WASHINGTON — People with migraine may have abnormal correlations between cortical thickness and pain thresholds, resulting in an inability to inhibit pain sensation by shifting attention away from pain, study results indicate.
Todd Schwedt, MD, of Mayo Clinic, presented the findings in a plenary session at the American Academy of Neurology 2015 Annual Meeting. Since people with migraine are known to be hypersensitive to painful stimuli, Schwedt and colleagues sought to compare cortical thickness-to-pain threshold correlations among adults with migraines and healthy controls.
The researchers conducted quantitative sensory testing to assess applied heat pain thresholds in 31 adults with migraine (average eight headache days per month for 16 years) and 32 healthy, matched controls. Cortical thickness was measured with 3T MRI and regional cortical thickness-to-pain threshold correlations were determined using a general linear model whole brain vertex-wise analysis. A pain threshold-by-group interaction analysis was conducted to estimate regions where subjects with migraine had alterations in pain threshold-to-cortical thickness correlations compared to controls.
Imaging results indicated that control subjects had negative correlations (P<0.01) between pain thresholds and cortical thickness in the left superior temporal/inferior parietal, left inferior temporal, left posterior cingulate/precuneus, right superior temporal, and right inferior parietal regions compared to migraine subjects, who had positive correlations (P<0.01) between pain thresholds and cortical thickness in the left superior temporal/inferior parietal, left inferior parietal, right precuneus, and right superior temporal/inferior parietal regions. Cortical thickness-to-pain threshold correlations between migraine and control subjects were sustained for the left superior temporal/inferior parietal region (P<0.01 Monte Carlo corrected).
“This could suggest that the absence of the normal correlations of the thickness of this region with pain threshold in migraineurs is more of a brain trait,” Schwedt said. “Perhaps this is something that’s more intrinsic to the migraine brain as opposed to being a result of recurring migraine attacks.”
“The TPJ [left temporal parietal junction] region participates in cognitive aspects of the pain process; more specifically it participates in [directing] attention towards or away from environmental stimuli, including painful stimuli,” Schwedt said. “So one can hypothesize that a lack of the normal correlation that we see in migraineurs could be a partial mechanism by which migraineurs have a difficult time distracting themselves from painful stimuli as well as other sensory stimuli.”
Although Schwedt emphasized that he was not recommending that imaging be used as a first-line tool in the diagnosis of migraine, developing an imaging biomarker “could optimize our clinical criteria,” especially for more difficult diagnoses, he said.
Using structural imaging to measure “volume, surface area, and thickness of brain regions would really be optimal, the reason being that the data you need to calculate these measurements can be obtained from a typical MRI scan.”