How do the cranial bones move in PRM?

• A. Each bone has specific normal axes and planes of motion; trauma may create abnormal motions
• B. All cranial bones move in identical single planes
• C. Cranial bones do not move once fused
• D. Only the occipital bone participates in motion

Answer: (A)

In the Primary Respiratory Mechanism, cranial bones aren’t moving as a single rigid block. Each bone has its own normal axes and planes of motion at its sutures and membranous attachments, and these tiny movements occur in multiple directions in a coordinated rhythm. Trauma or other factors can disrupt these patterns, producing abnormal motions or restrictions.

That’s why the best answer isn’t that all bones move in identical single planes, or that they stop moving after fusion, or that only one bone—like the occipital—participates. In PRM, many bones participate and each has distinct, small, multi-directional motions.