28. cephalalgia 2010_ p1514

Original Article

Differences in cervical musculoskeletalimpairment between episodic andchronic tension-type headache

J-H Sohn, H-C Choi, S-M Lee and A-Y Jun

Abstract

Background: Tension-type headache (TTH) is a headache in which musculoskeletal impairments of the craniocervical

region may play an important role in its pathogenesis. We investigated the presence of myofascial, postural and mechan-

ical abnormalities in patients with frequent episodic and chronic tension-type headache (ETTH and CTTH, respectively).

Methods: The study population consisted of 36 patients with ETTH, 23 with CTTH and 42 control subjects. Myofascial

trigger points (MTrPs) were identified in the upper trapezius, sternocleidomastoid, temporalis and suboccipital muscles.

Sagittal C7-tragus angle was measured to evaluate flexor head posture (FHP), and neck mobility was assessed using an

inclinometer.

Results: Only active MTrPs were significantly different between the ETTH and CTTH groups (p< .001). Patients withCTTH showed a larger sagittal C7-tragus angle (p .011), that is, greater FHP and restricted neck mobility for bothrotations compared to controls (p< .001). Although active MTrPs were correlated with the frequency and duration ofheadache, no correlations were observed for FHP or neck mobility.

Conclusion: Active MTrPs in the craniocervical region contribute to triggering or maintenance of TTH and posture or

neck mobility may be a result of chronic headache.

Keywords

Episodic tension-type headache, chronic tension-type headache, myofascial trigger point, flexor head posture, neck

mobility

Date received: 19 January 2010; revised: 12 April 2010; accepted: 18 April 2010

Introduction

Tension-type headache (TTH) is the most costly andcommon form of headache. The second edition of theInternational Headache Classication of HeadacheDisorders further subdivides TTH into episodic(ETTH) and chronic TTH (CTTH), mainly on thebasis of headache frequency. CTTH diers from theepisodic forms not only in frequency but also withrespect to pathophysiology, level of disability (greater),lack of response to most treatment strategies, rate ofmedication overuse (greater), and personal and socio-economic costs (higher) (1).

The specic cause and pathophysiology of TTH areunknown, but they are most likely multifactorial (28),and vary depending on the form and individual.Whether the pain in TTH originates from myofascialtissues or from central mechanisms in the brain is still amatter of debate. The current consensus is that periph-eral pain mechanisms probably play a role in ETTH,

whereas central dysnociception is predominant inCTTH (9). In most patients, TTH develops from theepisodic form to the chronic form (10). Prolongedperipheral nociceptive stimuli from pericranial myofas-cial tissues seem to be responsible for the conversion ofepisodic to chronic TTH (11,12). Therefore, identifyingthe source of peripheral nociception in patients withheadaches may provide an insight into the interactionbetween peripheral and central changes in TTH.

Peripheral factors have traditionally been consideredto be of major importance in TTH, and many studies

Hallym University College of Medicine, Republic of Korea.

Corresponding author:

A-Y Jun, Department of Rehabilitation Medicine, Chuncheon Sacred

Heart Hospital, Hallym University College of Medicine,153 Gyo-dong,

Chuncheon-si, Gangwon-do, 200-704, Republic of Korea

Email: [email protected]

Cephalalgia

30(12) 15141523

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DOI: 10.1177/0333102410375724

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have indicated that the most prominent clinical ndingsshow that patients suering from TTH have anincreased tenderness in response to palpation of peri-cranial myofascial tissues (1317). TTH is consideredthe prototype of headaches in which myofascial painplays an important role (13). The role of myofascialfactors in TTH, however, does not negate the impor-tance of other physical factors. Therefore, a betterunderstanding of musculoskeletal abnormalities of thecraniocervical region can provide more informationabout the pathophysiology of TTH and may facilitatethe development of new treatment programs usingphysical therapy.

Musculoskeletal impairment in the craniocervicalregion has traditionally been linked to various typesof headache (18,19). Simons et al. described headacheas the referred pain from myofascial trigger points(MTrPs) in the head and neck muscles (20). Increasedpericranial tenderness has been found in patients withboth ETTH and CTTH (17,21). In addition, migrain-eurs show increased tenderness in pericranial muscles,increased muscle sensitization to palpation, reducedpain threshold and an increased number of triggerpoints (19,2224).

Posture is also known to be related to headache. Themost frequently noted postural abnormality related toheadache is an excessive forward head position or for-ward head posture (FHP). Greater FHP is considered afeature of cervicogenic headache or post-concussionheadache, and it has also been reported in migraine,ETTH and CTTH (2428). These ndings suggest pos-sible impairment of the craniocervical musculoskeletalsystem in individuals with headache, but the cause-and-eect relationship is not yet clear.

The function of the neckshoulder region in head-aches has been a matter of discussion for several dec-ades. Reduced range of motion (ROM) in the neck hasbeen considered a major feature of cervicogenic head-ache and studies have reported restricted neck mobilityin migraine, ETTH and CTTH (24,25,2729).However, another study involving assessment of neckmobility found no signicant dierences betweenpatients with migraine or TTH and control subjects(29).

The present study was designed to investigate thepresence of myofascial, postural and mechanical abnor-malities in patients with ETTH and CTTH, and tocompare these ndings with the features of a head-ache-free control group.

This study was performed to measure several aspectsof pericranial and cervical musculoskeletal function inpatients with ETTH and CTTH, including MTrPs, pos-tural (FHP) and mechanical (cervical active range ofmotion, AROM) abnormalities. In addition, weassessed the relationships among MTrPs, FHP, cervical

AROM and several clinical parameters of headacherelated to the temporal prole and intensity ofheadache.

Methods

Subjects

For the ETTH and CTTH groups, we recruited patientswith TTH who had visited the headache clinic of atertiary care hospital between March and June 2008.The diagnoses of these headaches were made by theboard-certied attending neurologist using theInternational Headache Society criteria (30). Subjectswith ETTH were dened as those with headachesfrom 1 to 15 days per month (frequent ETTH).Subjects with infrequent ETTH were not included inthe ETTH group. As infrequent ETTH has very littleimpact, it is considered a normal phenomenon and nota disease. Patients with CTTH were those who hadheadaches for at least 15 days per month for morethan three successive months. To be included in theheadache group, subjects had to have at least a one-year history of headache and typical symptoms of TTHto distinguish from mixed headaches (i.e. coexistence ofTTH and migraine). Patients who were administeredanalgesics or muscle relaxants within 24 hours priorto the investigation or medication overuse headacheas dened by the International Headache Society wereexcluded (30). Patients with neurological decits orwith a history of trauma or previous neck injury werealso excluded.

The control group consisted of age- and sex-matchedvolunteers recruited from among hospital sta or therelatives or friends of patients. Participants in the con-trol group were free of headache for at least threemonths prior to the study and experienced no morethan occasional mild headache (occurring less thanve times per year), for which they had never soughtmedical treatment. Furthermore, they had no history ofcervical pain or injury for which they had sought treat-ment and no history of chronic pain.

All of the participants were examined physicallyand neurologically by an experienced neurologist.Computed tomography or MRI of the brain were per-formed in all headache patients. We also evaluated cer-vical-spine X-rays of all headache patients to excludeclear symptomatic causes such as fractures, congenitalabnormalities, bone tumors, myelopathy, abnormalitiesof the craniocervical junction or rheumatoid arthritiswith atlantoaxial subluxation (8). These radiologicalexaminations of the brain and cervical spine indicatedno pathological ndings in any subject. They wereasked to complete a questionnaire about their headachesymptoms, including frequency, duration and intensity

Sohn et al. 1515

of headache in the last four weeks. Headache frequency(days/week) was calculated by dividing the number ofdays with headache by four weeks. Headache duration(hours/day) was calculated by dividing the sum of thetotal hours of headache by the number of days withheadache and headache intensity (Visual AnalogueScale [VAS]: 010), which was then calculated fromthe mean of the VAS of the days with headaches.All subjects were examined on days when headacheintensity was less than three points on the VAS.All subjects gave their written informed consent to par-ticipation in the study, and the study was approvedby the local ethics committee.

Myofascial evaluation: Identification of myofascialtrigger points

For myofascial evaluation, the location and number ofMTrPs were determined. The rehabilitation doctor,who had no information about the patients (includingthe results of diagnosis), performed MTrP identica-tion in the bilateral upper trapezius, sternocleidomas-toid, temporalis and suboccipital muscles in headacheand control subjects. We used the methods of Gerwinet al. (31) to identify MTrPs.

The existence of MTrPs was investigated using snap-ping palpation (rst to locate a taut band of muscle,placing the ngertip at right angles, and then movingthe thumb tip back and forth to roll the underlyingbers) to induce a local twitch response and at palpa-tion (placing the padded aspect of the thumb at a rightangle on the muscle bers and applying pressureagainst the underlying tissue or bone) to induce localpain and referred pain. The presence of MTrPs wasdetermined according to the proposed diagnostic crite-ria of MTrPs (20): the presence of a palpable taut band,a tender spot within a taut band, a local twitch responseby snapping palpation of the taut band and referredpain evoked by at palpation of the tender spot thatreproduces pain on the typical headache site. A MTrPwas considered active if the referred pain evoked by itscompression reproduced the same headache in thepatient, whereas MTrPs were considered latent if theevoked referred pain failed to reproduce any familiarheadache symptoms (20,31). The numbers of active andlatent MTrPs on each muscle were calculated.

Posture abnormality evaluation: Measurement offlexor head posture

FHP was used for evaluating posture abnormalities.The physical measures of the cervical FHP were

conducted by an examiner blinded to the headache ornon-headache status of each subject. Photographs wereused to obtain a series of measurements of posturalalignment of the head and shoulders in sagittal planeswith the patient in a comfortable sitting position on astraight-backed chair. A camera was mounted on atripod, the center of the lens was 1 meter from the sub-ject, and the base of the camera was matched with theheight of the subjects shoulder. A plumb line was sus-pended from the ceiling, and horizontal lines weredrawn at the wall to provide vertical and horizontalreferences. Bony landmarks with red squares of 1 cm2

were attached at the left tragus and the C7 spinousprocess, which would be visible in photographs.Subjects were seated in a comfortable posture on abacked chair and the instructions were given to placetheir weight evenly on both buttocks and feet, maintainthe hips and knees at an angle of 90 and place thehands on their laps with their eyes looking forward.They were asked not to sit straight up in the best pos-ture because the purpose of the photograph was tocapture their habitual or usual sitting postures.

Measurements of FHP in the sagittal plane weremade from left-prole photographs of the subjects.The photographs were digitized in one dimension,and skin markers, anatomic landmarks and referencelines on the image were used to calculate the degree ofFHP.

The sagittal C7-tragus angle was determined(Figure 1); a line was drawn between the midpoint ofthe tragus of the left ear and the C7 spinous process,and the angle of this line to the horizontal was calcu-lated in degrees. This measurement was performedusing PiView STAR picture archiving and communica-tion systems (Innitt, Seoul, Korea). This sagittal C7-tragus angle described the position of the head relative

Figure 1. Measurement of the sagittal C7-tragus angle.

1516 Cephalalgia 30(12)

to C7. As the head was positioned further forward, thevalue increased. This procedure was described in a pre-vious study (32), and this method has already been con-rmed to have high reliability, with a high intraclasscorrelation coecient.

Mechanical abnormality evaluation: Measurementof the active range of neck motion

For evaluating mechanical abnormalities, measurementof neck mobility was performed in triplanar cervicalmotion. AROM was measured with a Dualer IQ elec-tronic dual inclinometer system (JTECH Medical, SaltLake City, UT, USA) according to the manufacturersinstructions and the technique recommended in theAmerican Medical Association Guides to theEvaluation of Permanent Impairment for the two-inclinometer method (33).

We recruited healthy control subjects to assess thereliability of the Dualer IQ electronic dual inclinometersystem. In addition, the range of neck motion was mea-sured in the directions of exion (forward), extension(backward), lateral exion (right, left) and axial rota-tion (right, left) of the cervical spine in six ways. Thesemeasurements were performed over two trials in each ofsix movement planes by one of the authors (JHS) and amedical resident of the participating institution. Oneweek later, one of the authors (JHS) measured thecervical mobility of the subjects repeatedly to checkintra-tester reliability. Then we assessed the inter- andintra-tester reliability of the digital inclinometer nd-ings. The results of reliability measurements for sub-jects showed high intra-tester reproducibility in allplanes (intra-tester reliability: forward 0.924, backward0.959, right lateral exion 0.866, left lateral exion0.793, right rotation 0.854, left rotation 0.982; inter-tester reliability: forward 0.843, backward 0.875, rightlateral exion 0.684, left lateral exion 0.712, right rota-tion 0.752, left rotation 0.681). Next, an examinerblinded to the condition of the patients measured theneck mobility of headache and control subjects. Thetest was conducted twice in each way and the averagevalue was recorded.

Statistical analysis

SPSS statistical software (version 12.0; SPSS, Chicago,IL, USA) was used for all analyses. The numbers ofactive and latent MTrPs and mean values of the C7-tragus angle and all cervical AROM were calculated.Dierences in the number of MTrPs and values of thesagittal C7-tragus angle and AROM of cervical mobil-ity between the study groups were assessed with theKruskalWallis analysis of variance (ANOVA) testwith the Mann-Whitney U-test. The chi-square test

was used to compare the presence of latent and activeMTrPs. Pearsons correlation test (r) was also used toanalyze the associations between the number of MTrPsor the sagittal C7-tragus angle or cervical AROM andheadache parameters (headache duration, frequency,intensity) in patients with TTH. Subsequently, the rela-tions of MTrPs, sagittal C7-tragus angle and cervicalAROM with headache parameters were investigated ineach headache group using a multiple linear regressionmodel and using the headache parameters as dependentvariables and using the measured musculoskeletalabnormalities as independent variables. Statistical anal-ysis was conducted at the 95% condence level. Inall analyses, p< .05 was considered statisticallysignicant.

Results

Subject demographics

The numbers of patients in the ETTH, CTTH and con-trol groups were 36, 23 and 42, respectively. The aver-age age of the participants was 51.8 years old. Theproportion of women was higher than that of men.No signicant dierences existed in age or sex amongthe three groups. The demographics of the patients andcontrol subjects are shown in Table 1.

Myofascial trigger points

The results of myofascial evaluations are shown inTable 2. The mean number of MTrPs for ETTH sub-jects was 4.11, of which 0.5 were active MTrPs and 3.57were latent MTrPs. The mean number of MTrPs forCTTH subjects was 6.17, of which 2.43 and 3.74 wereactive and latent MTrPs, respectively. The controlgroup had only 0.57 latent MTrPs. The numbers ofactive MTrPs and latent MTrPs in the ETTH andCTTH groups were signicantly greater than those inthe control group. No dierence was seen in the numberof latent MTrPs between the ETTH and CTTHgroups. However, the number of active MTrPs was sig-nicantly greater in the CTTH than in the ETTH group(p .001).

Table 3 shows the distributions of either latent oractive MTrPs in each study group. The distribution ofactive and latent MTrPs was signicantly dierentbetween the control and ETTH or CTTH group inthe upper trapezius (p< .01), sternocleidomastoid(p< .05) and suboccipital muscles (p< .01), but not inthe temporalis muscle. Dierences in the distribution ofMTrPs between the ETTH and CTTH groups were sig-nicant for active MTrPs in the upper trapezius(p .001) and suboccipital muscles (p .002).

Sohn et al. 1517

Flexor head posture

The results of statistical analyses revealed signicantdierences in the C7-tragus angle between the CTTHand control groups (137.74 7.68 vs. 133.31 5.6,p .011), indicating that patients with CTTH hadsevere FHP compared to headache-free subjects.However, no signicant dierence was observedbetween the ETTH group and the control group(134.99 7.61 vs. 133.31 5.6) (Figure 2). In analyzingthe correlation between MTrPs and FHP, a signicantpositive correlation was observed between the numberof active and latent MTrPs and the degree of the

sagittal C7-tragus angle (active MTrPs, p< .01; latentMTrPs, p< .05), indicating that FHP became moreserious as the number of MTrPs increased, especiallyactive MTrPs.

Cervical range of motion

Table 4 shows the results of neck mobility measure-ments as the means and standard deviation of cervicalAROM for the headache and non-headache controlgroup. A comparison between these subgroups indi-cated statistically signicant dierences only in rotation

Table 3. Distribution of subjects with myofascial trigger points in each study group

No. of subjects with active or latent MTrPs in each muscle (% in each study group)

Upper trapezius Sternocleidomastoid Suboccipital Temporalis

Group Active Latent Active Latent Active Latent Active Latent

ETTH 6 (16.7%)** 34 (94.5%) 4 (11.1%) 14 (38.9%) 0* 11 (30.6%) 0 3 (8.3%)

CTTH 14 (60.9%)** 19 (82.6%) 5 (21.7%) 13 (56.5%) 6 (26.1%)* 0 (26.1%) 2 (8.7%) 3 (13.0%)

Control 0 13 (31%) 0 3 (7.1%) 0 0 0 0

MTrp myofascial trigger point. ETTH episodic tension-type headache. CTTH chronic tension-type headache. p values were determined usingthe chi-square test.

*, ** Differences in the distribution of MTrPs between ETTH and CTTH groups. (*p .002.; **p .001).

Table 1. Demographic data and headache features

ETTH CTTH Control

N 36 N 23 N 42 p valueAge (years)* 51.11 14.42 53.43 16.97 51.69 16.18 NSSex (M:F) 7:29 2:21 8:34 NS

Frequency (days/week) 1.40 5.02

Duration (hours/day) 3.14 8.52

Intensity (VAS: 010) 5.64 5.96

NS not significant. VASVisual Analogue Scale. ETTH episodic tension-type headache. CTTH chronic tension-type headache.*Values are expressed as means standard deviation.

Table 2. Myofascial trigger point measurements of each study group

Group Significance of difference of intergroups

ETTH CTTH Control p value

ETTH

vs. control

CTTH

vs. control

ETTH

vs. CTTH

No. of active MTrP (SD) 0.50 (1.08) 2.43 (2.53) 0.00 (0.00) .000 0.003 0.000 0.001No. of latent MTrP (SD) 3.57 (2.00) 3.74 (2.49) 0.57 (0.88) .000 0.000 0.000 NSNo. of total MTrP (SD) 4.11 (2.09) 6.17 (3.21) 0.57 (0.88) .000 0.000 0.000 0.012SD standard deviation. MTrP myofascial trigger point. ETTH episodic tension-type headache. CTTH chronic tension-type headache.NS not significant.


of the cervical AROM between the CTTH and controlgroups.

Correlation between headache parameters andmusculoskeletal abnormalities

We examined the correlation between headacheparameters (frequency, duration, intensity) and

musculoskeletal abnormalities. While the number ofactive MTrPs was positively correlated with the fre-quency and duration of headache in the ETTH andCTTH groups (both p< .05), the number of latentMTrPs, FHP and neck mobility were not correlatedwith the headache parameters (Table 5). In addition,the results of multiple linear regression analysis, usingheadache parameters as dependent variables and themeasured musculoskeletal abnormalities (MTrPs,FHP, cervical AROM) as independent variables, wereadded. In the CTTH group, active MTrPs were signif-icantly related to frequency (regression coe-cient 0.551, p .002) and duration of headache(regression coecient 0.597, p .013). No clear cor-relation was detected between headache parameters andmusculoskeletal abnormalities in the ETTH group.

Discussion

The results of the present study indicated that the num-bers of active and latent MTrPs in the ETTH andCTTH groups were signicantly higher compared tothe control group. In the CTTH group, the numberof active MTrPs was signicantly greater than in theETTH group. In addition, patients with CTTH showedsevere FHP and restricted neck mobility compared tothe control group. Although the number of active

Table 4. Range of motion for cervical mobility of each study group

Group Significance of intergroup differences

Direction

ETTH

(degrees)

CTTH

(degrees)

Control

(degrees) p value

ETTH

vs. Control

CTTH

vs. Control

ETTH

vs. CTTH

Forward 45.88 11.2 46.17 14.2 48.45 9.9 NS NS NS NSBackward 48.44 11.2 47.31 10.5 50.15 17.2 NS NS NS NSLateral flexion (R) 41.31 13.1 37.58 8.3 38.75 8.0 NS NS NS NSLateral flexion (L) 41.32 10.6 40.06 7.7 41.23 9.9 NS NS NS NSRotation (R) 65.98 10.7 56.76 11.8 68.61 9.8 0.001 NS 0.000 0.013Rotation (L) 69.35 12.3 60.82 13.2 72.33 9.8 0.002 NS 0.000 0.03ETTH episodic tension-type headache. CTTH chronic tension-type headache. NS not significant. R right. L left.

Table 5. Correlation coefficients of headache characteristics from headache questionnaires and measured active MTrP numbers

Correlation coefficient (r) for the active MTrPs number

ETTH group CTTH group Total TTH group

Frequency of headache attacks (days) 0.369* 0.435* 0.662**

Duration of headache attacks (hours) 0.420* 0.445* 0.618**

Pain intensity of headache attacks (VAS) NS NS NS

ETTH episodic tension-type headache. CTTH chronic tension-type headache. VAS Visual Analogue Scale. MTrPs myofascial trigger points.NS not significant. *p< 0.05, **p< 0.01.

150

Sagi

ttal C

7-tra

gus

angl

e (de

gree)

140

130

120

0ETTH CTTH Control

Figure 2. Flexor head posture measurements of each study

group. *p .011 ETTH episodic tension-type headache.CTTH chronic tension-type headache.

Sohn et al. 1519

MTrPs was correlated with the frequency and durationof each headache, no correlations were found betweeneither FHP or neck mobility and any of the headacheparameters.

This study diered from earlier studies in that wesimultaneously evaluated cervical musculoskeletaldysfunction in ETTH and CTTH. In addition, weincorporated a control group that was carefully age-and sex-matched with the patients who had ETTHand CTTH.

Gerwin has suggested that the referred pain fromMTrPs and MTrPs themselves are important in thepatients perception of TTH (34). A headache is mostlikely due to referred pain from MTrPs in the head,neck and shoulder muscles, mediated through thespinal cord and the brain stem trigeminal nucleus cau-dalis, rather than direct tenderness of the pericranialmuscles themselves. Our results support the hypothesisthat MTrPs in the head, neck and shoulder musclesplay an important role in the etiology of TTH.Specically, the active MTrPs are estimated to be themost important contributing factors in causing, main-taining or perpetuating TTH.

Previous studies have indicated that active MTrPs inthe upper trapezius, sternocleidomastoid, temporalisand suboccipital muscles were also present in ETTH(27,35), to a similar degree as in CTTH (36).However, the results of the present study were dierentfrom those of previous studies. The number of latentMTrPs was similar in the ETTH and CTTH groups(3.57 vs. 3.74). The dierence between the ETTH andCTTH groups was in the number of active MTrPs,which was signicantly greater in the CTTH group(0.5 vs. 2.43, p .001).

Our results indicated more active and latent MTrPsin all headache groups compared to European studies,even taking into account dierences in study design andmethods. This may have been due to dierences insociocultural background and lifestyle. Furthermore,racial dierences seem to exist regarding the numberof MTrPs, with MTrPs being more prevalent inAsians than in Europeans. Dierences in expression,interpretation of pain and actual symptoms mayaccount for these racial dierences. In addition, astudy has suggested that the likelihood of developingpain-producing active MTrPs increases in middle age(20). Thus, the increased number of MTrPs in the pre-sent study may have been a secondary eect of the oldermean age of the study population.

Patients with TTH have been reported to showgreater numbers of active or latent MTrPs comparedto healthy subjects. However, this study did not inves-tigate the prevalence of TTH in which muscle MTrPswere more frequent (22). Within a cohort of 15 ETTHsuerers, the most prevalent MTrPs were found in

the temporalis (active MTrP, 86%; latent MTrP,60%), followed by the upper trapezius (active MTrP,46%; latent MTrP, 80%) and sternocleidomastoid(active MTrP, 33%; latent MTrP, 60%) muscles.Furthermore, active MTrPs of the suboccipital musclewere found in 6 of 10 patients (60%) with ETTH(27,35). In addition, another study with a cohort of25 CTTH suerers showed similar MTrP prevalencerates in the temporalis (active MTrPs, 68%; latentMTrPs, 72%) and upper trapezius (active MTrPs,60%; latent MTrPs, 72%), followed by the sternoclei-domastoid (active MTrPs, 44%; latent MTrPs, 68%)muscles. Moreover, active MTrPs of the suboccipitalmuscle were seen in 13 of 20 patients (65%) withCTTH (36,37).

These ndings correspond to the results of the pre-sent study, in which signicant dierences were foundin the distributions of both active and latent MTrPs formost muscles analyzed in patients with ETTH andCTTH compared to controls. However, our resultspartly contradict those of a previous study withregard to dierent aected muscle distribution ofMTrPs. However, these results were based on a rela-tively small sample size; large controlled clinical studiesare required. Our results indicated that active MTrPsare not only signicantly prevalent on the upper trape-zius and suboccipital muscles based on analysis of eachmuscle distribution, but are also greater in number inCTTH than in ETTH. Therefore, these results may sup-port the importance of active MTrPs in CTTH.

In addition, TTH subjects with active MTrPs in theupper trapezius, sternocleidomastoid, temporalis andsuboccipital muscles showed greater headache fre-quency and longer headache duration, but not head-ache intensity, compared to those with latent MTrPsin the same muscles. Active MTrPs were reported toshow greater headache duration and intensity thanlatent MTrPs in patients with CTTH (36). However,within the ETTH group, none of the headache clinicalparameters were related to the activity of MTrPs, thatis, active or latent (35). Nevertheless, our resultsshowed that the number of active MTrPs was signi-cantly and positively correlated with the headacheparameters in both ETTH and CTTH groups. Theseresults were similar to those reported previously forCTTH groups but dierent for ETTH. In addition, inmultiple regression analysis, only active MTrPs weresignicantly related to the frequency and duration ofheadaches in the CTTH group. These results thereforeindicated that active MTrPs were the most importantfactor in triggering and sustaining headaches.

Within our ndings, the intensity of headache wasnot correlated with the musculoskeletal abnormalitiesin the TTH groups. We used a headache questionnairepertaining to the previous four weeks that was


completed on the day of examination instead of a head-ache diary. We may have collected more sucient andprecise information about the required content of head-aches if we had used a headache diary instead of aheadache questionnaire.

Patients with CTTH showed greater FHP in the sit-ting position than headache-free subjects. However, nosignicant dierence in FHP was observed between theETTH and control groups. Our data showed that boththe TTH and control groups had a larger sagittal C7-tragus angle, suggesting more severe FHP compared toprevious studies (24,27,28,32,37). Several reasons existfor this result. The rst is age: previous investigationsdemonstrated that the relationship between the sagittalC7-tragus angle and age was statistically signicant(r 0.44), indicating that older subjects had a moreforward head posture, although the correlation wasnot strong (32). In contrast, the mean age of the par-ticipants in the present study was 10 years older thanthat of patients in previous studies and had greaterFHP. The second reason involves environmental fac-tors: lifestyle and sociocultural background may berelated to posture. The third relates to more prevalentMTrPs in the present study compared to the previousstudies. Any habitual posture that gives rise to pro-longed contraction of muscle bers may cause motor-endplate dysfunction and the development of MTrPs(38). In addition, postural abnormalities in the cervicalspine may be a powerful activator and perpetuator ofMTrPs (20). Conversely, the shortening of a muscle dueto long-term MTrP activity may cause posture abnor-malities and perpetuate MTrP activity. Therefore, ourresults showed that CTTH subjects with more MTrPshad a tendency to have greater FHP than ETTH andcontrol subjects.

In the measurement of neck mobility, six directionsof cervical motion showed a smaller angle in our studycompared to previous reports (3942). Measurement ofa normative cervical ROM lacks a scientic consensusdue to the use of a wide array of techniques and a lackof standardized procedures for its evaluation. Cervicalspine mobility has been shown to decrease with agebecause of degenerative changes. However, correlationanalyses showed a weak and inconsistent association.Therefore, age is not strongly associated with limitedmobility. Zwart found no dierences in neck mobilitybetween patients with TTH and controls. However, theepisodic and chronic patterns of headache were not dis-tinguished in this study (29), whereas the Fernandez-de-las-Penas et al. indicated that a group of patients withCTTH showed less neck mobility than healthy controls(43). Our results were in agreement with the previousdata. Compared to controls, individuals with CTTHhad a lower ROM in all six directions of cervicalmotion and signicant reductions in two directions

(right and left rotation). However, individuals withETTH and control subjects showed no dierences inROM in all six directions. Previous reports suggestedthat a reduction in neck mobility was likely a conse-quence of the protective posture against pain. In addi-tion, kinesiophobia of the cervical segment may haveoccurred given that head movements intensied painduring an attack (28,44). Muscles with active MTrPshave a restricted passive (stretch) ROM because ofpain, as reported previously (45). The limitation ofstretch due to pain is not as great with active movementas with passive lengthening of the muscle, at least partlydue to reciprocal inhibition. Therefore, more restrictedneck mobility may have occurred, as MTrPs were moreprevalent in the CTTH group. Head movement canworsen a headache, and this may induce kinesiophobicbehavior of the neck that may be manifested by reducedcervical ROM (46). The long duration of headaches inthe CTTH group may aect cervical mobility due to thedaily or near-daily kinesiophobic behavior. Further-more, in cervical motion, rotation showed largeranges of neck motion compared to lateral exion, for-ward exion or extension. Therefore, the limitation ofcervical motion may be accentuated to a greater extentin both rotation directions in patients with CTTH.However, restricted neck mobility did not aect thepatients with ETTH due to the intermittent nature ofthe condition. Furthermore, previous studies showedthat FHP could aect cervical mobility. FHP maylead to excessive compression of the facet joints andposterior surfaces of the vertebral bodies, thus aectingthe biomechanics of the head and the neck (47,48).

In conclusion, the active MTrPs may be the contrib-uting factor in causing and maintaining TTH.Although the FHP is suggested to activate MTrPsbecause it is related to the shortening of the head andneck muscles, the FHP may be the result of CTTH. Thedierences in neck mobility are also caused by abnor-mal head posture or chronic pain.

We showed that active MTrPs in the pericranial andneckshoulder area were present in both ETTH andCTTH groups, and more active MTrPs were found inpatients with CTTH. In addition, active MTrPs wererelated to headache clinical parameters. The results sug-gested that temporal and/or spatial summation ofperipheral stimuli may have a role in people predis-posed to the pathophysiological mechanisms ofETTH. The increased nociceptive input to a suprasp-inal structure may result in supraspinal sensitization.The central neuroplastic changes may aect the regula-tion of peripheral mechanism and lead, for example, toincrements in pericranial muscle activity or release ofneurotransmitters in the myofascial tissues. Our studysuggested that more active MTrPs in the CTTH groupwere the consequence of central sensitization.

Sohn et al. 1521

This study had some limitations. The sample sizewas small, and only TTH was included. In addition,patients with cervicogenic headaches may have beenincluded in the TTH group because of ambiguous diag-nostic criteria. Some diculties remain in dierentialdiagnosis, as considerable symptomatic overlap existsbetween cervicogenic headache and TTH. Therefore,evaluating changes in the headache clinical parameters,such as intensity after performing joint or nerve block,may be meaningful considering the possibility that cer-vicogenic headache may have been included in thegroup diagnosed with TTH.

Taken together, the results suggest that musculoskel-etal abnormalities in the craniocervical region can beone of the causes of TTH, and abnormalities in bothposture and neck mobility may be the result of chronicheadache. Specically, active MTrPs in the pericranialneckshoulder muscles play important roles in trigger-ing or maintaining TTH. Therefore, inactivation ofMTrPs in CTTH suerers would be expected toreduce headache symptoms, and trigger point-specicphysical therapy would be an eective treatment inpatients with TTH. In addition, clinicians should beaware of the relationship between chronic headacheconditions and poor craniocervical posture. Posturalcorrection and re-education of cervical posture shouldbe integral parts of both prevention and managementof patients with CTTH. Therefore, treatment methodstailored to the individual patient should be developed,focusing on myofascial and postural abnormality in thechronic headache treatment protocol.

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