“I know we are coming to the end of the year, but I want to raise cervicogenic headache (CGH),” requests Watson’s colleague. “Arghhhh! I wish we could delete the label ‘CGH’,” exclaims Watson.
“Why would you want that? It’s about the upper cervical spine and headache, right?” asks Watson’s colleague.
“Well, the label ‘CGH’ is an ‘intellectual straight jacket’,” comes Watson’s firm reply.
“Why is that?” inquires Watson’s colleague.
Is Cervicogenic Headache a Secondary Headache? The Paradox
Watson explains, “CGH is classified as a secondary headache, i.e. secondary to an identifiable lesion and a known pathophysiological process. But paradoxically, there’s nothing to see. I am sure this contributes significantly to the reported very low prevalence of CGH,” explains Watson. “The International Classification of Headache Disorders-3 (ICHD-3), as part of their diagnostic criteria, requires identification of a macroscopic lesion known to cause headache.”
“That sounds logical,” replies Watson’s colleague.
“Yes, but,” Watson counters, “as I may have mentioned before, an eminent neuroanatomist once said, ‘invisibility is not absence of evidence’. Just because we can’t see it doesn’t mean it is not it’s not there. Research using animal models has demonstrated headache-related neurophysiological phenomena in the dorsal horn from controlled, non-injurious loading (joint distraction ranging from 0.35mm to 0.9mm) of the zygapophyseal joint (z-joint) capsule, i.e. before the joint tensile strain threshold has been reached.”
The Validity of Translational Research
“But that’s in animals,” interjects Watson’s colleague.
“True,” acknowledges Watson, “however, animal models have been used extensively in migraine research, and extrapolating pathophysiological effects from mechanistic studies of the z-joint on animals to humans is generally considered to provide a satisfactory resemblance to human pain processes. So, coming back to this significant but unrecognised (ignored/dismissed?) volume of research… these studies imply that afferent information from z-joints has nociceptive (CGH) and central sensitisation (in primary headache?) potential. Furthermore, that symptomatic compromise of the z-joint can occur without a visible lesion.”
“Woah! That has significant implications for the role of cervical afferents in CGH and as a potential source of sensitisation in primary headache conditions,” replies Watson’s colleague, now grasping the significance.
Different Strokes for Different Folks
“Exactly,” Watson concludes, “the ICHD-3’s criteria for CGH, focusing on macroscopic lesions, is flawed. “Relevancy of cervical afferents in CGH and primary headache requires thorough and skilled examination of the upper cervical spine by discerning practitioners.”
“OK, now I am beginning to see why you think ‘CGH’ is an ‘intellectual straitjacket’,” realises Watson’s colleague.
“Yes,” Watson confirms, “the label ‘CGH’, I believe, is an ‘intellectual straitjacket’ as it restricts cervical afferents to a mechanistic role; it does a disservice to the role of cervical afferents as a source of central sensitisation in primary headache conditions.”
Realising that this is their last meeting before the end of the year holiday break, Watson’s colleague opens another 2012 Albert Bichot Cote de Nuits Villages Burgundy and discusses their plans for 2024.
