Etiology of structural asymmetry in schizophrenia: an alternative hypothesis.

During normal development of the fetal brain, the left hemisphere lags behind the right hemisphere in intrauterine growth, causing the left hemisphere to be smaller than the right hemisphere throughout the early and mid-prenatal period. By the end of the second trimester, the right hemisphere has achieved almost full-term size; thus second-trimester injuries affecting neurons, that is, anoxic, ischemic, toxic, or infectious insults that are systemic and bilateral, will affect the left hemisphere more than the right hemisphere. While other explanations for brain asymmetries in schizophrenia have been proposed, the embryological literature is consistent with the hypothesis that a prenatal injury may be one etiological factor in producing the structural brain asymmetries seen in psychotic adult patients.