 Instead of being a quarter of an inch thick, the skull is an inch and a half to two inches thick. It squeezes all 12 of the pairs of the cranial nerves formed in the brain coming through the tunnels in the skull to the outside world, so to speak. How did it get so thick, Doc? Well, when you have osteoporosis, the bone is being replaced with connective tissue, scar tissue, cartilage, and all that kind of stuff. And your body's trying to maintain the strength there.