A magnetic resonance imaging study of corpus callosum size in familial schizophrenic subjects, their relatives, and normal controls

Magnetic resonance imaging of brain anomalies in adult and pediatric schizophrenia patients: Experience of a Romanian tertiary hospital

Schizophrenia is a severe mental illness with a significant impact on the life of both the patient and the patient's family. Magnetic resonance imaging has proven a useful tool for studying structural changes of the brain in schizophrenia. However, interpreting the published literature presents several challenges. Despite thorough research in recent years, which has included anatomopathological, imaging, electrophysiological, and genetic studies, the intimate pathophysiological mechanisms of this disease are not yet fully elucidated. The present study included patients with schizophrenia diagnosed in the psychiatric clinics from the ‘Prof. Dr. Alexandru Obregia’ Clinical Psychiatry Hospital between September 2019 and December 2020. Three Tesla magnetic resonance neuroimaging studies were performed. In a significant number of cases, the neuroimaging studies showed association of cerebral modifications such as enlargement of the Virchow spaces, lesions of the white matter with demyelinating appearance, and inflammatory sinus reactions. Cortical atrophy and hemosiderotic spots were present in a statistically significant proportion in the patient group with an age range of 29-61 years. MRI is indicated as a useful technique in the follow-up process of schizophrenia patients. However, whether the anomalies revealed in this disorder can be utilised as diagnostic biomarkers is still being debated.

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.

Corpus callosum microstructural and macrostructural abnormalities in schizophrenia according to the stage of disease

Corpus callosum (CC) volume and surface (macrostructural) studies remain controversial and have not considered the illness duration (ID) systematically. Regardless of ID, some CC macrostructural studies have shown no difference between SZ patients and healthy controls (HC), whereas others have reported macrostructural abnormalities in SZ. Conversely, CC microstructural studies are more in agreement with alterations in CC integrity regardless of the patients' ID, but the direction and degree of these abnormalities over time remain unknown. Moreover, no study has explored both the micro- and macrostructure of the CC in SZ by considering the stage of disease. Both CC micro- and macrostructural data were investigated in 43 SZ patients and compared between two patient groups (21 patients with a short ID and 22 with a long ID) and HC (23 participants) using diffusion tensor and structural imaging. CC microstructural alterations were detected in both SZ groups compared to the HC group, without differences between the SZ groups. In contrast, CC macrostructural alterations were only found in the long ID group. CC microstructural alterations might be detected in schizophrenia at an early stage, without an increase of magnitude thereafter, while CC macrostructural alterations might become apparent at later stages of the illness.

Relationships between corpus callosum and language lateralization in patients with schizophrenia and bipolar disorders

OBJECTIVES

The question of whether there is a continuum or a dichotomy among patients with schizophrenia (SZ) and bipolar disorders (BD) has not been clearly resolved and remains a challenge. Thus, the identification of specific biomarkers of these disorders might be helpful. The present study investigated the volume of the corpus callosum (CC) and functional lateralization for language as potential biomarkers and their relationships in SZ and BD.

METHODS

The study included 20 patients with SZ, 20 patients with BD and 40 healthy controls (HC). A functional lateralization index (FLI) was computed for each participant within the language comprehension network. For each participant, the volume of the total CC and those of three subregions were extracted. These variables and their anatomo-functional relationships were investigated.

RESULTS

In comparison to HC, SZ patients presented a decreased leftward lateralization for language, whereas this was not found in BD patients. However, as compared to SZ patients and HC, BD patients showed a reduction in CC volume associated with a lower leftward lateralization for language.

CONCLUSIONS

Our study revealed that SZ patients displayed a reduction of the leftward functional lateralization for language; however, no reduction of CC volume was observed, whereas BD patients presented a decreased volume of the CC associated with a lower leftward asymmetry for language. The results of our study detected distinct anomalies in both SZ and BD that may be considered as specific biomarkers of these disorders related to neurodevelopmental models.

The myelinated fiber loss in the corpus callosum of mouse model of schizophrenia induced by MK-801

Previous magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) investigations have shown that the white matter volume and fractional anisotropy (FA) were decreased in schizophrenia (SZ), which indicated impaired white matter integrity in SZ. However, the mechanism underlying these abnormalities has been less studied. The current study was designed to investigate the possible reasons for white matter abnormalities in the mouse model of SZ induced by NMDA receptor antagonist using the unbiased stereological methods and transmission electron microscope technique. We found that the mice treated with MK-801 demonstrated a series of schizophrenia-like behaviors including hyperlocomotor activity and more anxiety. The myelinated fibers in the corpus callosum (CC) of the mice treated with MK-801 were impaired with splitting lamellae of myelin sheaths and segmental demyelination. The CC volume and the total length of the myelinated fibers in the CC of the mice treated with MK-801 were significantly decreased by 9.4% and 16.8% when compared to those of the mice treated with saline. We further found that the loss of the myelinated fibers length was mainly due to the marked loss of the myelinated nerve fibers with the diameter of 0.4-0.5 μm. These results indicated that the splitting myelin sheaths, demyelination and the loss of myelinated fibers with small diameter might provide one of the structural bases for impaired white matter integrity of CC in the mouse model of SZ. These results might also provide a baseline for further studies searching for the treatment of SZ through targeting white matter.

Absence of anatomic corpus callosal abnormalities in childhood-onset schizophrenia patients and healthy siblings

The corpus callosum (CC) has been implicated in the pathogenesis of schizophrenia, and CC deficits have been reported in adults with schizophrenia. We explored the developmental trajectory of the corpus callosum in childhood-onset schizophrenia (COS) patients, their healthy siblings (SIB) and healthy volunteers. We obtained 235 anatomic brain magnetic resonance imaging (MRI) scans from 98 COS patients, 153 scans from 71 of their healthy siblings, and 253 scans from 100 age- and gender-matched healthy volunteers, across ages 9-30 years. The volumes of five sub-regions of the CC were calculated using FreeSurfer, and summed to give the total volume. Longitudinal data were examined using mixed model regression analysis. There were no significant differences for the total or sub-regional CC volumes between the three groups. There were also no significant differences between the groups for developmental trajectory (slope) of the CC. This is the largest longitudinal study of CC development in schizophrenia and the first COS study of the CC to include healthy siblings. Overall, CC volume and growth trajectory did not differ between COS patients, healthy siblings, or healthy volunteers. These results suggest that CC development, at least at a macroscopic level, may not be a salient feature of schizophrenia.

Interhemispheric hypoconnectivity in schizophrenia: fiber integrity and volume differences of the corpus callosum in patients and unaffected relatives

Changes in hemispheric asymmetry and inter-hemispheric connectivity have been reported in schizophrenia. However, the genetic contribution to these alterations is still unclear. In the current study, we applied an automatic segmentation method to structural MRI and diffusion tensor imaging (DTI) data and examined volume and fiber integrity of the corpus callosum (CC), the main interhemispheric fiber tract, in 16 chronic schizophrenia (SZ) patients, matched first degree relatives and controls. SZ patients and relatives had smaller CC volumes than controls, particularly in the posterior genu, isthmus and splenium. Fractional anisotropy (FA), an indicator of fiber integrity, was reduced in patients and relatives in the whole CC, the inferior genu, the superior genu and the isthmus. Correspondingly, the mean diffusivity (MD) values of the whole CC and the isthmus were higher in patients and their unaffected relatives, indicating decreased compactness and increased intercellular space. Relatives had intermediate values in the volumetric and fiber integrity measurements between patients and controls. Lower CC volume and fiber integrity in SZ patients were associated with more severe auditory hallucinations. These results support the connectivity hypothesis of SZ (Friston, 1998) and particularly highlight the altered interhemispheric connectivity, which appears to be a genetic feature of SZ risk.

Putative structural neuroimaging endophenotypes in schizophrenia: a comprehensive review of the current evidence

The genetic contribution to schizophrenia etiopathogenesis is underscored by the fact that the best predictor of developing schizophrenia is having an affected first-degree relative, which increases lifetime risk by tenfold, as well as the observation that when both parents are affected, the risk of schizophrenia increases to approximately 50%, compared with 1% in the general population. The search to elucidate the complex genetic architecture of schizophrenia has employed various approaches, including twin and family studies to examine co-aggregation of brain abnormalities, studies on genetic linkage and studies using genome-wide association to identify genetic variations associated with schizophrenia. ‘Endophenotypes’, or ‘intermediate phenotypes’, are potentially narrower constructs of genetic risk. Hypothetically, they are intermediate in the pathway between genetic variation and clinical phenotypes and can supposedly be implemented to assist in the identification of genetic diathesis for schizophrenia and, possibly, in redefining clinical phenomenology.

The comprehension of idiomatic expressions in schizophrenic patients

Recent fMRI and TMS studies on idiom comprehension have shown that the prefrontal cortex is involved in idiom processing. Since schizophrenic patients exhibit prefrontal structural changes and dysexecutive behavioural deficits, we hypothesised an impairment in idiom comprehension, correlating with performance on executive tasks. In this study, idiom comprehension was evaluated by means of a sentence-to-picture-matching task in 45 schizophrenic patients and 45 control subjects, matched for age and educational level. The task included 62 idiomatic and 62 literal sentences. Participants were presented with a written sentence, either literal or idiomatic, followed by a picture, which appeared below the sentence. They were instructed to judge whether the picture represented the meaning of the sentence or not, and responded by pressing one of two response keys. Half of the items correctly represented the meaning, half did not. Reaction times and accuracy were measured. Schizophrenics were impaired in both types of idiomatic sentence. However, their performance was particularly poor in the case of ambiguous idioms. Wisconsin Card Sorting Test and Digit Sequencing were the unique predictors of performance for idiom comprehension in general, while thought disorganization was not. Cognitive decline either did not appear to predict performance.

Morphology of the corpus callosum in treatment-resistant schizophrenia and major depression

OBJECTIVE

To identify possible differences in the mean midsagittal corpus callosum (CC) total and subdivision areas in treatment-resistant schizophrenia and depression (TRS and TRD) patients.

METHOD

Areas of the total CC and its five equidistant subregions (from CC1 to CC5) obtained by parallel grid partitioning schemes were manually segmented from brain MRI of 42 TRS, 45 TRD patients and 30 healthy controls. The intracranial volume (ICV) normalized areas were calculated and compared between groups.

RESULTS

When compared with controls, patients with TRS had reduced ICV and a larger CC5, and TRD patients had a smaller CC4 while no significant difference in CC total area in patients with TRS or TRD was found. Multiple individual segments and total CC areas were significantly larger in TRS than TRD patients after normalization.

CONCLUSION

Patients with TRS and TRD have different CC morphological characteristics, and therefore there may be aberrant interhemispheric connectivity in schizophrenia and major depressive disorder patients.

Functional magnetic resonance imaging (fMRI) of attention processes in presumed obligate carriers of schizophrenia: preliminary findings

BACKGROUND

Presumed obligate carriers (POCs) are the first-degree relatives of people with schizophrenia who, although do not exhibit the disorder, are in direct lineage of it. Thus, this subpopulation of first-degree relatives could provide very important information with regard to the investigation of endophenotypes for schizophrenia that could clarify the often contradictory findings in schizophrenia high-risk populations. To date, despite the extant literature on schizophrenia endophenotypes, we are only aware of one other study that examined the neural mechanisms that underlie cognitive abnormalities in this group. The aim of this study was to investigate whether a more homogeneous group of relatives, such as POCs, have neural abnormalities that may be related to schizophrenia.

METHODS

We used functional magnetic resonance imaging (fMRI) to collect blood oxygenated level dependent (BOLD) response data in six POCs and eight unrelated healthy controls while performing under conditions of sustained, selective and divided attention.

RESULTS

The POCs indicated alterations in a widely distributed network of regions involved in attention processes, such as the prefrontal and temporal (including the parahippocampal gyrus) cortices, in addition to the anterior cingulate gyrus. More specifically, a general reduction in BOLD response was found in these areas compared to the healthy participants during attention processes.

CONCLUSION

These preliminary findings of decreased activity in POCs indicate that this more homogeneous population of unaffected relatives share similar neural abnormalities with people with schizophrenia, suggesting that reduced BOLD activity in the attention network may be an intermediate marker for schizophrenia.

M, Jain S. Corpus callosal area differences and gender dimorphism in neuroleptic-naïve, recent-onset schizophrenia and healthy control subjects

The study of corpus callosal morphometry is important to unravel the underlying connectivity disturbance in schizophrenia. We studied the corpus callosal area in schizophrenia subjects compared to healthy subjects, while controlling for several confounders that could affect morphometric measures of the corpus callosum (CC). Areas of the whole CC and its sub-regions obtained by two geometric partitioning schemes were studied in 23 right-handed neuroleptic-naïve, recent-onset, schizophrenia patients and compared with 23 right-handed age-, sex- and education-matched healthy subjects. The patients did not differ from controls in whole CC area. On tripartite division of the CC, the area of the anterior sub-region was significantly higher in patients compared to controls. On radial division into 5 sub-regions, the anterior truncus area was significantly higher in patients compared to controls. There was a significant effect of gender (F>M) on the area measures; however there was no significant diagnosis()gender effect. Age, age of onset, duration of illness and psychopathology ratings did not show any significant correlations with whole CC area and area of CC sub-regions. The finding of increased area of the anterior truncus that possibly comprises white fibres connecting the temporal association cortices could be indicative of an "abnormal functional hyperconnection" involving these regions in positive symptom schizophrenia. Additionally, the finding of females having larger areas of the whole CC and of the anterior and middle sub-regions could reflect a "normal hyperconnection" underlying increased ambilaterality in females.

Meta-analysis of magnetic resonance imaging studies of the corpus callosum in schizophrenia

OBJECTIVES

The corpus callosum plays a pivotal role in inter-hemispheric transfer and integration of information. Magnetic resonance studies have reported callosal abnormalities in schizophrenia but findings have been inconsistent. Uncertainty has persisted despite a meta-analytic evaluation of this structure several years ago. We set out to perform a further meta-analysis with the addition of the numerous reports published on the subject to test the hypothesis that the corpus callosum is abnormal in schizophrenia.

METHOD

A systematic search was carried out to identify suitable magnetic resonance studies which reported callosal areas in schizophrenia compared to controls. Results from the retrieved studies were compared in a meta-analysis whilst the influence of biological and clinical variables on effect size was ascertained with meta-regression analysis.

RESULTS

Twenty-eight studies were identified. Corpus callosum area was reduced in schizophrenia in comparison to healthy volunteers. This effect was larger in first episode patients. Similarly, heterogeneity detected among the studies was associated with course of illness indicating that chronic subjects with schizophrenia showed larger callosal areas. There was no evidence of publication bias.

CONCLUSIONS

This study confirms the presence of reduced callosal areas in schizophrenia. The effect is of a larger magnitude at first presentation and less so in subjects with a chronic course generally medicated with antipsychotics.

Evidence of normal hearing laterality in familial schizophrenic patients and their relatives

Dichotic listening (DL) has been used as a tool to investigate possible left cerebral dysfunction in schizophrenia. However, the wide range of DL tests (e.g., words, emotions, sentences) as well as patient groups ("heterogeneity") has introduced several confounders. Assessing relatives of patients with schizophrenia may overcome some of these problems, and may be more useful in determining if loss of functional cerebral laterality in schizophrenia is a state or a trait phenomenon. The fused consonant-vowel DL test was administered to 114 subjects: 20 individuals with familial schizophrenia, 42 of their healthy relatives, and 52 healthy volunteers. We did this to investigate whether the normal language processing asymmetry-a right ear advantage (REA)-is present, and whether it could serve as a marker for genetic liability. General performance accuracy level was lower in schizophrenia patients and their relatives but the expected REA was present in all groups. Adjusting for age, accuracy, and obligate status made no difference. In conclusion, familial schizophrenic patients and their relatives have normal REA and hearing laterality on the fused DL test.

MRI brain volume abnormalities in young, nonpsychotic relatives of schizophrenia probands are associated with subsequent prodromal symptoms

Schizophrenia is characterized by subtle but well-replicated total and regional (frontal and temporal) brain tissue volume deficits. Studies of individuals at-risk for developing schizophrenia suggest that the onset of brain volume decrement may closely pre-date overt manifestations of schizophrenia, making brain volume abnormalities potential predictors for early identification. In an ongoing longitudinal morphometric MRI study of young, nonpsychotic first- or second-degree relatives of schizophrenia probands, we compared brain volumes in 46 relatives who are still within age range for developing schizophrenia against comparison groups of 46 schizophrenia patients and 46 healthy volunteers without family history of schizophrenia. Relatives had similar brain volume abnormalities as schizophrenia patients albeit less severe. Relatives had significantly larger whole brain, frontal, temporal and parietal gray matter (GM) volumes than patients. Relatives also had significantly smaller frontal GM volumes than healthy volunteers. Both relatives and patients had significantly larger whole brain WM (specifically parietal WM) volumes compared to healthy volunteers. Abnormally greater WM volumes in relatives and patients are suggestive of genetically-mediated dysmaturation of the age-expected myelination during adolescence through mid adulthood. On prodromal symptoms assessed in relatives one year after MRI brain scans, initial GM deficits as well as larger WM volumes correlated significantly with greater severity of subsequent prodromal symptoms. Together with previous genetic high-risk studies of adolescent or young adult relatives, these findings indicate that premorbid MRI brain abnormalities may be of predictive value for the early identification of schizophrenia.

Genetically mediated brain abnormalities in schizophrenia

Schizophrenia is a highly heritable, neurobehavioral disorder; however, the mode of inheritance is complex, and linkage findings have been difficult to replicate. Some consistent linkage findings have emerged on chromosomes 1, 6, 8, 11, 13, 15, and 22. New methods are being developed for candidate gene identification, including the use of neurobiologic phenotypes observed in relatives of persons with schizophrenia. Neuroimaging studies of relatives implicate abnormal hippocampal structure and inefficient prefrontal network functioning, probably representing mild variants of the abnormalities observed in schizophrenia. These characteristics may represent stable markers of vulnerability to schizophrenia, because they are not confounded by effects of antipsychotic drugs or psychosis. Recent studies provide evidence for a small role of the catechol-O-methyltransferase gene on 22q, and the serotonin receptor transporter gene on 17q11-q12 in the development of schizophrenia. Linking genes and brain regions or networks is an important step in identification of the pathophysiology of schizophrenia.

Schizophrenia, neurodevelopment and corpus callosum

The Zeitgeist favors an interpretation of schizophrenia as a condition of abnormal connectivity of cortical neurons, particularly in the prefrontal and temporal cortex. The available evidence points to reduced connectivity, a possible consequence of excessive synaptic pruning in development. A decreased thalamic input to the cerebral cortex appears likely, and developmental studies predict that this decrease should entail a secondary loss of both long- and short-range cortico-cortical connections, including connections between the hemispheres. Indeed, morphological, electrophysiological and neuropsychological studies over the last two decades suggest that the callosal connections are altered in schizophrenics. However, the alterations are subtle and sometimes inconsistent across studies, and need to be investigated further with new methodologies.

Genetic contributions to altered callosal morphology in schizophrenia

Patients with schizophrenia exhibit abnormalities in midsagittal corpus callosum area, shape, and/or displacement. Our goal was to confirm these findings and to establish the genetic and nongenetic contributions to altered callosal morphology in schizophrenia. Relationships between ventricular enlargements potentially contributing to callosal displacements were assessed as a secondary goal. High-resolution magnetic resonance images were obtained from co-twins of monozygotic and dizygotic pairs discordant for schizophrenia and healthy control twins (N = 40 pairs). Investigators blind to group status segmented the corpus callosum and ventricles in native brain volumes aligned using a rigid-body transformation with no scaling. Total and parcellated midsagittal callosal areas and measures indexing vertical displacements of the corpus callosum were used in statistical tests to identify schizophrenia and sex effects and to dissociate genetic and nongenetic influences on morphology. Anatomical mesh modeling methods provided group average and surface variability maps of the callosum. Callosal areas did not differ between groups defined by sex or biological risk. Vertical displacements of the callosum, pronounced in male patients, were confirmed in schizophrenia and observed between dizygotic, but not monozygotic co-twins discordant for schizophrenia. Like their affected twins, however, unaffected monozygotic co-twins of the schizophrenia probands exhibited significant callosal displacements. Lateral and third ventricle enlargements were related to callosal displacements. Results clearly support that genetic rather than disease-specific or shared environmental influences contribute to altered callosal morphology in schizophrenia. An upward bowing of the callosum may thus provide an easily identifiable neuroanatomic marker to screen individuals possessing a biological vulnerability for schizophrenia.

Increased hippocampal volume in schizophrenics' parents with ancestral history of schizophrenia

OBJECTIVE

Decreased hippocampal volume is one of the hypothesized pathological features of schizophrenia, but it is not known if this abnormality is familially transmitted. The aim of this study was to measure the hippocampal volume of the parents of schizophrenic probands, in relationship to the apparent transmission of genetic risk.

METHOD

Eighteen subjects from families consisting of a schizophrenic proband and two clinically unaffected parents were studied. Probands were compared to six control subjects, matched for age, sex, and educational level. The six families were selected so that only one parent had an ancestral family history of schizophrenia. The volumes of both hippocampi were measured by magnetic resonance imaging and adjusted for age and whole brain volume.

RESULTS

The total hippocampal volumes of the parents with ancestral family history of schizophrenia were significantly larger than those of their schizophrenic offspring.

CONCLUSIONS

This study suggests that decreased hippocampal volume in schizophrenia is not a familially transmitted abnormality. Rather, it appears that clinically unaffected parents who transmit apparent genetic risk for schizophrenia may have increased hippocampal volume, which may be a protective factor against the illness.

Interhemispheric transfer and laterality effects in simple visual reaction time in schizophrenics

INTRODUCTION

There is evidence that schizophrenics have an abnormal corpus callosum and an abnormal pattern of cerebral asymmetries. We investigated whether there are corresponding functional abnormalities in interhemispheric transfer (IT) and laterality effects.

METHODS

Medicated schizophrenic patients and matched controls were tested in the Poffenberger paradigm, that is, a simple manual reaction time (RT) paradigm with laterally presented visual stimuli designed to provide a behavioural estimate of IT. By subtracting RT averaged across the uncrossed hand-hemifield conditions, from RT averaged across the crossed hand-hemifield conditions, one can obtain an estimate of IT time.

RESULTS

In schizophrenic patients the difference between crossed and uncrossed conditions was 0 because of an unusually prolonged RT in the uncrossed condition right hand/ right field. A broadly similar result has been obtained previously in the tactile modality (Ditchfield & Hemsley, 1990) and is consistent with a left hemisphere impairment. This effect was still present when the patients were retested about 2 years later.

CONCLUSIONS

These results demonstrate the existence in schizophrenic patients of a consistent slowing down of simple visuomotor responses subserved by the left hemisphere.

The brain in schizotypal personality disorder: a review of structural MRI and CT findings

Studies of schizotypal personality disorder (SPD) are important because the condition is genetically related to schizophrenia and because data accumulating to confirm its biological underpinnings are challenging some traditional views about the nature of per-sonality disorders. This review of 17 structural imaging studies in SPD indicates that individuals with this disorder show brain abnormalities in the superior temporal gyrus, parahippocampus, temporal horn region of the lateral ventricles, corpus callosum, thalamus, and septum pellucidum, as well as in total cerebrospinal fluid volume, similar to those seen in persons with schizophrenia. Differences between SPD and schizophrenia include lack of abnormalities in the medial temporal lobes and lateral ventricles in SPD. Whether the normal volume, and possibly normal functioning, of the medial temporal lobes in individuals with SPD may help to suppress psychosis in this disorder remains an intriguing but still unresolved question. Such speculation must be tempered due to a paucity of studies, and additional work is needed to confirm these preliminary findings. The imaging findings do suggest, however, that SPD probably represents a milder form of disease along the schizophrenia continuum. With further clarification of the neuroanatomy of SPD, researchers may be able to identify which neuroanatomical abnormalities are associated with the frank psychosis seen in schizophrenia.

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)