Dose response and efficacy of spinal manipulation for chronic cervicogenic headache: a pilot randomized controlled trial

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Dose response and efficacy of spinal manipulation for chronic cervicogenic headache: a pilot randomized controlled trial

Mitchell Haas, DC, Adele Spegman, PhD, RN, David Peterson, DC,
Mikel Aickin, PhD, Darcy Vavrek, ND

Center for Outcomes Studies,
Western States Chiropractic College,
2900 NE 132nd Ave., Portland, OR 97230, USA.
mhaas@wschiro.edu


PURPOSE:
  To compare the efficacy of two doses of SMT and two doses of light massage (LM) for CGH.BACKGROUND CONTEXT:   Systematic reviews of randomized controlled trials suggest that spinal manipulative therapy (SMT) is efficacious for care of cervicogenic headache (CGH). The effect of SMT dose on outcomes has not been studied.

PATIENT SAMPLE:   Eighty patients with chronic cervicogenic headache (CGH).

MAIN OUTCOME MEASURES:   Modified Von Korff pain and disability scales for CGH and neck pain (minimum clinically important difference = 10 on 100-point scale), number of headaches in the last 4 weeks, and medication use. Data were collected every 4 weeks for 24 weeks. The primary outcome was the CGH pain scale.

METHODS:   Participants were randomized to either 8 or 16 treatment sessions with either SMT or a minimal light massage (LM) control. Patients were treated once or twice per week for 8 weeks. Adjusted mean differences (AMD) between groups were computed using generalized estimating equations for the longitudinal outcomes over all follow-up time points (profile) and using regression modeling for individual time points with baseline characteristics as covariates and with imputed missing data.

RESULTS:   For the CGH pain scale, comparisons of 8 and 16 treatment sessions yielded small dose effects: |AMD|< /=5.6. There was an advantage for SMT over the control: AMD=-8.1 (95% confidence interval=-13.3 to -2.8) for the profile, -10.3 (-18.5 to -2.1) at 12 weeks, and -9.8 (-18.7 to -1.0) at 24 weeks. For the higher dose patients, the advantage was greater: AMD=-11.9 (-19.3 to -4.6) for the profile, -14.2 (-25.8 to -2.6) at 12 weeks, and -14.4 (-26.9 to -2.0) at 24 weeks. Patients receiving SMT were also more likely to achieve a 50% improvement in pain scale: adjusted odds ratio=3.6 (1.6 to 8.1) for the profile, 3.1 (0.9 to 9.8) at 12 weeks, and 3.1 (0.9 to 10.3) at 24 weeks. Secondary outcomes showed similar trends favoring SMT. For SMT patients, the mean number of CGH was reduced by half.

CONCLUSION:   Clinically important differences between SMT and a control intervention were observed favoring SMT. Dose effects tended to be small.


From the FULL TEXT Article:

Introduction

Primary headaches are one of the most common ailments, with a point prevalence in the general population of about 16%. [1] Epidemiological studies report that 5% of adults suffer from headaches on a daily basis [2]; approximately 7 million adults report suffering from headaches every other day. [3] Three types of headaches have been shown to account for the majority of these episodes: migraine, tension type, and cervicogenic. [4] The impact on quality of life can be comparable to patients with heart disease. [5] In terms of the financial burden, it has been estimated that headaches account for 157 million days per year lost from work, costing society approximately $50 billion in absenteeism and medical benefits. [6]

Cervicogenic headache (CGH) is associated with neck pain and dysfunction. [7, 8] Point prevalence estimates range from 0.4% to 4.6%. [9-11] Substantial consumer utilization of complementary and alternative medicine for the care of headache and neck pain has been demonstrated; perceived ‘‘helpfulness’’ compared with conventional medicine for symptomatic relief was cited as the reason for the preference. [12, 13]

The efficacy of spinal manipulative therapy (SMT) for the relief of chronic CGH has been summarized in systematic reviews of randomized controlled trials. One review found insufficient evidence to reach a conclusion. [14] However, the majority of these reviews found evidence for efficacy of SMT in terms of headache intensity, frequency, or duration. [15-19] In particular, higher quality trials showed manipulation to be superior to deep massage [20], placebo [21], and no treatment. [22] To date, one small feasibility trial (n524) by Haas et al. [23] has evaluated the dose response of SMT in combination with physical modalities for the care of CGH (3–12 treatments in 3 weeks). The authors found significant sustained reduction in headache pain from 4 to 12 weeks after randomization.

Although there is accumulating evidence of efficacy for spinal manipulation in the treatment of headache, treatment visits vary widely in randomized trials: up to twice per week for 3 to 8 weeks. This variability reflects a lack of consensus on the appropriate dose of manipulation that is needed to achieve maximal relief of symptoms. We therefore conducted a pilot study with sufficient power to compare a higher dose versus lower dose of SMT on CGH pain intensity. The study was also designed to test the hypothesis of no difference between SMT and a low-intensity manual therapy control (light massage [LM]).


Discussion

This was the first randomized trial to study the effect of SMT dose on headache and the efficacy of SMT across dose conditions. There were several notable findings. Regarding dose, there was little difference between 8 and 16 treatment sessions for a battery of headache and neck outcome measures. Although somewhat greater improvement was generally seen for 16 SMT visits, the greatest dose effect found for CGH pain did not reach clinical importance in the primary analysis. Still, a dose effect in the range of 8 to 16 treatment sessions for SMT cannot be unequivocally ruled out. The alternative analysis without imputed data did suggest some clinically important differences. Second, clinically important and statistically significant differences between SMT and LM were observed for CGH pain and disability. The largest intervention effects were found consistently at the higher dose of 16 treatment sessions. However, this pilot study was not powered to evaluate an interaction effect, and the hypothesis that there is a greater advantage for SMT over a control at the higher dose than at the lower dose could not be tested. Overall, the intervention effect sizes (standardized mean differences) for CGH pain were moderate to large for the main effects in Table 2 and for 16 sessions in Table 3 (between 0.5 and 1.0). [52] The odds ratios for 50% reduction in CGH pain also substantially favored SMT (O3.0). Third, there was substantial and sustainable reduction in CGH pain and number of headaches concomitant with decreased use of over-the-counter pain medication. This suggests that confounding effects of medication on pain improvement were likely minimal. The decrease in medication use was also only durable to 24 weeks for SMT. This implies that the differences between SMT and control may have been underestimated for follow-up in the longer term.

Finally, Figs. 2 and 3 showed that the average SMT patient could cut the number of headaches in half by 8 weeks. The average higher dose SMT patient could achieve a clinically important improvement (20 of 100 points). [53, 54] However, the figures make it clear that there is further room for improvement in CGH outcomes. This can be explored with study of the inclusion of ancillary modalities and integrative care models.

The prevalence of self-reported migraine headaches was unexpectedly low (28%) at baseline, given the high representation of migraine (O90%) in CGH sufferers observed by Fishbain et al. [27]. The lower prevalence may have been because of advertisement without mention of migraine, type of care offered, and exclusion from the study for prophylactic use of medication. It is interesting to note that migraine appeared to have little effect in this study on CGH pain and disability outcomes for the longitudinal profile (data not shown). This may be attributed to independence of mechanisms [55-57] or the influence of treatment observed in the study on other headaches (migraine and/or tension type). A clinical benefit for SMT in the treatment of all three headache types has been noted in systematic reviews. [15-17, 19, 58]

Important strengths of our trial design were the inclusion of a control treatment across dose of intervention, as well as control of attention and the effects of touching the patient. The principal limitation was sample size, and our pilot study findings should be considered preliminary. There is reasonable confidence in the analysis of main effects because comparisons had 40 in each group. However, the pairwise comparisons had only 20 per group and were more susceptible to the effects of unmeasured confounding variables and imprecise estimates of group differences (ie, wide CIs).

The absence of blinding made the study susceptible to the confounding effects of patient expectation and the patient- provider encounter. Expectations were balanced at baseline (Table 1). Other analysis, to be published elsewhere, demonstrated that patient perception of chiropractor enthusiasm was also balanced across groups and that both patient expectation and the patient-provider encounter were poor determinants of outcomes (Haas M, Aickin M, Vavrek D. A path analysis of expectancy and patient-provider encounter in an open-label randomized controlled trial of spinal manipulation for cervicogenic headache. J Manipulative Physiol Ther [accepted]).

The medication usage from our study cannot be generalized to that seen in practice. It is underestimated because participants taking analgesics regularly as a preventive measure were excluded from the study. This was necessary to minimize confounding in a trial with pain as the primary outcome. The length of study follow-up was limited by the duration of the grant support. A future study will include follow-up to at least 1 year. Finally, it is unknown at this time what subpopulations and CGH etiologies would most benefit from SMT. This requires further exploration.


Conclusions

Our pilot study adds to an emerging picture of SMT dose for the treatment of headache. It showed that a plateau in intervention effect might be found in the range of 8 to 16 treatment sessions, although a dose effect at these treatment levels cannot be ruled out. The study also adds to the support of SMT in moderate doses as a viable option for the treatment of CGH. What remains to be determined is a more precise estimate of the dose-response relationship with more dose conditions and whether it is dependent on ancillary care and duration of intervention in practice. That is, is short-term concentrated care or long-term care with less frequent visits more effective and cost effective and is there an effect on dose response of physical modalities, lifestyle changes, other ancillary procedures, and an integrative care approach across health care professions?