During the Extension Phase of Cranial Motion, which movement occurs at the SBS?

• A. SBS moves caudad
• B. SBS moves cephalad
• C. SBS moves anterior
• D. SBS remains stationary

Answer: (A)

The movement pattern of the cranial bones follows a rhythmic cycle with two phases: flexion and extension. In flexion, the SBS moves upward toward the head; in extension, the opposite occurs—the SBS moves downward toward the base of the skull.

During the Extension Phase, the vault settles and the SBS descends, i.e., it moves caudally. This downward motion is the defining change of the extension phase, opposite to the cephalad movement seen in flexion. The downward shift aligns with the overall pattern of the cranial rhythmic motion and helps explain why caudad movement at the SBS is the correct description for extension.