Developments in brain imaging techniques have given rise to a growing body of speculation that the cause of schizophrenia will be found in abnormalities in brain architecture. Brain scanning has revealed that the ratio of blood in the frontal lobes, between the front and the back, is lower in the brains of schizophrenics than in the brains of normal people. This has led to speculation that it is frontal lobe dysfunction that causes the positive symptoms of schizophrenia. Another theory that has developed out of apparent abnormalities detected by brain scans is that the cause of schizophrenia is to be found is some kind of trauma that has been experienced in the womb. Brain scans have revealed,
"increased amounts of cerebrospinal fluid (CSF) in the brain of many schizophrenics. A correspondingly slightly smaller brain volume has also been found. Since physical brain abnormalities do not progress further as the patient ages, levels of neuropathology may be present before birth." [20]
Apparent evidence from computed tomography (CT) scans of degeneration in a particular part of the brain called the cerebellar vermis has contributed to a brain atrophy hypothesis for schizophrenia.[21] Magnetic resonance imaging (MRI) scans have indicated that schizophrenic brains have a smaller average volume of total brain tissue than do the brains of normal people. The smaller brain volume is also found to be offset by an increase in the volume of cerebrospinal fluid in schizophrenic brains. The frontal lobes is the area where specific decreases seem most apparent. These findings have led researchers to conclude that:
"In addition to the generalised brain abnormalities observed in schizophrenia, a regional abnormality may be present in frontal regions. Since the frontal lobes integrate multimodality information and perform a variety of ‘higher’ cognitive and emotional functions that are impaired in schizophrenia, the frontal abnormality noted is consistent with the clinical presentation of the illness. Impaired frontal function and a disruption in its complex circuitry (including thalamocortical projections) may explain why patients with schizophrenia often have significant deficits in formulating concepts and organising their thinking and behaviour."[22]
There is no mention, however, in the description of this research as to whether the schizophrenics had been treated with neuroleptic medication prior to the MRI scans. It is therefore likely that the findings might simply be artefacts of the treatment.
One group of researchers used MRI to scan the brains of fifteen pairs of identical twins where one twin in each pair had schizophrenia. The schizophrenic twin in fourteen of the fifteen pairs was found to have enlarged ventricles. To deal with the problem of prior neuroleptic treatment, the degree of ventricle enlargement was cross-checked to see if it correlated with the length of time the schizophrenic twins had been on medication: ‘Brain abnormalities were not more severe among the schizophrenics with a long history either of the disorder or of antipsychotic drug treatment. Thus, the changes appear linked directly to schizophrenia.’[23]
These findings have led to speculations that early in brain development there might be some kind of viral infection, birth injury or autoimmune disorder which underlies abnormal brain development in schizophrenics. These abnormalities could go unnoticed until late adolescence when the central nervous system undergoes maturational changes. This is the time of life when the symptoms of schizophrenia most commonly emerge.
One problem with this is that the possible contribution of neuroleptic medication to the abnormalities is not properly discounted. The approach presupposes that if neuroleptics play a role then the longer they are used the greater would be the abnormality, but no evidence is supplied to support this assumption.
Another problem is that in most groups of schizophrenics there are some schizophrenics who do not have large ventricles. One investigation found that it was only the males in a group of schizophrenics who had large ventricles. On top of this it has been found that some people with Alzheimer’s disease and others with manic depression also have large ventricles, so that this abnormal feature is neither necessary for schizophrenia, nor is it associated solely with schizophrenia.[24]
Despite the enthusiasm of some research reports proponents of the enlarged ventricle theory remain on the margins of mainstream psychiatry: ‘a simple statement that “schizophrenics have larger ventricles than controls” will be marked wrong in an MCQ examination of the Royal College of Psychiatrists, as the ventricles of the brains of most schizophrenics have scores within the normal range’.[25]
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[20] Daniel R. Weinberger, ‘From neuropathology to neurodevelopment’, pp. 552–8.
[21] R. Sandyk et al., ‘Atrophy of the Cerebellar Vermis: Relevance to the Symptoms of Schizophrenia’, pp. 205–12.
[22] Nancy C. Andreasen et al., ‘Regional brain abnormalities in schizophrenia measured with magnetic resonance imaging’, pp. 1763–70.
[23] B. Bower, ‘Brain Anatomy Yields Schizophrenia Clues’, p. 182.
[24] Ibid.
[25] D. B. Double, ‘Understanding Schizophrenia’.