Physical Therapy in Tension-Type Headache: A Systematic Review of Randomized Controlled Trials

(1) Objective: The aim of this study is to synthesize the effects of physical therapy on pain, frequency, or duration management in the short, medium, and long term in adult patients diagnosed with Tension-type headache (TTH). (2) Background: Tension-type headache (TTH) is the most common headache with migraine and its pathophysiology and treatment has been discussed for years without reaching a consensus. (3) Methods: A systematic review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The review was registered in PROSPERO (CRD42020175020). The systematic search for clinical trials was performed in the databases PubMed, CINAHL, Cochrane Central Register of Controlled Trials, PEDro, Scopus, SciELO and Dialnet. Articles were selected according to the inclusion and exclusion criteria, regarding the effectiveness of physical therapy interventions on adult patients with TTH published in the last 11 years with a score ≥ 6 in the PEDro Scale (Physiotherapy Evidence Database). (4) Results: In total, 120 articles were identified, of which 15 randomized controlled trials were finally included in order to determine the inclusion criteria. Changes in pain intensity, headache frequency or headache duration of individual studies were described (5) Conclusions: This systematic review shows that there is no standardized physical therapy protocol for the approach to tension headache, although all the techniques studied to date address in one way or another the cranio-cervical-mandibular region. The approach to the cranio-cervical-mandibular region reports significant effects in terms of decreasing the intensity of pain and frequency of headache episodes in the short and medium term. More long-term longitudinal studies are needed.


Introduction
The most frequent type of headache, tension-type headache (TTH), is addressed frequently but there is no agreement on its pathogenesis, making adequate care difficult for medical professionals [1]. According to the Global Burden of Disease (GBD, 2019), headaches are among the most prevalent conditions worldwide, with tension-type headaches (TTH) estimated worldwide at an average of 26.0% (22.7-29.5%), with 23.4% in men and 27.1% in women [2]. Geographically, the prevalence of TTH ranged from 11.1% (Southeast and East Asia and Oceania) to 33.1% in South Asia. However, when adjusting the population residing geographically in the different regions, it is found that the prevalence of TTH was 21.1% [2]. of greater intensity, frequency and duration as well as with a greater hypersensitivity to pressure on them [10].
At the European level, tension headache is a very high economic cost. This is due to the consumption of drugs, the performance of diagnostic tests and visits to the Emergency Room. To all the above, the high indirect cost represented by the days of sick leave and the decrease in performance at work [3].
Among the therapeutic approaches for TTH is Physiotherapy [6], since it can help reduce the intensity and frequency of headaches, improving mobility and functionality, which will result in an improvement in the quality of life of these patients.
Non-pharmacological treatments may include counseling (postural and ergonomic education), biofeedback, manipulative therapy, muscle relaxation training, massage, therapeutic exercise and acupuncture, as part of the physiotherapy care process to help reduce TTH symptoms. In order to achieve a positive effect with these techniques, once the origin of the problem has been correctly diagnosed, an adequate and personalized muscular, postural and biomechanical evaluation must be initiated, which will allow the choice of the most appropriate therapeutic procedure for the patient's condition [4].
The aim of this study is to synthesize the effects of physical therapy on pain, frequency, or duration management in the short, medium, and long term in adult patients diagnosed with tension-type headache.

Eligibility Criteria
The purpose of this study is to find and synthesize the results of the RCTs published in the last 11 years with a score of ≥6 in the PEDro Scale examining the effectiveness of physical techniques on adult patients with Tension-Type Headache (TTH).
Our research question was established following recommendations from the PICO model (Population, Intervention, Comparison and Outcome measures). Patients included were both male and female adult subjects, clinically diagnosed of TTH. Intervention was any type of physical therapy modality compared with another intervention group, control or placebo. Outcome measures were pain intensity, headache frequency and headache duration.

Information Sources and Search Strategy
This systematic review of Randomized Controlled Trials (RCTs) was performed following PRISMA guidelines (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) [12]. An electronic search was conducted in January 2022 on the following databases: PubMed, CINAHL, Cochrane Central Register of Controlled Trials (CENTRAL), PEDro, SCOPUS, SciELO and Dialnet. Strategy search was a combination of the following MeSH-listed key words: ((physical therapy modalities) OR (physical therapy interventions)) AND (Tension-type headache). The restriction of the year of publication was 11 years. RCTs in Spanish and English language were included.

Study Selection
The inclusion criteria were: Articles which were published prior to January 2011.

Data Collection Process
Articles were selected by screening title and abstract, and duplicates were removed. After that, the analysis of selected full text studies was performed. Inclusion and exclusion criteria were then checked by two independent reviewers. When articles for this research were identified, quality assessment (risk of bias) was conducted independently by three investigators. Any disagreement on quality assessment was resolved by consensus.
The data extraction process extracted the following information from each study: first author, publication year, sample size, population main characteristics, treatment methods and duration, comparison group characteristics, measurement tools and follow up period. Main outcomes were pain intensity and headache frequency. The secondary outcome was headache duration.

Risk of Bias in Individual Studies and Summary Measures
The methodological quality of the RCTs was assessed according to the PEDro scale (Physiotherapy Evidence Database) [13]. Although the scale is composed of 10 questions with YES/NO answers, only questions regarding internal validity were used. Accordingly, a clinical trial evaluated with the PEDro scale which presents 6 or more affirmative responses is considered level I (6-8: good and 8-10: excellent) and a clinical trial with a score equal to or less than 5 is considered level II (4-5: fair and <4: poor).
Main outcomes were pain intensity and headache frequency. The secondary outcome was headache duration. Results for primary and secondary outcome measures were thoroughly described. p value > 0.05 was considered statistically significant.

Study Characteristics and Risk of Bias within Studies
Of the 15 RCTs included in the present review, 33% of them obtained a PEDro Scale score of 6/10, 47% a score of 7/10, 13% a score of 8/10 and 7% a score of 9/10. In all of them, outcome measures were obtained for at least one of the study variables (intensity, frequency or duration of headache). These data are grouped in Table 1.

Study Characteristics and Risk of Bias within Studies
Of the 15 RCTs included in the present review, 33% of them obtained a PEDro Scale score of 6/10, 47% a score of 7/10, 13% a score of 8/10 and 7% a score of 9/10. In all of them, outcome measures were obtained for at least one of the study variables (intensity, frequency or duration of headache). These data are grouped in Table 1.
The characteristics of all the studies included in this review are set out in Table 2.

Results of Individual Studies
Castien et al. [83] reported in their study that the techniques of mobilization of the cervical and thoracic spine accompanied by a postural re-education program of the head and neck significantly improved in the medium term, 8 weeks after intervention, the intensity (p = 0.003) and the frequency of chronic tension headache (p < 0.001). The techniques do notoverlaps with the others.
They also improved significantly in the long term, 26 weeks post-intervention, pain intensity (p = 0.027) and frequency of episodes (p < 0.001). The duration of headache episodes was significantly reduced in the medium term, 8 weeks post-intervention (p = 0.013). Ajimsha [84] concluded in his study that both direct myofascial release techniques and indirect myofascial release techniques significantly decrease the frequency of tension headache episodes in the medium term, 3 months post-intervention (p < 0.001).
Da Silva et al. [85] showed that traditional acupuncture and splenium trigger points of the neck, masseter and temporal decreases the intensity of tension headache in pregnant women in the medium term, 3 months post intervention (p = 0.035).
Berggreen et al. [86] demonstrated that the treatment of trigger points of the craniocervical-mandibular musculature significantly decreases the morning intensity of headache in patients with chronic tension headache in the short term, post-intervention period (p = 0.047).
Espí-López et al. [87] concluded that suboccipital inhibition decreases the intensity of tension headache in the short term, after the intervention period (p = 0.04). In addition, the manipulation of the upper cervical vertebrae decreases in the short term, after the intervention period, the intensity (p = 0.004) and the frequency of episodes of tension headache (p = 0.03). Finally, when the intervention combines suboccipital inhibition and manipulation of the upper cervical vertebrae, tension headache (p = 0.01) and the frequency of episodes (p = 0.02) also decrease significantly in the short term, after the intervention period.
Moraska et al. [88] showed that massage therapy and treatment of trigger points significantly decreases the frequency of headache episodes in the short term, 1 month after the intervention, (p = 0.026).
Chassot et al. [89] showed that electroacupuncture significantly decreases the intensity of tension headache in the short term, after the intervention period, (p = 0.005).
Espí-López et al. [90] concluded that manipulation of upper cervical spine combined with head and neck massage therapy decreases the frequency of headache episodes in the medium term, 2 months post-intervention (p < 0.01).
Ferragut-Garcías et al. [91] concluded that craniocervical soft tissue techniques, craniocervical neural mobilization techniques and combined treatment of both decrease the intensity (p < 0.001) and frequency (p < 0.001) of short-term, post-intervention period and 1-month post-intervention tension headache episodes.
Georgoudis et al. [92] concluded that microwave waves combined with myofascial treatment of the cranio-cervical-mandibular region decrease the intensity of tension headache in the short term, post-intervention period (p < 0.05).
Pérez-Llanes et al. [93] concluded that the combined treatment of suboccipital inhibition and interference currents does not significantly reduce the intensity of chronic tension headache in the short term, 1-month post-intervention (p = 0.18) Schiller et al. [94] revealed that patients who received a combined treatment of acupuncture and medical training reduced in the medium term, 3 months after intervention, their mean pain intensity compared to the control group (p = 0.012), as well as the values of maximum intensity (p = 0.014) and minimum (p = 0.03). The frequency of pain (days/month) did not reflect significant differences between the different groups. In all groups, the duration of painful episodes and medication was reduced, showing a response rate of more than 90%. They concluded that tension headaches with pericranial sensitivity responded better to separate medical training, and those without sensitivity to treatment with acupuncture or combined with medical training.
Corum et al. [95] concluded that cervical manipulation significantly decreases the frequency of tension headache in the short, post intervention period (p < 0.05) and in the medium term, 3 months after intervention (p < 0.05) as well as the intensity of tension headache in the short term, post intervention period (p < 0.05) and medium term, 3 months after intervention (p < 0.05). They also concluded in their study that suboccipital inhibition significantly decreases the frequency of tension headache in the short term, post-intervention period, (p < 0.05) and in the medium term, 3 months post-intervention (p < 0.05). Finally, suboccipital inhibition decreases the intensity of tension headache in the short term, after the intervention period (p < 0.05) and in the medium term, 3 months after intervention (p < 0.05).
Gopichandran et al. [96] concluded that progressive relaxation of the jaw and neck muscles combined with deep breathing exercises decrease the intensity of chronic tension headache in the short term, 4 post intervention (p < 0.001) and medium term, 8 weeks and 3 months post intervention (p < 0.001).
Runa et al. [97] concluded that the combined treatment of moxibustion at the temples and the taking of the drug Deanxit decrease the intensity (p < 0.05), frequency (p < 0.05) and duration (p < 0.5) of tension headache in patients with anxiety in the short term, post intervention period. The summary of individual results of each study in this review are set out in Table 3.

Discussion
This systematic review focuses on analyzing the effectiveness of physical therapy in adult patients diagnosed with Tension-type headache (TTH). The guiding line when showing the results of the articles, follows an axis of effectiveness in time (short, medium or long term). In the short term: direct treatment of trigger points [86,88], suboccipital inhibition and manipulation of the upper cervical vertebrae (applied singly or together) [87,95], electroacupuncture [89], techniques of craniocervical soft tissue and upper craniocervical neural mobilization techniques (applied singly or together) [91], microwave waves combined with myofascial therapy [92], progressive relaxation of the jaw and neck muscles combined with deep breathing exercises [96] and moxibustion on the temples. Without short-term effect, the combined treatment of suboccipital inhibition and interferential currents is also found [93].
In the medium term, between 8 weeks and 3 months after treatment, there are mobilization techniques accompanied by a postural re-education program [83], direct and indirect myofascial release techniques [84], traditional acupuncture together with treatment of trigger points in the face and neck or with medical training [85,94], manipulation of the upper cervical spine alone or in combination with head and neck massage [90,95], suboccipital inhibition [95] and progressive relaxation of the jaw and neck muscles combined with deep breathing exercises [96].
In the long term, beyond 36 weeks of intervention, only the mobilization techniques accompanied by a postural re-education program applied by Castien et al. [38].
Four of the studies included in this systematic review have also reported results for the variable "duration of headache episodes" [83,86,94,97] and only one reported significant differences for this variable [83].
In the last eleven years, different protocols of action have been studied, such as mobilization of the cervical and thoracic spine accompanied by a program of postural re-education of the head and neck [83], myofascial release techniques [84], traditional acupuncture and in splenium trigger points of the neck, masseter and temporary [85], treatment of head trigger points, neck and jaw [86], suboccipital inhibition and manipulation of the upper cervical vertebrae, isolated and combined [87], massage therapy and treatment of trigger points in the cranio-cervical-mandibular region [88], general electroacupuncture [89], manipulation of upper cervical vertebrae [90], neural mobilization techniques and relaxation of the cranio-cervical soft tissue [91], microwave and myofascial treatment of the cranio-cervical-mandibular region [92], suboccipital inhibition combined with interference currents in lower cervical spine [93], acupuncture, training and combined treatment of both [94], cervical manipulation combined with suboccipital inhibition [95], progressive relaxation of the jaw and neck muscles combined with deep breathing exercises [96] or moxibustion in temples combined with taking the drug Deanxit [97].
Although the physical therapy protocols in the treatment of adult patients with tension headache are very varied. All of them, except the general electroacupuncture [86], address in one way or another, neck, head and/or mouth.
General electroacupuncture has only been reported to significantly reduce the intensity of tension headache in the short term [89]. General acupuncture and trigger points acupuncture on cranio-cervical-mandibular musculature, such as splenium, masseter and temporal muscles, has been studied in the medium term, three months after treatment, reporting significant improvement in the intensity of tension headache in pregnant women [85]. Acupuncture combined with a training program has also been shown to significantly improve the intensity of chronic headache in the medium term, three months post-intervention [94].
The manipulation of upper cervicalspine did not report significant differences in the short term either for the intensity of pain or for the frequency of headache episodes when compared with massage of the cranio-cervical region [90]. Nevertheless, it did report significative intragroup differences in pre-post treatment results when isolated [87].
Only the mobilization of the cervical and thoracic spine accompanied by a program of postural re-education of the head and neck in patients with chronic tension headache has reported significant long-term results, 26 weeks post-intervention, for frequency and intensity of headache episodes variables [83]. In this study, the duration of headache episodes did not decrease significantly in the long term, but it did in the medium term, eight weeks post-treatment.
In general, all studies reported significant improvement in some of the study variables. A recent study related to our systematic review of Krøll et al. [98], conclude that non-pharmacological treatment approaches for TTH, used as an adjunct, are safe, free of significant adverse effects and with positive effects, although with low or very low evidence, especially [98]: The evidence after the analysis of the results is very low, in fact the authors justify that solid conclusion cannot be drawn from this review [98]. However, in our review, one of the inclusion criteria for the analysis of the RCTs was that they had a score equal to or greater than 6 on the PEDro scale, so the methodological quality is higher and the conclusions obtained are more solid.

Conclusions
This systematic review found that, to date, there is no consensus on a single physical therapy protocol in the treatment of adult patients diagnosed with tension headache.
The techniques used to address this pathology are very diverse. So, there is no standardized physical therapy protocol for tension-type headache treatment, although all the techniques studied to date address in one way or another the cranio-cervical-mandibular region. The approach of the cranio-cervical-mandibular region reports significant effects in terms of decreasing the intensity of pain and frequency of headache episodes.
The studies included in this systematic review are heterogeneous in methodology and only one of them performed long term follow-ups on the intervention, 26 weeks post-intervention, for two study variables, intensity and frequency of pain: mobilization of the cervical and thoracic spine accompanied by a postural reeducation program of the head and neck.From these results, it would be interesting for future studies to analyze in depth etiological factors such as the relationship between the appearance of chronic tension headaches and the position of the head and neck..
Finally, this systematic review can serve as useful basis for promoting a consensus on non-pharmacological approaches to tension-type headache.

Limitations
The studies included in this systematic review are heterogeneous in methodology and only one of them performed long term follow-ups on the intervention, 26 weeks post-intervention.
The effectiveness of physical therapy with respect to the duration of headache episodes has not been analyzed by almost any of the studies. For that reason, more studies are needed regarding the effects of long-term physical therapy, as well as its effects on the duration of headache episodes in people with tension headache. Funding: The APC has been funded by IBIMA Plataforma BIONAND and University of Málaga (Spain).

Institutional Review Board Statement:
The systematic review was registered in PROSPERO with registration number (CRD42020175020) on 5 July 2020. The principles of the Declaration of Helsinki were followed.