An Association Between Carpal Tunnel Syndrome and Migraine Headaches

National Health Interview Survey, 2010

Huay-Zong Law, MD; Bardia Amirlak, MD; Jonathan Cheng, MD; Douglas M. Sammer, MD

Disclosures

Plast Reconstr Surg Glob Open. 2015;3(3):E333 

In This Article

Discussion

The current study is the first to demonstrate an association between carpal tunnel syndrome and migraine headache. Carpal tunnel syndrome is the most common disease process within the larger family of compression neuropathies. Migraine headache, on the other hand, has not historically been considered to be a compression neuropathy. Although some authors previously proposed an extracranial component to migraine pathogenesis,[42,43] further recent evidence supports that some migraine headaches may be associated with nerve compression within the head and neck.[28–30,34,44] This concept remains controversial and is debated heavily within the medical community.[45] Of note, a recent survey of members of the American Headache Society reported that nerve blocks and trigger point injections are commonly used by its members to treat migraine headache,[46] and several other studies support targeted injections of botulinum toxin or local anesthetic for the treatment of migraine headaches.[33–38,47–49]

There are several limitations to this study. The most notable is that the survey question for migraine headache was worded "migraine or severe headache." This lack of specificity may have led to a number of false-positive respondents without true migraine headaches. Respondents with other types of headaches such as occipital neuralgia, new daily persistent headaches, cluster headaches, and others could have been included. However, the migraine prevalence in the current study, both in terms of overall prevalence (16.3%) and prevalence by age group and gender, is consistent with previously published migraine-specific studies.[6,7,9,12] In a 2006 study of 145,335 participants, the prevalence of migraine headache in the adult population using the International Classification of Headache Disorders (ICHD) criteria was found to be 15%.[9,50] Using the International Classification of Headache Disorders-2 criteria, they calculated that over 30% of additional respondents fulfill the criteria for Probable Migraine, a subtype in which greater than 1 in 4 patients should be considered for preventive migraine care.[9,51,52] In our study, there was additional concordance with the published literature on migraine epidemiology with the positive correlations seen between migraine and risk factors such as obesity[53–56] and smoking.[57,58] Finally, it should be noted that numerous other studies have used the same database (NHIS) to study migraine headache, providing precedent for the use of this database in our current study.[12,55,59–61] However, even though the migraine headache overall prevalence and subgroup prevalence found in this study are consistent with the existing literature, and the NHIS database has previously been used for studying migraine headache, the wording of the survey remains an important limitation. The results of this study should be interpreted within this limited context.

Another limitation is the fact that this was a survey-based study and did not consist of patients with carpal tunnel syndrome or migraine headache diagnoses confirmed by a medical professional. The survey questions rely upon the respondents' understanding of their own health status. Respondents with mild or early symptoms may not have been aware of their disease process, such as can occur with carpal tunnel syndrome. This may have led to underreporting or resulted in a bias toward more severe manifestations of disease. Also, because of the survey design, noncivilian and institutionalized persons were not accounted for, which could skew the results. Smaller ethnic groups such as Native American Indian and Alaskan Native were unable to be separately analyzed due to an insufficient number of respondents. Socioeconomic data, such as income, are missing for a large number of records and could not be incorporated into the model. Other studies have demonstrated a higher prevalence of migraine headache among households in lower income groups.[6,7,62]

Another limitation is that carpal tunnel syndrome and migraine headache are treatable conditions, so the wording of the survey questions (eg, "within the last 12 months") likely resulted in negative respondents who may have had either disease process in the past. Furthermore, because carpal tunnel syndrome and migraine headache have different age distributions, with migraine headache more prevalent in younger age groups and carpal tunnel prevalence increasing with age, the wording of the questions may underestimate the true strength of the association. For example, the association would be missed for a person who had migraine headaches that resolved at a younger age, followed by the development of carpal tunnel syndrome at an older age. The association may have been stronger had it been possible to identify patients who had ever had migraine headache.

One of the strengths of the current study is that the NHIS is designed to be nationally representative, adding to the generalizability of our study.[39] Also, the survey design allows for inclusion of underrepresented age groups and ethnicities such as the elderly, Asian, Hispanic, and non-Hispanic Black populations. This can be especially useful for identifying populations at significantly higher or lower risk, providing clues about etiology. This study is also consistent with previously identified risk factors as above for both carpal tunnel syndrome and migraine headache, supporting the validity of the analysis. Furthermore, these risk factors were adjusted for in the statistical analysis, making the aOR a more realistic indicator of association.

Similar to other peripheral neuropathies such as carpal tunnel syndrome, the precise pathophysiology of migraine headache remains unclear. The underlying cause connecting seemingly unrelated compression neuropathies such as carpal tunnel syndrome and cubital tunnel syndrome,[20,21] and between carpal tunnel syndrome and thoracic outlet syndrome,[25,26] currently remains unknown. The contributing factors may include a common associated comorbidity[4,11,58,63–67] or a common genetic factor,[68,69] leading to increased susceptibility to compression within the peripheral nervous system. In 1988, Dellon et al[70] demonstrated in an animal model that the nerves of animals with diabetes are more susceptible to compression than the nerves of animals without diabetes. However, diabetes was adjusted for within the current study, making this an unlikely cause for the association between migraine headache and carpal tunnel syndrome. Furthermore, although diabetes is a well-defined risk factor for carpal tunnel syndrome,[4,63,64] the association between diabetes and migraine headache is less clear in the literature.[11,65,66]

Multiple compression neuropathies have also been noted in other situations. The "double-crush" phenomenon is well described and occurs when compression of a nerve at one location impedes axonal flow, making the nerve more susceptible to compression at another location.[25,71] Although this may explain some cases of associated compression neuropathies within the same nerve tract, it does not explain associated compression neuropathies that occur within anatomically distinct peripheral nerves and would not explain the association between carpal tunnel syndrome and migraine headache.

Hereditary neuropathy with liability to pressure palsies (HNPP) is an uncommon condition that results in recurrent focal compression neuropathies, primarily of the median, ulnar, and peroneal nerves.[68,69] Hereditary neuropathy with liability to pressure palsies is an autosomal dominant disease and has been attributed to a defect in chromosome 17 that results in abnormal myelin protein 22.[72,73] Although this rare disease does not account for the association between carpal tunnel syndrome and migraine headache, it does demonstrate that an underlying genetic abnormality can result in susceptibility to nerve compression throughout the entire peripheral nervous system.

There is increasing recognition of a central nervous system component to peripheral neuropathies.[74–76] Similarly, our understanding of migraine headaches is growing to incorporate peripheral nervous system contributions to what is often considered a purely central pathology. We are not proposing that migraines are purely peripheral phenomena, though, especially because some migraineurs who are pain-free after surgical release continue to experience auras.[31] An alternative explanation is that peripheral compression or irritation leads to central sensitization which increases the likelihood of suffering from future peripheral neuropathy in other areas.[77] Because migraine headache is more common in younger patients, and carpal tunnel syndrome is more prevalent in older patients, migraine headache could conceivably sensitize the central nervous system to develop pain from later nerve compression in the carpal tunnel.

Based on the findings of this study and prior studies, it may be worthwhile in patients with migraine to perform an examination for peripheral nerve compression in the head and neck. Potential compression points include the supraorbital and supratrochlear,[27,29,48,78–80] auriculotemporal,[29,81,82] zygomaticotemporal,[83,84] greater occipital,[44,47,48,85] third occipital,[86,87] and lesser occipital[48,86,88] nerves. Accurate clinical assessment of the origin of any peripheral pain based on history and physical examination of these surface landmarks may broaden our knowledge of the relative contribution of these nerves to migraine symptoms.

Further research is warranted to determine the value of migraine headache as an early indicator of patients who are more likely to develop carpal tunnel syndrome in the future. Identification of migraine headache as a predictor of future carpal tunnel syndrome would allow for earlier diagnosis and treatment, or even prevention, of carpal tunnel syndrome by modification of risk factors. Further research also needs to be performed to evaluate predisposing and genetic factors in those with higher prevalence, protective factors in those with lower prevalence, and the efficacy of interventions to prevent the development of these diseases.

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