Comprehensive Osteopathic Medical Licensing Examination (COMLEX USA) Practice

What defines the naming of cranial side bending rotation?

1. Position of the skull base

2. Position of basisphenoid - anterior or posterior

3. Position of basisphenoid - superior or inferior shear

4. Position of the midline bones

The correct answer is: Position of basisphenoid - superior or inferior shear

Cranial side bending rotation is defined by the positional relationship of the cranial bones, specifically in terms of the basisphenoid's movement within the cranium. In this context, the basisphenoid acts as a critical reference point: during cranial side bending, one side of the basisphenoid moves superiorly while the opposite side moves inferiorly, resulting in a rotational movement of the skull. This superior and inferior shear movement is integral to understanding the three-dimensional dynamics of cranial bone movement and is essential in osteopathic manipulative treatment, where cranial movement patterns are assessed and treated. The other elements mentioned, like the position of the skull base or the midline bones, do not capture the specific mechanics that occur during cranial side bending rotation. These alternative choices might involve different anatomical relationships, but they do not effectively describe the characteristic motion of the basisphenoid that is seen in cranial side bending rotation. This specificity highlights the importance of understanding the basisphenoid's position in the context of cranial osteopathy.