Normal pituitary volumes in children and adolescents with bipolar disorder: a magnetic resonance imaging study

Anterior pituitary gland volume mediates associations between pubertal hormones and changes in transdiagnostic symptoms in youth

The pituitary gland (PG) plays a central role in the production and secretion of pubertal hormones, with documented links to the emergence and increase in mental health symptoms known to occur during adolescence. Although much of the literature has focused on examining whole PG volume, recent findings suggest that there are associations among pubertal hormone levels, including dehydroepiandrosterone (DHEA), subregions of the PG, and elevated mental health symptoms (e.g., internalizing symptoms) during adolescence. Surprisingly, studies have not yet examined associations among these factors and increasing transdiagnostic symptomology, despite DHEA being a primary output of the anterior PG. Therefore, the current study sought to fill this gap by examining whether anterior PG volume specifically mediates associations between DHEA levels and changes in dysregulation symptoms in an adolescent sample ( N = 114, 9 - 17 years, M age = 12.87, SD = 1.88). Following manual tracing of the anterior and posterior PG, structural equation modeling revealed that greater anterior, not posterior, PG volume mediated the association between greater DHEA levels and increasing dysregulation symptoms across time, controlling for baseline dysregulation symptom levels. These results suggest specificity in the role of the anterior PG in adrenarcheal processes that may confer risk for psychopathology during adolescence. This work not only highlights the importance of separately tracing the anterior and posterior PG, but also suggests that transdiagnostic factors like dysregulation are useful in parsing hormone-related increases in mental health symptoms in youth.

MRI atlas of the pituitary gland in young female adults

The probabilistic topography and inter-individual variability of the pituitary gland (PG) remain undetermined. The absence of a standardized reference atlas hinders research on PG volumetrics. In this study, we aimed at creating maximum probability maps for the anterior and posterior PG in young female adults. We manually delineated the anterior and posterior parts of the pituitary glands in 26 healthy subjects using high-resolution MRI T1 images. A three-step procedure and a cost function-masking approach were employed to optimize spatial normalization for the PG. We generated probabilistic atlases and maximum probability maps, which were subsequently coregistered back to the subjects' space and compared to manual delineations. Manual measurements led to a total pituitary volume of 705 ± 88 mm³, with the anterior and posterior volumes measuring 614 ± 82 mm³ and 91 ± 20 mm³, respectively. The mean relative volume difference between manual and atlas-based estimations was 1.3%. The global pituitary atlas exhibited an 80% (± 9%) overlap for the DICE index and 67% (± 11%) for the Jaccard index. Similarly, these values were 77% (± 13%) and 64% (± 14%) for the anterior pituitary atlas and 62% (± 21%) and 47% (± 17%) for the posterior PG atlas, respectively. We observed a substantial concordance and a significant correlation between the volume estimations of the manual and atlas-based methods for the global pituitary and anterior volumes. The maximum probability maps of the anterior and posterior PG lay the groundwork for automatic atlas-based segmentation methods and the standardized analysis of large PG datasets.

The Morphology of the Pituitary Gland: A Meta-Analysis with Implications for Diagnostic Imaging

The objective of this meta-analysis was to present transparent data on the morphology of the pituitary gland (PG) using the available data in the literature. The main online medical databases, such as PubMed, Embase, Scopus, and Web of Science, were searched to gather all relevant studies regarding PG morphology. The mean overall volume of the PG was found to be 597.23 mm³ (SE = 28.81). The mean overall height of the PG was established to be 5.64 mm (SE = 0.11). The mean overall length of the PG was found to be 9.98 mm (SE = 0.26). In the present study, the PG's overall morphology and morphometric features were analyzed. Our results showed that, on average, females from Asia have the highest volume of PG (706.69 mm³), and males from Europe have the lowest (456.42 mm³). These values are crucial to be aware of because they represent the normal average properties of the PG, which may be used as reference points when trying to diagnose potential pathologies of this gland. Furthermore, the present study's results prove how the PG's size decreases with age. The results of the present study may be helpful for physicians, especially surgeons, performing procedures on the PG.

Pituitary gland shrinkage in bipolar disorder: The role of gender

BACKGROUND

Hyperactivity of the Hypothalamic-Pituitary-Adrenal Axis (HPAA) has been consistently reported in mood disorders. However, only few studies investigated the Pituitary gland (PG) in Bipolar Disorder (BD) and the results are so far contrasting. Therefore, the aim of this study is to explore the integrity of the PG as well as the role of gender and the impact of clinical measurements on this structure in a sample of BD patients compared to healthy controls (HC).

METHODS

34 BD patients and 41 HC underwent a 1.5 T MRI scan. PG volumes were manually traced for all subjects. Psychiatric symptoms were assessed by means of the Brief Psychiatry Rating Scale, the Hamilton Depression Rating Scale and the Bech Rafaelsen Mania Rating Scale.

RESULTS

We found decreased PG volumes in BD patients compared to HC (F = 24.9, p < 0.001). Interestingly, after dividing the sample by gender, a significant PG volume decrease was detected only in female BD patients compared to female HC (F = 9.1, p < 0.001), but not in male BD compared to male HC (F = -0.12, p = 0.074). No significant correlations were observed between PG volumes and clinical variables.

CONCLUSIONS

Our findings suggest that BD patients have decreased PG volumes, probably due to the long-term hyperactivity of the HPAA and to the consequent strengthening of the negative feedback control towards the PG volume itself. This alteration was particularly evident in females, suggesting a role of gender in affecting PG volumes in BD. Finally, the absence of significant correlations between PG volumes and clinical variables further supports that PG disruption is a trait feature of BD, being independent of symptoms severity and duration of treatment.

Pituitary gland in Bipolar Disorder and Major Depression: Evidence from structural MRI studies: Special Section on "Translational and Neuroscience Studies in Affective Disorders". Section Editor, Maria Nobile MD, PhD. This Section of JAD focuses on the relevance of translational and neuroscience studies in providing a better understanding of the neural basis of affective disorders. The main aim is to briefly summarise relevant research findings in clinical neuroscience with particular regards to specific innovative topics in mood and anxiety disorders

BACKGROUND

The function of the hypothalamo-pituitary-adrenal axis (HPA) has been widely investigated in mood disorders based on its role in regulating stress response. Particularly, Magnetic Resonance Imaging (MRI) reports have explored pituitary gland (PG) in both bipolar disorder (BD) and major depressive disorder (MDD). In this context, the present review summarizes the results from MRI studies with the final aim of commenting on the presence of common or distinct PG structural alterations between these two disabling illnesses.

METHODS

A bibliographic search on PUBMED of all MRI studies exploring PG volumes in BD and MDD as well as first-degree relatives (RELs) from 2000 up to October 2016 was performed.

RESULTS

Following the screening process of the available literature it can be said that a) PG enlargement has been found in both BD and MDD, therefore potentially representing a common neurobiological marker characterizing mood disorders, and b) PG volumes are moderated by age and sex in both illnesses, although the direction and the extent of this moderation are still not fully clear.

LIMITATIONS

Few MRI studies with heterogeneous results.

CONCLUSIONS

These hypotheses must be taken with caution especially because the heterogeneity of the results of the studies reviewed does not allow for a definite answer about the role of PG in affective disorders. Therefore, larger longitudinal studies investigating PG volumes in BD and MDD patients at the early phases of the illness, by considering females and males separately, are needed to further corroborate these findings.

Pituitary gland volumes in bipolar disorder

BACKGROUND

Bipolar disorder has been associated with increased Hypothalamic-Pituitary-Adrenal axis function. The mechanism is not well understood, but there may be associated increases in pituitary gland volume (PGV) and these small increases may be functionally significant. However, research investigating PGV in bipolar disorder reports mixed results. The aim of the current study was twofold. First, to assess PGV in two novel samples of patients with bipolar disorder and matched healthy controls. Second, to perform a meta-analysis comparing PGV across a larger sample of patients and matched controls.

METHODS

Sample 1 consisted of 23 established patients and 32 matched controls. Sample 2 consisted of 39 medication-naïve patients and 42 matched controls. PGV was measured on structural MRI scans. Seven further studies were identified comparing PGV between patients and matched controls (total n; 244 patients, 308 controls).

RESULTS

Both novel samples showed a small (approximately 20mm(3) or 4%), but non-significant, increase in PGV in patients. Combining the two novel samples showed a significant association of age and PGV. Meta-analysis showed a trend towards a larger pituitary gland in patients (effect size: .23, CI: -.14, .59).

LIMITATIONS

While results suggest a possible small difference in pituitary gland volume between patients and matched controls, larger mega-analyses with sample sizes greater even than those used in the current meta-analysis are still required.

CONCLUSIONS

There is a small but potentially functionally significant increase in PGV in patients with bipolar disorder compared to controls. Results demonstrate the difficulty of finding potentially important but small effects in functional brain disorders.

Pituitary gland in psychiatric disorders: a review of neuroimaging findings

In this paper, it was reviewed neuroimaging results of the pituitary gland in psychiatric disorders, particularly schizophrenia, mood disorders, anxiety disorders, and somatoform disorders. The author made internet search in detail by using PubMed database including the period between 1980 and 2012 October. It was included in the articles in English, Turkish and French languages on pituitary gland in psychiatric disorders through structural or functional neuroimaging results. After searching mentioned in the Methods section in detail, investigations were obtained on pituitary gland neuroimaging in a variety of psychiatric disorders. There have been so limited investigations on pituitary neuroimaging in psychiatric disorders including major psychiatric illnesses like schizophrenia and mood disorders. Current findings are so far from the generalizability of the results. For this reason, it is required to perform much more neuroimaging studies of pituitary gland in all psychiatric disorders to reach the diagnostic importance of measuring it.

Neuroprogression in bipolar disorder

OBJECTIVE

Recent theories regarding the neuropathology of bipolar disorder suggest that both neurodevelopmental and neurodegenerative processes may play a role. While magnetic resonance imaging has provided significant insight into the structural, functional, and connectivity abnormalities associated with bipolar disorder, research assessing longitudinal changes has been more limited. However, such research is essential to elucidate the pathophysiology of the disorder. The aim of our review is to examine the extant literature for developmental and progressive structural and functional changes in individuals with and at risk for bipolar disorder.

METHODS

We conducted a literature review using MEDLINE and the following search terms: bipolar disorder, risk, child, adolescent, bipolar offspring, MRI, fMRI, DTI, PET, SPECT, cross-sectional, longitudinal, progressive, and developmental. Further relevant articles were identified by cross-referencing with identified manuscripts.

CONCLUSIONS

There is some evidence for developmental and progressive neurophysiological alterations in bipolar disorder, but the interpretation of correlations between neuroimaging findings and measures of illness exposure or age in cross-sectional studies must be performed with care. Prospective longitudinal studies placed in the context of normative developmental and atrophic changes in neural structures and pathways thought to be involved in bipolar disorder are needed to improve our understanding of the neurodevelopmental underpinnings and progressive changes associated with bipolar disorder.

Structural studies of the hypothalamus and its nuclei in mood disorders

A large body of evidence indicates that the hypothalamus is involved in pathogenetic mechanisms of mood disorders. It has been suggested that functional abnormalities of the hypothalamus are associated with structural hypothalamic changes. Structural neuroimaging allows in vivo investigation of the hypothalamus that may shed light on the underlying pathogenetic mechanisms of unipolar and bipolar disorder. Clearly, the detection of subtle structural cerebral changes depends on the limitations of the neuroimaging technique used. Making a comprehensive database search, we reviewed the literature on hypothalamic macrostructure in affective disorders, addressing the specific question of what structural magnetic resonance imaging might be expected to show. Studies with convincing methodology, although rare, suggest a global volume decrease in the hypothalamus in affective disorders, a decrease which is not shown by the two specific nuclei investigated, the paraventricular and supraoptic nuclei. We discuss the implications of these findings and provide directions for future research.

Pituitary volume prospectively predicts internalizing symptoms in adolescence

BACKGROUND

Early adolescence is a critical time for the development of both internalizing and externalizing disorders. We aimed to investigate whether pituitary volume, an index of hypothalamic-pituitary-adrenal (HPA) axis function, represents a vulnerability factor for the emergence of internalizing and externalizing symptoms during adolescence using a prospective, longitudinal design.

METHODS

One hundred and fifty-five adolescents completed 3T structural magnetic resonance imaging (MRI), symptom rating scales and a diagnostic interview during early adolescence (M age 12.6 years, SD .5 years); symptom rating scales were re-administered approximately three years later (M age 15.2 years). The volume of the pituitary gland was estimated by manually delineating its structure on MR images. The degree to which pituitary volumes prospectively predicted change in internalizing and externalizing symptoms across the two time-points was assessed using hierarchal linear regression, after controlling for the influence of gender, age, pubertal stage and intracranial volume.

RESULTS

Larger pituitary volumes prospectively predicted an increase in internalizing, but not externalizing, symptoms from early adolescence to mid-adolescence.

CONCLUSIONS

This study provides the first evidence that increased pituitary volume might represent a specific vulnerability marker for the development of internalizing symptoms during early to mid-adolescence.

Pituitary volume and third ventricle width in euthymic patients with bipolar disorder

BACKGROUND

Many of the clinical and neuroendocrine features of bipolar disorder involve hypothalamic structures. Although current neuroimaging techniques inadequately resolve the structural components of the hypothalamus, evidence of derangement can be sought by examining the adjacent third ventricle and the functionally related pituitary.

AIMS

To investigate the structure and function of the hypothalamic-pituitary-adrenal axis in euthymic patients with bipolar disorder.

METHOD

Euthymic adult patients with bipolar disorder (n=49) were compared with matched normal control subjects (n=47). Pituitary volume and third ventricle width were assessed on MRI scans. Basal salivary cortisol levels were measured.

RESULTS

The width of the third ventricle in patients with bipolar disorder exceeded that of controls (mean +/- SD (in mm): 3.87 +/- 1.96 versus 2.56 +/- 1.34; d=0.76, ANOVA F=12.7, p=0.001), with the greatest differences found in males. Third ventricle width increased with age across the groups (F=16.97, p<0.001). Pituitary volumes did not differ between patients and controls (mean +/- SD (in mm(3)): 632 +/- 176 versus 679 +/- 159). Overall, females had larger pituitaries than males (703 +/- 160 versus 595 +/- 161; d=0.67, F=9.65, p=0.003; all subjects), but female patients had smaller pituitaries compared to female controls (637 +/- 178 versus 756 +/- 126; d=0.65, F=5.04, p=0.03). No difference was found in a comparable analysis of males. Pituitary volume did not differ between patients prescribed and not prescribed antipsychotic drugs. Basal salivary cortisol levels did not differ between patients and controls.

CONCLUSIONS

In euthymic patients with normal basal cortisol levels, pituitary volume and third ventricle width were found to differ from normal controls. These differences were related to gender, may be important in the pathogenesis of bipolar disorder and could link the vegetative and endocrine abnormalities seen in this condition. Such findings may reflect a trait abnormality or be a consequence of previous episodes.

Pituitary volume in patients with bipolar disorder and their first-degree relatives

BACKGROUND

Hypothalamic-pituitary-adrenal (HPA) axis dysregulation has been reported in bipolar disorder (BD), but previous magnetic resonance imaging (MRI) studies of pituitary gland volume in BD have yielded inconsistent findings. In addition, the contribution of genetic factors to the pituitary changes in BD remains largely unknown.

METHOD

We used MRI to investigate the pituitary volume in 29 remitted patients with BD, 49 of their first-degree relatives (of whom 15 had a diagnosis of Major Depressive Disorder), and 52 age- and gender-matched healthy controls.

RESULTS

BD patients had a significantly larger pituitary volume compared with their relatives and healthy controls. Pituitary volume did not differ between controls and healthy relatives or relatives diagnosed with major depression.

LIMITATIONS

Direct measures of HPA function (i.e., hormonal levels) were not available.

CONCLUSIONS

These findings suggest that enlarged pituitary volume is associated with disease expression but not genetic susceptibility to BD.

The role of dopamine in bipolar disorder

OBJECTIVE

Despite effective pharmacological treatments for bipolar disorder, we still lack a comprehensive pathophysiological model of the illness. Recent neurobiological research has implicated a number of key brain regions and neuronal components in the behavioural and cognitive manifestations of bipolar disorder. Dopamine has previously been investigated in some depth in bipolar disorder, but of late has not been a primary focus of attention. This article examines the role of dopamine in bipolar disorder, incorporating recent advances into established models where possible.

METHODS

A critical evaluation of the literature was undertaken, including a review of behavioural, neurochemical, receptor, and imaging studies, as well as genetic studies focusing on dopamine receptors and related metabolic pathways. In addition, pharmacologic manipulation of the central dopaminergic pathways and comparisons with other disease states such as schizophrenia were considered, principally as a means of exploring the hypothesised models.

RESULTS

Multiple lines of evidence, including data from pharmacological interventions and structural and functional magnetic resonance imaging studies, suggest that the dopaminergic system may play a central role in bipolar disorder.

CONCLUSION

Future research into the pathophysiological mechanisms of bipolar disorder and the development of new treatments for bipolar disorder should focus on the dopaminergic system.

Increased pituitary volume in patients with established bipolar affective disorder

Hypothalamic-pituitary-adrenal (HPA) axis dysfunction has been demonstrated in bipolar disorder (BD), but previous magnetic resonance imaging (MRI) studies of pituitary gland volume in BD have reported variable findings. In this MRI study we investigated pituitary volume in 26 patients with established bipolar I disorder (8 males and 18 females, mean age=38.4 years) and 24 matched controls (7 males and 17 females, mean age=38.7 years). The BD patients had a significantly larger pituitary volume as compared with controls, but there was no association between pituitary volume and illness duration, number of manic/depressive episodes, daily medication dosage, family history, or clinical subtype (i.e., psychotic and nonpsychotic). Pituitary volume was larger in females than in males for both groups. These results support previous neuroendocrine findings that implicate HPA axis dysfunction in the core pathophysiological process of BD.

Magnetic resonance imaging studies in bipolar disorder and schizophrenia: meta-analysis

BACKGROUND

Several magnetic resonance imaging (MRI) studies have identified structural abnormalities in association with bipolar disorder. The literature is, however, heterogeneous and there is remaining uncertainty about which brain areas are pivotal to the pathogenesis of the condition.

AIMS

To identify, appraise and summarise volumetric MRI studies of brain regions comparing bipolar disorder with an unrelated control group and individuals with schizophrenia.

METHOD

A systematic review and random-effects meta-analysis was carried out to identify key areas of structural abnormality in bipolar disorder and whether the pattern of affected areas separated bipolar disorder from schizophrenia. Significant heterogeneity was explored using meta-regression.

RESULTS

Participants with bipolar disorder are characterised by whole brain and prefrontal lobe volume reductions, and also by increases in the volume of the globus pallidus and lateral ventricles. In comparison with schizophrenia, bipolar disorder is associated with smaller lateral ventricular volume and enlarged amygdala volume. Heterogeneity was widespread and could be partly explained by clinical variables and year of publication, but generally not by differences in image acquisition.

CONCLUSIONS

There appear to be robust changes in brain volume in bipolar disorder compared with healthy volunteers, although most changes do not seem to be diagnostically specific. Age and duration of illness appear to be key issues in determining the magnitude of observed effect sizes.

Pituitary volumes in relatives of bipolar patients: high-risk study

BACKGROUND

Increased, decreased, as well as unchanged pituitary volumes have been reported in bipolar disorders (BD). It is unclear, whether abnormal pituitary volumes increase vulnerability for BD (primary vulnerability marker), or are secondary to burden of illness. To address this question, we performed the first high-risk study of pituitary volumes in affected and unaffected relatives of bipolar subjects.

METHOD

High-risk participants (age range 15-30 years) were recruited from families multiply affected with BD and included 24 unaffected, 19 affected subjects with first or second degree bipolar I or II relative, matched by age and sex with 31 controls without a personal or family history of psychiatric disorders. Pituitary volumes were measured on 1.5 T 3D anatomical MRI images using standard methods.

RESULTS

We found comparable pituitary volumes among unaffected, affected relatives of bipolar patients and controls. There were no differences in pituitary volumes between male and female subjects nor was there any sex by group interaction. Analyzing 26 participants with bipolar I parent or excluding 5 medicated subjects did not change the results. There were no differences between subjects from families containing bipolar I versus families containing only bipolar II subjects.

CONCLUSIONS

The lack of abnormalities in unaffected and also affected subjects early in the course of illness in our study, as well as previous investigations of bipolar and familial unipolar children and adolescents, suggest that pituitary volume abnormalities are unlikely to be a primary risk factor for mood disorders.

Pituitary volume in unaffected relatives of patients with schizophrenia and bipolar disorder

BACKGROUND

Hypothalamic-pituitary-adrenal (HPA) axis hyperactivity has been demonstrated in both schizophrenia and bipolar disorder, but the mechanisms underlying this abnormality are still unclear. Enlarged pituitary volume has been recently reported in patients with first episode psychosis and been interpreted as a consequence of an increased activation of the HPA axis. The aim of this study was to assess the contribution of familial liability to pituitary volume in schizophrenia and bipolar disorder. Pituitary volume may be an indirect measure of HPA axis activity.

METHODS

MRI brain scans and measurements of pituitary volumes were obtained for 183 subjects: 26 patients with established schizophrenia or schizoaffective disorder, 44 of their unaffected first-degree relatives (22 familial schizophrenia, 22 non-familial schizophrenia), 29 patients with established bipolar disorder, 38 of their unaffected first-degree relatives, and 46 healthy comparison subjects.

RESULTS

We found a significantly larger pituitary volume (effect size=0.7) in unaffected relatives of patients with schizophrenia compared with controls (p=0.002); the pituitary was even larger in relatives of patients with familial schizophrenia (effect size=0.8, p=0.005). We did not find a significant difference in pituitary volume when comparing the relatives of bipolar patients with controls. Among patients, those with schizophrenia who were receiving prolactin-elevating antipsychotics had an increased pituitary volume compared with controls (effect size=1.0, p=0.006).

CONCLUSIONS

These results suggest that the larger pituitary volume previously reported in first episode schizophrenia could be partly due to a genetic susceptibility to over-activate the HPA axis.

Pituitary volume in psychosis: the first review of the evidence

The pituitary gland regulates hypothalamic-pituitary-adrenal (HPA) axis activity by secreting adrenocorticotropic hormone (ACTH), and HPA axis abnormalities have been described in psychosis. Moreover, the pituitary gland secretes prolactin, and some antipsychotics increase the secretion of this hormone. Therefore, it is possible that psychosis is associated with an abnormal volume of the pituitary, as a consequence of a dysfunction in either or both these hormonal systems. The present review of the studies conducted so far clearly indicates that the pituitary is a dynamic organ, which changes differently at different stages of the psychotic disorder, in response to both the disorder itself and the treatment with antipsychotics. Specifically, the pituitary is larger in the months immediately preceding or following the psychosis onset, independently from antipsychotic treatments. However, following this initial enlargement, the pituitary tends to become smaller, as suggested by studies in patients with psychosis of at least two years of duration. On top of these dynamic changes that are linked to the course of the disorder, antipsychotics, and especially antipsychotics inducing hyperprolactinaemia, exert additional enlarging effects on pituitary volume. We suggest that the increased pituitary volume associated with the development of psychosis is due to activation of the hormonal stress response and, specifically, to an increase in the size and number of corticotroph cells producing ACTH, while the increased pituitary volume induced by antipsychotics is linked to the stimulating effects of these drugs on lactotroph cells producing prolactin. Future studies should address these issues that are relevant in improving the care of patients with psychosis.

Pituitary gland volume in adolescent and young adult bipolar and unipolar depression

OBJECTIVES

Few studies have examined pituitary gland size in mood disorders, particularly in adolescents. We hypothesized increase in the pituitary gland size in early-onset mood disorders.

METHODS

Thirty subjects between the ages of 13 and 20 years participated in the study. Three groups (control, bipolar I depression and unipolar depression) of 10 subjects each (4 male, 6 female) underwent volumetric magnetic resonance imaging at 1.5 T.

RESULTS

Analysis of covariance (covarying for age, sex and intracranial volume) revealed a significant difference in pituitary gland volume amongst the groups [F(2,24) = 7.092, p = 0.014]. Post hoc analysis revealed that controls had a significantly smaller pituitary gland volume than both bipolar patients (p = 0.019) and depressed patients (p = 0.049). Bipolar and depressed subjects did not differ significantly from each other with regard to pituitary gland volume (p = 0.653). Control females had larger pituitary glands than control males [F(1,8) = 10.523, p = 0.012], but no sex differences were noted in the mood disorder groups.

CONCLUSIONS

Pituitary glands are enlarged in adolescents with mood disorders compared to controls. Healthy young females have larger pituitary glands than males, but such a difference is not evident in individuals with unipolar depression or bipolar disorder. These findings provide new evidence of abnormalities of the pituitary in early onset mood disorders, and are consistent with neuroendocrine dysfunction in early stages of such illnesses.

Volumetric neuroimaging investigations in mood disorders: bipolar disorder versus major depressive disorder

BACKGROUND

As patients with mood disorders manifest heterogeneity in phenomenology, pathophysiology, etiology, and treatment response, a biological classification of mental disease is urgently needed to advance research. Patient and methodological variability complicates the comparison of neuroimaging study results and limits heuristic model development and a biologically-based diagnostic schema.

OBJECTIVE

We have critically reviewed and compared the magnetic resonance neuroimaging literature to determine the degree and directionality of volumetric changes in brain regions putatively implicated in the pathophysiology of major depressive disorder (MDD) versus bipolar disorder (BD).

METHODS

A total of 140 published magnetic resonance imaging investigations evaluating subjects with BD or MDD were selected to provide a summary and interpretation of volumetric neuroimaging results in MDD and BD. Further commentary on the pathophysiological implications, and putative cellular and pharmacological mechanisms, is also provided.

RESULTS

While whole brain volumes of patients with mood disorders do not differ from those of healthy controls, regional deficits in the frontal lobe, particularly in the anterior cingulate and the orbitofrontal cortex, appear to consistently differentiate subjects with mood disorders from the general population. Preliminary findings also suggest that subcortical structures, particularly the striatum, amygdala, and hippocampus, may be differentially affected in MDD and BD.

CONCLUSIONS

Structural neuroimaging studies have consistently identified regional abnormalities in subjects with mood disorders. Future studies should strive to definitively establish the influence of age and medication.

Normal pituitary volumes in chronic schizophrenia

Pituitary volumes were shown to be abnormally large in pre- or first-psychotic episode patients and abnormally reduced in established schizophrenia by magnetic resonance imaging (MRI) studies. We present here the results of the second ever published MRI study exploring pituitary size in a large population of patients with chronic schizophrenia recruited from the geographically defined catchment area of South Verona, Italy. No significant differences for pituitary volumes were reported between 65 subjects with chronic schizophrenia and 65 normal individuals (mean age+/-S.D.=42.31+/-11.44 and 40.54+/-11.12 years). In contrast to Pariante et al. (2004), normal pituitary size was found in our population of chronic schizophrenia. Discrepancies between these two studies may partially be accounted by sample age and gender. Considering increased pituitary volumes in pre- or first-psychotic episode patients, we put forward the hypothesis that pituitary size may normalize or reduce with the progression of the illness as a result of reduced numbers of acute episodes and consequent diminished hypothalamus-pituitary-adrenal axis activity. To better test this hypothesis, future large MRI studies should investigate pituitary volumes in chronic schizophrenia longitudinally, also collecting pituitary hormones and cortisol, and comparing the effects of typical and atypical antipsychotics on pituitary size in a randomized trial.

Pituitary volume in treatment-naïve pediatric major depressive disorder

BACKGROUND

Prior pilot investigation identified a larger pituitary gland volume (PGV) in pediatric patients with major depressive disorder (MDD) compared with healthy pediatric control subjects that was most prominent in boys with MDD. In this independent sample, we focus on gender differences in pituitary volume in a larger sample of pediatric patients with MDD.

METHODS

Volumetric magnetic resonance imaging studies were conducted in 35 psychotropic drug-naïve children (15 boys, 20 girls), ages 8-17 years, and 35 case-matched healthy control subjects.

RESULTS

The MDD boys had larger PGV (19%) compared with male control subjects. No significant diagnostic group differences in pituitary volume were observed in girls. Healthy boys had significantly smaller PGV (27%) than healthy girls, whereas MDD boys did not differ from girls with MDD. Nonfamilial (without a family history of mood disorder) boys with MDD had significantly larger PGV (35%) than male healthy control subjects and tended to have a larger PGV (27%) than familial (at least one first-degree relative with MDD) boys with MDD. Boys with familial MDD did not differ from control subjects.

CONCLUSIONS

These findings provide new evidence of increased pituitary volume in psychotropic-naïve pediatric patients with MDD that seems to be more prominent in male patients with nonfamilial MDD.

Rational approaches to the neurobiologic study of youth at risk for bipolar disorder and suicide

OBJECTIVES

The aims of this paper are to provide an overview of neuroimaging findings specific to bipolar disorder and suicide, and to consider rational approaches to the design of future in vivo studies in youth at risk.

METHODS

Neuroimaging and related neurobiological literature pertaining to bipolar disorder and suicide in adult and pediatric samples was reviewed in a non-quantitative manner.

RESULTS

Specific structural and functional brain findings in bipolar disorder are described, where possible in the context of relevant current neurobiological theories of etiology. Diagnostic and prognostic implications are discussed.

CONCLUSIONS

The simultaneous use of complementary neurobiological approaches may be a powerful way of identifying and validating factors reliably associated with bipolar disorder and suicide. A profile of neurobiological markers with which to screen for bipolar disorder and suicide risk may provide for earlier and more accurate diagnosis, perhaps even in the pre- or subsyndromal stages in high-risk youth.

The neurophysiology of childhood and adolescent bipolar disorder

INTRODUCTION

Children and adolescents with bipolar disorder often present with higher rates of mixed episodes, rapid cycling, and co-occurring attention-deficit/hyperactivity disorder than adults with bipolar disorder. It is unclear whether the differences in clinical presentation between youth and adults with bipolar disorder are due to differences in underlying etiologies or developmental differences in symptom manifestation. Neuroimaging studies of children and adolescents with bipolar disorder may clarify whether neurobiological abnormalities associated with early- and adult-onset bipolar disorder are distinct. Moreover, children and adolescents with bipolar disorder are typically closer to their illness onset than bipolar adults, providing a window of opportunity for identifying core neurobiological characteristics of the illness (ie, disease biomarkers) that are independent of repeated affective episodes and other confounding factors associated with illness course.

METHODS

Peer-reviewed publications of neuroimaging studies of bipolar children and adolescents were reviewed.

RESULTS

Structural, neurochemical, and neurofunctional abnormalities in prefrontal and medical temporal and subcortical limbic structures, including the striatum, amygdala, and possibly hippocampus, are present in children and adolescents with bipolar disorder.

CONCLUSION

Differences between neurobiological abnormalities in bipolar youth and adults as well as recommendations for future research directions are discussed.

Magnetic resonance spectroscopic studies of pediatric mood disorders: a selective review

PURPOSE OF REVIEW

This review article presents a summary of the recent magnetic resonance spectroscopic studies of pediatric mood disorders.

RECENT FINDINGS

Magnetic resonance imaging is a promising tool for investigating the biologic substrates of neuropsychiatric disorders without the use of ionizing radiation. This novel technique has been recently applied to pediatric patients with mood disorders. Structural, chemical, and functional abnormalities in pediatric patients with mood disorders have been reported.

SUMMARY

To date, only modest numbers of pediatric studies using magnetic resonance imaging have been conducted. Most of these studies have small sample sizes and heterogeneous subject groups. These studies have provided important information regarding the underlying neuro-circuitry and pathophysiology of these complex and disabling disorders, however.

Increased pituitary volume in antipsychotic-free and antipsychotic-treated patients of the AEsop first-onset psychosis study

Subjects at their first psychotic episode show an enlarged volume of the pituitary gland, but whether this is due to hypothalamic-pituitary-adrenal (HPA) axis hyperactivity, or to stimulation of the prolactin-secreting cells by antipsychotic treatment, is unclear. We measured pituitary volume, using 1.5-mm, coronal, 1.5 T, high-resolution MRI images, in 78 patients at the first psychotic episode and 78 age- and gender-matched healthy controls. In all, 18 patients were antipsychotic-free (12 of these were antipsychotic-naïve), 26 were receiving atypical antipsychotics, and 33 were receiving typical antipsychotics. As hypothesized, patients had a larger pituitary volume than controls (+22%, p< 0.001). When divided by antipsychotic treatment, and compared to controls, the pituitary volume was 15% larger in antipsychotic-free patients (p=0.028), 17% larger in patients receiving atypicals (p=0.01), and 30% larger in patients receiving typicals (p<0.001). Patients receiving typicals not only had the largest pituitary volume compared to controls but also showed a trend for a larger pituitary volume compared to the other patients grouped together (+11%, p=0.08). When divided by diagnosis, and compared to controls, the pituitary volume was 24% larger in patients with schizophrenia/schizophreniform disorder (n=40, p<0.001), 19% larger in depressed patients (n=13, p=0.022), 16% larger in bipolar patients (n=16, p=0.037), and 12% larger in those with other psychoses (n=9, p=0.2). In conclusion, the first-episode of a psychotic disorder is associated with a larger pituitary independently of the presence of antipsychotic treatment, and this could be due to activation of the HPA axis. Typical antipsychotics exert an additional enlarging effect on pituitary volume, likely to be related to activation of prolactin-secreting cells. This activation of the hormonal stress response could participate to the important metabolic abnormalities observed in patients with psychosis.

Neuroanatomical abnormalities as risk factors for bipolar disorder

OBJECTIVE

Neuroimaging studies show structural brain abnormalities in bipolar patients. Some of the abnormalities may represent biological risk factors conveying vulnerability for the disease. This paper aims to identify neuroanatomical risk factors for bipolar disorder (BD).

METHODS

We reviewed magnetic resonance imaging (MRI) findings in populations in which the effects of the disease or treatment are minimal or where the chances of finding genetically coded risk factors shared within the families are increased. Such populations include unaffected relatives of bipolar patients, first-episode patients, children or adolescents with BD and patients with familial BD.

RESULTS

MEDLINE search revealed 30 relevant scientific papers. Abnormalities in the volume of the striatum, left hemispheric white matter, thalamus and anterior cingulate as well as quantitative MRI signal hyperintensities were identified already in unaffected relatives of bipolar patients. Subjects in the early stages of the disease showed volume changes of the ventricles, white matter, caudate, putamen, amygdala, hippocampus and the subgenual prefrontal cortex. Reduction in the subgenual prefrontal cortex volume was replicated in three of four studies in patients with familial BD.

CONCLUSIONS

Possible candidates for neuroanatomical risk factors for BD are volumetric abnormalities of the subgenual prefrontal cortex, striatum, white matter, and probably also the hippocampus and amygdala. Qualitative finding of white matter hyperintensities was already utilized as an endophenotype.

Fronto-limbic brain abnormalities in juvenile onset bipolar disorder

BACKGROUND

Advances in brain imaging techniques and cognitive neuropsychology have brought new possibilities for the in vivo study of the pathophysiology of neuropsychiatric disorders, including bipolar disorder (BD). Recently, such studies have been extended to the pediatric age range. Here we review the neuroimaging and neuropsychological studies conducted in BD children and adolescents.

METHODS

A review of the peer-reviewed published literature was conducted in Medline for the period of 1966 to April 2005.

RESULTS

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) studies suggest abnormalities in fronto-limbic structures in pediatric BD patients, similar to those found in adults. A notable exception in pediatric BD patients is smaller amygdala volumes compared to healthy controls, contrary to what has been reported in most adult studies.

CONCLUSIONS

Further research evaluating children and adolescents is needed to study the normal neurodevelopmental process and to answer how and when the illness processes that result in bipolar disorder exert their effects on the developing brain.