Planar relationships of the semicircular canals in man

Principal-component analyses were determined on a series of points measured from the dissected bony labyrinth of ten human skulls, resulting in planar equations for each of the six semicircular canals. Following this, angles were calculated between the ipsilateral canal planes, between opposite synergistically acting canal planes and between each canal and the Reid stereotaxic planes. Results indicated that pairs of ipsilateral canals were nearly perpendicular, with the excpetion of the angle formed between the anterior and horizontal canal (mean = 111 degrees). Pairs of contralateral synergistic canal planes formed angles of 19 degrees between right and left horizontal canal planes and 23-24 degrees between vertical canal pairs. The horizontal canals formed an angle of 25 degrees with the Reid horizontal plane. Mathematical equations of the semicircular canals were used to predict the optimal head position for rotational and caloric stimulation.