Cerebral ventricular enlargement as a generalized feature of schizophrenia: a distribution analysis on 502 subjects

Enlargement of cerebral ventricles is one of the most replicated biological features, and the one quantitatively most deviant in schizophrenia. It occ urs in the early phases of the disease and may have pathogenetic relevance. Whether this abnormality is limited to a specific subgroup of patients or is a common feature to most or all patients affected by schizophrenia, howe ver, is still a matter of debate. The answer to this question would improve our comprehension of the nature of this abnormality and contribute to the debate between the competing hypotheses of biological homogeneity vs hetero geneity of schizophrenia. We performed a distribution analysis of lateral ventricular dimensions of 3 40 schizophrenic patients and 162 nonpsychiatric controls. All subjects und erwent cerebral computerized tomographic scan, and ventricular dimensions w ere expressed as ventricular brain ratio (VBR). After removing the effect o f confounding variables (age, sex and type of scanner) on individual VER. d ata were power-transformed and different distribution hypotheses were teste d by means of the maximum log-likelihood ratio method. Our findings indicate that, in the mixed sample of patients and controls, a mixture of two gaussian curves represents the distribution better than a s ingle gaussian curve, but no evidence emerged leading to rejection of the n ormality hypothesis in the schizophrenic patients sample. Lateral ventricular enlargement in schizophrenia is not a marker of a discr ete subgroup of schizophrenia, but occurs in most, if not all, schizophreni c patients. This supports the hypothesis of biological homogeneity of the d isease, at least relative to its major brain morphological abnormality. (C) 2000 Elsevier Science B.V. All rights reserved.