Patients with severe migraine pain may be more likely to experience central sensitization, researchers reported at the 54th Annual Scientific Meeting of the American Headache Society (June 21-24, 2012, Los Angeles, Calif). The study measured the relationship between allodynia, a clinical presentation of central sensitization, and migraine severity level.
However, although both duration and severity of migraine were hypothesized to contribute to allodynia, the data do not indicate a relationship between migraine duration and allodynia.
“The previous observation of duration of migraine as a factor for the development of allodynia was probably due to the coincidence that longer duration migraines also tend to be more severe, in some cases. In our analysis involving a larger population, migraine severity and duration appear to be independent of each other,” study coauthor Emilee Connors, PhD, of MAP Pharmaceuticals, Inc, in Mountain View, California, told Neurology Reviews.
The investigators retrospectively analyzed data from 792 persons in a phase III, randomized placebo-controlled clinical trial of MAP0004, an investigational acute treatment for migraine.
Migraine and allodynia
Using an electronic diary, patients recorded the duration of their migraine, which was defined as the time from migraine onset to the time of treatment. Patients also recorded whether migraine pain was mild, moderate, or severe at the time of treatment.
The researchers administered a standard questionnaire at the time of treatment via electronic diary to collect baseline allodynia information. Based on the data collected in the diary, they subsequently assessed correlations among the severity of migraine, the duration of migraine, and the percentage of patients who had allodynia using Fisher’s exact test and chi-square test.
“This was a single migraine attack study, and, therefore, frequency of migraines was not a factor that was evaluated as contributing to the presence of allodynia,” commented Biao Lu, PhD, Senior Director at MAP Pharmaceuticals, and his colleagues.
“Since allodynia is a clinical presentation of central sensitization, these data could be interpreted as finding a correlation between the progression of migraine into a form that is more resistant to treatment and migraine severity,” said Dr. Connors.
The level of migraine severity was also found to affect allodynia. Patients with a severe level of migraine pain experienced significantly more allodynia (58.4%) than those with a moderate level of pain (48.2%). Migraine severity level did not affect the relationship between allodynia and duration of migraine—no correlation was observed.
Dr. Connors noted that future research might examine allodynia in relation to other migraine factors, including migraine frequency. In addition, basic science research could explore the mechanism that leads to central sensitization. “The more we understand about the progression of migraine, the more we can potentially do to reverse it,” said Dr. Connors.