SYLVIAN FISSURE ASYMMETRIES IN MONOZYGOTIC TWINS - A TEST OF LATERALITY IN SCHIZOPHRENIA

To address prior reports that schizophrenia is associated with loss of normal brain asymmetry and that it might be linked to a defect of a g ene controlling cerebral lateralization, we measured on three-dimensio nal cortical renderings from magnetic resonance imaging (MRI) scans th e lengths and angles of the sylvian fissures in 10 normal monozygotic (MZ) twin pairs (n=10 pairs) and in 10 MZ pairs discordant for schizop hrenia (n=10 pairs). We confirmed in both sets of twins the expected n ormal asymmetries of length and angle of the sylvian fissure. We also confirmed that the length asymmetry occurs solely in the region of the planum temporale. In the discordant twins, affected and unaffected tw ins did not differ in asymmetry measures, thus failing to support an a ssociation between illness per se and diminished asymmetry. Moreover, the discordant twins as a group did not differ from the normal twins a s a group, thus failing to confirm the hypothesis of a genetic associa tion with abnormal asymmetry. The implications of variations in method ology and patient samples are discussed.