The human striatum in schizophrenia. I. Increase in overall relative striatal volume in schizophrenics

Postmortem volumetry of the human striatum and its subdivisions (putamen, n.caudatus, n.accumbens) was performed on serial coronal sections of complete hemispheres. Both hemispheres of 9 male schizophrenic patients younger than 65 years were closely matched in age with the hemispheres of 9 male control individuals. All obtained values were corrected with individual and region-specific shrinkage factors; the intrarater reliability was 1% difference in volume. The absolute striatal volume was significantly correlated with the volume of the hemisphere (r = 0.931; P = 0.0003***). Reflecting differences in the hemispheric volumes of the schizophrenic and the control group, the absolute striatal volume consequently did not differ between both groups (P > 0.55). However, we found a clear increase in the volume density (i.e. the relative striatal portion of the hemisphere; the relative striatal volume) in the schizophrenic group, highly significant on both sides (P = 0.003** for the right striatum, P = 0.002** for the left striatum). The increase in volume density concerned both the putamen (P = 0.003** for the right side) and the n.caudatus/n.accumbens (P = 0.01* for the right side). Discrepant volumetric results of previous authors who compared only absolute volume values in samples not matched for identical hemispheric volume could thus be explained by this high positive correlation with the hemispheric volume. Since exact matching for identical hemispheric volume is not feasible and examined groups will never be large enough to rule out the influence of the hemispheric volume, the determination of relative volumes (i.e. volume densities) seems to be advantageous for future volumetric studies.