J Manipulative Physiol Ther 1995 (Mar); 18 (3): 148–154
Patrick Boline, DC, Northwestern College of Chiropractic
Kassem Kassak, MPH, PhD, American University, Beirut, Lebanon
Gert Bronfort, DC, PhD, Northwestern College of Chiropractic
Craig Nelson, DC, Northwestern College of Chiropractic
A.V. Anderson, DC, MD, Pain Assment & Rehabilitation Center, Edina, MN
Funding was provided by:
the Foundation for Chiropractic Education and Research (FCER)
This study compared the effects of spinal manipulation and pharmaceutical treatments for chronic tension headaches. Four weeks following the cessation of treatment, the pharmaceutical group demonstrated no improvement from the baseline. In the spinal manipulation group, headache intensity dropped 32 percent; frequency dropped 42 percent; and there was an overall improvement of 16 percent in functional health status.
Background: In the United States headaches are responsible for more than 18 million office visits annually, and are the most common reason for using over-the-counter medications. It is estimated that 156 million work days are lost each year because of headaches, translating to $25 billion in lost productivity. Of the categories of chronic headaches, tension-type headaches are most common.
Headaches are commonly treated by chiropractic doctors with spinal manipulation, and several studies have reported good outcomes. These trials however, suffered from either a lack of a control group or inadequate statistical power. The purpose of this randomized clinical trial was to evaluate the effectiveness of spinal manipulation and a common pharmaceutical treatment (amitriptyline) for chronic tension-type headache.
Methods: One-hundred-fifty patients between the ages of 18 and 70 were randomly assigned to receive either six weeks of chiropractic or pharmaceutical treatment which was preceded by a two week baseline period and included a four week, post-treatment follow up period. Main outcome measures were change in patient-reported daily headache intensity, weekly headache frequency, over-the-counter medication usage, and functional health status using the SF-36 Health Survey.
Results: During the treatment period both groups improved at very similar rates in all primary outcomes. Four weeks following the cessation of treatment patients who received spinal manipulative therapy showed a reduction of 32% in headache intensity, 42% in headache frequency, 30% in over-the-counter medication usage and 16% in functional health status. By comparison, patients that received amitriptyline showed no improvement or a slight worsening from baseline values in the same outcome measures. The group differences at four week post-treatment follow up were considered to be clinically important and statistically significant. There is further need to assess the effectiveness of spinal manipulative therapy beyond four weeks and to compare spinal manipulative therapy to an appropriate placebo such as sham manipulation in future clinical trials.
Conclusion: The results of this study show that spinal manipulative therapy is an effective treatment for tension headaches. Amitriptyline was slightly more effective in reducing pain by the end of the treatment period, but was associated with more side effects. Four weeks after cessation of treatment however, patients who received spinal manipulation experienced a sustained therapeutic benefit in all major outcomes in contrast to the amitriptyline group, who reverted to baseline values. The sustained theraputic benefit associated with spial manipulation seemed to result in a decreased need for over-the-counter medication. There is a need to assess the effectiveness of spinal manipulative therapy beyond four weeks and to compare SMT to an appropriate placebo such as sham manipulation in future clinical trials. (see the Problem with Placebo/Shams Page for problems issues to shams.)
Key words: clinical guidelines; low back pain; evidence based medicine; systematic reviews
From the Full-Text Article:
Headaches lead to more than 18 million office visits annually in the United States. In 1986, the Nuprin Pain Report showed that 156 million full-time work days are lost each year because of headaches, at an estimated cost of $25 billion in lost productivity . Headaches are also the most common reason for using over-the-counter analgesic medications . Chronic headaches are one of the most common presenting complaints in ambulatory care clinics [2, 3]. Of the two broad categories of chronic headaches, migraine and tension-type, migraine headaches are likely to be more severe and disabling; however, tension-type headaches are more common . A Canadian study showed that among chronic headache sufferers, 14% suffered from migraine headaches and 36% from tension-type headaches, 14% met the criteria for both headache types and the remaining 36% could not be classified .
A study of unconventional health care practices indicated that headaches are commonly treated by chiropractors . Several studies without control groups on spinal manipulative therapy for headaches have reported good outcomes [6-10]. The results of two randomized controlled trials suggested that spinal manipulation may be an effective treatment for both cervi co genic headache and migraine, but both studies suffered from inadequate statistical power [11, 12].
The pharmaceutical treatment for tension-type headaches consists of both symptomatic and prophylactic strategies. Symptomatic treatments include the use of analgesics, nonste-roidal anti-inflammatory drugs (NSAID) and, occasionally, mild narcotics [13-15]. The most commonly used and best studied prophylactic medication for tension-type headaches is the tricyclic antidepressant amitriptyline [16-20]. Diamond and Baltes found amitriptyline at a dosage of 10-30 mg per day to be superior to both a placebo and a higher dosage of the drug (25-75 mg) in reducing pain; it also produced fewer reported side effects than the 25-75 mg dose .
The purpose of this study was to test the hypothesis that patients who receive spinal manipulative therapy, in compari-son with amitriptyline therapy, would show reduced headache intensity, frequency, over-the-counter medication use and im-proved functional status 4 wk after cessation of active therapy. The rationale behind this hypothesis is twofold: first, Bovim et al. and Bogduk et al. [21-23] have shown that tension head-ache-like pain can be elicited by noxiously stimulating upper cervical spine structures. If spinal manipulation is effective in treating tension-type headaches, it may be so because it is correcting aberrant cervical spine function and thereby elimi-nating a source of headache pain. One would expect such corrections to have an effect beyond the cessation of treatment. Second, amitriptyline therapy is not expected to provide any relief beyond the treatment period.
Enrolled patients were randomized into either the spinal manipulation therapy or the amitriptyline therapy treatment group using a 1:1 allocation ratio. Mter a 2-wk baseline period, patients received treatment for 6 wk. Treatment was then discontinued and patients entered a 4-wk follow-up period.
Patient Recruitment and Selection
Patients were recruited from the Minneapolis/St. Paul, Min-nesota metro area with radio and newspaper advertisements, public service announcements, flyers and a news story on a local television station. All advertisements indicated that pa-tients would receive free treatment, either chiropractic or med-ical, for tension-type headaches. Respondents were screened by telephone and then examined at the Wolfe-Harris Center for Clinical Studies at Northwestern College of Chiropractic in Bloomington, Minnesota. A history and physical examination were performed by a team consisting of one medical and two chiropractic physicians.
Patients between the ages of 18 and 70 yr with a duration of headaches of at least 3 months and with at .least one episode per week were considered eligible for the study. The diagnosis of tension-type headache was determined by the examining team according to the criteria set by the International Headache Society (IRS) . It has long been recognized that there is considerable clinical and diagnostic overlap between migraine and tension-type headache . It is not uncommon for a particular patient to simultaneously meet the diagnostic criteria for both tension-type and migraine headache . Such pa-tients were included in this trial if, in the judgment of the examining doctors, their headache problem was predominantly tension-type in nature.
Exclusion criteria were: pregnancy, active treatment for headaches within the past three months by any provider, con-traindications to amitriptyline therapy (e.g., cardiac arrhyth-mias and glaucoma) or spinal manipulative therapy (e.g., me-tastases, fractures, inflammatory disease), as determined by history, physical and radiological examination.
Simple randomization was used. A computer-generated list was prepared that ensured a 1:1 allocation ratio. The group designations were placed in sealed envelopes that were opened by the patients at the time of randomization. A designated college administrative assistant outside the trial setting verified the correctness of the preparation of this allocation list and ensured that the investigators were blind to group allocation at the time of randomization.
Patients in the spinal manipulation group were treated twice weekly for 6 wk. Each therapy session typically lasted 20 min. The spinal manipulation group received spinal manipulation of a type described as short-lever, low-amplitude, high-velocity thrust techniques . At each visit, the treating doctor deter-mined, by manual palpation, the cervical, thoracic or lumbar spinal segments to be manipulated [28, 29] with regard to the findings of Bovim et al. and Bogduk et al. [21-22]. The investigative team thought that the greatest therapeutic effect would be achieved by paying particular attention to the upper three cervical segments. In preparation for the spinal manipu-lation, an average of 5-10 min of moist heat and 2 min of light massage were administered to the cervicothoracic musculature. Patients in the amitriptyline therapy group received amitripty-line daily for 6 wk. The dosage of 10 mg per day for the first week was increased to 20 mg per day the next week and to 30 mg per day thereafter. Patients were instructed to take the medication at bedtime. The dose was reduced if adverse effects such as drowsiness and dry mouth were not tolerated by the patient. The same medication protocol was used by Diamond and Baltes to minimize side effects while maintaining treat-ment effects . Patients were instructed to continue to use over-the-counter medication on an as-needed basis throughout the study.
Assessment of Outcomes
Four main outcome measures were used. The first three measures, headache pain intensity, headache frequency and over-the-counter medication usage, were obtained using the Blanchard headache diary, which has been shown to be a reliable and valid tool in the outcomes assessment of headaches [30, 31]. The pain ratings consisted of patient-reported head-ache intensity recorded four times daily (morning, afternoon, dinner-time and bedtime) using a six-point ordinal scale (0 = no pain; 1 = very mild pain; 2 = mild pain, pain could be ignored at times; 3 = moderate pain, pain is noticeably present; 4 = severe pain, difficult to concentrate, can do undemanding tasks and 5 = extremely intense pain, incapacitated). A mean daily headache pain intensity score on a scale of 0-20 for each period was derived from the pain ratings by totaling the ratings per period and dividing by the number of days in each period. The patient diaries were filled out four times daily during the 2-wk baseline, 6-wk treatment and 4-wk follow-up periods. Headache frequency was derived from the diaries by recording all ratings of 2 or above (a headache rating of 1 (very mild pain) was regarded as being clinically insignificant). Thus, the possible weekly headache frequency was between 0 and 28. Patients recorded their use of over-the-counter medications, such as salicylates, acetaminophen, and ibuprofen, that were used for symptomatic relief of their headaches. Both the type and number of tables of these medications were recorded in their pain diaries. The fourth main outcome, the impact of chronic tension-type headache on functional health status, was assessed by the SF-36, a self-administered, 36-item, generic health status questionnaire, which has been found to be both reliable and valid [32-35]. This instrument measures these dimensions: physical functioning, social functioning, role function, mental health, vitality, bodily pain, general health perception and general health change. The SF-36 was filled out at baseline and four weeks after the end of active intervention. For the purpose of this study, the sum of all dimensions was transformed into a global health status score.
An analysis of covariance was employed using headache intensity, headache frequency, over-the-counter medication use and health status data [36, 37]. The ANCOVA compared each group at the end of treatment (8th wk) and at the end of the follow-up period (12th wk). The analysis used the baseline as a covariate since there were some observed differences at baseline between the two groups. To avoid increasing the risk of Type I error by performing four individual outcome measure comparisons, the ex level of .05 was adjusted to .0125 for each of the tests using the Bonferroni correction . The analysis was performed using the Statistical Package for the Social Sciences (SPSS/PC+), ver. 4.0 .
A total of 448 people responded to recruitment advertise-ments. Of these, 113 were excluded from the study on the initial phone interview, mostly because they did not fit the eligibility criteria or decided not to participate. Of the remain-ing 335 subjects, 57 did not show up for examination and 128 were excluded after the examination. Of the excluded patients, 121 were diagnosed with migraine headache, three with cluster headache and one with os odontoidium, considered a contra-indication to spinal manipulation. Three had a history of sen-sitivity to tricyclic antidepressants. A total of 150 subjects were enrolled into the study.
Five patients (6.6%) of the spinal manipulation group dropped out: one because of increased neck pain, three because of personal problems that prevented them from keeping their appointments and one because of an automobile accident dur-ing the trial that required neck surgery. Nineteen patients (27.1 %) of the amitriptyline therapy group dropped out: ten decided against treatment after randomization and never started treatment, five because of adverse side effects and four because they were unable to keep their appointments. Further analysis was done to detect any differences in the clinical and sociode-mographic characteristics of the dropouts as compared to those who completed the study. No such significant difference was detected. Baseline characteristics of all participants are shown in Table 1.
Compliance and Cointervention
To be included in the analysis, patients had to complete 80% of their pain diaries. The mean of those included in the analysis was 88%. Patients in the spinal manipulation group were scheduled for 12 treatments each and the number of actual visits ranged from 10 to 12. No patient received less than 10 treatments. All patients in the amitriptyline therapy group were seen twice: once at the initiation of treatment and once 6 wk later. Patients in the amitriptyline group were required to have taken their medication at least 80% of the days during the treatment phase to be included in the analysis. The mean compliance rate of patients included in the analysis was 85% based on the patients' diaries. During the active intervention period and the 4-wk follow-up period none of the study pa-tients in either group reported having received nonstudy ther-apeutic intervention.
Of the patients who completed the study, 46 (82.1 %) in the amitriptyline group had side effects, including dry mouth, drowsiness or weight gain. In the spinal manipulation group three (4.3%) of the patients reported neck stiffness after the first treatment that disappeared in all cases after the first 2 wk of treatment.
At the end of the 6-wk treatment period there were no clinically important or statistically significant differences be-tween the two treatment groups; they both improved at similar rates from their original baseline measures. The amitriptyline group showed more improvement in headache intensity (see Table 2). Four weeks after the end of intervention, the spinal manipulation group showed a 32% reduction in headache in-tensity, 42% in headache frequency, 30% in over-the-counter medication usage, and a 16% improvement in functional health status, in relation to baseline values. The amitriptyline therapy group showed no improvement or slight worsening compared with baseline values in the same four main outcome measures. All group differences at 4 wk after withdrawal of therapy were considered to be clinically important and were statistically significant. The means of all outcome measures were adjusted to control for observed baseline differences. The results in Table 2 and Table 3 include the adjusted means by group, the group differences and the 95% confidence intervals of those differ-ences. The weekly group differences in headache intensity, frequency and over-the-counter medication usage throughout the 12-wk study are shown in Figure 1, Figure 2, and Figure 3. The differences between the two groups in headache intensity, frequency and over-the-counter medication usage during 4 wk after the intervention were statistically significant (p < .005). The differences in the SF-36 global scores were also statistically significant(p = .008). Of the nine dimensions of the SF-36, five were found to be significantly different, all five in favor of spinal manipulation. The group difference in physical functioning was 4.3% (p = 0.002); in energy/fatigue, 6.5% (p = 0.02); in bodily pain, 6.7% (p = 0.02); in general health perception, 5.1% (p = 0.02) and in general health change, 7.7% (p = 0.02).
Before randomization, each patient was asked to rate his/her expectation of both potential treatments on a four-point ordinal scale (worse, no change, better, and much better). Nine percent of the patients expected no improvement from spinal manipu-lative therapy, 38% expected to get better and 53% expected to get much better. Thirteen percent of the patients expected no improvement from medication, 53% expected to get better and 34% expected to get much better. Although not statistically significant, patients expected a slightly better outcome from spinal manipulative therapy compared with amitriptyline therapy.
Since there were observed differences in patients' gender, family history of headache and expectation of the outcome of treatment between the two groups, these three variables were analyzed as intervening variables in the outcomes of the ther-apies. As such, these variables were individually treated as a covariate in each outcome measure's analysis of covariance. The inclusion of these variables in the analysis did not change the outcome.
Best/Worst Case Analysis
Although baseline characteristics of drop-outs from both groups were similar to patients who completed the study, we decided to conduct a best- and worst-case analysis. Four-wk posttreatment scores were compared using baseline scores as covariates. In the best-case analysis, it was assumed that at 4 wk after cessation of treatment, all five drop-outs in the spinal manipulation group had an improvement in the four major outcome measures corresponding to the mean improvement of the patients who completed the trial in that group and that all 19 drop-outs in the amitriptyline therapy group did not change from their baseline values. The significant difference between the groups increased slightly in favor of the spinal manipula-tion group in all four major outcome measures tested and remained highly significant (p < .001).
In the worst-case analysis, we assumed that at 4 wk after cessation of treatment, the five drop-outs from the spinal manipulation group did not change from baseline values and that all 19 drop-outs from the amitriptyline therapy group had an improvement in the four major outcome measures corre-sponding to the mean improvement of the patients who completed the study in that group. This analysis did not change the significant difference between groups, favoring the spinal ma-nipulation group, of any of the four major outcome measures tested at four weeks posttreatment. For headache intensity, headache frequency, and over-the-counter medication the p-value remained at or below .001 and for global SF-36 score the p-value changed to .025.
There are no comparable studies on spinal manipulation and tension-type headaches but there are a number of studies that offer some basis for comparison. The mean daily headache index scores reported by patients in this study are typical of chronic tension-type headache sufferers as reported by Blan-chard and Andrasik . The amitriptyline trials by Lance and Curran , Diamond and Baltes  and Pfaffenrath et al. , although using slightly different outcome measures, showed results that are generally consistent with those in this study. The similarities include treatment outcomes, drop-out rates and side effects.
A previously reported randomized trial on spinal manipula-tion and cervicogenic headache found spinal manipulation to be substantially superior to both no treatment and spinal mo-bilization after 3 wk, but the difference disappeared after three months' follow-up . This study suffered from inadequate patient description and low statistical power.
A theoretical basis for the therapeutic effects of spinal ma-nipulation on tension-type headaches already exists. As men-tioned earlier, Bogduk and Marsland and others have shown that head pain similar to that of tension-type headache can be induced by noxiously stimulating structures innervated by cer-vical nerve roots C1-C3 [21-23]. These include joint capsule, ligaments and paraspinal suboccipital muscles. Headache pain may result from a common pathway shared by the trigeminal system and the upper three cervical nerves. Primary afferent nociceptors from these nerves converge upon common second-order spinothalamic neurons. As a result, cortical pain centers may then interpret stimulation from cervical structures as aris-ing from the areas of the head innervated by the trigeminal system . Since the manipulation was primarily directed to the cervical spine and particularly to the upper three segments of the cervical spine, it is possible that the manipulation results in reduction of nociceptive stimuli.
The mechanism for the effects of amitriptyline is better understood. Tension-type headache patients are known to have lowered levels of the neurotransmitter serotonin [40, 41]. Serotonin acting at the level of the second order spinothalamic neuron has an antinociceptive effect that diminishes pain sen-sations. Thus, lowered levels of serotonin have the effect of lowering the pain threshold. Amitriptyline is a serotonin agonist. It inhibits the uptake of serotonin from the neural cleft and enhances the antinociceptive effects of serotonin .
Explanations for the results of this study other than the effectiveness of spinal manipulation are possible. The group receiving spinal manipulative therapy received much more attention during treatment than the medical group. They were seen twice a week for 6 wk compared with twice overall (once at the beginning and once at the end of treatment) for the medical group. The additional attention received by the pa-tients in the manipulation group may have had additional therapeutic effects. Similarly, for each group there may have been a different level of placebo effect that was not controlled for in this study. The light massage and heat administered to the patients were brief, nonspecific and only used as prepara-tion to the manipulation. It is not likely that the heat and massage contributed significantly to the overall therapeutic effects of the manipulation, although this possibility cannot be ruled out. Patients recruited were aware that the study was being conducted at a chiropractic institution and were, presum-ably, favorably disposed toward receiving spinal manipulative therapy. The analysis of patient expectations did not indicate that this was an important factor.
In spite of our efforts to ensure that patients randomized into either group were willing to receive their specified treatment, ten patients randomized into the medication group declined treatment, whereas none randomized to the spinal manipulation group declined treatment. Missing data due to a drop-out rate that was three times higher in the amitriptyline group may have confounded the results, but our best- and worst-case analysis did not change the results of this study. Nonstudy cointerven-tion during the active treatment phase and the 4-wk follow-up period may likewise have confounded the results. According to the patient diaries, no one received nonstudy treatment for headaches during the course of the study.
The reduction in over-the-counter medication use seen in the spinal manipulation group might well be interpreted as the cause of a decrease in headache pain rather than the result. Analgesic abuse and subsequent rebound headaches are a well-documented phenomenon; thus, a reduction in over-the-counter medication use can result in fewer headaches. How-ever, patients in this study were not.instructed to discontinue or reduce over-the-counter medication. They were instructed to continue this medication as needed for symptomatic relief. Therefore, the conclusion that the reduced medication use is a reflection of less headache pain seems warranted.
Kudrow  demonstrated that the effectiveness of amitriptyline is reduced by the concomitant use of additional medi-cations. These include over-the-counter medications (aspirin, acetaminophen, ibuprofen) as well as prescription medication (barbiturates, narcotics and muscle relaxants). Patients in our study were prohibited from using any other prescription med-ications and their use of over-the-counter medication was at a much lower level than that in Kudrow's sample, an average of six tablets per day. Thus, we think the effectiveness of ami-triptyline was fairly assessed. The study limitations notwithstanding and with particular reference to the sustained improvements after the cessation of treatment in the spinal manipulation group, the most plausible explanation for the observed results is the therapeutic effects of spinal manipulation. Further research is needed to compare the cost-effectiveness of the two treatments and compare it with an appropriate placebo such as sham manipulation in future clin-ical trials. The long-term effectiveness has been evaluated in a 1-yr follow-up study that will be presented in a separate pub-lication.
The results of this study show that spinal manipulative therapy is an effective treatment for tension headaches. Ami-triptyline therapy was slightly more effective in reducing pain at the end of the treatment period but was associated with more side effects. Four wk after the cessation of treatment, however, the patients who received spinal manipulative therapy experi-enced a sustained therapeutic benefit in all major outcomes in contrast with the patients that received amitriptyline therapy, who returned to baseline values. The sustained therapeutic benefit associated with spinal manipulation seems to result in a decreased need for over-the-counter medication.
Because the study was not placebo controlled, the question remains: did spinal manipulative therapy result in a therapeutic effect beyond that provided by placebo? However, two ele-ments of the study tend to support the notion that it did. First, spinal manipulative therapy was compared with and proved as effective as a therapy (amitriptyline) that has been shown to be efficacious in double-blind, placebo-controlled trials on ten-sion-type headaches; second, there was sustained therapeutic benefit of spinal manipulative therapy 4 wk after the cessation of treatment, presumably after the reduction or disappearance of placebo effects.
Examining and treating doctors were Craig Nelson, D.C., Gert Bronfort, D.C., Alfred Anderson, D.C., M.D., and Zachary Zachman, D.C. We are indebted to the staff and interns
at the Center for Clinical Studies for help in processing patients. We also wish to thank John Meyer, D.C., for his help in the initial stages of concept and design, Charlie Goldsmith, Ph.D., for his critical review of the manuscript and Krista Boline, D.C., for her invaluable role as project manager.
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