Are auditory hallucinations the consequence of abnormal cerebral lateralization? A morphometric MRI study of the sylvian fissure and planum temporale

Background: Auditory verbal hallucinations (AVHs) are a characteristic feat ure of schizophrenia. Patients with schizophrenia have been found to have r educed volumes of a variety of brain structures as well as a reduction in r ight-left asymmetries, using postmortem and magnetic resonance imaging (MRI ) measures. There is also evidence that patients with AVHs differ in these structural asymmetries, relative to those patients who do nor hallucinate. The aim of this study was to examine whether patients with and without a pr ominent history of AVHs differ both from each other and in comparison with normal subjects, in the asymmetry of the sylvian fissure (SF) and planum te mporale (PT), Methods: We recruited 74 DSM-IV male patients with schizophrenia (on the ba sis of their AVH history) and 32 marched normal control subjects. Thirty pa tients had no history of AVHs and 44 had a strong definitive history of AVH s. The SF length and PT area and volume were measured on a three-dimensiona l MRI spoiled GRASS volume sequence. Absolute measures and laterality coeff icients were calculated. Results: All groups had the normal leftward asymmetry in both the SF and PT . Planum temporale volume and surface area and SF length were all larger in the left hemisphere. There were no significant differences in any measures between the two patient groups or between schizophrenic patients and contr ol subjects. Greater leftward asymmetry of the SF correlated with hallucina tions and thought disorder within the prominent hallucinator group. An asso ciation was found between handedness and brain size, bur this did not inter act with diagnosis. Conclusions: The results of this study do nor confirm reports, based on sma ller samples, of reduced structural asymmetries of either the SF or PT in s chizophrenia, nor do they indicate a specific relationship to a propensity to experience AVHs. A modest correlation between leftward asymmetry of the SF and some positive symptomatology was found (C) 2001 Society of Biologica l Psychiatry.