Table 2.

Accepted structural causes of cervicogenic headache (14–16).

Source	Innervation	Referred pain	Physical exam	Diagnosis	Therapy
O-C1 (atlanto-occipital joint)	C2 ventral ramus	Occipital Suboccipital (Temporal)	Pain on head nodding	Atlanto-occipital joint injection	Maximize conservative treatment Atlanto-occipital joint injection
C1-2 (lateral atlanto-axial joint)	C2 ventral ramus	Suboccipital Occipital (Vertex, orbit, ear)	Tender C1-2 joint Restricted passive rotation of C1 on C2 Pain on rotation with a flexed neck	Atlanto-axial joint injection	Atlanto-axial joint injection Atlanto-axial joint RFA Surgical Fusion
C2 nerve root	N/A	Occipital	Associated lacrimation, ciliary injection, rhinorrhea	Selective C2 nerve root block	C2 nerve root injection C2 nerve root pulsed RFA
C2-3 disc	Unknown	Unknown	Unknown	Provocative discography	Fusion
C2-3 facet joint	Third occipital nerve (C3 dorsal ramus)	Upper neck Occipital (Parietal, frontal, orbit)	Tender C2-3 joint	Third occipital nerve block	Third occipital nerve block Third occipital nerve RFA C2-3 facet joint injection

RFA, radiofrequency ablation.