Amygdalar and hippocampal volumetry in control participants: differences regarding handedness.

BACKGROUND AND PURPOSE Amygdalar and hippocampal volume measurements indicate a right-greater-than-left asymmetry for right-handed normal participants in most studies. The purpose of this study was to compare amygdalar and hippocampal volume ratios between right- and left-handed participants. METHODS Amygdalar and hippocampal volume measurements were performed in 34 (20 right-handed and 14 left-handed) normal participants. All participants completed a 10-item handedness questionnaire. The MR imaging sequence was a 3D T1-weighted gradient-echo acquisition of the whole brain (24/6 [TR/TE]; flip angle, 25 degrees). MR images were spatially normalized, and volumes were painted with a 1.0-mm(3) resolution cursor on an SGI workstation. RESULTS In right-handed participants, the amygdala and hippocampus (P <.001 for both) were significantly larger on the right side than on the left. The left-handed group did not show a significant difference between right- and left-sided structures. Right-to-left volume ratios differed significantly between right- and left-handed participants for both amygdalar (P <.02) and hippocampal (P <.01) structures. Gender did not affect right-to-left amygdalar and hippocampal volume ratios in right- or left-handed participants. CONCLUSION Handedness, but not gender, seems to affect right-to-left amygdalar and hippocampal volume ratios.