Discussion
The purpose of the present review was to critically evaluate the evidence for or against the effectiveness of SM for the treatment of CGH. Nine RCTs met our eligibility criteria. The results of 6 RCTs suggested that SM is effective for treating CGH compared to physical therapy, light massage, drug therapy, or no intervention.[4,14,15,17–19] Three RCTs showed no differences in pain, headache duration and frequency compared to placebo manipulation, physical therapy, massage, or wait list controls. Most trials had major methodological flaws (Table 2 and Table 3). Three (out of 5) RCTs were of low quality and these favored SM.[15,17,19] Three (out of 4) RCTs that were of high quality favored SM.[4,14,18] One high-quality study (out of 4) showed no effect.[13] Six RCTs adhered to International Headache Society diagnostic criteria or these described by Sjaastad et al.[4,13–15,18,19] Three RCTs failed to adhere to any diagnostic criteria.[16,17,20] The evidence from RCTs of SM for treatment of CGH is thus ambiguous and, for several reasons, inconclusive.
Our findings should be viewed in the context of other reviews. Vernon et al[21] published a review of complementary and alternative therapies in the treatment of tension-type headache and CGH. Even though it included several RCTs of SM, its focus was not on summarizing the totality of the evidence for or against SM. In a similar vein, Fernández de las Peñas et al[22] included 2 RCTs only, ie, 22.2% of the available data we managed to locate. Therefore, this review failed to evaluate the totality of the available evidence.
Populations of individuals with CGH were relatively homogenous across RCTs.[4,13–15,17,18] However, control interventions were heterogeneous ranging from sham manipulation,[13] light massage,[4] drugs,[17] physical therapy,[15,16] to no intervention.[14,18] Primary outcome measures were also heterogeneous ranging from numeric rating scale,[16] Modified Von Korff pain and disability scale,[4,14] visual analog scale,[15] and diaries (percentage of days with headache, total duration of headache, days with school absence due to headache, consumption of analgesics, intensity of headache, headache intensity per episode, and number of headache hours per day).[13,15,18] Frequency and duration of SM sessions varied across RCTs from 1 session only[13,17] to 22 sessions.[15] Most RCTs failed to describe SM technique in sufficient depth (Table 4).[14–17,19,20] Given such variability and lack of standardization of SM treatments, it is difficult to independently replicate these studies and/or draw any firm conclusions.
Four of the 9 RCTs reported adverse effects (AEs).[13,18–20] Five RCTs failed to provide that information (Table 5).[4,14–17] The non-reporting of AEs is in violation of all guidelines of reporting clinical trials and, arguably, of medical ethics. It is also worth noting that several hundred severe complications after upper spinal manipulations have been reported (eg, Ernst[23] and Terrett[24]).
A particular concern relates to vascular accidents caused by arterial dissection after upper spinal manipulation.[25–28] The estimates as to the incidence of these complications vary hugely.[10] Underreporting of AEs in RCTs is likely to generate a false impression about the safety of SM.
Three of the 6 RCTs that suggested SM to be effective were conducted by chiropractors.[4,14,15] Three RCTs performed by non-chiropractors showed no effect (Table 6).[13,16,20] This could either indicate a degree of bias on the side of chiropractors, as noted previously[29] or mean that chiropractors are better trained in SM and therefore more effective than other professions administering this treatment.
Our review has several limitations. Even though our searches were extensive, we cannot be entirely sure that all relevant articles were located. Publication bias may have resulted in negative studies remaining unpublished. The number of trials included in our review, their total sample size, and their methodological quality were too low to allow definitive judgments. Even though all included RCTs were considered to have relatively homogenous CGH populations, statistical pooling was not feasible due to lack of reporting of sufficient raw data. However, this review has several strengths including the comprehensive search strategy, the inclusion of only the highest quality trial design and use of suggested methods for systematic reviews of interventions for CGH.
Future studies of SM should be in line with accepted standards of trial design and reporting (eg, CONSORT guidelines). In particular, studies should be of adequate sample size based on power calculations, use validated outcome measures, control for non-specific effects, and minimize other sources of bias. Reporting of these studies should be such that results can be independently replicated.
In conclusion, the evidence that SM is effective for CGH is not conclusive. Further rigorous research in this area is needed. Until conclusive data are available, SM cannot be regarded as an evidence-based approach in the treatment of CGH.
Headache. 2011;51(7):1132-1139. © 2011 Blackwell Publishing
Cite this: Spinal Manipulations for Cervicogenic Headaches - Medscape - Aug 01, 2011.
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