An investigation of the contribution of cervical factors to headache

This thesis reports on the contribution of cervical factors to headache, which occurred in the absence of a history of trauma to the neck. Individuals who had never sustained an injury to the neck were randomly selected from the electoral rolls of two southern Tasmanian municipalities for this crosssectional observational study. Five hundred and twenty-three individuals were invited to participate, and following exclusions and refusals, 490 subjects were examined. Twenty subjects participated in a pilot study of the device designed to measure cervical posture, 427 subjects participated in the main study, which examined the association between headache and habitual cervical resting posture in sitting, and 43 subjects supplied data on which the predictive model was tested. New measures needed to be developed because no appropriate measures were available in a clinical setting. A diagnostic tool for headache was constructed from colloquial descriptions of three of the seven pain patterns attributed by Jull (1981) to headache of cervical origin. Non-diseased status was conferred upon those subjects who failed to identify all elements of the diagnostic tool. Headache frequency was measured retrospectively using a seven level nominal scale. Headache frequency in the study sample ranged from one headache every couple of months to daily. Cervical resting posture in sitting was measured by the Linear Excursion Measurement Device (LEMD), as the excursion of the superior-most tip of the helix of the ear (an anatomical point chosen to represent the distal aspect of the cervical spine) and the spinous process of C7 (a point chosen to represent the proximal aspect of the cervical spine), when subjects moved from a standard corrected posture to their habitual resting posture. All 427 subjects participating in the main study were asked to recall the frequency of their headaches in the preceding month. A subset of these subjects (93 subjects) also supplied prospective headache data by completing a headache diary for a month. A comparison of retrospective and prospective data indicated that, over a two month period, the headache characteristic was stable and consistent. Compared with the prospective headache diary, men tended to over-report headache retrospectively while women tended to under-report it. Headache was expressed in frequencies of occasional and frequent: occasional headache occurred less frequently than twice per month, and frequent headache occurred at least twice a month. The prevalence in the sample data, of headache specifically associated with cervical factors, was 63.7 per cent. Occasional headache was suffered by 55.5 per cent of headache sufferers and frequent headaches were suffered by the remaining 44.5 per cent of headache sufferers. Significantly more women reported headache than men. The excursion of the two chosen anatomical points was reproducible over days, and over a month. Angles of excursion of 11.5 degrees or more, traced by the spinous process of C7, were associated with frequent headache. The crude odds ratios (C.O.R.) were similar for men and women (2.29 (95%CL 1.03-5.01) and 2.43 (95%CL 1.00-5.81) respectively). Angles of excursion of 6 degrees or more, traced by the superior-most tip of the helix of the ear, were associated with frequent headache for men but not for women (C.O.R. of 1.73 (95%CL 0.86-3.49) and 1.06 (95%CL 0.52-2.14) respectively). There was no convincing association between occasional headache and large angles of excursion at the spinous process of C7 and the superior-most tip of the helix of the ear, for either men or women. The cervical resting posture described by large angles of excursion of the superior-most tip of the helix of the ear, and of the spinous process of C7 was characterised by a forward leading chin with the occiput of the skull caudally rotated within, or slightly anterior to, the vertical axis. The cervical lordosis was habitually extended in this resting head position. In order to inform future studies on headache, and to control for confounding effects on the association between frequent headache and cervical excursion angles, a number of other causes of headache were proposed and measured. There was little biological theory to guide these investigations. Two scenarios were proposed to more clearly define the nature of the relationship of headache with its causes. One scenario was proposed where causes of headache were associated in an antecedent fashion with cervical resting posture during postural development, and during moment-by-moment postural manoeuvres. The second scenario described the independent action of selected variables with headache, acting on established posture. There were gender differences in estimates of the strength of association, between headache, cervical resting posture and the other proposed causes of headache. The cross-sectional nature of the data precluded more specific examination of these relationships. Under the scenario of independence of action with headache, wearing dentures confounded the association between C7 excursion angles and frequent headache for men but not for women. A predictive model for frequent headache was developed. It included only the dummy predictor for C7 excursion angles, as no other variable was identified as an important inclusion. This model predicted frequent headache with moderate sensitivity and fair specificity, but predicted less well in an independent data set.