44. Reduced left Heschl’s gyrus volume in schizotypal personality disorder

Abstract

Schizotypal personality disorder (SPD) shares the same genetic diathesis as the schizophrenia spectrum disorders, yet persons with SPD are not psychotic and generally have not been prescribed neuroleptics. Therefore, they may represent an ideal group to study the underlying structural abnormalities in the spectrum disorders. Previously we showed SPD subjects to have enlarged CSF volumes, parahippocampal aysmmetry, and reduced left superior temporal gyrus (STG) gray matter volumes compared with normal control subjects. The STG consists anatomically of the anterior pole, Heschl’s gyrus (primary auditory sensory cortex) and planum temporale (auditory unimodal association cortex). In order to better define this STG abnormality, we examined Heschl’s gyrus and planum temporale in an extended group of subjects. Subjects: SPD subjects were all right-handed males (N = 24) and age-matched within 3 years to the comparison subjects (N = 23)), with no difference in IQ, years of education or parental socio-economic status. SPD subjects did have lower socioeconomic status. Image processing: The STG was manually drawn on the acquired coronal images consisting of 124 slices. To correct for the effects of head tilt, the images were realigned and resegmented to form a new set of images with over 200 slices and isotropic voxels. The drawings were edited as necessary and the boundaries were extended to their anterior and posterior most extent with high interrator reliability (intraclass r > 0.99). The effect of brain volume on region size was accounted for using a regression procedure. The resultant residual volume for left Heschl’s gyrus was not normally distributed and Mann-Whitney U statistics were used. There was no difference in volume of the total intracranial contents. The SPD subjects showed a 21% reduction in left Heschl’s gyrus volume, but no difference in right Heschl or planum temporale volume or Heschl or planum asymmetry. These findings suggest that the reduced left STG finding may be, in part, due to the volume reduction of Heschl’s gyrus. This is intriguing as Heschl’s gyrus participates in early processing of auditory stimuli (tones) and is consistent with the finding of abnormal P300 amplitude in a similar group of SPD subjects.