Discussion
We found that in contrast with individuals without aura and without headaches, migraineurs with aura oscillated significantly when standing in the bipodal position, and this was true for when experiments were conducted with OE and CE. They also oscillated more than migraineurs without aura when standing on one foot. Subjects with migraine (MA and MO) were incapable of remaining on one foot for the 30 seconds required by the test. Mobility, as measured by the TUG, was also reduced in individuals with MA and MO.
Several other studies suggested that balance is impaired in migraine, and differences are more evident when studies are conducted with eyes open, although definitive conclusions have been limited by sample size and by other methodological discrepancies.[21,25] Other studies found differences only when the eyes were closed.[17] We found differences in both situations,[25,26] and our data support the influence of aura on static balance.
We emphasize that although individuals with MA had increased oscillation when standing on the bipodal and unipodal positions with eyes opened, they were incapable (and this was seen for MO as well) to complete the testing with their eyes closed. These findings raise the question whether migraineurs are at increased risk of falling in situations such as walking in the dark. Our findings also point to the influence of age on test results. It may be that elderly migraineurs are at a particular increased risk of falling than elderly individuals without migraine, and this should be tested in further studies.
In addition to age, migraine frequency (chronic vs episodic) seems to impair balance in individuals with migraine.[26] Chronic migraine is associated with an increased number of subclinical lesions on the vestibular and cerebellar systems in addition to measurable changes in eye motricity. Taken together, data suggest a central cause for increased oscillation in migraineurs.[26,27] Individuals with MA are also more likely to have similar lesions in the posterior fossa,[9,28,29] suggesting that aura and frequency independently could contribute to the lesions.
We failed to identify an association between time since migraine onset, frequency of attacks, and duration of attacks with balance and mobility. We excluded individuals with chronic migraine, and our sample of individuals with episodic migraineurs was certainly underpowered to properly detect the influence of headache frequency.
Findings from measurements of static balance confirmed those of mobility. Similar impairments in mobility in migraineurs were also seen by Wrisley, although with a sample of older age than ours, which may explain the higher magnitude of impairment found by them.[30]
We performed static and dynamic tests in order to evaluate balance in migraneurs and CG, and found subclinical impairments in those with migraine. Future studies should obtain similar information with different tests (ie, functional tasks) aiming to assess if the impairments are of clinical relevance and if they increase the risk of falls among those with migraine.[31]
The relationship between vestibular disease[32] and dizziness in migraineurs is well established.[13,14,20,33–35] Furthermore, migraneurs with aura are more likely to have abnormalities on visual stabilization[36] and more visual dependence in order to maintain proper balance.[37] In our sample, 80% of individuals with MA had experienced dizziness, and the risks of the symptom were increased enormously in these individuals relative to CG. Similar findings were reported by others, who also described improvement in symptoms following vestibular rehabilitation,[30,38] suggesting the benefit of education and of physical therapy.
We enrolled individuals with migraine as per the ICHD-2.[3] It is possible that individuals with vestibular migraine were, therefore, included. Future studies could benefit by excluding individuals with ictal dizziness from the MA or MO group treating them separately.
A final limitation, the odds ratio presented in our study should be interpreted with caution because they are often broad. Nonetheless, the differences were significant. The changes are real, but the point estimates may be better refined by increasing sample size and homogeneity.
One strength of our study was that the sample size was calculated a priori in order to not only detect difference but to detect clinically meaningful differences after some adjustments. We also stratified migraine as a function of aura. Future studies should include the assessment of persistence of symptoms and of impairment over time, as well as the influence of migraine therapies and of physical therapy on balance, mobility, and dizziness.
Headache. 2013;53(7):1116-1122. © 2013 Blackwell Publishing