Brain morphometric comparison of first-episode schizophrenia and temporal lobe epilepsy

Magnetic resonance imaging in schizophrenia: Luxury or necessity? (Review)

Schizophrenia, one of the most common psychiatric disorders, with a worldwide annual incidence rate of approximately 0.3-0.7%, known to affect the population below 25 years of age, is persistent throughout lifetime and includes people from all layers of society. With recent technological progress that allows better imaging techniques, such as the ones provided by computed tomography and particularly magnetic resonance imaging (MRI), research on schizophrenia imaging has grown considerably. The purpose of this review is to establish the importance of using imaging techniques in the early detection of brain abnormalities in patients diagnosed with schizophrenia. We reviewed all articles which reported on MRI imaging in schizophrenia. In order to do this, we used the PubMed database, using as search words ‘MRI’ and ‘schizophrenia’. MRI studies of first episode patients and chronic patients, suggest reduction of the whole brain volume. Enlargement of lateral ventricles was described as positive in 15 studies out of 19 and was similar to findings in chronic patients. Moreover, for the first episode patients, all data collected point to important changes in medial temporal lobe structures, diminished hippocampal volume, the whole frontal lobe, asymmetry in prefrontal cortex, diminished volume in cingulate, corpus callosum, and cavum septum pellucidum reported abnormalities. MRI is recommended as an important tool in the follow-up process of patients with schizophrenia. Yet, it is still under debate whether the abnormalities described in this condition are able to be used as diagnostic biomarkers.

The prevalence of psychosis in epilepsy; a systematic review and meta-analysis

BACKGROUND

Epilepsy has long been considered to be a risk factor for psychosis. However there is a lack of consistency in findings across studies on the effect size of this risk which reflects methodological differences in studies and changing diagnostic classifications within neurology and psychiatry. The aim of this study was to assess the prevalence of psychosis in epilepsy and to estimate the risk of psychosis among individuals with epilepsy compared with controls.

METHODS

A systematic review and meta-analysis was conducted of all published literature pertaining to prevalence rates of psychosis in epilepsy using electronic databases PUBMED, OVIDMEDLINE, PsychINFO and Embase from their inception until September 2010 with the following search terms: prevalence, incidence, rate, rates, psychosis, schizophrenia, schizophreniform illness, epilepsy, seizures, temporal lobe epilepsy.

RESULTS

The literature search and search of reference lists yielded 215 papers. Of these, 58 (27%) had data relevant to the review and 157 were excluded following a more detailed assessment. 10% of the included studies were population based studies. The pooled odds ratio for risk of psychosis among people with epilepsy compared with controls was 7.8. The pooled estimate of prevalence of psychosis in epilepsy was found to be 5.6% (95% CI: 4.8-6.4). There was a high level of heterogeneity. The prevalence of psychosis in temporal lobe epilepsy was 7% (95% CI: 4.9-9.1). The prevalence of interictal psychosis in epilepsy was 5.2% (95% CI: 3.3-7.2). The prevalence of postictal psychosis in epilepsy was 2% (95% CI: 1.2-2.8).

CONCLUSIONS

Our systematic review found that up to 6% of individuals with epilepsy have a co-morbid psychotic illness and that patients have an almost eight fold increased risk of psychosis. The prevalence rate of psychosis is higher in temporal lobe epilepsy (7%). We suggest that further investigation of this association could give clues to the aetiology of psychosis.

A patient with medication-resistant epilepsy featuring psychosensorial and psychotic symptoms presenting with significant functional improvement on psychotherapeutic treatment: a case report

Background

Partial complex epilepsy with psychosensorial and psychotic symptoms remains a relatively rare condition that can sometimes be mistaken for an axis I psychiatric disorder. There is no specific treatment for this particular type of epilepsy, anti-epileptic medication being the cornerstone of therapeutic intervention with the occasional addition of neuroleptics. Lack of response to anti-epileptic agents is often a sign of poor prognosis and requires risky and sometimes invasive interventions with high morbidity for patients.

Case presentation

We report the case of a 21-year-old right-handed Caucasian man of French-Canadian descent who was living with his mother immediately before being hospitalized in a psychiatric setting for the first time. He seemed obsessed with developing new concepts to reach a more ‘perfect’ existence. He also claimed feeling odd sensations in his mind and in his body that could be linked to some sort of ‘evolutionary’ process resulting from spiritual uplift. He reported non-specific visual hallucinations and what sounded like auditory hallucinations and telepathic powers. The first diagnosis was a possible schizophreniform disorder and our patient was hospitalized. Shortly afterwards, an electroencephalogram showed an important subcortical epileptic activity, compatible with partial complex epilepsy with psychosensorial and psychotic symptoms. Despite a negative response to medication, symptoms proper to this type of epilepsy were substantially alleviated using a psychotherapeutical treatment intended for patients with psychotic disorders, namely integrated psychological therapy (IPT). Significant functional improvement in our patient has been achieved since then.

Conclusions

This case report illustrates that despite a negative response to medication, symptoms proper to this type of epilepsy could be substantially alleviated using psychotherapeutical treatment modalities. To the best of our knowledge, this is the first time such a finding has been reported in the scientific literature. This could open the way for new research themes and therapeutic interventions for such patients.

Predicting risk and the emergence of schizophrenia

This article gives an overview of genetic and environmental risk factors for schizophrenia. The presence of certain molecular, biological, and psychosocial factors at certain points in the life span, has been linked to later development of schizophrenia. All need to be considered in the context of schizophrenia as a lifelong brain disorder. Research interest in schizophrenia is shifting to late childhood/early adolescence for screening and preventative measures. This article discusses those environmental risk factors for schizophrenia for which there is the largest evidence base.

Evidence for shared susceptibility to epilepsy and psychosis: a population-based family study

BACKGROUND

There is emerging evidence of an etiological overlap between a range of neurodevelopmental disorders, including schizophrenia and epilepsy. Here we investigate shared familial vulnerability to psychotic illness and epilepsy in a family-based study.

METHODS

The study population consisted of parents and their children born in Helsinki between 1947 and 1990. The Finnish Hospital Discharge Register was used to determine psychiatric and neurological outcomes in adulthood for all offspring. Parental history of psychosis and epilepsy was determined by linking the Hospital Discharge Register and the Finnish Population Register.

RESULTS

Our total sample comprised 9653 families and 23,404 offspring. Individuals with epilepsy had a 5.5-fold increase in the risk of having a broadly defined psychotic disorder, an almost 8.5-fold increase in the risk of having schizophrenia, and a 6.3-fold increase in the risk of having bipolar disorder. There was strong evidence of clustering of the association between epilepsy and psychosis within families. Individuals with a parental history of epilepsy had a 2-fold increase in the risk of developing psychosis, compared with individuals without a parental history of epilepsy. Individuals with a parental history of psychosis had, reciprocally, a 2.7-fold increase in the risk of having a diagnosis of generalized epilepsy, compared with individuals without a parental history of psychosis. Post hoc analyses showed that these associations were not driven by the comorbidity of epilepsy and psychosis in the parents.

CONCLUSIONS

These findings support recent evidence of overlapping etiological factors between epilepsy and schizophrenia, especially recent evidence of a genetic overlap between these disorders.

Medial temporal structures and memory functions in adolescents with heavy cannabis use

Converging lines of evidence suggest an adverse effect of heavy cannabis use on adolescent brain development, particularly on the hippocampus. In this preliminary study, we compared hippocampal morphology in 14 "treatment-seeking" adolescents (aged 18-20) with a history of prior heavy cannabis use (5.8 joints/day) after an average of 6.7 months of drug abstinence, and 14 demographically matched normal controls. Participants underwent a high-resolution 3D MRI as well as cognitive testing including the California Verbal Learning Test (CVLT). Heavy-cannabis users showed significantly smaller volumes of the right (p < 0.04) and left (p < 0.02) hippocampus, but no significant differences in the amygdala region compared to controls. In controls, larger hippocampus volumes were observed to be significantly correlated with higher CVLT verbal learning and memory scores, but these relationships were not observed in cannabis users. In cannabis users, a smaller right hippocampus volume was correlated with a higher amount of cannabis use (r = -0.57, p < 0.03). These data support a hypothesis that heavy cannabis use may have an adverse effect on hippocampus development. These findings, after an average 6.7 month of supervised abstinence, lend support to a theory that cannabis use may impart long-term structural and functional damage. Alternatively, the observed hippocampal volumetric abnormalities may represent a risk factor for cannabis dependence. These data have potential significance for understanding the observed relationship between early cannabis exposure during adolescence and subsequent development of adult psychopathology reported in the literature for schizophrenia and related psychotic disorders.

Schizophrenia and epilepsy: is there a shared susceptibility?

Individuals with epilepsy are at increased risk of having psychotic symptoms that resemble those of schizophrenia. More controversial and less searched is if schizophrenia is a risk factor for epilepsy. Here we review overlapping epidemiological, clinical, neuropathological and neuroimaging features of these two diseases. We discuss the role of temporal and other brain areas in the development of schizophrenia-like psychosis of epilepsy. We underline the importance of ventricular enlargement in both conditions as a phenotypic manifestation of a shared biologic liability that might relate to abnormalities in neurodevelopment. We suggest that genes implicated in neurodevelopment may play a common role in both conditions and speculate that recently identified causative genes for partial complex seizures with auditory features might help explain the pathophysiology of schizophrenia. These particularly include the leucine-rich glioma inactivated (LGI) family gene loci overlap with genes of interest for psychiatric diseases like schizophrenia. Finally, we conclude that LGI genes associated with partial epilepsy with auditory features might also represent genes of interest for schizophrenia, especially among patients with prominent auditory hallucinations and formal thought disorder.

Brain volume in first-episode schizophrenia: systematic review and meta-analysis of magnetic resonance imaging studies

BACKGROUND

Studies of people with schizophrenia assessed using magnetic resonance imaging (MRI) usually include patients with first-episode and chronic disease, yet brain abnormalities may be limited to those with chronic schizophrenia.

AIMS

To determine whether patients with a first episode of schizophrenia have characteristic brain abnormalities.

METHOD

Systematic review and meta-analysis of 66 papers comparing brain volume in patients with a first psychotic episode with volume in healthy controls.

RESULTS

A total of 52 cross-sectional studies included 1424 patients with a first psychotic episode; 16 longitudinal studies included 465 such patients. Meta-analysis suggests that whole brain and hippocampal volume are reduced (both P<0.0001) and that ventricular volume is increased (P<0.0001) in these patients relative to healthy controls.

CONCLUSIONS

Average volumetric changes are close to the limit of detection by MRI methods. It remains to be determined whether schizophrenia is a neurodegenerative process that begins at about the time of symptom onset, or whether it is better characterised as a neurodevelopmental process that produces abnormal brain volumes at an early age.

A specific test of hippocampal deficit in schizophrenia

Despite numerous studies in which hippocampal abnormalities were found, schizophrenia patients' hippocampal neural activity has not been systematically evaluated on a specific hippocampal-dependent task. The transverse-patterning task (TP) is sensitive to the relational mnemonic capabilities of the hippocampus. Ten schizophrenia patients and 10 controls performed TP and control tasks that are not hippocampal dependent. As predicted, patients displayed a behavioral impairment in TP and not in control tasks. Magnetoencephalography showed controls activating right hippocampus during TP performance. Patients showed more bilateral or left hippocampal activation during TP, and greater left lateralization was associated with better performance on TP. Patients' abnormal hippocampal lateralization may play a role in the hippocampal-dependent behavioral deficit.

Long-term effects of amygdala GABA receptor blockade on specific subpopulations of hippocampal interneurons

Growing evidence indicates that the amygdala modulates hippocampal functions. To test the hypothesis that this modulation may involve long-lasting effects on interneuronal networks in the hippocampus, changes in the expression of neurochemical markers specific for different interneuronal subpopulations were assessed in adult rats 96 h following acute infusion of low doses of the GABAA receptor antagonist picrotoxin into the amygdala. The numerical density (Nd) of somata showing immunoreactivity (IR) for parvalbumin (PVB) was decreased in dentate gyrus (DG) and the CA4-2 region, while that of calretinin (CR)-IR was decreased in DG and CA2. The Nd of calbindin D28k (CB)-IR somata was decreased in CA3-2. The densities of axon terminals arising from PVB-IR and cholecystokinin (CCK)-IR basket neurons were also altered, with those of CCK-IR terminals increased across all sectors, while PVB-IR terminals were decreased only in the CA region. Increases in CCK-IR terminals were paralleled by increases of terminals with IR for the 65-kD isoform of glutamate decarboxylase (GAD65). Mixed-effects statistical models, adapted specifically for these analyses, indicated that perturbations of amygdalar inputs to the hippocampus significantly alter the drive that hippocampal PVB-, CR-, and CB-IR neurons within the dentate gyrus/CA4 region exercise on CCK-IR terminals within the same region as well as in CA3-1. These results suggest that amygdalar modulation of specific neuronal subpopulations may induce lasting and far-reaching changes in the hippocampus during normal functioning, as well as in diseases involving a disruption of amygdalar activity. In particular, changes in specific interneuronal markers within selective hippocampal sectors detected in the present results are strikingly similar to those reported in this region in schizophrenia. These similarities suggest that, in this disease, a disruption of GABAergic transmission within the amygdala may play a significant role in the induction of abnormalities in the hippocampus.

Schizophrenias and epilepsies: why? when? how?

Detailed studies of the association between the epilepsies and the schizophrenias extend over 40 years. Recent studies are abundant and make fertile use of new technologies. However, the pathological changes described in schizophrenias are quite varied. Studies fail to recognize that "epilepsies" and "schizophrenias" have varied in definition over time, and have always been weak categories with which to do science. Now that it is possible to measure deficits in brain structure, it would be better to see what behavioral problems are associated with specific cerebral pathology. It would be wise to be very precise in describing the behaviors and the nature and timing of their emergence rather than using terms such as psychoses. Schizophrenias have neurological, neuropsychological, and behavioral antecedents in childhood. Those associated with later epilepsies show biases, persistent in many studies over a number of years, toward relative excess of females, left temporal lobe structural deficits, and non-right-handedness. Schizophrenia should now be a predictable eventuality in certain people with epilepsies, an important factor in medical and surgical treatment.

Selective deficit of hippocampal N-acetylaspartate in antipsychotic-naive patients with schizophrenia

BACKGROUND

Studies using proton magnetic resonance spectroscopy in schizophrenia have demonstrated abnormality of N-acetylaspartate but are confounded by the effects of phase of illness and medication. There is mounting evidence that antipsychotic medication influences N-acetylaspartate.

METHODS

A group of first-episode patients who had received no, or minimal, antipsychotic medication was examined at baseline and after 3 months treatment. Normal comparison subjects were examined at the same interval. Ratios of N-acetylaspartate, creatine plus phosphocreatine, and choline-containing compounds in the left prefrontal cortex, hippocampus, and basal ganglia were measured.

RESULTS

The mean duration of symptoms for all patients was 31.6 (SD 26.1) weeks. A significant reduction of hippocampal N-acetylaspartate/creatine plus phosphocreatine was found in the antipsychotic-naive group relative to those previously treated and to controls at baseline (F = 7.3, p <.002). No group differences were found at follow-up.

CONCLUSIONS

Hippocampal N-acetylaspartate/creatine plus phosphocreatine appears to be selectively affected early in the course of illness. The finding of neurochemical differences between treatment naive and previously treated patients confirms the relevance of medication status in proton magnetic resonance spectroscopy studies. Further investigation of the influence of medication at this stage of illness is warranted.

Quantification of frontal and temporal lobe brain-imaging findings in schizophrenia: a meta-analysis

Magnetic resonance imaging (MRI) and positron emission tomography (PET) studies of the frontal and temporal lobes in schizophrenia patients and healthy controls have proliferated over the past 2 decades, but there have been relatively few attempts to quantify the evidence. In this meta-analytic review, 155 studies on frontal and temporal lobe neurobiology were synthesized, reflecting results from 4043 schizophrenia patients and 3977 normal controls. Cohen's d was used to quantify case-control differences, and moderator variable analysis indexed the relation of sample and imaging characteristics to the magnitude of these differences. Frontal metabolic and blood flow deficiencies in conjunction with cognitive activation tasks ("hypofrontality") emerged as the strongest body of evidence, demonstrating abnormalities that distinguish approximately half of schizophrenia patients from healthy people. Most case-control comparisons with structural and functional imaging yield small and in many cases unstable findings. Technical scanning parameters like slice thickness and magnet strength did not vary with case-control differences consistently across the meta-analyses. However, patient sample characteristics including sample size, handedness and gender composition emerged frequently as moderators of brain-imaging effect sizes.

Brain structure, genetic liability, and psychotic symptoms in subjects at high risk of developing schizophrenia

BACKGROUND

Structural magnetic resonance imaging (MRI) of the brain in patients with schizophrenia has consistently demonstrated several abnormalities. These are thought to be neurodevelopmental in origin, as they have also been described in first episode cases, although there may be a progressive component. It is not known at which point in development these abnormalities are evident, nor to what extent they are genetically or environmentally mediated.

METHODS

One hundred forty-seven high-risk subjects (with at least two affected first or second degree relatives), 34 patients in their first episode, and 36 healthy control subjects received an MRI scan covering the whole brain. After inhomogeneity correction, regions of interest were traced by three group-blind raters with good inter-rater reliability. Regional brain volumes were related to measures of genetic liability to schizophrenia and to psychotic symptoms elicited at structured psychiatric interviews.

RESULTS

High-risk subjects had statistically significantly reduced mean volumes of the left and right amygdalo-hippocampus and thalamus, as compared to healthy control subjects. They also had bilaterally larger amygdalo-hippocampi and bilaterally smaller lenticular nuclei than the schizophrenics. High-risk subjects with symptoms had smaller brains than those without. The volumes of the prefrontal lobes and the thalamus were the only consistent associates of genetic liability.

CONCLUSIONS

Subjects at high risk of developing schizophrenia have abnormalities of brain structure similar to but not identical to those found in schizophrenia. Our results suggest that some structural abnormalities are genetic trait or vulnerability markers, others are environmentally mediated, and that the development of symptoms is associated with a third overlapping group of structural changes. Particular risk factors for schizophrenia may interact at discrete time points of neurodevelopment with different effects on specific brain regions and may represent relatively distinct disease processes.

A review of MRI findings in schizophrenia

After more than 100 years of research, the neuropathology of schizophrenia remains unknown and this is despite the fact that both Kraepelin (1919/1971: Kraepelin, E., 1919/1971. Dementia praecox. Churchill Livingston Inc., New York) and Bleuler (1911/1950: Bleuler, E., 1911/1950. Dementia praecox or the group of schizophrenias. International Universities Press, New York), who first described 'dementia praecox' and the 'schizophrenias', were convinced that schizophrenia would ultimately be linked to an organic brain disorder. Alzheimer (1897: Alzheimer, A., 1897. Beitrage zur pathologischen anatomie der hirnrinde und zur anatomischen grundlage einiger psychosen. Monatsschrift fur Psychiarie und Neurologie. 2, 82-120) was the first to investigate the neuropathology of schizophrenia, though he went on to study more tractable brain diseases. The results of subsequent neuropathological studies were disappointing because of conflicting findings. Research interest thus waned and did not flourish again until 1976, following the pivotal computer assisted tomography (CT) finding of lateral ventricular enlargement in schizophrenia by Johnstone and colleagues. Since that time significant progress has been made in brain imaging, particularly with the advent of magnetic resonance imaging (MRI), beginning with the first MRI study of schizophrenia by Smith and coworkers in 1984 (Smith, R.C., Calderon, M., Ravichandran, G.K., et al. (1984). Nuclear magnetic resonance in schizophrenia: A preliminary study. Psychiatry Res. 12, 137-147). MR in vivo imaging of the brain now confirms brain abnormalities in schizophrenia. The 193 peer reviewed MRI studies reported in the current review span the period from 1988 to August, 2000. This 12 year period has witnessed a burgeoning of MRI studies and has led to more definitive findings of brain abnormalities in schizophrenia than any other time period in the history of schizophrenia research. Such progress in defining the neuropathology of schizophrenia is largely due to advances in in vivo MRI techniques. These advances have now led to the identification of a number of brain abnormalities in schizophrenia. Some of these abnormalities confirm earlier post-mortem findings, and most are small and subtle, rather than large, thus necessitating more advanced and accurate measurement tools. These findings include ventricular enlargement (80% of studies reviewed) and third ventricle enlargement (73% of studies reviewed). There is also preferential involvement of medial temporal lobe structures (74% of studies reviewed), which include the amygdala, hippocampus, and parahippocampal gyrus, and neocortical temporal lobe regions (superior temporal gyrus) (100% of studies reviewed). When gray and white matter of superior temporal gyrus was combined, 67% of studies reported abnormalities. There was also moderate evidence for frontal lobe abnormalities (59% of studies reviewed), particularly prefrontal gray matter and orbitofrontal regions. Similarly, there was moderate evidence for parietal lobe abnormalities (60% of studies reviewed), particularly of the inferior parietal lobule which includes both supramarginal and angular gyri. Additionally, there was strong to moderate evidence for subcortical abnormalities (i.e. cavum septi pellucidi-92% of studies reviewed, basal ganglia-68% of studies reviewed, corpus callosum-63% of studies reviewed, and thalamus-42% of studies reviewed), but more equivocal evidence for cerebellar abnormalities (31% of studies reviewed). The timing of such abnormalities has not yet been determined, although many are evident when a patient first becomes symptomatic. There is, however, also evidence that a subset of brain abnormalities may change over the course of the illness. The most parsimonious explanation is that some brain abnormalities are neurodevelopmental in origin but unfold later in development, thus setting the stage for the development of the symptoms of schizophrenia. Or there may be additional factors, such as stress or neurotoxicity, that occur during adolescence or early adulthood and are necessary for the development of schizophrenia, and may be associated with neurodegenerative changes. Importantly, as several different brain regions are involved in the neuropathology of schizophrenia, new models need to be developed and tested that explain neural circuitry abnormalities effecting brain regions not necessarily structurally proximal to each other but nonetheless functionally interrelated. (ABSTRACT TRUNCATED)

Amygdalar activation alters the hippocampal GABA system: "partial" modelling for postmortem changes in schizophrenia

Abnormalities in amygdala and hippocampus have been shown to coexist in schizophrenia (SZ). In the hippocampus, compelling evidence suggests that a disruption of GABA neurotransmission is present mainly in sectors CA4, CA3, and CA2. The amygdala sends important inputs to the hippocampus and is also believed to have a defective GABA system in schizophrenia. To explore the possibility that changes in the hippocampal GABAergic system could be related to an increased inflow of activity originating in the amygdala, a "partial" animal model has been developed. In awake, freely moving, rats a GABA(A) receptor antagonist was infused locally into the basolateral nuclear complex of the amygdala (BLn). Within 2 hours, a decreased density of both the 65- and 67-kDa isoforms of glutamate decarboxylase (GAD(65) and GAD(67)) -immunoreactive (IR) terminals was detected on neuron somata in sectors CA3 and CA2, but not in CA1, CA3, or dentate gyrus. An increase of GAD(67)-IR somata was also found in the dentate gyrus and CA4. In anterograde tracer studies, amygdalo-hippocampal projection fibers were exclusively found in CA3 and CA2, but not CA1. Taken together, these results indicate that activation of amygdalo-hippocampal afferents is associated with the induction of significant changes in the GABA system of the hippocampus, with a subregional distribution that is remarkably similar to that found in SZ. Under pathologic conditions, an excessive discharge of excitatory activity emanating from the amygdala could be capable of altering inhibitory modulation along the trisynaptic pathway. This mechanism may potentially contribute to disturbances of GABAergic function in the major psychoses. Such "partial" rodent modelling provides an important strategy for deciphering the effect of altered cortico-limbic circuits in SZ.

Differential neuropsychological patterns of frontal- and temporal-lobe dysfunction in patients with schizophrenia

The frontal and temporal lobes have been implicated as pathogenic sites for schizophrenia, although there is a marked heterogeneity of brain function and structure between individual patients. It is currently unclear whether some patients with schizophrenia exhibit primarily frontal lobe dysfunction, while others exhibit primarily temporal-lobe dysfunction. The current investigation examined this issue in a preliminary way by using neurocognitive tests to discriminate test performances of patients with schizophrenia from patients without schizophrenia who had definitive neurological evidence of either frontal- or temporal-lobe dysfunction. Of the patients with schizophrenia, 20.7% were classified as having a frontal lobe dysfunction profile, while 19.3% had a temporal lobe dysfunction profile. Results further clarify neurobiological heterogeneity in schizophrenia by demonstrating that a substantial number of patients with schizophrenia exhibit either primarily frontal- or temporal-lobe dysfunction. Results may partially explain the inadequacy of neurobiological models for schizophrenia that do not consider these differential patterns of dysfunction.

Structural brain imaging in schizophrenia: a selective review

Structural neuroimaging studies have provided some of the most consistent evidence for brain abnormalities in schizophrenia. Since the initial computed tomography study by Johnstone and co-workers, which reported lateral ventricular enlargement in schizophrenia, advances in brain imaging technology have enabled further and more refined characterization of abnormal brain structure in schizophrenia in vivo. This selective review discusses the major issues and findings in structural neuroimaging studies of schizophrenia. Among these are evidence for generalized and regional brain volume abnormalities, the specificity of anatomic findings to schizophrenia and to men versus women with schizophrenia, the contribution of genetic influences, and the timing of neuroanatomic pathology in schizophrenia. The second section reviews new approaches for examining brain structure in schizophrenia and their applications to studies on the pathophysiology of schizophrenia.

MRI anatomy of schizophrenia

Structural magnetic resonance imaging (MRI) data have provided much evidence in support of our current view that schizophrenia is a brain disorder with altered brain structure, and consequently involving more than a simple disturbance in neurotransmission. This review surveys 118 peer-reviewed studies with control group from 1987 to May 1998. Most studies (81%) do not find abnormalities of whole brain/intracranial contents, while lateral ventricle enlargement is reported in 77%, and third ventricle enlargement in 67%. The temporal lobe was the brain parenchymal region with the most consistently documented abnormalities. Volume decreases were found in 62% of 37 studies of whole temporal lobe, and in 81% of 16 studies of the superior temporal gyrus (and in 100% with gray matter separately evaluated). Fully 77% of the 30 studies of the medial temporal lobe reported volume reduction in one or more of its constituent structures (hippocampus, amygdala, parahippocampal gyrus). Despite evidence for frontal lobe functional abnormalities, structural MRI investigations less consistently found abnormalities, with 55% describing volume reduction. It may be that frontal lobe volume changes are small, and near the threshold for MRI detection. The parietal and occipital lobes were much less studied; about half of the studies showed positive findings. Most studies of cortical gray matter (86%) found volume reductions were not diffuse, but more pronounced in certain areas. About two thirds of the studies of subcortical structures of thalamus, corpus callosum and basal ganglia (which tend to increase volume with typical neuroleptics), show positive findings, as do almost all (91%) studies of cavum septi pellucidi (CSP). Most data were consistent with a developmental model, but growing evidence was compatible also with progressive, neurodegenerative features, suggesting a "two-hit" model of schizophrenia, for which a cellular hypothesis is discussed. The relationship of clinical symptoms to MRI findings is reviewed, as is the growing evidence suggesting structural abnormalities differ in affective (bipolar) psychosis and schizophrenia.

GABA-ergic neurons and the neurobiology of schizophrenia and other psychoses

There are a number of disorders in the Diagnostic and Statistical Manual of Mental Disorders (DSM IV) that are characterised by having psychotic symptoms as the defining feature [17]. The narrowest definition of psychosis is restricted to delusions or prominent hallucinations, with the hallucinations occurring in the absence of insight into their pathological nature. Schizophrenia is the most prevalent form of psychosis, but this may also occur due to other medical conditions (e.g., Prader-Willi syndrome, epilepsy), in the early post-partum period, at menopause, and as a result of drug use. This article attempts to draw together an underlying causation across the various forms of psychotic disorder and, by integrating this with what is known about the genetics, neuroanatomy and neuropharmacology of the positive symptoms in schizophrenia, produce a broader understanding. At the cellular level, gamma-aminobutyric acid (GABA)-ergic interneurons are a common feature in psychotic states, and are a principal focus for serotonin and dopamine innervations, as well as playing an important role in cortical development. At the systems level, prefrontal and medial temporal cortices are implicated with activity levels out of synchrony in schizophrenics. How these vast areas of disparately functioning cortical networks are "bound" together to provide coherent conscious experiences is again a function of GABA-ergic interneurons. These interneurons have highly divergent inhibitory projections to large numbers of pyramidal neurons and are themselves synchronised by the ascending dopamine and serotonin innervations.

Mapping of grey matter changes in schizophrenia

Studies of brain changes in schizophrenia have suggested that the disorder is associated with reductions in both global and regional grey matter. In this study, we used structural neuroimaging to differentiate between these two types of change and to examine regional grey matter throughout the whole brain. Grey matter from magnetic resonance images was segmented and transformed into stereotactic space, and patients with schizophrenia and controls were compared with respect to regional grey matter (after compensating for global grey matter differences). In two preliminary analyses to test our methodology, we demonstrated that: (1) in the transformed grey matter maps, voxel values at the location of the caudate nuclei were correlated with region-of-interest measurements of caudate area in native image space, and (2) the technique detected regional grey matter changes resulting from artificial lesions created in the native images. We then used a factorial design to examine data from two studies, comprising a total of 42 schizophrenics and 52 controls. Analysis of the main effect of schizophrenia on regional grey matter revealed significant reductions in (a) the right temporal pole, insula and amygdala, (b) the left temporal pole, insula and dorsolateral prefrontal cortex.

Structural brain imaging in schizophrenia

The subtle pathomorphology of schizophrenia is gradually being unraveled through the application of increasingly sophisticated brain imaging techniques. There is now compelling evidence of subtle brain abnormalities in patients with schizophrenia. It less clear, however, whether these reflect a widespread cortical involvement, or more selective involvement among interconnected neural systems, or more focal pathology. The extent of brain changes, their etiopathologic significance, and putative clinical correlates are reviewed in this article.