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Relationship between Handedness and the Geometry of the Branches of the Aortic Arch

Handedness is the most obvious behavioural asymmetry in humans. Asymmetrical regional cerebral blood volume changes, particularly in the left premotor and parietal regions, occur contra-lateral to hand dominance during mental and motor activity. While a potential link between hemispheric and anatomical lateralisation has been investigated, research into the influence of asymmetrical vascular geometry is severely lacking. This study explores the relationship between handedness and the geometry of the arterial branches of the aortic arch, analysing potential asymmetries between the left common carotid (LC) and the combined right common carotid and brachiocephalic trunk (RC-BT complex) of left-handed and right-handed individuals. Selected geometric parameters of the vessels were measured, including minimum, mean, and maximum diameters, length, angle deviation, mean artery angle, and calculated resistance to blood flow. A revised version of the Edinburgh Handedness Inventory classified a sample of 71 participants, aged 21 to 96, into relevant handedness categories (left-handed = 8; right-handed = 62). An in-depth analysis of computed tomography angiography scans with RadiAnt DICOM Viewer (64-bit) imaging software was conducted. The findings confirm that right-handed individuals had dominant LC arteries (21.57% increased flow) that are presumably responsible for the higher metabolic demand of the left hemisphere of the brain (5.7%) in such individuals. Conversely, left-handed individuals had dominant RC-BT complex arteries (61.57% increased flow) that are responsible for a higher metabolic demand of the right hemisphere (16.21%). This difference was particularly evident in the geometric parameters of minimum and maximum arterial diameters, and calculated resistance to blood flow. Measurements of right-handers' alternate arterial branching patterns showed a significant increase in overall blood flow resistance in both vessels, with a particular increase in RC-BT complex resistance. Therefore, despite the branching abnormality, a handedness-related bias was still evident. The findings concur with existing hemodynamic studies of the carotid arteries.