The main function of the cranial bones is to protect the important content, the brains. Living bones are relatively soft and accommodating, they were designed to absorb pressure from trauma.
In my practice, I almost daily see horses with dents in their skull from suffering a blow. I also often see horses where the occiput bone is lower than it should be, which means it is compressed. Pulling back on a halter often causes this. Compression is also caused by the daily use of halters, bits and bridles and dental work.
The cranial bones are connected through sutures. These sutures breathe along with the cranialsacral rhythm. Cranial compression causes blockages in the rhythm which then influences health and biomechanics in the whole body.
Craniosacral therapy can remove restrictions in the tissue so the cranial bones can regain their original shape. If a horse with cranial compression is left untreated it can result in many symptoms like pollen allergies, headshaking, spookiness, oversensitivity to sound en other behavioral issues.
