On the neuropathology of schizophrenia and its dementia: neurodevelopmental, neurodegenerative, or both?
The neuropathology of schizophrenia has begun to emerge following renewed investigation in the past 20 years. However, there remain inconsistencies in the data and their interpretation. In particular, although the brains of schizophrenics have been reported to show an excess of neurodegenerative changes, especially astrocytic gliosis and Alzheimer's disease, it is unclear whether these features are an intrinsic part of the neuropathology of schizophrenia. Nor is it apparent how they relate to the symptoms of dementia which afflict a proportion of schizophrenics. This review focuses upon these questions. Two main conclusions are drawn. Firstly, the neuropathological features of schizophrenia together support a neurodevelopmental pathogenesis wherein the aforementioned degenerative changes are either epiphenomenal, artefactual, or are limited to a subgroup of cases which are otherwise indistinguishable clinically or pathologically. Secondly, the dementia of schizophrenia is not attributable to Alzheimer's disease nor to any other recognized neuropathological substrate.