Is there evidence of brain white-matter abnormalities in obsessive-compulsive disorder?: a narrative review

Corpus callosum morphology in major mental disorders: a magnetic resonance imaging study

Mental disorders diagnosis is based on specific clinical criteria. However, clinical studies found similarities and overlapping phenomenology across a variety of disorders, which suggests a common neurobiological substrate. Thus, there is a need to measure disease-related neuroanatomical similarities and differences across conditions. While structural alterations of the corpus callosum have been investigated in obsessive-compulsive disorder, schizophrenia, major depressive disorder and bipolar disorder, no study has addressed callosal aberrations in all diseases in a single study. Moreover, results from pairwise comparisons (patients vs. controls) show some inconsistencies, possibly related to the parcellation methods to divide the corpus callosum into subregions. The main aim of the present paper was to uncover highly localized callosal characteristics for each condition (i.e. obsessive-compulsive disorder, schizophrenia, major depressive disorder and bipolar disorder) as compared either to healthy control subjects or to each other. For this purpose, we did not rely on any sub-callosal parcellation method, but applied a well-validated approach measuring callosal thickness at 100 equidistant locations along the whole midline of the corpus callosum. One hundred and twenty patients (30 in each disorder) as well as 30 controls were recruited for the study. All groups were closely matched for age and gender, and the analyses were performed controlling for the impact of antipsychotic treatment and illness duration. There was a significant main effect of group along the whole callosal surface. Pairwise post hoc comparisons revealed that, compared to controls, patients with obsessive-compulsive disorder had the thinnest corpora callosa with significant effects almost on the entire callosal structure. Patients with schizophrenia also showed thinner corpora callosa than controls but effects were confined to the isthmus and the anterior part of the splenium. No significant differences were found in both major depressive disorder and bipolar disorder patients compared to controls. When comparing the disease groups to each other, the corpus callosum was thinner in obsessive-compulsive disorder patients than in any other group. The effect was evident across the entire corpus callosum, with the exception of the posterior body. Altogether, our study suggests that the corpus callosum is highly changed in obsessive-compulsive disorder, selectively changed in schizophrenia and not changed in bipolar disorder and major depressive disorder. These results shed light on callosal similarities and differences among mental disorders providing valuable insights regarding the involvement of the major brain commissural fibre tract in the pathophysiology of each specific mental illness.

Comparative Neuropsychiatry: White Matter Abnormalities in Children and Adolescents with Schizophrenia, Bipolar Affective Disorder, and Obsessive-Compulsive Disorder

Background:

There is considerable evidence that white matter abnormalities play a key role in the pathogenesis of a number of major psychiatric disorders, including schizophrenia, bipolar affective disorder, and obsessive-compulsive disorder. Few studies, however, have compared white matter abnormalities early in the course of the illness.

Methods:

A total of 102 children and adolescents participated in the study, including 43 with early-onset schizophrenia, 13 with early-onset bipolar affective disorder, 17 with obsessive-compulsive disorder, and 29 healthy controls. Diffusion tensor imaging scans were obtained on all children and the images were assessed for the presence of non-spatially overlapping regions of white matter differences, a novel algorithm known as the pothole approach.

Results:

Patients with early-onset schizophrenia and early-onset bipolar affective disorder had a significantly greater number of white matter potholes compared to controls, but the total number of potholes did not differ between the two groups. The volumes of the potholes were significantly larger in patients with early-onset bipolar affective disorder compared to the early-onset schizophrenia group. Children and adolescents with obsessive-compulsive disorder showed no differences in the total number of white matter potholes compared to controls.

Conclusions:

White matter abnormalities in early-onset schizophrenia and bipolar affective disorder are more global in nature, whereas children and adolescents with obsessive-compulsive disorder do not show widespread differences in FA.

Comparison of psychiatric disturbances in patients with multiple sclerosis and neuromyelitis optica

Although both multiple sclerosis (MS) and neuromyelitis optica (NMO) are demyelinating diseases, their psychiatric disturbances may differ given differences in the neurological manifestations. We used subjective and objective measurements to compare the psychiatric disturbances in patients with MS and NMO.Psychiatric disturbances were assessed in 24 MS and 35 NMO patients using the Beck Hopelessness Scale, Symptom Checklist-95 and the brief version of World Health Organization Quality of Life. Personality was assessed using the Big Five Inventory-10. Disease-related function was assessed using the Fatigue Severity Scale, Short-Form McGill Pain Questionnaire, and the Global Assessment of Function. Positivity offset (PO) and negativity bias (NB) and heart rate variability (HRV) were measured using a modified implicit affect test and photoplethysmograph, respectively. Data were analyzed using analysis of covariance with age and sex as covariates.MS patients had higher levels of depression, anxiety, panic attacks, obsessive-compulsiveness, aggression, paranoia, interpersonal sensitivity, self-regulation problems, stress vulnerability, and lower psychological quality of life (QOL) compared with NMO patients. The PO and NB and HRV values were not significantly different between groups. However, NMO patients had lower QOL, and higher levels of hopelessness, suicidality, and fatigue than the normal range. Disease duration was associated with hopelessness in NMO patients and with several psychiatric disturbances, but not hopelessness, in MS patients.Subjective psychiatric disturbances were more severe in patients with MS than in those with NMO, whereas PO and NB and HRV in patients with NMO were comparable with those of MS patients. Our findings highlight the need for different clinical approaches to assess and treat psychiatric disturbances in patients with MS and NMO.

Neuroimaging Studies in Obsessive Compulsive Disorder: A Narrative Review

Obsessive compulsive disorder (OCD) is a relatively common psychiatric illness with a lifetime prevalence of 2-3% in general population. The pathophysiology of OCD is not yet fully understood, however over the last few decades, evidence for abnormalities of cortico-striatal-thalamic-cortico (CSTC) circuitry in etiopathogenesis of OCD has accumulated. Recent brain imaging techniques have been particularly convincing in suggesting that CSTC circuits are responsible for mediation of OCD symptoms. Neuroimaging studies, especially more recent studies using functional neuroimaging methods have looked for possible changes seen in the brain of patients with OCD, the specificity of the findings (as compared to other psychiatric illnesses) and the effects of treatment (pharmacotherapy/psychotherapy) on such changes were observed. This narrative review discusses the neuroimaging findings seen in patients with OCD with a special focus on relatively more recent neuroimaging modalities such as magnetic resonance spectroscopy and magnetoencephalography.

Brain white matter integrity and association with age at onset in pediatric obsessive-compulsive disorder

Background

Obsessive-compulsive disorder (OCD) is a common and debilitating neuropsychiatric illness thought to involve abnormal connectivity of widespread brain networks, including frontal-striatal-thalamic circuits. At least half of OCD cases arise in childhood and their underlying neuropathology may differ at least in part from that of adult-onset OCD. Yet, only a few studies have examined brain white matter (WM) integrity in childhood-onset OCD using diffusion tensor imaging (DTI), and none have examined potential associations with age at onset.

Results

In this study, 17 youth with OCD and 19 healthy control subjects, ages 10 to 19 years, underwent DTI on a 3T Siemens scanner. DSM-IV diagnoses were established with standardized interviews, and OCD symptom severity was evaluated using the Children’s Yale-Brown Obsessive-Compulsive Scale (CY-BOCS). Voxel-wise analyses were conducted on data processed with tract-based spatial statistics (TBSS) to derive measures of fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD). OCD patients had significantly lower FA in seven WM clusters, with over 80% of significant voxels in bilateral frontal cortex and corpus callosum (CC). There were no regions of significantly higher FA in patients compared with controls. Patients also had significantly higher RD in right frontal cortex and right body of the CC. Earlier age at onset of OCD correlated significantly with lower FA in the right thalamus and with higher RD in the right CC. FA and RD were not significantly associated with symptom severity.

Conclusions

These findings point to compromised WM integrity and reduced myelination in some brain regions of children with OCD, particularly the CC and fiber tracts that connect the frontal lobes to widespread cortical and subcortical targets. They also suggest that age at onset may be a moderator of some of the WM changes in pediatric OCD.

Diffusion tensor imaging (DTI) studies in patients with obsessive-compulsive disorder (OCD): a review

This review presents an overview of studies investigating white-matter integrity in patients with obsessive-compulsive disorder (OCD) using diffusion tensor imaging (DTI). There is increasing evidence for white matter alterations in OCD. In adult patients the majority of all studies reported abnormalities in terms of decreased fractional anisotropy (FA) compared to healthy volunteers. Although findings are heterogeneous, the cingulate bundle, the corpus callosum and the anterior limb of the internal capsule are most commonly affected by decreased white matter integrity in adult OCD patients. In pediatric and adolescent patients initial evidence points more towards increased white matter connectivity. Thus, current results suggest alterations in various white matter regions in both pediatric and adult OCD patients. They indicate that alterations may vary as a function of clinical characteristics and may be amenable to pharmacologic treatment. Although the findings have important implications for the neurobiology of OCD they also raise a number of important questions that are discussed in this review and need to be taken into consideration in future studies.

Abnormal topological organization in white matter structural networks revealed by diffusion tensor tractography in unmedicated patients with obsessive-compulsive disorder

BACKGROUND

Obsessive-compulsive disorder (OCD) is a chronic psychiatric disorder defined by recurrent thoughts, intrusive and distressing impulses, or images and ritualistic behaviors. Although focal diverse regional abnormalities white matter integrity in specific brain regions have been widely studied in populations with OCD, alterations in the structural connectivities among them remain poorly understood.

OBJECTIVE

The aim was to investigate the abnormalities in the topological efficiency of the white matter networks and the correlation between the network metrics and Yale-Brown Obsessive-Compulsive Scale scores in unmedicated OCD patients, using diffusion tensor tractography and graph theoretical approaches.

METHODS

This study used diffusion tensor imaging and deterministic tractography to map the white matter structural networks in 26 OCD patients and 39 age- and gender-matched healthy controls; and then applied graph theoretical methods to investigate abnormalities in the global and regional properties of the white matter network in these patients.

RESULTS

The patients and control participants both showed small-world organization of the white matter networks. However, the OCD patients exhibited significant abnormal global topology, including decreases in global efficiency (t = -2.32, p = 0.02) and increases in shortest path length, Lp (t = 2.30, p = 0.02), the normalized weighted shortest path length, λ (t = 2.08, p=0.04), and the normalized clustering coefficient, γ (t = 2.26, p = 0.03), of their white matter structural networks compared with healthy controls. Further, the OCD patients showed a reduction in nodal efficiency predominately in the frontal regions, the parietal regions and caudate nucleus. The normalized weighted shortest path length of the network metrics was significantly negatively correlated with obsessive subscale of the Yale-Brown Obsessive-Compulsive Scale (r = -0.57, p = 0.0058).

CONCLUSIONS

These findings demonstrate the abnormal topological efficiency in the white matter networks in OCD patients.

Multimodal voxel-based meta-analysis of white matter abnormalities in obsessive-compulsive disorder

White matter (WM) abnormalities have long been suspected in obsessive-compulsive disorder (OCD) but the available evidence has been inconsistent. We conducted the first multimodal meta-analysis of WM volume (WMV) and fractional anisotropy (FA) studies in OCD. All voxel-wise studies comparing WMV or FA between patients with OCD and healthy controls in the PubMed, ScienceDirect, Google Scholar, Web of Knowledge and Scopus databases were retrieved. Manual searches were also conducted and authors were contacted soliciting additional data. Thirty-four data sets were identified, of which 22 met inclusion criteria (five of them unpublished; comprising 537 adult and pediatric patients with OCD and 575 matched healthy controls). Whenever possible, raw statistical parametric maps were also obtained from the authors. Peak and raw WMV and FA data were combined using novel multimodal meta-analytic methods implemented in effect-size signed differential mapping. Patients with OCD showed widespread WM abnormalities, but findings were particularly robust in the anterior midline tracts (crossing between anterior parts of cingulum bundle and body of corpus callosum), which showed both increased WMV and decreased FA, possibly suggesting an increase of fiber crossing in these regions. This finding was also observed when the analysis was limited to adult participants, and especially pronounced in samples with a higher proportion of medicated patients. Therefore, patients with OCD may have widespread WM abnormalities, particularly evident in anterior midline tracts, although these changes might be, at least in part, attributable to the effects of therapeutic drugs.

Neuroimaging for psychotherapy research: current trends

OBJECTIVE

This article reviews neuroimaging studies that inform psychotherapy research. An introduction to neuroimaging methods is provided as background for the increasingly sophisticated breadth of methods and findings appearing in psychotherapy research.

METHOD

We compiled and assessed a comprehensive list of neuroimaging studies of psychotherapy outcome, along with selected examples of other types of studies that also are relevant to psychotherapy research. We emphasized magnetic resonance imaging (MRI) since it is the dominant neuroimaging modality in psychological research.

RESULTS

We summarize findings from neuroimaging studies of psychotherapy outcome, including treatment for depression, obsessive compulsive disorder (OCD), and schizophrenia.

CONCLUSIONS

The increasing use of neuroimaging methods in the study of psychotherapy continues to refine our understanding of both outcome and process. We suggest possible directions for future neuroimaging studies in psychotherapy research.

Searching for the immune basis of obsessive-compulsive disorder

The etiopathogenesis of obsessive-compulsive disorder (OCD) remains elusive. Clinical observation of the elevated frequency of obsessive-compulsive symptoms in patients with rheumatic fever, a post-streptococcal autoimmune disease, prompted the study of immune parameters in OCD. Anti-basal ganglia antibodies have been described in a subset of OCD patients. The assessment of circulating cytokines and immune cells confirmed unequivocal changes in at least some patients, although it is difficult to establish a particular immune profile in OCD. Several factors, including the use of psychotropic drugs and the presence of comorbid conditions, seem to influence these immune parameters.

Widespread decreased grey and white matter in paediatric obsessive-compulsive disorder (OCD): a voxel-based morphometric MRI study

Obsessive-compulsive disorder (OCD) is a chronic, relapsing anxiety disorder. To date, neuroimaging investigations of OCD have been variable and few studies have examined paediatric populations. Eight children with OCD and 12 typically developing children matched for age, gender, handedness and performance IQ underwent a high resolution T1-weighted structural magnetic resonance imaging (MRI) scan. A voxel-based morphometry (VBM) protocol (using DARTEL) compared the brains of the paediatric OCD children with those of typically developing children. Overall, children with OCD demonstrated significantly lower intra-cranial volume (ICV) and grey- and white-matter volumes. ICV was significantly reduced (∼9%) in the OCD group compared with the typically developing group. The VBM analysis demonstrated lower volumes in widespread grey matter in bilateral frontal, cingulate, temporal-parietal, occipital-frontal and right precuneus regions for OCD. Lower white matter volume was found bilaterally in the cingulate and occipital cortex, right frontal and parietal and left temporal regions, and the corpus callosum. In summary, this study provides further evidence of brain dysmorphology in paediatric OCD patients. In addition to fronto-striatal-thalamic neural networks, abnormalities in other brain regions, such as the parietal lobe and corpus callosum, were demonstrated. These brain regions may play an additional role in the pathophysiology of OCD.

Widespread changes of white matter microstructure in obsessive-compulsive disorder: effect of drug status

Diffusion tensor imaging (DTI) allows the study of white matter (WM) structure. Literature suggests that WM structure could be altered in obsessive-compulsive disorder (OCD) proportional to the severity of the disease. Heterogeneity of brain imaging methods, of the studied samples, and of drug treatments make localization, nature, and severity of the WM abnormalities unclear. We applied Tract-Based Spatial Statistics (TBSS) of DTI measures to compare fractional anisotropy (FA), mean, axial, and radial diffusivity of the WM skeleton in a group of 40 consecutively admitted inpatients affected by severe OCD (18 drug-naive, and 22 with an ongoing drug treatment) and 41 unrelated healthy volunteers from the general population. Data were analyzed accounting for the effects of multiple comparisons, and of age, sex, and education as nuisance covariates. Compared to controls, OCD patients showed a widespread reduction of FA with a concurrent increase of mean and radial diffusivity. In no brain areas patients had higher FA or lower diffusivity values than controls. These differences were observed in drug-treated patients compared to drug-naive patients and healthy controls, which in turn did not differ among themselves in any DTI measure. Reduced FA with increased mean and radial diffusivity suggests significant changes in myelination of WM tracts, without axonal loss. Drug treatments could modify the structure of cell membranes and myelin sheaths by influencing cellular lipogenesis, cholesterol homeostasis, autophagy, oligodendrocyte differentiation and remyelination. Changes of DTI measures in drug-treated OCD patients could reflect pathophysiological underpinnings of OCD, or a yet unexplored part of the mechanism of action of drugs.

Surface anatomical profile of the cerebral cortex in obsessive-compulsive disorder: a study of cortical thickness, folding and surface area

BACKGROUND

Studying the distribution of anatomical abnormalities over the entire cortical surface can help to identify key neural circuits implicated in generating symptoms of neuropsychiatric disorders. There is a significant inconsistency among studies investigating the neuroanatomy of obsessive-compulsive disorder (OCD) because of the confounding influence of co-morbid depression and medication use and the lack of unbiased estimation of whole-brain morphometric changes. It is also unknown whether the distinct surface anatomical properties of thickness, surface area and gyrification, which collectively contribute to grey matter volume (GMV), are independently affected in OCD. Method The cortical maps of thickness, gyrification and surface areal change were acquired from 23 unmedicated OCD patients and 20 healthy controls using an unbiased whole-brain surface-based morphometric (SBM) method to detect regional changes in OCD. Subcortical structures were not assessed in this study.

RESULTS

Patients showed a significant increase in the right inferior parietal cortical thickness. Significant increases in gyrification were also noted in the left insula, left middle frontal and left lateral occipital regions extending to the precuneus and right supramarginal gyrus in OCD. Areal contraction/expansion maps revealed no significant regional differences between the patients and controls. In patients, gyrification of the insula significantly predicted the symptom severity measured using Yale-Brown Obsessive-Compulsive Scale (YBOCS).

CONCLUSIONS

An alteration in the cortical surface anatomy is an important feature of OCD seen in unmedicated samples that relates to the severity of the illness. The results underscore the presence of a neurodevelopmental aberration underlying the pathophysiology of OCD.

Increased orbital frontal gray matter volume after cognitive behavioural therapy in paediatric obsessive compulsive disorder

OBJECTIVES

Identify differences in regional brain volume between medication-free pediatric OCD patients and controls and examine changes after cognitive behavioural therapy.

METHODS

We assessed 29 medication-free paediatric OCD patients (Age: M = 13.78 years; SD = 2.58; range 8.2-19.0) and 29 controls, matched on age and gender, with T1-weighted MR scans in a repeated measures, pre-post treatment design. Voxel based morphometry (VBM) following diffeomorphic anatomical registration through exponential lie algebra (DARTEL) was used to test voxel-wise for the effects of diagnosis and treatment on regional gray matter (GM) and white matter (WM) volumes.

RESULTS

After cognitive behavioural therapy, orbitofrontal GM and capsula externa WM increased in paediatric OCD relative to controls. In patients, changes in symptom severity (delta CY-BOCS) correlated positively with GM volume in the orbitofrontal cortex after treatment. Furthermore, before treatment, paediatric OCD patients, compared to the controls, showed larger GM volume in left frontal pole and left parietal cortex and larger WM volume in cingulum and corpus callosum.

CONCLUSIONS

Our findings underscore the involvement of the ventral frontal-striatal circuit in paediatric OCD and the plasticity of this circuit in response to the modulatory effects of CBT. The possible relation to brain development is discussed.

Putative neuroprotective agents in neuropsychiatric disorders

In many individuals with major neuropsychiatric disorders including depression, bipolar disorder and schizophrenia, their disease characteristics are consistent with a neuroprogressive illness. This includes progressive structural brain changes, cognitive and functional decline, poorer treatment response and an increasing vulnerability to relapse with chronicity. The underlying molecular mechanisms of neuroprogression are thought to include neurotrophins and regulation of neurogenesis and apoptosis, neurotransmitters, inflammatory, oxidative and nitrosative stress, mitochondrial dysfunction, cortisol and the hypothalamic-pituitary-adrenal axis, and epigenetic influences. Knowledge of the involvement of each of these pathways implies that specific agents that act on some or multiple of these pathways may thus block this cascade and have neuroprotective properties. This paper reviews the potential of the most promising of these agents, including lithium and other known psychotropics, aspirin, minocycline, statins, N-acetylcysteine, leptin and melatonin. These agents are putative neuroprotective agents for schizophrenia and mood disorders.

White matter integrity in hair-pulling disorder (trichotillomania)

Hair-pulling disorder (trichotillomania, HPD) is a disabling condition that is characterized by repetitive hair-pulling resulting in hair loss. Although there is evidence of structural grey matter abnormalities in HPD, there is a paucity of data on white matter integrity. The aim of this study was to explore white matter integrity using diffusion tensor imaging (DTI) in subjects with HPD and healthy controls. Sixteen adult female subjects with HPD and 13 healthy female controls underwent DTI. Hair-pulling symptom severity, anxiety and depressive symptoms were also assessed. Tract-based spatial statistics were used to analyze data on fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD). There were no differences in DTI measures between HPD subjects and healthy controls. However, there were significant associations of increased MD in white matter tracts of the fronto-striatal-thalamic pathway with longer HPD duration and increased HPD severity. Our findings suggest that white matter integrity in fronto-striatal-thalamic pathways in HPD is related to symptom duration and severity. The molecular basis of measures of white matter integrity in HPD deserves further exploration.

Reduced ventral cingulum integrity and increased behavioral problems in children with isolated optic nerve hypoplasia and mild to moderate or no visual impairment

Objectives

To assess the prevalence of behavioral problems in children with isolated optic nerve hypoplasia, mild to moderate or no visual impairment, and no developmental delay. To identify white matter abnormalities that may provide neural correlates for any behavioral abnormalities identified.

Patients and Methods

Eleven children with isolated optic nerve hypoplasia (mean age 5.9 years) underwent behavioral assessment and brain diffusion tensor imaging, Twenty four controls with isolated short stature (mean age 6.4 years) underwent MRI, 11 of whom also completed behavioral assessments. Fractional anisotropy images were processed using tract-based spatial statistics. Partial correlation between ventral cingulum, corpus callosum and optic radiation fractional anisotropy, and child behavioral checklist scores (controlled for age at scan and sex) was performed.

Results

Children with optic nerve hypoplasia had significantly higher scores on the child behavioral checklist (p<0.05) than controls (4 had scores in the clinically significant range). Ventral cingulum, corpus callosum and optic radiation fractional anisotropy were significantly reduced in children with optic nerve hypoplasia. Right ventral cingulum fractional anisotropy correlated with total and externalising child behavioral checklist scores (r = −0.52, p<0.02, r = −0.46, p<0.049 respectively). There were no significant correlations between left ventral cingulum, corpus callosum or optic radiation fractional anisotropy and behavioral scores.

Conclusions

Our findings suggest that children with optic nerve hypoplasia and mild to moderate or no visual impairment require behavioral assessment to determine the presence of clinically significant behavioral problems. Reduced structural integrity of the ventral cingulum correlated with behavioral scores, suggesting that these white matter abnormalities may be clinically significant. The presence of reduced fractional anisotropy in the optic radiations of children with mild to moderate or no visual impairment raises questions as to the pathogenesis of these changes which will need to be addressed by future studies.

White matter abnormalities in pediatric obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a prevalent and often severely disabling illness with onset generally in childhood or adolescence. Although white matter deficits have been implicated in the neurobiology of OCD, few studies have been conducted in pediatric patients when the brain is still developing and have examined their functional correlates. In this study, 23 pediatric OCD patients and 23 healthy volunteers, between the ages of 9 and 17 years, matched for sex, age, handedness, and IQ, received a diffusion tensor imaging exam on a 3T GE system and a brief neuropsychological battery tapping executive functions. Patient symptom severity was assessed using the Children's Yale-Brown Obsessive-Compulsive Scale (CY-BOCS). Patients with OCD exhibited significantly greater fractional anisotropy compared to matched controls in the left dorsal cingulum bundle, splenium of the corpus callosum, right corticospinal tract, and left inferior fronto-occipital fasciculus. There were no regions of significantly lower fractional anisotropy in patients compared to controls. Higher fractional anisotropy in the splenium was significantly correlated with greater obsession severity on the CY-BOCS in the subgroup of psychotropic drug-naïve patients. Among patients, there was a significant association between greater fractional anisotropy in the dorsal cingulum bundle and better performance on measures of response inhibition and cognitive control. The overall findings suggest a pattern of greater directional coherence of white matter tracts in OCD very early in the course of illness, which may serve a compensatory mechanism, at least for response inhibition functions typically subserved by the cingulum bundle.

White matter abnormalities in children and adolescents with obsessive-compulsive disorder: a diffusion tensor imaging study

BACKGROUND

There is paucity of data on white matter (WM) abnormalities in juvenile obsessive-compulsive disorder (OCD). This study aimed to identify WM microstructure changes in juvenile OCD.

METHODS

Fifteen children and adolescents with OCD and 15 matched healthy controls underwent diffusion tensor imaging using a 3 Tesla (Achieva, Best, The Netherlands) magnetic resonance imaging scanner. Voxelwise analyses were conducted on data processed through tract-based spatial statistics (TBSS).

RESULTS

Patients significantly differed from controls in axial as well as radial diffusivities, but not in fractional anisotropy. Patients demonstrated significantly increased axial diffusivity in corpus callosum (genu, body, and splenium), right and left superior longitudinal fasciculi, left inferior longitudinal fasciculus, right and left cingulum, bilateral anterior thalamic radiations, bilateral anterior limb of internal capsule, left posterior limb of the internal capsule, and middle cerebellar peduncle. In addition, significantly increased radial diffusivity was seen in patients in genu of the corpus, right and left superior longitudinal fasciculi, left inferior longitudinal fasciculus, right and left uncinate fasciculi, bilateral anterior thalamic radiation, bilateral inferior fronto-occipital fasciculus, left posterior limb of internal capsule, right superior cerebellar peduncle, middle cerebellar peduncle, and right inferior cerebellar peduncle.

CONCLUSIONS

Our findings suggest involvement of multiple WM tracts in juvenile OCD. In addition to the widely proposed hypothesis of orbitofrontal-striato-thalamo-cortical circuitry deficits in the development of OCD, our findings suggest involvement of additional brain regions, possibly parietal cortex, lateral prefrontal cortex, and limbic system. The widespread differences in WM among cases and controls also points to the possibility of underlying myelination changes.

Evidence for fractional anisotropy and mean diffusivity white matter abnormalities in the internal capsule and cingulum in patients with obsessive-compulsive disorder

BACKGROUND

There is evidence to suggest that obsessive-compulsive disorder (OCD) is associated with structural abnormalities in cortico-striato-thalamic circuits, yet the extent of white matter abnormalities is not well established. In this study, we used diffusion tensor imaging (DTI) to examine white matter integrity in specific regions of interest (ROIs) in patients with OCD.

METHODS

Patients with OCD and sex-, age- and IQ-matched healthy controls underwent DTI. The primary objective was to explore whether patients with OCD had white matter abnormalities in the anterior limb of the internal capsule (ALIC), the uncinate fasciculus, the genu of the corpus callosum and the cingulum. The secondary objective was to evaluate the relation between fractional anisotropy and mean diffusivity in these ROIs and other clinical variables (including age at onset of OCD, OCD severity and levels of depressive and anxiety symptomatology) in patients with OCD.

RESULTS

There were 15 patients and 17 controls enrolled in our study. Compared with healthy controls, patients with OCD showed increased fractional anisotropy in bilateral regions of the ALIC adjacent to the body of the caudate, as well as decreased fractional anisotropy in the right anterior limb near the head of the caudate. Patients also had decreased mean diffusivity in the body of the right cingulum and the left anterior cingulum compared with controls. Correlational analyses revealed significant associations of fractional anisotropy and mean diffusivity in select circuits with OCD, depression and anxiety severity scores.

LIMITATIONS

Inclusion of patients with OCD receiving pharmacotherapy may have been a limitation. In addition, the patients were heterogeneous in terms of their obsessive-compulsive symptom profiles; we did not distinguish between different obsessive-compulsive symptom dimensions.

CONCLUSION

The study results provide further evidence for OCD-related white matter abnormalities in the ALIC and cingulum, consistent with a cortico striatal model of OCD.