Die Non-Coplanarit�t der horizontalen Bogeng�nge und ihre Auswirkung auf die experimentelle Vestibularispr�fung

Abstract

It is generally accepted that the horizontal semicircular canals are coplanar. One hundred three elliptic tomograms of human temporal bones have been evaluated for their planar relationship. The median was 180 degrees. However, the values varied between 160 degrees and 223 degrees. Differences of more than +/- 10 degrees were found in 31% of all cases. These anatomic variations are important for experimental vestibular testing, if, e.g., vestibulo-spin al effects result in a deviation or a torsion. With rotatory testing, stimulus intensity is a function of head inclination in relation to the stimulus plane. Non-coplanarity associated with head inclination results in asymmetric stimulus strength. With thermic testing, the effective stimulus is a function of the angle between temperature gradient across the canal and gravitation. Besides deviations from the perpendicular plane, rotations within this plane, according to Brünings "Schiefoptimumstellung", additionally cause asymmetrical errors.