This interesting new research confirms how dysfunction of the atlas-axis vertebrae can result in head pain. I’ve written extensively about this condition that I term an “atlas wedge.” See: https://erikdalton.com/blog/suboccipital-triangle-headaches/

Sources of Cervicogenic Headache Among the Upper Cervical Synovial Joints

“In patients in whom headache was the dominant complaint, diagnostic blocks succeeded in establishing the source of pain in 75% of patients. The C2-3 joint was the source of pain in 62%, followed by the C1-2 (7%) and C3-4 (6%). In patients in whom headache was less severe than neck pain, blocks were successful in 67%. C2-3 was the source of pain in 42%, followed by lower cervical joints in 18% and the C3-4 joint in 7%.”

Source: Pain Medicine Journal, Jan 23, 2021