Human cerebral asymmetries evaluated by computed tomography.

The handedness of seventy-five persons without evidence of neurological disease, was assessed with a standardised test. An analysis of the CT scans of the same persons was performed to determine (1) presence and lateralisation of frontal and occipital "petalia," (2) width of frontal and occipital lobes of each hemisphere, (3) direction of straight sinus deviation. Results suggest that handedness and cerebral asymmetries are independent variables. There were no significant differences between right-handers and non-right-handers. Also there were no significant differences between strongly left-handed and ambidextrous individuals, nor were there differences between right-handers with or without family history of left-handedness. Irrespective of handedness, left occipital "petalia" was more common than right (p < 0.01), right frontal petalia was more common than left (p < 0.01), and straight sinus deviation was more commonly toward the right. The study does not support the concept that cerebral "symmetry" or "reverse asymmetry" are associated with left-handedness or ambidexterity. The noted asymmetries are more likely to be direct correlates of cerebral language dominance, than of handedness. Furthermore, the possibility that outside forces acting on the bone contributes to the asymmetries cannot be excluded. CT scan may be of value as a direct predictor of cerebral dominance.