There is a relationship between CSM and hypertension, probably a cause/effect relationship, and investigators term this type of hypertension "cervicogenic hypertension". Abnormally functioning serotonergic pacemaker cells in the dorsal raphe nucleus inappropriately activate and inhibit parts of the central and autonomic nervous systems as part of a chronic stress response, which causes hypertension and migraine. This theory is now being expanded to encompass both CSM and essential hypertension, the idea being that these two conditions are intimately related.