Changes in regional cerebral blood flow demonstrated by single photon emission computed tomography in depressive disorders: comparison of unipolar vs. bipolar subtypes

Investigating the association between depression and cerebral haemodynamics-A systematic review and meta-analysis

BACKGROUND

Vascular mechanisms may play a role in depression. The aim of this review is to summarise the evidence on alterations in cerebral haemodynamics in depression.

METHODS

MEDLINE (1946- present), Embase (1947-present), Web of Science (1970-present), PsycINFO (1984-present), CINAHL (1976-present) and CENTRAL were searched using a predefined search strategy. A meta-analysis was conducted in four groups: 1) global cerebral blood flow (CBF) in ml/min/100 g, 2) CBF velocity (CBFv) in cm/s (maximum flow of left middle cerebral artery, 3) combined CBF and CBFv, 4) Ratio of uptake of Tc 99 m HMPAO (region of interest compared to whole brain). Data are presented as mean difference or standardised mean difference and 95% confidence interval (95% CI). A narrative synthesis of the remaining studies was performed.

RESULTS

87 studies were included. CBF was significantly reduced in depressed patients compared to HC [15 studies, 538 patients, 416 HC, MD: -2.24 (95% CI -4.12, -0.36), p = 0.02, I² = 64%]. There were no statistically significant differences in other parameters. The narrative synthesis revealed variable changes in CBF in depressed patients, particularly affecting the anterior cingulate and prefrontal cortices.

LIMITATIONS

There were various sources of heterogeneity including the severity of depression, use of antidepressant medication, imaging modality used and reporting of outcomes. All of these factors made direct comparisons between studies difficult.

CONCLUSIONS

The reduction in CBF in depressed patients compared to HCs may indicate a role for assessment and CBF altering interventions in high-risk groups. However, results were inconsistent across studies, warranting further work to investigate specific subgroups.

Call to action regarding the vascular-bipolar link: A report from the Vascular Task Force of the International Society for Bipolar Disorders

OBJECTIVES

The association of bipolar disorder with early and excessive cardiovascular disease was identified over a century ago. Nonetheless, the vascular-bipolar link remains underrecognized, particularly with regard to how this link can contribute to our understanding of pathogenesis and treatment.

METHODS

An international group of experts completed a selective review of the literature, distilling core themes, identifying limitations and gaps in the literature, and highlighting future directions to bridge these gaps.

RESULTS

The association between bipolar disorder and vascular disease is large in magnitude, consistent across studies, and independent of confounding variables where assessed. The vascular-bipolar link is multifactorial and is difficult to study given the latency between the onset of bipolar disorder, often in adolescence or early adulthood, and subsequent vascular disease, which usually occurs decades later. As a result, studies have often focused on risk factors for vascular disease or intermediate phenotypes, such as structural and functional vascular imaging measures. There is interest in identifying the most relevant mediators of this relationship, including lifestyle (eg, smoking, diet, exercise), medications, and systemic biological mediators (eg, inflammation). Nonetheless, there is a paucity of treatment studies that deliberately engage these mediators, and thus far no treatment studies have focused on engaging vascular imaging targets.

CONCLUSIONS

Further research focused on the vascular-bipolar link holds promise for gleaning insights regarding the underlying causes of bipolar disorder, identifying novel treatment approaches, and mitigating disparities in cardiovascular outcomes for people with bipolar disorder.

Cerebral blood flow in bipolar disorder: A systematic review

BACKGROUND

Neuroimaging of cerebral blood flow (CBF) can inform our understanding of the pathophysiology of bipolar disorder (BD) as there is increasing support for the concept that BD is in part a vascular disease. Despite numerous studies examining CBF in BD, there has not yet been a review of the literature on the topic of CBF in BD.

METHODS

A systematic review of the literature on CBF in BD was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). Studies included measured CBF by single-photon emission computerized tomography (SPECT), positron emission tomography (PET), arterial spin labelling (ASL) or perfusion weighted imaging (PWI) in a group of BD patients.

RESULTS

Thirty-three studies with a total of 508 subjects with BD and 538 controls were included (n = 15 SPECT; n = 8 PET; n = 7 ASL; n = 1 PWI; n = 2 other). The majority of studies in BD depression and mania reported widespread resting hypoperfusion in cingulate gyrus, frontal, and anterior temporal regions in comparison to healthy controls (HC). Findings in euthymic BD subjects and in symptomatically heterogeneous groups were less consistent. Studies that examined CBF responses to cognitive or emotional stimuli in BD subjects have reported hypoperfusion or different regions involved in comparison to HC.

LIMITATIONS

Important methodological heterogeneity between studies, and small number of subjects per study.

CONCLUSIONS

The most consistent findings to date are hypoperfusion in BD mood episodes, and hypoactive CBF responses to emotional or cognitive challenges. Future studies examining CBF are warranted, including prospective studies, studies examining CBF as a treatment target, and multimodal imaging studies.

Determinants of brain SPECT perfusion and connectivity in treatment-resistant depression

This study aims to characterize and compare functional brain single photon emission tomography (SPECT) perfusion and connectivity in treatment-resistant depression (TRD) according to distinct demographic or clinical profiles (male vs. female; old vs. young; unipolar vs. bipolar) and to study their relationship to the severity and the duration of episode/illness. We retrospectively included 127 consecutive patients who met DSM-IV criteria for a nonpsychotic major TRD episode. All patients were studied using (99m)Tc-ethyl cysteinate dimer SPECT. Whole-brain, voxel-based, between-groups analyses were performed according to demographic and clinical data and in comparison to 37 healthy subjects. Voxel-wise interregional correlation was also performed to compare functional SPECT connectivity. Finally, relationships were searched for regarding severity and duration of episode/illness. The whole group of patients exhibited significant hypoperfusion within bilateral fronto-temporal, insular, and anterior cingulate cortices, as well as within the left caudate. Functional connectivity between left frontal and left cerebellar regions was higher in patients than in healthy subjects. Gender, age, and type of mood disorder did not influence these SPECT patterns. A significant relationship was found between brain SPECT perfusion and either duration or global severity of illness in particular frontal areas. Our data support the hypothesis of a shared SPECT pattern, whatever the profile of TRD, involving fronto-temporal regions and the cerebellum.

Cerebral blood flow, metabolic, receptor, and transporter changes in bipolar disorder: the role of PET and SPECT studies

The basic concepts of positron emission tomography (PET) and single photon emission computed tomography (SPECT) scanning are introduced, and the two modalities are compared. Applications to bipolar disorder (BD) are reviewed. Regional cerebral metabolic rate and blood flow, often used as surrogate measures of neuronal synaptic activity, are increased in the frontal lobes in both unipolar and bipolar depression. In mania, metabolism increases in the dorsal cingulate cortex, striatal regions, and the nucleus accumbens, as well as in limbic structures of the temporal lobes, but decreases in dorsolateral prefrontal cortex, possibly reflecting its loss of modulatory control over limbic structures. Specifically targeted PET radioligands are used to investigate neurotransmitter systems. D1 receptor binding potentials are reduced in frontal cortex, but striatal D2 receptor density is normal in all phases of non-psychotic BD. Psychotic BD patients show higher D2 receptor densities in the caudate, which correlate with the degree of psychosis but not mood symptoms. The serotonin transporter shows increased density in the thalamus, dorsal cingulate cortex, medial preftontal cortex, and insula of depressed BD patients. In the dorsal cingulate cortex and insula, it correlates with anxiety (and in the cingulate, with suicide attempts).

A single photon emission computerized tomography (SPECT) study of regional cerebral blood flow in bipolar disorder

Data on functional imaging of bipolar disorder (BD) utilizing single photon emission computerized tomography (SPECT) is limited. This study assessed regional cerebral blood flow (rCBF), using (99m)Tc-ECD SPECT, among patients with BD, with mania (N=10) or depression (N=10), compared with 10 patients with unipolar depression and 10 normal controls. Regions of interest were analysed using a semi-automatic brain quantification programme. Compared to controls, patients with mania had significantly reduced perfusion mainly in the left frontal area, also in the left anterior cingulate and parietal cortices; those with bipolar depression had significantly lowered rCBF principally in the anterior temporal regions bilaterally, as well as the left parietal area. Patients with unipolar depression had significantly lowered perfusion than controls in most of the regions examined, chiefly in the anterior temporal and frontal cortices bilaterally; they also had lowered perfusion in the right anterior temporal and frontal areas, as well as the right middle temporal area and the right thalamus, compared to patients with mania. Increased severity of psychotic symptoms was associated with reduced rCBF in patients. These results indicate that altered blood flow in the frontal-subcortical systems characterises patients with BD, as well as those with unipolar depression.

The value of HMPAO SPECT in predicting treatment response to citalopram in patients with major depression

Alterations of regional cerebral blood flow (rCBF) in prefrontal cortex and the anterior cingulate cortex are conspicuous imaging findings in patients with major depression (MD). While these rCBF changes have been suggested as functional disease markers, data in large patient samples examining treatment response prediction to antidepressant therapy are limited. This study examined the predictive value of Tc-99m-HMPAO-SPECT for subsequent treatment response to antidepressant therapy with citalopram in an unprecedented large collective of patients. Ninety-three patients with MD were examined with Tc-99m-HMPAO-SPECT twice, at the beginning of citalopram-treatment (T1) and after 4 weeks of treatment (T2). To determine the impact of rCBF changes associated with treatment response, the patient sample was divided into two subgroups: responders (44 patients) and non-responders (49 patients). A two-sample t-test was used to determine group-specific rCBF-differences. Age, gender and initial Hamilton Rating Scale for Depression (HRSD) were treated as regressors of no interest. The responder group revealed significant relative rCBF increases at T1 in a large region en-compassing predominantly prefrontal and temporal cortices as well as subgenual cingulate cortex. No relative rCBF decreases were detected in this group. The comparison between T1 and T2 revealed trends of rCBF decreases in inferior frontal gyrus and rCBF increases in premotor cortex in the responder group. Our data show that rCBF measurements with TC-99M-HMPAO-SPECT provide a predictor estimate for subsequent treatment response in depressed patients undergoing antidepressant therapy with citalopram. This effect is highly significant and, most notably, independent of the initial HRSD score.

Reduced insight in bipolar I disorder: neurofunctional and neurostructural correlates: a preliminary study

BACKGROUND

To correlate measures of insight for own psychopathology to structural and functional brain imaging findings in 21 patients with DSM-IV bipolar I disorder.

METHODS

Insight was assessed using the Scale to Assess Unawareness of Mental Disorder (SUMD). Resting single photon emission computed tomography (SPECT) and computed tomography (CT) was conducted in patients and 21 normal comparison subjects matched for age, gender and handedness.

RESULTS

Reduced general insight and symptom awareness, but not symptom attribution, were significantly related to cortical and subcortical atrophy, respectively. No correlations between SPECT and insight measures were identified.

LIMITATIONS

Limited sample size and the use of resting state SPECT.

CONCLUSIONS

General and symptom awareness were related to measures of brain atrophy but not to neurofunctioning as measured by SPECT. Future research should consider the structure and function of specific cortical regions, including the frontal and parietal cortices.

Decreased prefrontal, anterior cingulate, insula, and ventral striatal metabolism in medication-free depressed outpatients with bipolar disorder

This study explored whether cerebral metabolic changes seen in treatment resistant and rapid cycling bipolar depression inpatients are also found in an outpatient sample not specifically selected for treatment resistance or rapid cycling. We assessed 15 depressed outpatients with bipolar disorder (six type I and nine type II) who were medication-free for at least 2 weeks and were not predominantly rapid cycling. The average 28-item Hamilton Depression Scale (HAM-D) total score was 33.9. The healthy control group comprised 19 age-matched subjects. All participants received a resting quantitative 18F-fluoro-deoxyglucose positron emission tomography scan. Data analyses were performed with Statistical Parametric Mapping (SPM5). Analyses revealed that depressed patients exhibited similar global metabolism, but decreased absolute regional metabolism in the left much more than right dorsolateral prefrontal cortex, bilateral (left greater than right) insula, bilateral subgenual prefrontal cortex, anterior cingulate, medial prefrontal cortex, ventral striatum, and right precuneus. No region exhibited absolute hypermetabolism. Moreover, HAM-D scores inversely correlated with absolute global metabolism and regional metabolism in the bilateral medial prefrontal gyrus, postcentral gyrus, and middle temporal gyrus. Analysis of relative cerebral metabolism yielded a similar, but less robust pattern of findings. Our findings confirm prefrontal and anterior paralimbic metabolic decreases in cerebral metabolism outside of inpatients specifically selected for treatment resistant and rapid cycling bipolar disorder. Prefrontal metabolic rates were inversely related to severity of depression. There was no evidence of regional hypermetabolism, perhaps because this phenomenon is less robust or more variable than prefrontal hypometabolism.

Changes in regional cerebral blood flow demonstrated by 99mTc-HMPAO SPECT in euthymic bipolar patients

Single photon emission computed tomography (SPECT) with 99mTc-HMPAO was used to compare regional cerebral blood flow (rCBF) in patients with bipolar disorder and in healthy controls. The sample of this study consisted of 16 euthymic bipolar patients who met the DSM-IV criteria and 10 healthy control subjects. The mean regional cerebral blood flow values of the bipolar euthymic patients were significantly lower than those of the controls in the bilateral medial-basal temporal, occipital; medial frontal; parietal regions and in the cingulate gyrus; the hypoperfusion in the cingulate had the highest significant P value (.001, Bonferroni correction). No significant differences in rCBF emerged between right and left-brain regions. The most important findings of the current study are the presence of regional cerebral perfusion alterations, particularly in the cingulate gyrus in the euthymic bipolar patients. Our results imply that underlying brain dysfunction may be independent from manic or depressive episodes in bipolar disorder. Because of the small number of subjects, however, this finding should be viewed as preliminary.

Identifying functional neuroimaging biomarkers of bipolar disorder: toward DSM-V

Bipolar disorder is one of the most debilitating and common illnesses worldwide. Individuals with bipolar disorder frequently present to clinical services when depressed but are often misdiagnosed with unipolar depression, leading to inadequate treatment and poor outcome. Increased accuracy in diagnosing bipolar disorder, especially during depression, is therefore a key long-term goal to improve the mental health of individuals with the disorder. The attainment of this goal can be facilitated by identifying biomarkers reflecting pathophysiologic processes in bipolar disorder, namely impaired emotion regulation, impaired attention, and distractibility, which persist during depression and remission and are not common to unipolar depression. In this critical review, we examine the feasibility of identifying biomarker of bipolar disorder by discussing existing findings regarding functional abnormalities in neural systems underlying emotion processing (amygdala centered), working memory, and attention (dorsolateral prefrontal cortex centered) that persist through bipolar depression and remission and are bipolar specific rather than common to unipolar depression. We then focus on future research goals relating to major clinical problems in bipolar disorder, including, the identification of biomarkers allowing detection of individuals at risk of subsequent development of the disorder. Bipolar disorder is a common, debilitating, and potentially fatal disorder. Current and future research in bipolar disorder should focus on identification of disorder biomarkers to improve diagnostic accuracy and the mental heath of those with the disorder.

Is depression different in older adults?

Psychiatric disorders such as depression are common conditions in older adults. Depression presents similarly to younger adults, but with more psychotic symptoms and apathy. Research has suggested that genetics play a less important role in the etiology of depression in the elderly, but that other biological factors may be more significant. Vascular pathology in particular is thought to be especially important. White-matter hyperintensities are found in the frontal lobes and basal ganglia in greater numbers in older adults with depression, with damage to the frontal–subcortical circuits thought to be particularly important. It is associated with treatment resistance. Prognosis is poor if depression is not detected and treated adequately and this may lead to a higher risk of dementia and death. However, treatment with selective serotonin reuptake inhibitors and other antidepressants, plus psychological therapies, are effective in the older depressed patient and reduce morbidity and mortality.

Regional cerebral blood flow changes in depression after electroconvulsive therapy

A large number of studies have documented regional cerebral blood flow (rCBF) abnormalities in depression. A smaller yet significant number of studies have examined changes in rCBF before and after treatment. The findings, however, have been variable with regard to changes before and after electroconvulsive therapy (ECT). A consecutive series of patients (n=10) with drug-resistant major depressive episode according to DSM-IV with 17-item Hamilton Rating Scale for Depression (HRSD) scores greater than or equal to 14 gave their informed consent and were studied with technetium-99m ethyl cysteinate dimer single-photon emission computed tomography (99mTc-ECD SPECT) before and after a course of ECT. The results were analyzed with statistical parametric mapping version 99. No region showed significant positive correlations between rCBF patterns of changes and HRSD changes, but three clusters emerged as showing significant negative correlations. These regions corresponded with left frontopolar gyrus, left amygdala, globus pallidus and nucleus accumbens, and left superior temporal gyrus. It was speculated that ECT affected both the prefrontal cortex, commonly assumed to be involved in depression, and the amygdala, known to play a central role in the processing of emotional stimuli, through the limbic-cortical-striatal-pallidal-thalamic circuit.

Functional neuroimaging studies in mood disorders

BACKGROUND

Our understanding of the neural circuitry involved in mood disorders is rapidly expanding through the ever-increasing application of functional brain imaging techniques.

OBJECTIVES

A selective review of functional neuroimaging studies in patients with primary mood disorders was undertaken in order to identify points of commonality and controversy in the existing literature.

METHODS

Articles published between 1980 and July 2005 were identified using a range of keywords from relevant on-line databases and key journals.

RESULTS

Increased activity within limbic regions has been consistently associated with depressive states and may also be present in manic states too. Dorsal and ventral prefrontal regions appear compromised as suggested by emerging evidence of cortical inefficiency within prefrontal regions or reductions in their connectivity with limbic areas. Most of the functional changes observed are at least partly reversible following clinical remission although deficits in prefrontal regions may be state-related.

CONCLUSIONS

Despite the use of disparate functional imaging modalities, there is a convergence of findings, and the results described do not appear to differ between unipolar and bipolar depression. However, further data are required in order to fully determine the functional changes occurring during manic states. Future work will also need to elucidate the effects of medication, the utility of specific cognitive tasks, and blood oxygenation level-dependent interactions within these affective states.

Effect of low-frequency transcranial magnetic stimulation on an affective go/no-go task in patients with major depression: role of stimulation site and depression severity

Repetitive transcranial magnetic stimulation (rTMS) holds promise as a therapeutic tool in major depression. However, a means to assess the effects of a single rTMS session on mood to guide subsequent sessions would be desirable. The present study examined the effects of a single rTMS session on an affective go/no-go task known to measure emotional-cognitive deficits associated with major depression. Ten patients with an acute episode of unipolar major depression and eight partially or completely remitted (improved) patients underwent 1 Hz rTMS over the left and right dorsolateral prefrontal cortex prior to task performance. TMS over the mesial occipital cortex was used as a control. We observed significantly improved performance in depressed patients following right prefrontal rTMS. This beneficial effect declined with decreasing depression severity and tended to reverse in the improved group. Left prefrontal rTMS had no significant effect in the depressed group, but it resulted in impaired task performance in the improved group. Our findings indicate that the acute response of depressed patients to rTMS varies with the stimulation site and depression severity. Further studies are needed to determine whether the present paradigm could be used to predict antidepressant treatment success or to individualize stimulation parameters according to specific pathology.

Normal N400 in mood disorders

Individuals diagnosed with major depression have been characterized as having a variety of cognitive problems based on a number of behavioral and psychophysiological measures, but it is not clear whether there is a consistent language processing abnormality in depression. Three studies sought to determine whether diverse mood disordered samples show abnormal semantic processing, as indexed by a failure to show increased N400 event-related brain potential amplitudes to passively viewed incongruent, relative to congruent sentence endings. Individuals with major depression (N = 50) or dysthymia (N = 14) had N400 amplitudes similar to those of controls (N = 41) in this sentence processing paradigm. These results are consistent with a small behavioral literature suggesting intact semantic processing in depression and further indicate that abnormal controlled processing in some tasks does not simply reflect a generalized deficit.

The use of single photon emission computed tomography in depressive disorders

Single photon emission computed tomography (SPECT) and positron emission tomography (PET) have advanced our understanding of the biological underpinnings of depression. There is, however, considerable variability in the literature. Depression is a complex disorder with marked heterogeneity in diagnosis and treatment. There is also evidence of heterogeneity in pathophysiology. In addition, the literature is marked by inconsistencies in the use of imaging techniques and data-analytical procedures. In this review we have attempted to focus on the SPECT studies that have used more refined methodologies and more homogenous clinical sub-groups of patients. We have focused on the main diagnostic sub-types of depression and on specific issues such as treatment response, correlates of neuroimaging abnormalities in depression, and so-called 'emotional circuitry' - the connectivity of regions implicated in depression. The future of molecular imaging in depression will be determined by the pace of the development of useful ligands and the exciting opportunities emerging in the field of imaging genomics. Future studies must attend to several key confounds including clinical heterogeneity, medication and the problems surrounding recruitment of drug-naive patients. It remains the case that longitudinal studies are the design of choice if questions relating to state and trait are to be addressed. Molecular imaging will be used increasingly to quantify neuroreceptor and transporter binding, and the activity of neurtransmitters, allowing the neurochemistry of this complex condition to be explored.

Altering the course of neurodevelopment: a framework for understanding the enduring effects of psychotropic drugs

Childhood is a time filled with wondrous changes, as brain plasticity permits experiences to shape the immature brain to meet the demands of the environment. Change occurs at various levels--from neuroanatomy, including within a given region and its connectivity to other regions, to the function of neurotransmitter systems and their reactivity to pharmacological agents in the short- and long-term. The nature and degree to which drug exposure influences the final adult topography is influenced greatly by the maturational phase of these critical factors. Moreover, evidence is slowly emerging that suggests that the long-term effects of drug exposure are delayed and expressed once the vulnerable system reaches maturation (i.e., typically during adulthood). This phenomenon is known as neuronal imprinting and occurs when the effects of drug exposure outlast the drug itself. Thus, understanding the persistent effects critically depends on the window of observation. Embracing this concept should influence how we conduct preclinical assessments of developmental drug exposure, and ultimately how we conduct clinical assessments of drug efficacy, effectiveness, and safety for the treatment of childhood psychiatric disorders. In this article, we present a model to provide a heuristic framework for making predictions about imprinted effects of childhood drug exposure. We then review epidemiological data on attention deficit hyperactivity disorder (ADHD) and childhood depression, prescription practices, and what is known regarding the long-term consequences of drug exposure in these populations. We conclude with a discussion of the current status of preclinical studies on juvenile stimulant exposure.

A functional MRI study of working memory task in euthymic bipolar disorder: evidence for task-specific dysfunction

OBJECTIVES

Even when euthymic bipolar disorder patients can have persistent deficits in working memory, but the neural basis of this deficit remains unclear. We undertook an functional magnetic resonance imaging investigation of euthymic bipolar disorder patients performing two working memory paradigms; the two-back and Sternberg tasks, selected to examine the central executive and the phonological loop respectively. We hypothesized that neuronal dysfunction would be specific to the network underlying the executive rather than the phonological loop component of working memory.

METHODS

Twelve right-handed euthymic bipolar I males receiving lithium carbonate monotherapy were matched with 12 controls. The two-back task comprised a single working memory load contrasted with baseline vigilance condition. The Sternberg paradigm used a parametric design incorporating variable working memory load with fixed delay between presentation of an array of items to be remembered and a target item. Functional activation data were acquired during performance of the tasks and were analysed to produce brain activation maps representing significant group differences in activation (ANOVA). Load-response curves were derived from the Sternberg task data set.

RESULTS

There were no significant between-group differences (t-test) in performance of the two-back task, or in 2 x 5 group by memory load ANOVA for the performance data from Sternberg task. In the two-back task, compared with controls bipolar disorder patients showed reductions in bilateral frontal, temporal and parietal activation, and increased activations with the left precentral, right medial frontal and left supramarginal gyri. No between-group differences were observed in the Sternberg task at any working memory load.

CONCLUSIONS

Our findings support the notion that, in euthymic bipolar disorder, failure to engage fronto-executive function underpins the core neuropsychological deficits.

The regional cerebral blood flow changes in major depressive disorder with and without psychotic features

Depressive patients with psychotic features demonstrate distinct biological abnormalities in the hypothalamic-pituitary-adrenal axis (HPA), dopaminergic activity, electroencephalogram sleep profiles and measures of serotonergic function when compared to nonpsychotic depressive patients. However, very few functional neuroimaging studies were specifically designed for studying the effects of psychotic features on neuroimaging findings in depressed patients. The objective of the present study was to compare brain Single Photon Emission Tomography (SPECT) images in a group of unmedicated depressive patients with and without psychotic features. Twenty-eight patients who fully met DSM-IV criteria for major depressive disorder (MDD, 12 had psychotic features) were included in the study. They were compared with 16 control subjects matched for age, gender and education. Both psychotic and nonpsychotic depressed patients showed significantly lower regional cerebral blood flow (rCBF) values in the left and right superior frontal cortex, and left anterior cingulate cortex compared to those of controls. In comparison with depressive patients without psychotic features (DwoPF), depressive patients with psychotic features (DwPF) showed significantly lower rCBF perfusion ratios in left parietal cortex, left cerebellum but had higher rCBF perfusion ratio in the left inferior frontal cortex and caudate nucleus. The present study showed that DwPF have a different rCBF pattern compared to patients without psychotic features. Abnormalities involving inferior frontal cortex, striatum and cerebellum may play an important role in the generation of psychotic symptoms in depression.

New insights help define the pathophysiology of bipolar affective disorder: neuroimaging and neuropathology findings

Bipolar affective disorder (BD) is a severe mental illness, characterized by episodes of mania and depression. With the development of Magnetic Resonance Imaging (MRI), neuroimaging methods are now allowing investigation of the neurocircuitry involved in this disorder. This in turn has aided further neuropathological exploration of the brain. Structural MRI and Magnetic Resonance Spectroscopy studies suggest that brain abnormalities in BD are mostly regional, as global measures (cerebral, white and gray matter and ventricular volumes) do not seem to be affected in the majority of patients. The prefrontal and anterior cingulate cortices, and amygdalae are consistently implicated in BD, whilst the evidence for hippocampal involvement is less convincing. Functional studies have found that the activity of the dorsal prefrontal cortex and the anterior cingulate are closely associated with mood symptoms. Activity in the ventral and orbital prefrontal cortex appears reduced both during episodes and in remission. In contrast, amygdala activity shows a persistent increase. We suggest that abnormal interaction between the amygdala and the ventral/orbitofrontal cortex may be a central feature of the pathophysiology of BD.

Decreased N-acetylaspartate in children with familial bipolar disorder

BACKGROUND

Relatively low levels of brain N-acetylaspartate, as measured by magnetic resonance spectroscopy, may indicate decreased neuronal density or viability. Dorsolateral prefrontal levels of N-acetylaspartate have been reported to be decreased in adults with bipolar disorder. We used proton magnetic resonance spectroscopy to investigate dorsolateral prefrontal N-acetylaspartate levels in children with familial bipolar disorder.

METHODS

Subjects were 15 children and adolescents with bipolar disorder, who each had at least one parent with bipolar disorder, and 11 healthy controls. Mean age was 12.6 years for subjects and controls. Subjects were allowed to continue current medications. Proton magnetic resonance spectroscopy at 3-Tesla was used to study 8 cm(3) voxels placed in left and right dorsolateral prefrontal cortex.

RESULTS

Bipolar subjects had lower N-acetylaspartate/Creatine ratios only in the right dorsolateral prefrontal cortex (p <.02). No differences in myoinositol or choline levels were found.

CONCLUSIONS

Children and adolescents with bipolar disorder may have decreased dorsolateral prefrontal N-acetylaspartate, similar to adults with BD, indicating a common neuropathophysiology. Longitudinal studies of at-risk children before the onset and during the early course of bipolar disorder are needed to determine the role of prefrontal N-acetylaspartate as a possible risk marker and/or indication of early bipolar illness progression.

Regional cerebral blood flow in depressed patients with white matter magnetic resonance hyperintensity

BACKGROUND

Functional neuroimaging studies have consistently demonstrated decreased regional cerebral blood flow (rCBF) or metabolism in the frontal lobe, temporal lobe, or anterior cingulate gyrus of depressed patients. On the other hand, white matter hyperintensity as defined by magnetic resonance imaging (MRI) has been the most consistently replicated finding in structural neuroimaging studies on depression; however, these functional and structural neuroimaging findings of depression have not been well integrated. We aimed to clarify the possible associations of MRI-defined subcortical hyperintensities with rCBF changes in depressed patients.

METHODS

Twelve depressed patients with subcortical hyperintensities defined by MRI, 11 depressed patients without MRI hyperintensities, and 25 healthy volunteers underwent 99mTc ECD SPECT. Group comparisons of their rCBF and correlation analysis between MRI hyperintensity and rCBF in patients were performed with a voxel-based analysis using statistical parametric mapping (SPM) software.

RESULTS

Depressed patients showed decreased rCBF compared with control subjects in the frontal lobe, temporal lobe, and anterior cingulate gyrus whether subcortical hyperintensity existed or not; however, the patients with MRI hyperintensity showed decreased rCBF in the thalamus, basal ganglia, and brainstem in addition to cortical areas. Further, the score for white matter hyperintensity correlated negatively with rCBF in subcortical brain structures, including the thalamus and right basal ganglia.

CONCLUSION

Our study indicates that depressed patients with MRI hyperintensities may have dysfunction in subcortical brain structures in addition to dysfunction in the fronto-temporal cortical structures.

Changes in neural circuitry of language before and after treatment of major depression

Language tasks requiring semantic analysis of word meaning activate distinct brain areas including the anterior cingulate gyrus at about 200 msec after the stimulus onset, the left lateral prefrontal cortex at about 250 msec, and the left temporo-parietal (Wernicke's) area at 500-600 msec. Reading the same words activate the insula around 800 msec and left occipital cortex around 200 msec stronger than the semantic analysis in normal subjects. Many of these brain areas also show abnormal activity in resting state in patients with major unipolar depression. We measured 128-channel event-related brain potentials (ERPs) and statistical probability mapping in the use generation task carried out with single visual nouns to explore the topography and time course of these cortical activations related to semantic processing in 11 patients with major unipolar depression before and 8 weeks after treatment with the selective serotonin reuptake inhibitor (SSRI) citalopram. Before treatment in depressed state, the time course for the left prefrontal cortex activation did not show slowing, but was accompanied by the right prefrontal activation with a similar time course. The left posterior temporo-parietal activation appeared later than in normals. Treatment was accompanied by the complete elimination of the right prefrontal activation in the same use generation task. Time course of the posterior left temporo-parietal area showed a trend toward normalization. Insula-related activation in reading task was not seen in depressed state, but was evident in the same patient group after the depression has lifted, presumably as a result of treatment with citalopram.

Correlation of cerebral blood flow and treatment effects of repetitive transcranial magnetic stimulation in depressed patients

The aims of this study were to: (1) assess the effects of repetitive transcranial magnetic stimulation (rTMS) on brain activity in depressed patients as measured by single photon emission tomography (SPECT); (2) evaluate the predictive value of brain SPECT on the antidepressant efficacy of rTMS. Patients (n=17) received 1600 rTMS stimuli at a rate of 10 Hz, 5 days per week for 2 weeks to the left dorsolateral prefrontal cortex. Whole brain SPECT data were acquired using Tc99m-Bicisate. Regional cerebral blood flow (rCBF) was correlated with the % change in the 28-item Hamilton Depression Rating Scale Score (Delta-HDRS) and a semiquantitative region of interest (ROI) analysis was conducted. Prior to rTMS there was a significant left-right asymmetry favoring the right, whereas 2 weeks after the rTMS treatment this asymmetry was reversed. The rCBF in limbic structures was negatively correlated with the outcome and rCBF in several neocortical areas was positively correlated. Brain SPECT can provide information about mechanisms of action of rTMS and may have predictive value for the antidepressant efficacy of rTMS.

Psychotic symptoms in major depressive disorder are associated with reduced regional cerebral blood flow in the subgenual anterior cingulate cortex: a voxel-based single photon emission computed tomography (SPECT) study

BACKGROUND

Delusions and/or hallucinations are not an uncommon feature in severe major depressive episodes. Functional imaging studies of depression have been widely reported in the literature, but few of these have attempted to investigate the neurophysiological correlates of psychotic symptoms.

METHODS

We measured resting regional cerebral blood flow (rCBF) with the (99m)Tc-ECD SPECT technique in patients with major depressive disorder with (n=9) and without (n=12) psychotic features, as well as in a group of healthy volunteers (n=12). Between-group rCBF comparisons were performed using the voxel-based statistical parametric mapping method.

RESULTS

Major depressed patients with psychotic features showed decreased rCBF in the left subgenual anterior cingulate cortex relative to both non-psychotic patients and healthy controls (P<0.001 one-tailed, uncorrected for multiple comparisons). Relative to the non-psychotic group, depressed patients with psychotic symptoms also had a focus of decreased rCBF in the right inferior frontal cortex, with the voxel of maximal significance in the insula (P<0.031, corrected for multiple comparisons). A similar pattern of significant between-group rCBF differences between psychotic and non-psychotic patients emerged after covarying the analysis for the confounding influence of overall illness severity.

CONCLUSIONS

These results provide preliminary evidence that psychotic symptoms in major depression may be associated with abnormalities in ventral paralimbic regions previously implicated in mood regulation and depression.

SPECT and neuropsychological performance in severe depression treated with ECT

BACKGROUND

In severe depression, studies of regional cerebral blood flow (rCBF) by SPECT have not produced uniform results. The association between changes in SPECT and electroconvulsive therapy (ECT) has shown somewhat conflicting data. No data are available on benzodiazepine receptor function SPECT studies in ECT.

METHODS

Twenty drug-resistant adult inpatients fulfilling the DSM-IIIR criteria for major depression were studied by SPECT (rCBF by relative ECD uptake in all, and benzodiazepine receptor function by iomazenil uptake in five subjects) before and 1 week after clinically successful bitemporal ECT. Clinical and neuropsychological test scores were used as references for the possible changes in SPECT.

RESULTS

An increased perfusion after ECT was observed in right temporal and bilateral parietal cortices, whereas no reductions in relative ECD uptake were seen after ECT. Iomazenil-SPECT revealed a highly significant increase in the benzodiazepine receptor uptake in all studied cortical regions except temporal cortices.

CONCLUSIONS

Clinically successful ECT was associated with changes in vascular perfusion and GABAergic neurotransmission, providing new evidence for the mechanism of action of ECT and for the neurobiology of severe drug-resistant depression.

SPECT mapping of cerebral activity changes induced by repetitive transcranial magnetic stimulation in depressed patients. A pilot study

Repetitive transcranial magnetic stimulation (rTMS) is being investigated as an alternative treatment for depression. However, little is known about the clinical role and the neurophysiological mechanisms of the action of rTMS in these patients. In this study, 99mTc-HMPAO single photon emission computed tomography (SPECT) was used to map the effects of left dorsolateral prefrontal rTMS on prefrontal activity in seven patients who met DSM-IV criteria for major depression resistant to pharmacological treatment. rTMS consisted of 30 trains of 2-s duration stimuli (20 Hz, 90% of motor threshold), separated by 30-s pauses. Each patient underwent three SPECTs: at baseline; during the first rTMS; and 1 week after 10 daily sessions of rTMS. Regional cerebral blood flow (rCBF) of each cerebral region was normalized to the rCBF value in the cerebellum and relative changes in normalized rCBF were addressed using a region-of-interest analysis. The Hamilton Depression Rating Scale (HDRS) was used for clinical evaluation before and after rTMS. A significant rCBF increase after the 10 sessions of rTMS was found in the left prefrontal region (MANOVA F=5.29, d.f.=2,10, P=0.027), but no significant rCBF changes were found during the first rTMS session. The remaining cerebral regions showed no significant rCBF changes at any time. Only two patients showed a clinical improvement after rTMS, with 50% reduction of the initial HDRS score. The study was repeated under placebo conditions (identical design but addressing coil discharges to the air) in these two patients, who failed to show any rCBF increase during sham-rTMS. No relationship was found between the percentage of left prefrontal rCBF change and the clinical findings. In conclusion, rTMS of the left prefrontal cortex induces a significant rCBF increase in this region, despite the limited clinical effect in our sample of depressed patients. Cerebral perfusion SPECT is a useful tool to map cerebral activity changes induced by rTMS.

Regional cerebral blood flow changes in drug-resistant depressed patients following treatment with transcranial magnetic stimulation: a statistical parametric mapping analysis

Changes of regional cerebral blood flow (rCBF) in five drug-resistant depressed patients were examined by single photon emission computed tomography (SPECT) with 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO) before and after treatment with transcranial magnetic stimulation (TMS). The SPECT images were analysed with the Statistical Parametric Mapping (SPM) package. TMS administered in the region of the left dorsolateral prefrontal cortex (DLPFC) of the depressed patients was associated with an increase of rCBF at a focal region some distance from the stimulation site. No change was observed at any other remote region.

Diffuse cortical reduction of neuronal activity in unipolar major depression: a retrospective analysis of 337 patients and 321 controls

Reduction of neuronal activity in frontocortical and limbic circuits is considered a characteristic of depression. We aimed to test this hypothesis by pooling all available data from experimental literature. All investigations were included comparing regional cerebral blood flow (rCBF) or glucose metabolism (rCMRGlc) between acutely depressed unipolar major depressive patients and healthy controls. For cortical and subcortical regions we computed the percentage difference between depressives (n = 337) and controls (n = 321). In patients with unipolar major depression rCBF and rCMRGlc were lowered in left (-4.4%, P = 0.022) and right frontal (-3.2%, P = 0.053), left (-1.7%, P = 0.061) and right temporal (-3.0%, P=0.003), left (-6.5%, P = 0.002), and right parietal (-8.8%, P=0.001), and left (-6.6%, P = 0.083) and right occipital cortex (-4.2%, P = 0.02). Moreover, there were reductions in left (-6.3%, P = 0.029) and right basal ganglia (-4.8%, P = 0.002), left (-3.4%, P = 0.114) and right thalamus (-3.1%, P = 0.036), and left limbic system (-2.2%, P = 0.127). Parameters were increased by 1.0% (P = 0.714) only in the right limbic system. There were no hemispheric asymmetries (P > 0.05). Moreover, there was no indication for an anterior-posterior gradient (P > 0.05), and thus no 'hypofrontality'. In contrast to the current view, the data indicate a diffuse cortical rather than regionalized reduction of neuronal activity in unipolar major depression.

Neuroimaging in bipolar disorder

OBJECTIVE

The authors reviewed neuroimaging studies of bipolar disorder in order to evaluate how this literature contributes to the current understanding of the neurophysiology of the illness.

METHOD

Papers were reviewed as identified, using the NIMH PubMed literature search systems that reported results of neuroimaging studies involving a minimum of five bipolar disorder patients compared with healthy comparison subjects.

RESULTS

Structural neuroimaging studies report mixed results for lateral and third ventriculomegaly. Recent studies suggest subcortical structural abnormalities in the striatum and amygdala, as well as the prefrontal cortex. Proton spectroscopic studies suggest that abnormalities in choline metabolism exist in bipolar disorder, particularly in the basal ganglia. Additionally, phosphorous MRS suggests that there may be abnormalities in frontal phospholipid metabolism in bipolar disorder. Functional studies have identified affective state-related changes in cerebral glucose metabolism and blood flow, particularly in the prefrontal cortex during depression, but no clear abnormalities specific to bipolar disorder have been consistently observed.

CONCLUSIONS

The current literature examining the neurophysiology of bipolar disorder using neuroimaging is limited. Nonetheless, abnormalities in specific frontal-subcortical brain circuits seem likely. Additional targeted studies are needed to capitalize on this burgeoning technology to advance our understanding of the neurophysiology of bipolar disorder.