Asymmetries in the superior temporal lobe in male and female first-episode schizophrenic patients: measures of the planum temporale and superior temporal gyrus by MRI.

Schizophrenia has been hypothesized to be associated with an underlying brain developmental anomaly, specifically affecting normal brain asymmetries. The most pronounced asymmetries are present on the superior surface of the temporal lobes, the left plane, as measured along the sylvian fissure (planum temporale) being longer than the right in the majority of normal individuals. These asymmetries encompass Wernicke's area, the anatomical substrate for language, and have been found to be less pronounced in individuals with developmental language problems, i.e. dyslexia. Since disordered language is one of the hallmarks of schizophrenia, the present study focuses on the planum temporale and related superior temporal gyrus. Eighty-five first-episode schizophrenic patients and 40 controls had measurements of the sylvian fissure taken from coronal slices. The pattern of asymmetry in controls was for the right length to be longer than the left in anterior slices, and for left to be longer than right in posterior slices (corresponding to the planum temporale). Schizophrenic patients as a group demonstrated less asymmetry (R > L) in anterior slices, and female patients showed a trend for less (L > R) asymmetry in posterior slices. In contrast to the report of Barta et al. (1990), the volume of the anterior superior temporal gyrus did not differ from controls in first-episode schizophrenic patients. Neither the presence of formal thought disorder nor auditory hallucinations defined a subgroup of patients with reduced size or lateralization of the planum temporal or superior temporal gyrus.