortex (OFC), the anterior cingulate cortex (ACC), the dorsolateral prefrontal cortex (DLPC), the head of the caudate nucleus and the thalamus. The OFC is involved in the significance attributed to the consequences of action, thereby subserving decision-making, whereas the ACC is particularly activated in situations in which there are conflicting options and a high likelihood of making an error. The DLPC plays a critical part in the cognitive processing of relevant information. This cortical information is then integrated by the caudate nucleus, which controls behavioral programs. A dysfunction of these networks at one or several stages will result in the emergence and maintenance of repetitive thoughts and characteristic OCD behavior.

Increased medial thalamic choline found in pediatric patients with obsessive-compulsive disorder versus major depression or healthy control subjects: a magnetic resonance spectroscopy study

BACKGROUND

Neurobiologic abnormalities in medial thalamus have been implicated in the pathogenesis of obsessive-compulsive disorder (OCD). We previously used multislice proton magnetic resonance spectroscopic imaging (1-H MRSI) to identify localized functional neurochemical marker alterations in choline (Cho) in medial but not lateral thalamus in treatment-naïve pediatric patients with OCD compared with matched control subjects. Altered brain Cho levels have also been implicated in the pathogenesis of mood disorders.

METHODS

We used 1-H MRSI to study absolute Cho concentrations in 18 psychotropic-naïve pediatric patients with major depressive disorder (MDD) not suffering from OCD, 9-17 years of age, 18 case-matched healthy control subjects, and 27 nondepressed, psychotropic-naïve pediatric patients with OCD, 7-16 years of age.

RESULTS

Significantly increased left and right medial thalamic Cho concentrations were observed in OCD patients compared with both healthy control subjects and patients with MDD. Medial thalamic Cho concentrations did not differ significantly between patients with MDD and control subjects.

CONCLUSIONS

These results suggest that localized functional neurochemical marker alterations in medial thalamic Cho differentiate patients with OCD from healthy control subjects and patients with MDD. Although these results must be considered preliminary, further study of the diagnostic specificity of Cho as a relevant biomarker in OCD is clearly warranted.

Proton magnetic resonance spectroscopic imaging in pediatric major depression

BACKGROUND

Neurobiologic abnormalities in dorsolateral prefrontal cortex (DLPFC) are believed to be involved in the pathophysiology of major depressive disorder (MDD). Although MDD commonly emerges during childhood and adolescence, to our knowledge, no prior study has examined the DLPFC in pediatric patients with MDD.

METHODS

In this study, choline compounds (Cho), N-acetylaspartate (NAA), and creatine/phosphocreatine (Cr) were measured in left and right DLPFC using a multislice proton magnetic resonance spectroscopic imaging sequence with validated phantom replacement methodology in 11 treatment-naïve MDD patients, 10-16 years of age, and 11 case-matched healthy control subjects.

RESULTS

A significant increase in Cho was observed in left but not right DLPFC in MDD patients versus control subjects (32.5% higher). No significant differences in NAA or Cr were observed between case-control pairs.

CONCLUSIONS

These results provide new evidence of localized functional neurochemical marker alterations in left DLPFC in pediatric MDD. Our results must be considered preliminary, however, given the small sample size.