The similarity of twin brains.

Purpose: To test the assumption underlying every morphometric twin study th at the brains of monozygotic twins are almost identical. Methods: High reso lution MRI of the neurocranium of 26 monozygotic twin pairs were acquired a nd the volumes of 36 cerebral structures were measured. The same twins serv ed as control group after rearranging them into non-related pairs of same s ex and matching them for age, body height and body weight. Results: For mos t of the examined structures the correlations within the twins were signifi cant (R = 0,97-0,59). Except for total forebrain volume the controls showed no significant similarity. Conclusions: For almost every measured cerebral structure the assumption, that significant similarities exist between heal thy monozygotic twins is correct. Therefore discordant monozygotic twins re present an excellent sample when investigating cerebral correlates of neuro logic and psychiatric disorders.