Regional neural dysfunctions in chronic schizophrenia studied with positron emission tomography

Objective: Whether chronicity of illness produces progressive neural abnorm ality is an important question in current schizophrenia research. Positron emission tomography (PET) offers an opportunity to visualize and measure bl ood flow in vivo to address this issue. The authors previously compared hea lthy volunteers with neuroleptic-naive patients experiencing their first ep isode of schizophrenia and reported that abnormalities in blood flow, inclu ding lower flow in prefrontal regions and higher flow in the thalamus and c erebellum, are present at the early stage of schizophrenic illness. The goa l of the present study was to measure blood flow with PET in patients with chronic schizophrenia. Method: PET was used to examine regional cerebral bl ood flow (rCBF) in 30 patients with chronic schizophrenia and 30 normal com parison subjects. To determine if the patterns of flow abnormality in the p atients with chronic schizophrenia were similar to those of patients experi encing their first episode of schizophrenia, the same cognitive condition w as examined as in the earlier study. The patients with chronic schizophreni a in the current study had been neuroleptic-free for at least 3 weeks. Resu lts: As in the authors' previous study, the chronically ill patients showed lower flow in prefrontal areas and higher flow in thalamic and cerebellar regions than normal comparison subjects, suggesting that a similar neural d ysfunction occurs in both first-episode and chronic schizophrenia. Conclusi ons: rCBF abnormalities in patients with chronic schizophrenia are not due to chronicity of illness or the effects of medication. These results provid e evidence that the primary neural abnormalities in schizophrenia may occur in cortical, cerebellar, and thalamic regions and that the dysfunction in these regions may explain the "loosening of associations" that Bleuler cons idered to be the fundamental cognitive phenotype of schizophrenia. These ab normalities can be reconceptualized as "cognitive dysmetria".