Controversy: Repetitive transcranial magnetic stimulation or transcranial direct current stimulation shows efficacy in treating psychiatric diseases (depression, mania, schizophrenia, obsessive-complusive disorder, panic, posttraumatic stress disorder)

Brain imaging studies performed over the past 20 years have generated new knowledge about the specific brain regions involved in the brain diseases that have been classically labeled as psychiatric. These include the mood and anxiety disorders, and the schizophrenias. As a natural next step, clinical researchers have investigated whether the minimally invasive brain stimulation technologies (transcranial magnetic stimulation [TMS] or transcranial direct current stimulation [tDCS]) might potentially treat these disorders. In this review, we critically review the research studies that have examined TMS or tDCS as putative treatments for depression, mania, obsessive-complusive disorder, posttraumatic stress disorder, panic disorder, or schizophrenia. (Separate controversy articles deal with using TMS or tDCS to treat pain or tinnitus. We will not review here the large number of studies using TMS or tDCS as research probes to understand disease mechanisms of psychiatric disorders.) Although there is an extensive body of randomized controlled trials showing antidepressant effects of daily prefrontal repetitive TMS, the magnitude or durability of this effect remains controversial. US Food and Drug Administration approval of TMS for depression was recently granted. There is much less data in all other diseases, and therapeutic effects in other psychiatric conditions, if any, are still controversial. Several issues and problems extend across all psychiatric TMS studies, including the optimal method for a sham control, appropriate coil location, best device parameters (intensity, frequency, dosage, and dosing schedule) and refining what subjects should be doing during treatment (activating pathologic circuits or not). In general, TMS or tDCS as a treatment for most psychiatric disorders remains exciting but controversial, other than prefrontal TMS for depression.

Restoring melancholia in the classification of mood disorders

The present DSM criteria for major depression poorly identify samples for treatment selection, prognosis, and assessments of pathophysiology. Melancholia, in contrast, is a disorder with definable clinical signs that can be verified by laboratory tests and treatment response. It identifies more specific populations than the present system and deserves individual identification in psychiatric classification. Its re-introduction will refine diagnosis, prognosis, treatment selection, and studies of pathophysiology of a large segment of the psychiatrically ill.

Changes in brain metabolism associated with remission in unipolar major depression

OBJECTIVE

Functional brain correlates of remission in patients with major depressive disorder (MDD) are measured with positron emission tomography (PET) and 18F-fluorodeoxyglucose.

METHOD

Glucose metabolism was measured in patients (n = 41) with moderate to severe MDD during acute depression and in the remitted state defined as a period of asymptomatic condition over 12 weeks. Data analyses used a region-of-interest (ROI) approach and statistical parametric mapping (SPM).

RESULTS

There were significant decreases in metabolism upon remission with respect to the baseline scan in left prefrontal, anterior temporal and anterior cingulate cortex and bilateral thalamus (SPM analysis) and bilateral putamen and cerebellum (SPM and ROI analyses). There was a significant asymmetry in prefrontal and anterior cingulate cortex metabolism with lower metabolism in the left hemisphere that persisted despite clinical remission.

CONCLUSION

These findings support the hypothesis that selective monoamine reuptake inhibition leads to an attenuation of a brain circuit that mediates depressive symptomatology.

Insulin resistance, affective disorders, and Alzheimer's disease: review and hypothesis

Affective disorders (ad) and Alzheimer's disease (AD) have been associated for almost a century, and various neurophysiologic factors have been implicated as common biologic markers. Yet, links between ad and AD still await elucidation. We propose that insulin resistance (IR) is one of the missing links between ad and AD. IR with hyperinsulinemia and subsequent impairment of glucose metabolism especially in ad patients may promote neurodegeneration and facilitate the onset of AD. According to our hypothesis, IR may persist even into ad remission in some patients. Persistent regional hypometabolism and vascular changes resulting from long-standing IR may lead to currently irreversible structural changes. Evidence in support of the hypothesis is reviewed and clinical implications suggested.

Reduced volume of orbitofrontal cortex in major depression

BACKGROUND

Functional neuroimaging studies have implicated dysfunction of orbitofrontal cortex in the symptoms of depression, and a recent postmortem study of depressed patients found reduced density of neurons and glia in this area. The purpose of this study was to measure volume of orbitofrontal cortex and other frontal cortical subregions in patients with major depression.

METHODS

Magnetic resonance imaging was used to measure volume of the orbitofrontal cortex and other frontal cortical regions in patients with major depression in remission (n = 15) and comparison subjects (n = 20).

RESULTS

Patients with depression had a statistically significant 32% smaller medial orbitofrontal (gyrus rectus) cortical volume, without smaller volumes of other frontal regions including anterior cingulate Brodmann's area 24 (subgenual gyrus), anterior cingulate Brodmann's area 32, subcallosal gyrus (Brodmann's area 25), or whole brain volume. The findings were significant after statistically controlling for brain size.

CONCLUSIONS

These findings are consistent with smaller orbitofrontal cortical volume in depression.

Regional cerebral glucose utilization in patients with a range of severities of unipolar depression

BACKGROUND

Patients with unipolar depression are most often reported to have decreased regional cerebral glucose metabolism (rCMRglu) in dorsal prefrontal and anterior cingulate cortices compared with healthy control subjects, often correlating inversely with severity of depression.

METHODS

We measured rCMRglu with fluorine-18 deoxyglucose positron emission tomography (PET) in 38 medication-free patients with unipolar depression and 37 healthy control subjects performing an auditory continuous performance task to further investigate potential prefrontal and anterior paralimbic rCMRglu abnormalities in patients attending to this task.

RESULTS

Compared with control subjects, the subgroup of patients with Hamilton depression scores of 22 or greater demonstrated decreased absolute rCMRglu in right prefrontal cortex and paralimbic/amygdala regions as well as bilaterally in the insula and temporoparietal cortex (right > left); they also exhibited increased normalized metabolic activity bilaterally in the cerebellum, lingula/cuneus, and brain stem. Severity of depression negatively correlated with absolute rCMRglu in almost the entire extent of the right cingulate cortex as well as bilaterally in prefrontal cortex, insula, basal ganglia, and temporoparietal cortex (right > left).

CONCLUSIONS

Areas of frontal, cingulate, insula, and temporal cortex appear hypometabolic in association with different components of the severity and course of illness in treatment-resistant unipolar depression.

Cerebral blood flow and metabolism in late-life depression and dementia

Late-life depression (LLD) is characterized by abnormalities in cerebral blood flow (CBF) and cerebral metabolic rate (CMR) for glucose. Unlike younger adults with major depression, global cortical CBF and CMR reductions have been reported in LLD. Patients with LLD are also characterized by topographic abnormalities, most commonly involving selective prefrontal, superior temporal, and anterior parietal cortex. The fate of these abnormalities with response to antidepressant treatment is highly uncertain, and heterogeneous findings have been reported in younger samples with major depression. The limited data in LLD suggest that response to electroconvulsive therapy or antidepressant medications does not involve reversal of baseline abnormalities but rather accentuation of prefrontal deficits. At minimum, these paradoxical findings suggest that abnormalities in CBF and CMR may be persistent in LLD and a trait characteristic. Characteristic profiles of CBF and CMR abnormalities have also been demonstrated in samples with Alzheimer's disease (AD) and other types of dementia. Functional imaging has shown sensitivity to disease severity and progression. Nonetheless, there is limited information regarding the sensitivity and specificity of the functional imaging modalities in the differential diagnosis of dementias. At present, the evidence does not support the use of functional imaging in isolation as a diagnostic tool. Rather, these imaging modalities may be considered as an adjunct to careful clinical assessment, either to improve diagnosis in early cases or to assist in subtyping difficult cases.

Brain metabolic changes in major depressive disorder from pre- to post-treatment with paroxetine

Functional brain imaging studies of subjects with Major Depressive Disorder (MDD) have suggested that decreased dorsolateral (DLPFC) and increased ventrolateral (VLPFC) prefrontal cortical activity mediate the depressed state. Pre- to post-treatment studies indicate that these abnormalities normalize with successful treatment. We performed [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) scans on 16 outpatients with MDD before and after treatment with paroxetine (target dose = 40 mg/day). Regions of interest (ROIs) for this analysis were drawn by a rater blind to subject identity on the magnetic resonance image of each subject and transferred onto their coregistered PET scans. We hypothesized that DLPFC metabolism would increase, while ventral frontal metabolism [in the VLPFC, the orbitofrontal cortex (OFC), and the inferior frontal gyrus (IFG)] would decrease with successful treatment. Treatment response was defined as a decrease in the Hamilton Depression Rating Scale of > 50% and a Clinical Global Improvement Scale rating of 'much' or 'very much' improved. By these criteria, nine of the subjects were classified as treatment responders. These responders had significantly greater decreases in normalized VLPFC and OFC metabolism than did non-responders. There were no significant effects of treatment response on change in the DLPFC or IFG in this sample. However, there was a positive correlation between change in HAM-D scores and change in normalized IFG and VLPFC metabolism. There were no significant interactions with laterality. On pre-treatment scans, lower metabolism in the left ventral anterior cingulate gyrus was associated with better treatment response. These findings implicate ventral prefrontal-subcortical brain circuitry in the mediation of response to serotonin reuptake inhibitors in MDD.

Functional neuroimaging studies of depression: the anatomy of melancholia

Functional brain imaging techniques, which permit noninvasive measures of neurophysiology and neuroreceptor binding, are powerful and sensitive tools for research aimed at elucidating the pathophysiology of major depression. The application of these technologies in depression research has produced several studies of resting cerebral blood flow (BF) and glucose metabolism in subjects imaged during various phases of illness and treatment. This review examines these data and the principles relevant to their interpretation and discusses the insights they provide into the anatomical correlates of depression. Within the anatomical networks implicated in emotional processing by other types of evidence, these BF and metabolic data demonstrate that major depression is associated with reversible, mood state-dependent, neurophysiological abnormalities in some structures and irreversible, trait-like abnormalities in other structures. In some of the regions in which trait-like abnormalities appear, abnormal metabolic activity appears at least partly related to the anatomical abnormalities identified in magnetic resonance imaging (MRI) studies of depression.

Changes in regional cerebral blood flow following light treatment for seasonal affective disorder: responders versus nonresponders

BACKGROUND

Several brain imaging studies of antidepressant pharmacologic treatment utilizing single photon emission computed tomography (SPECT) have reported a normalization of deficits in cerebral blood flow (CBF) associated with recovery; other studies report no change, or a reduction in CBF following successful treatment. There have been no published SPECT studies of seasonal affective disorder (SAD) assessing response to light treatment in relation to changes in regional CBF (rCBF). In this study, we sought to test the hypothesis that increases in rCBF would be observed in SAD patients who responded to light treatment.

METHODS

Ten depressed patients with SAD underwent functional brain imaging studies with 99mTc-hexamethylpropyleneamine oxime SPECT before and after light treatment.

RESULTS

Relative increases in rCBF were observed in all brain regions compared to cerebellum in treatment responders, whereas nonresponders showed no change or decreases in rCBF relative to cerebellum. Significant differences in mean percentage change in rCBF between responders (n = 5) and nonresponders (n = 5) were detected in frontal and cingulate cortex, and thalamus.

CONCLUSIONS

These findings provide preliminary support for the hypothesis that an increase in rCBF is associated with recovery from depression in SAD.

A review of functional neuroimaging in mood disorders: positron emission tomography and depression

OBJECTIVE

To examine the progress of positron emission tomography (PET) as a tool for understanding the psychobiology of mood disorders, particularly major depression and bipolar disorder.

METHOD

Review of the literature on functional imaging of mood disorders.

RESULTS

Functional imaging techniques have been used in psychiatric research as a noninvasive method to study the behaviour and function of the brain. Techniques used so far have involved the manipulation of emotion in healthy volunteers, the evaluation of depressed (unipolar and bipolar as well as secondary depression), manic, and normal subjects under resting and various activation conditions, such as cognitive activation, acute pharmacological challenge, and chronic thymoleptic treatments. As a result, functional imaging studies tend to support abnormalities in specific frontal and limbic regions.

CONCLUSION

Different PET methods demonstrate consistent abnormalities in the prefrontal, cingulate, and amygdala regions. These findings are in agreement with past animal and clinical anatomical correlates of mood and emotions.