Abstract
Forward head posture (FHP) and neck mobility were objectively assessed in 25 patients with chronic tension-type headache (CTTH) and 25 healthy controls. Side-view pictures were taken in a sitting position to measure the craniovertebral angle. A cervical goniometer was employed to measure the range of all cervical motions. Patients with CTTH showed a smaller cranio-vertebral angle (45.3° ± 7.6°) than controls (54.1° ± 6.3°), thus presenting a greater FHP (P < 0.001). Patients also had lesser neck mobility for all cervical movements, except for right lateral flexion (P < 0.01). There was a positive correlation between the craniovertebral angle and neck mobility. Within the CTTH group, a negative correlation was found between the cranio-vertebral angle and headache frequency, but neck mobility did not correlate with headache parameters. Further research is needed to define a potential role of FHP and restricted neck mobility in the origin or maintenance of TTH.
Introduction
Tension-type headache (TTH) is the most frequent headache disorder seen in adults. Population-based studies indicate 1-year prevalence rates of 38.3% for episodic TTH, and 2.2% for chronic TTH (1). In spite of the social impact of TTH, the pathogenesis has not been completely clarified.
Cervical musculoskeletal abnormalities have been traditionally linked to different headaches (2, 3). One frequently noted abnormal posture is an excessive forward head position, or forward head posture (FHP) (4, 5). FHP is usually associated with shortening of the posterior cervical extensor muscles and with tightening of the anterior cervical muscles. FHP has been related to neck pain (6), temporomandibular disorders (7), cervicogenic headache (CeH) (8), and postconcussional headache (9). Marcus et al. (10) reported that patients with TTH showed a greater number of postural abnormalities than healthy control subjects. FHP was included among the posture abnormalities; however, differences in FHP between both study groups were not specified.
On the other hand, some authors have claimed that neck mobility might be limited in CeH, TTH and migraine patients (11). Limited neck mobility has been considered a major feature of CeH (12), but it is not included among the clinical signs that lead to the diagnosis of TTH or migraine (13). Scientific data referring to neck mobility in TTH are scarce, even though we usually perceive in our clinical practice that TTH patients show restricted neck mobility. The only study assessing neck mobility in TTH did not find any significant difference among migraine patients, TTH patients and healthy control subjects (14). Still, further studies of neck mobility in subjects with TTH are required.
To our knowledge, there has not been any paper in the peer-reviewed literature focusing on possible connections among FHP, neck mobility and headache parameters in patients suffering from TTH. This paper describes some differences in the presence of both FHP and neck mobility between patients with chronic TTH and healthy control subjects. In addition, we assessed the relationship among FHP, neck mobility and several clinical variables concerning the intensity and the temporal profile of headache.
Materials and methods
Subjects
Twenty-five patients suffering from chronic tension-type headache (CTTH) and 25 healthy age- and sex-matched subjects without headache during the previous year participated in this study from April 2004 to February 2005. Patients with CTTH were diagnosed by an experienced neurologist according to the criteria of the International Headache Society (IHS) (13). CTTH patients had to have headache on at least 15 days per month. A headache diary was kept for 4 weeks in order to confirm the diagnosis (15). Medication-overuse headache as defined by the IHS (13) was ruled out in all cases. All patients were examined on days in which headache intensity was less than 4 points on a 10-cm horizontal visual analogue scale. The health status of all participants was clinically stable, without current symptoms of any other concomitant chronic disease.
This study was supervised by the Departments of Physical Therapy and Neurology of Rey Juan Carlos University and Fundación Hospital Alcorcón, Spain, and it was also approved by the local ethics committee. All subjects signed an informed consent prior to their inclusion.
Forward head posture assessment
A picture of the lateral view of each subject was taken to assess FHP objectively (8, 16). The base of the camera was set at the height of the subject's shoulder. The tragus of the ear was clearly marked and a plastic pointer was taped to the skin overlying the spinous process of the seventh cervical vertebra (C7). The examiner located the C7 spinous process by the following procedure. First, he palpated the most prominent spinous process (C6 or C7) at the base of the cervical spine. After it was identified, he passively flexed and extended the lower cervical spine to verify which one moved first: C6 vertebra should be more mobile, whereas C7 should demonstrate less motion. Once the picture was obtained, it was used to measure the cranio-vertebral angle (8, 16): the angle between the horizontal line passing through C7 and a line extending from the tragus of the ear to C7 (Fig. 1). A smaller cranio-vertebral angle indicated a greater FHP. Raine and Twomey (16) have reported the reliability of this procedure as high [intraclass correlation coefficient (ICC) = 0.88].
Measurement of the cranio-vertebral angle. The angle was assessed directly from a side-view picture using a protractor image and a straight edge.
In each examination, FHP was assessed in a relaxed sitting position. For this purpose, all subjects were asked to sit comfortably on a high-backed chair with both feet flat on the floor, hips and knees positioned at 90° angles, and buttocks positioned against the back of the chair. They were requested to rest their hands on their laps, and to keep their shoulders against the back of the chair. They were also instructed to focus visually on a point directly ahead on the wall of the room. The visual focal point was confirmed by the examiner after the subject had assumed his/her comfortable sitting position. This minimized the tendency towards flexion or extension of the neck while maintaining a relaxed head position. Finally, a picture of the lateral view of each subject was taken.
Neck mobility assessment
A cervical goniometric device manufactured by Performance Attainment Associates (St Paul, MN, USA) was employed for neck mobility assessment (Fig. 2). The cervical goniometer has already obtained an intratester reliability ranging from 0.7 to 0.9, and an intertester reliability ranging from 0.8 to 0.87 (17, 18). Moreover, goniometric measurements have proved to be highly correlated with radiographic measurements of cervical flexion and extension motions (r = 0.97; P < 0.001) (19).
Cervical goniometer used in neck mobility assessment.
Neck mobility was also assessed in a relaxed sitting position. It was recorded as the total range of motion for different types of movement, i.e. flexion/extension, lateral flexion, and rotation; as well as for half-cycles, namely movements in a single direction, i.e. flexion or extension, and right or left. For this purpose, all subjects were asked again to sit comfortably on the chair with both feet flat on the floor, hips and knees positioned at 90° angles, and buttocks positioned against the back of the chair. Then, the goniometer was placed at the top of their head. Once the goniometer was set in neutral position, they were asked to move the head as far as possible in a standard form: forwards (flexion), backwards (extension), right lateral flexion, left lateral flexion, right rotation, and left rotation. Two measurements were recorded for each type of movement, and the mean was employed in further statistical analysis.
Study protocol
All subjects had two appointments within a 4-week period. In the first visit, assessor 1 gave a headache diary to CTTH patients. Patients had to register on this diary the headache intensity, on a 10-cm horizontal visual analogue scale (VAS; range: 0 = no pain, to 10 = maximum pain) (20), the headache duration (in hours per day), and the days with headache. This headache diary was kept for 4 weeks. Assessor 1 also informed healthy control subjects about physical therapy and headache, but did not give them a headache diary. A second assessor, blinded to the subjects’ condition, took both FHP and neck mobility measurements. Assessor 2 stayed in an adjacent room while the headache diary was given to CTTH patients or while control subjects were informed; so blinding of this assessor was successful.
Four weeks later, assessor 2 repeated the same head posture and neck mobility assessment. Finally, CTTH patients gave their headache diary to assessor 1, who calculated the following variables: (i) headache intensity, which was calculated from the mean of the VAS of the days with headache; (ii) headache frequency, which was calculated dividing the number of days with headache by 4 weeks (days per week); and (iii) headache duration, which was calculated dividing the sum of the total hours of headache by the number of days with headache (hours per day).
Since no significant differences were found between the two measurements in either neck mobility or FHP (paired Student's t-test), data for further analysis were derived from the average of both separate values corresponding to each appointment.
Statistical analysis
Data were analysed with the SPSS statistical package (version 12.0). A normal distribution of quantitative data was assessed by means of the Kolmogorov–Smirnov test (P > 0.05). Those data without a normal distribution (i.e. headache intensity, duration and frequency) were analysed with non-parametric tests, whereas data with a normal distribution (i.e. cranio-vertebral angle, neck mobility, and age) were analysed with parametric tests. Differences in FHP and neck mobility between both study groups were assessed with the unpaired Student's t-test. Student's t-test was also used to assess possible gender differences in both neck mobility and FHP. The Spearman's ρ (rs) test was used to analyse the association between the cranio-vertebral angle (FHP) or neck mobility and the clinical variables relating to headache (headache intensity, frequency and/or duration) in CTTH patients. The Pearson′ correlation test (r) was used to analyse the association between the cranio-vertebral angle (FHP) and neck mobility for each cervical motion. Finally, the Pearson's correlation test (r) was also used to assess the association between age and both the cervical range of motion and FHP within each study group. In general, a P-value < 0.05 was considered statistically significant; however, when two related comparisons were performed (i.e. cervical flexion and extension, right and left lateral flexions, and right and left rotations) a corrected P-value of <0.025 was taken (Bonferroni correction).
Results
A total of 25 CTTH patients, 11 men and 14 women, 20–70 years old (mean age 42 ± 18 years) were studied. Headache history ranged from 1 to 36 years (mean duration 9.3 ± 11.7 years). All patients were examined on days in which headache intensity was <4 on the VAS (mean 2.8 ± 0.6). Control subjects were 25 healthy volunteers, 12 men and 13 women, aged 22–70 (mean age 40 ± 12 years).
Within the control group, there was a negative correlation between age and cervical flexion (r =−0.5; P = 0.03), extension (r =−0.7; P < 0.001), and both lateral flexions (r =−0.7; P < 0.001 on the left, and r =−0.7; P < 0.001 on the right); age did not seem to influence the range of cervical rotation. Conversely, neck mobility was not correlated with age in CTTH patients. FHP was not correlated with age in any study group. There were no significant differences in either neck mobility or FHP between males and females in either group.
Patients with CTTH showed a smaller cranio-vertebral angle (mean angle 45.3° ± 7.6°) than healthy control subjects (mean angle 54.1° ± 6.3°). Thus, FHP was greater in CTTH patients than in controls (P < 0.001). CTTH patients also showed lesser neck mobility than healthy controls in the total range of motion as well as in half-cycles (except for right lateral flexion). Table 1 shows neck mobility measurements in each study group.
Range of motion for all cervical movements of each study group
Values are expressed as mean ± standard deviation.
P-values derived from the unpaired Student's t-test (P < 0.025 was considered statistically significant).
NS, Non-significant; CTTH, chronic tension-type headache.
A positive correlation was found between the cranio-vertebral angle and neck mobility in all cervical motions: flexion (r = 0.4; P < 0.01), extension (r = 0.5; P < 0.001), left lateral flexion (r = 0.4; P < 0.05), right lateral flexion (r = 0.5; P < 0.001), left rotation (r = 0.5; P < 0.001) and right rotation (r = 0.4; P < 0.01): the smaller the cranio-vertebral angle, i.e. the greater the FHP, the lesser the neck mobility These correlations did not differ between both study groups. Otherwise, within the CTTH group a negative correlation was found between the cranio-vertebral angle and headache frequency (r s =−0.5; P < 0.04): the smaller the cranio-vertebral angle, the greater the frequency of headache. Finally, a negative correlation was also found between right cervical rotation and both headache duration (r s =−0.5; P < 0.05) and headache frequency (r s =−0.4; P < 0.05) in CTTH patients. The range of motion for other cervical movements was not correlated with headache parameters.
Discussion
This controlled study demonstrated that patients with CTTH had a greater FHP, i.e. a smaller cranio-vertebral angle, than control subjects. FHP has been previously related to other headache disorders. For instance, Watson and Trott (8) found that patients suffering from CeH showed a lesser cranio-vertebral angle than controls (44.5° ± 5.5° vs. 49.1° ± 2.9°; P < 0.001). Besides, Treleaven et al. (9) found a lesser cranio-vertebral angle, but not significant, in postconcussional headache patients (46.7° ± 2.8°) than in control subjects (50.7° ± 7.9°). For the first time, we have provided evidence that CTTH patients also show a lesser cranio-vertebral angle than normal controls. The cranio-vertebral angle in our CTTH group (45.3° ± 7.6°) was similar to that found in CeH patients (8) and postconcussional headache patients (9), whereas the mean cranio-vertebral angle in our non-headache group (54.1° ± 6.3°) was slightly higher than that found in healthy subjects in the aforementioned studies. In any case, we can regard our healthy control group as having a normal posture, while our CTTH group presented an altered posture. Furthermore, CTTH patients with a smaller cranio-vertebral angle, i.e. a greater FHP, reported a higher headache frequency than those with a greater cranio-cervical angle. These results suggest that FHP might be relevant in the genesis of CTTH. However, we cannot exclude that FHP might be a consequence, i.e. an antalgic posture trying to reduce pain, rather than a cause of headache. Whether FHP contributes to the origin or the perpetuation of CTTH must be verified by future research.
Neck mobility was also lesser in CTTH patients than in controls. Our results are in disagreement with those reported by Zwart, who did not find any significant difference between TTH subjects and controls (14). However, we have to consider that neck mobility reported by Zwart for TTH patients (127° ± 19.6° in flexion/extension; 91° ± 12.8° in lateral flexion; 168° ± 17.2° in rotation) and for healthy subjects (129° ± 17.9° in flexion/extension; 94° ± 17.9° in lateral flexion; 170° ± 22.1° in rotation) was greater than that in our study (see Table 1). Chen et al. have recently reported that neck mobility depends on the technology or the method of assessment, i.e. goniometer, inclinometer, potentiometer, etc. (21). In their meta-analysis, Chen et al. established the following normative values: flexion/extension 150° to 116°; flexion 69° to 48°; extension 93° to 61°; whole lateral bending 108° to 76°; right or left side-bending 49° to 38°; whole rotation 186° to 136°; and right or left rotation 93° to 70° (21). Based on these results, neck mobility of our non-headache group falls within the normative range, whereas neck mobility of our CTTH patients falls below normative values. Moreover, cervical mobility has been shown to decrease with age (22, 23). The present study confirmed that situation in our control group, but not in our CTTH group. Age cannot explain the decreased neck mobility found in CTTH patients, as both study groups showed the same age distribution. Therefore, we may conclude that our healthy control group had normal neck mobility, and that our CTTH group presented a decrease in neck mobility.
A positive correlation was found between FHP, i.e. the cranio-vertebral angle, and neck mobility in all cervical motions. Therefore, subjects with a greater FHP, i.e. lesser cranio-vertebral angle, showed lesser neck mobility. Our results are in agreement with those reported by Walmsley et al. (24) and by Ordway et al. (25), who also showed that FHP could dramatically affect neck mobility This is expected, as FHP may lead to excessive compression on the facet joints and posterior surfaces of the vertebra bodies, thus affecting the biomechanics of the head and the neck.
Finally, neck mobility did not correlate with any clinical variable concerning the intensity and the temporal profile of headache. Our results are in agreement with those reported by Griegel-Morris et al., who did not find an association between the severity of postural abnormalities and the severity and frequency of pain in patients presenting with neck pain (4) Restricted neck mobility is most likely to be a consequence of the abnormal head posture, the pain, or both, rather than a causative factor for headache. Regardless, further studies are required to define clearly the connections among neck mobility, FHP and TTH.
This is the first study in the literature analysing the relationship among FHP, neck mobility and clinical features in headache. However, it has some limitations. First, only patients with CTTH were included. Hence, our results cannot be extrapolated to the episodic form of TTH or to other headache disorders. It would certainly be interesting to repeat the same procedure with patients suffering from other conditions. The second limitation was the sample size. To establish definitely a link between the abnormalities of head posture or neck mobility and TTH, our findings must be confirmed in a large number of subjects. Moreover, determination of the clinical significance of neck abnormalities in TTH awaits future investigation. The assessment of some physical therapy programmes might eventually help elucidate the influence of neck posture and motion in the clinical course of TTH.
In conclusion, CTTH patients showed greater FHP and lesser neck mobility than healthy controls. Neck mobility was correlated with FHP: the greater the FHP, the lesser the cervical range of motion. In CTTH patients, there was a positive correlation between FHP and headache frequency. Finally, neck mobility was not correlated with headache parameters. Further research is needed to define clearly the potential role of both FHP and restricted neck mobility in the genesis or maintenance of TTH.