J Manipulative Physiol Ther 2000 (Feb); 23 (2): 91–95 ~ FULL TEXT
Peter J. Tuchin, GradDipChiro, DipOHS,
Henry Pollard, GradDipChiro, GradDipAppSc, Rod Bonello, DC, DO
Department of Chiropractic,
Macquarie University, New South Wales, Australia.
Objective: To assess the efficacy of chiropractic spinal manipulative therapy (SMT) in the treatment of migraine.
Design: A randomized controlled trial of 6 months' duration. The trial consisted of 3 stages: 2 months of data collection (before treatment), 2 months of treatment, and a further 2 months of data collection (after treatment). Comparison of outcomes to the initial baseline factors was made at the end of the 6 months for both an SMT group and a control group.
Setting: Chiropractic Research Center of Macquarie University.
Participants: One hundred twenty–seven volunteers between the ages of 10 and 70 years were recruited through media advertising. The diagnosis of migraine was made on the basis of the International Headache Society standard, with a minimum of at least one migraine per month.
Main Outcome Measures: Participants completed standard, headache diaries during the entire trial noting the frequency, intensity (visual analogne score), duration, disability, associated symptoms, and use of medication for each migraine episode.
Results: The average response of the treatment group (n = 83) showed statistically significant improvement in migraine frequency (P < .005), duration (P < .01), disability (P < .05), and medication use (P < .001) when compared with the control group (n = 40). Four persons failed to complete the trial because of a variety of causes, including change in residence, a motor vehicle accident, and increased migraine frequency. Expressed in other terms, 22% of participants reported more than a 90% reduction of migraines as a consequenc of the 2 months of SMT. Approximately 50% more participants reported significant improvement in the morbidity of each episode.
Conclusion: The results of this study support previous results showing that some people report significant improvement in migraines after chiropractic SMT. A high percentage (>80%) of participants reported stress as a major factor for their migraines. It appears probable that chiropractic care has an effect on the physical conditions related to stress and that in these people the effects of the migraine are reduced.
From the FULL TEXT Article:
The Migraine Foundation of Australia estimates that some 12% of Australians aged 15 years and over experience migraines.  However, the true number of subjects with migraines is unknown because not all such subjects visit a general practitioner.  A study performed in Australia estimated the cost of migraines to society as more than $750 million per annum.  The estimated cost of migraines in the United States is over $17 billion (in US dollars) per annum. 
The Headache Classification Committee of the International Headache Society (IHS) defines migraines as having the following qualities:
moderate or severe intensity, and
being aggravated by routine physical activity.
During the headache, the person must also experience either nausea, vomiting, or both or photophobia, phonophobia, or both. 
In addition, there is no suggestion, either by history, physical examination, or neurologic examination, that the person has a headache listed in groups 5 to 11 of their classification system. 
The aura is the feature that distinguishes migraines with aura from migraines without aura. An aura usually consists of homonymous visual disturbances; unilateral parethesias, numbness, or both; unilateral weakness; aphasia; or unclassifiable speech difficulty.  Some subjects with migraines have described the aura as an opaque object or a zigzag line around a cloud, and cases of tactile hallucinations have even been recorded.  The new terms migraine with aura and migraine without aura replace the old terms classic migraine and common migraine, respectively. 
IHS diagnostic criteria for migraine with aura (category 1.2) requires at least 3 of the following:
one or more fully reversible aura symptoms indicating focal cerebral cortex dysfunction, brainstem dysfunction, or both;
one or more fully reversible aura symptoms indicating focal cerebral cortex dysfunction, brainstem at least one aura symptom developing gradually over more than 4 minutes or 2 or more symptoms occurring in succession;
one or more fully reversible aura symptoms indicating focal cerebral cortex dysfunction, brainstem no aura symptom lasting for more than 60 minutes; and
one or more fully reversible aura symptoms indicating focal cerebral cortex dysfunction, brainstem headache after aura, with a free interval of less than 60 minutes.
Recent pharmaceutic treatment for migraine has focused on the serotonergic system or antiemetic symptoms. These include sumatriptan (Imigran), ergotamine (Ergodryl), dihydroergotamine (Dihydergot), or combinations of pharmaceuticals, such as caffeine and ergotamine (Cafergot).  Research on these pharmaceuticals suggest significant short-term relief but have not established any long-term benefit. [9–15] For example, Winner  assessed results of subcutaneous dihydroergotamine mesylate (DHE-45) versus subcutaneous sumatriptan succinate (Imitrex) on a cohort of 295 patients with migraine. In 2 hours 73% of those receiving DHE-45 versus 85% of those receiving sumatriptan succinate had relief from the migraine. However, 45% of the sumatriptan succinate group and 18% of the dihydroergotamine mesylate group had a recurrence of the migraine within 24 hours after treatment.
Clinical observations suggest that migraines may be aggravated or potentially caused by cervical spine conditions.  Even though migraines related to cervicogenic conditions are clinically recognizable, the exact mechanisms are unknown. [18–22] The role of the trigeminocervical nucleus in relation to migraine also remains unclear. The nucleus receives input from the upper 3 cervical spine segments, and therefore spinal problems may contribute to nerve facilitation.  One proposed mechanism for how chiopractic treatment could influence migraine is through alteration of the pain sensitivity of the central nervous system.  The trigeminal nucleus innervates the cranium, as well as many intracranial and extracranial blood vessels.  Afferents from the first 3 cervical vertebrae nerve roots also innervate the duramater, the scalp, and many suboccipital muscles.  This is a similar mechanism to regional pain syndromes, and it is also suggested as one mechanism for serotonin action. [26, 27]
The cervical spine has been reported to be involved in headache, dizziness, and other referred pain. [20–24, 28–31] Surgical decompression of the C2 nerve root has also resulted in reduction of nausea, photophobia, phonophobia, and vomiting.  However, the term cervicogenic migraine has been used infrequently and with some controversy because some authors doubt that the cervical spine is a potential etiologic factor for migraine.  Most subjects with migraine have numerous symptoms and therefore many potential diagnoses. [2, 7, 14, 17, 20, 21, 24, 32] Some authors believe there is a continuum between migraine, tension-type headache, and cervicogenic headache. [18, 19] In addition, the precipitating or aggravating factors for headaches and migraines are often the same or similar. [5, 17, 20, 21, 33]
This article will assess the results of a randomized controlled trial for chiropractic spinal manipulative therapy (CSMT) in migraine treatment in regard to alteration in symptoms, clinical features, and morbidity.
The majority of participants had chronic migraines; on average, they had experienced migraines for 18.1 years. However, the results demonstrated a significant (P < .005) reduction in migraine episodes and associated disability. The mean number of migraines per month was reduced from 7.6 to 4.1 episodes (Table 3).
Episodes, Average number of migraines per month; VAS scores, 100–mm visual analogue scale for average episode; duration, hours for an average episode; disability, hours before return to normal activities for an average episode; medications, average number of medications taken per month; NS, not significant.
The greatest area for improvement was medication use (P < .001), for which participants were asked to note the use of medication for each episode. A significant number of participants recorded that their medication use had reduced to zero by the end of the 6–month trial.
A 6–month study gives the results more validity than those of previous studies because one criticism of some of those studies was that the length of the trial was too short to allow for the cyclical nature of migraines. However, the study was limited in sample size and the fact that the trial was a pragmatic study that did not consider what aspects of chiropractic SMT had contributed to the improvement in the migraines.
In addition, the study was limited because of the type of control group; interferential does not mimic SMT. However, it could be argued that participants acted as their own form of control subjects because of the baseline (2 months) data collection, especially given the fact that this group consisted of subjects with chronic migraines. Perhaps a better control group would be a group undergoing sham SMT, in which participants receive a manipulative thrust into the cervicothoracic junction that was designed to be ineffective.
A further limitation of this study, as with other studies of migraine or headache, was that there was substantial overlap in diagnosis and classification of migraines. The questionnaire used for diagnosis in this study proved to have good reliability when compared with the number of participants that had previously received a diagnosis from a specialist. However, there is a strong suggestion that many subjects with headaches may have more than one type of headache. [17–21, 24, 32] An advantage of the design of this study is that regardless of an exact diagnosis of the migraine, self-reported improvement of outcome measures allows assessment of the validity of the therapy in question. 
This study also appears to confirm that there are a number of precipitating or aggravating factors involved in migraine episodes, and therefore a single treatment regimen may prove ineffective in the long term. [17, 20–22]
There have now been several studies demonstrating significant improvement in headaches or migraines after chiropractic SMT. [17, 22, 30, 36–39] Some of these studies were limited by lack of control subjects, poor control subjects, small sample sizes, and other methodological flaws. However, the level of evidence is steadily increasing to the point where there is now seen to be a moderate level of efficacy for chiropractic SMT in the treatment of headaches or migraines.
A high percentage (83%) of participants in this study reported stress as a major factor for their migraines. It appears probable that chiropractic care has an effect on the physical conditions related to stress and that in these people the effects of the migraine are reduced. However, further studies are required to assess how chiropractic SMT may have an effect on migraine morbidity. Another study currently being completed will assess the effect in other associated symptoms commonly experienced with migraines.
A further question that needs to be answered is how to assess the results of other forms of chiropractic SMT in the treatment of headaches or migraines. The results of this study appear to support previous results indicating that some people report significant improvement in migraines after chiropractic SMT. However, future studies may demonstrate that some specific forms of chiropractic SMT do not achieve the same results.