On the concept of third occipital headache.

One of the putative causes of headache is osteoarthritis of the C2-3 zygapophysial joint. A technique for blocking the third occipital nerve which innervates this joint was devised and used as a screening procedure for headache mediated by this nerve. Seven out of ten consecutive patients presenting with suspected cervical headache were found to suffer pain mediated by the third occipital nerve and stemming from a C2-3 zygapophysial joint. Because third occipital headache may be indistinguishable clinically from tension or other forms of headache, third occipital nerve blocks are advocated as means of establishing this largely unrecognised diagnosis.