Brain density and symmetry in pedophilic and sexually aggressive offenders

Brain area and optical density were computed for each hemisphere and for 4 sections within the hemispheres at the level of the temporal horns for 18 pedophiles, 12 incest offenders, 34 sexually aggressive offenders of adult females and 12 nonviolent nonsex offender controls. Brain length and width was also computed, using the pineal gland as reference. From the width measures, an index of brain symmetry was computed. Results showed that the brains of sex offenders were relatively smaller in the left hemisphere compared to controls, but there were no significant group differences in optical density. There were no subgroup differences in brain area but the segments corresponding to the left frontal and temporal areas were smaller in sex offenders than controls. There were no significant differences in brain length but sex offenders had smaller widths in both hemispheres than controls. Analysis of symmetry showed that 66.7% of pedophiles and 53.1% of sexual aggressives had asymmetric brains compared to 8.3% of incest offenders and 20.0% of controls. Pedophiles showed smaller left hemispheres than right whereas sexual aggressives were equally split between left and right asymmetry. These results support earlier findings of temporal horn dilatation in pedophiles and sexual aggressives.