"The association of these two distinct disease processes is a fascinating connection that needs to be explored further," study investigator Douglas M. Sammer, MD, chief of the Hand and Upper Extremities Division, Department of Plastic Surgery, University of Texas Southwestern Medical Center at Dallas, said in a statement.
"This association suggests the possibility, although not demonstrated in this study, of a common systemic or neurologic risk factor," the authors write. In addition, migraine headache may be an early warning sign of increased risk for future CTS, they say.
The study was published online in Plastic and Reconstructive Surgery.
In a cross-sectional analysis of 25,880 adults who responded to the 2010 National Health Interview Survey, 952 (3.7%) had CTS and 4212 (16.3%) had migraine headache.
A case of CTS was defined as a respondent who answered "yes" to two questions: "Have you ever been told by a doctor or other health professional that you have a condition affecting the wrist and hand called carpal tunnel syndrome?" and "During the past 12 months have you had carpal tunnel syndrome?"
A case of migraine was defined as a respondent who answered "yes" to the question, "During the past 3 months, did you have severe headache or migraine?"
The study team found that migraine prevalence was higher in those with than without CTS (34% vs 16%; adjusted odds ratio [aOR], 2.60; 95% confidence interval [CI], 2.16 - 3.13).
CTS prevalence was also higher in persons with than without migraine headache (8% vs 3%; aOR, 2.67; 95% CI, 2.22 - 3.22).
CTS was associated with older age, female sex, obesity, diabetes, and smoking. Migraine headache was associated with younger age, female sex, obesity, diabetes, and smoking.
"Although we have theories, at this time we simply don't know why people with carpal tunnel syndrome are more likely to have migraines, and vice versa," Dr Sammer said. "A deeper understanding of how and why this connection exists may lead to earlier diagnosis or even the ability to implement preventive measures," he added.
Unlike CTS, migraine has not historically been considered a compression neuropathy, the researchers note in their article. However, some recent evidence suggests that some migraine headaches may be associated with nerve compression around the head and neck and that some migraines may be successfully treated by targeted peripheral nerve decompression, they note.
"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," the authors suggest.
A key limitation of the study, say the researchers, 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, they point out.
Another limitation is the fact that this was a survey-based study and did not consist of patients with CTS or migraine headache diagnoses confirmed by a medical professional.
Experts Weigh In, Urge Caution
Reached for comment, Matthew S. Robbins, MD, director, Inpatient Services, Montefiore Headache Center, chief of neurology, Einstein Division, Montefiore Medical Center, Bronx, New York, told Medscape Medical News that the study is "interesting and does address this connection for the first time."
"From my own clinical practice, I do believe in the study results reported," Dr Robbins said. "However, the emphasis on peripheral nerve compression as a cause or major factor for migraine is highly disputed, and most of us who diagnose, treat, and study patients with migraine regularly know that migraine is a problem of the brain."
He added, "The labeling of the disorder as 'migraine headache' rather than 'migraine' also reflects a lack of emphasis on this point, as migraine features so many other symptoms aside from headache, as any patient would describe. Migraine is a disorder where there is an inherited sensitivity of the nervous system, and with time there is sensitization of broader pain pathways that elevate the risk of experiencing other pain conditions. That is why migraine is associated not just with carpal tunnel syndrome but low back pain, fibromyalgia, temporomandibular dysfunction, and other pain conditions — the list is long."
Dr Robbins agrees that the methods for defining migraine in this study were "not ideal, [but] the authors took advantage of a large, established national database with immense power, so within the study mechanism this is a limitation to concede. However, it is likely that the question does capture many of those with active migraine."
But Stephen Silberstein, MD, director of the Headache Center at Thomas Jefferson University, Philadelphia, Pennsylvania, has major concerns about the methods. The "crucial fundamental flaw" is defining migraine as having severe headache or migraine in the last 3 months.
"The only way to show an association is lifetime prevalence of migraine as opposed to any headache in the last 3 months, so the criteria questions they used are not adequate," he told Medscape Medical News.
The study had no commercial funding. The authors have disclosed no relevant financial relationships.
Plast Reconstr Surg. Published online March 19, 2015. Full text