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., Ne w 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 convin ced that schizophrenia would ultimately be linked to an organic brain disor der. Alzheimer (1897: Alzheimer, A., 1897. Beitrage zur pathologischen anat omie der hirnrinde und zur anatomischen grundlage einiger psychosen. Monats schrift fur Psychiarie und Neurologie. 2, 82-120) was the first to investig ate the neuropathology of schizophrenia, though he went on to study mon tra ctable 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 sch izophrenia by Johnstone and colleagues. Since that time significant progres s has been made in brain imaging, particularly with the advent of magnetic resonance imaging (MRI), beginning with the first MRI study of schizophreni a by Smith and coworkers in 1984 (Smith, R.C., Calderon. M., Ravichandran, G.K., et al. (1984). Nuclear magnetic resonance in schizophrenia: A prelimi nary study. Psychiatry Res. 12, 137-147). MR in vivo imaging of the brain n ow confirms brain abnormalities in schizophrenia. The 193 peer reviewed MRI studies reported in the current review span the p eriod from 1988 to August, 2000. This 12 year period has witnessed a burgeo ning of MRI studies and has led to more definitive findings of brain abnorm alities in schizophrenia than any other time period in the history of schiz ophrenia research. Such progress in defining the neuropathology of schizoph renia 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 sc hizophrenia. Some of these abnormalities confirm earlier post-mortem findin gs, and most are small and subtle, rather than large, thus necessitating mo re advanced and accurate measurement tools. These findings include ventricu lar 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 amygd ala, 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 repor ted abnormalities. There was also moderate evidence for frontal lobe abnorm alities (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. Additio nally, there was strong to moderate evidence for subcortical abnormalities (i.e. cavum septi pellucidi-92% of studies reviewed, basal ganglia-68% of s tudies reviewed, corpus callosum-63% of studies reviewed, and thalamus-42% of studies reviewed), but more equivocal evidence for cerebellar abnormalit ies (31% of studies reviewed).